*Changes in v25*: - Do proper filtering on hole as well (hole got missed earlier)
*Changes in v24*: - Rebase on top of next-20230710 - Place WP markers in case of hole as well
*Changes in v23*: - Set vec_buf_index in loop only when vec_buf_index is set - Return -EFAULT instead of -EINVAL if vec is NULL - Correctly return the walk ending address to the page granularity
*Changes in v22*: - Interface change: - Replace [start start + len) with [start, end) - Return the ending address of the address walk in start
*Changes in v21*: - Abort walk instead of returning error if WP is to be performed on partial hugetlb
*Changes in v20* - Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
*Changes in v19* - Minor changes and interface updates
*Changes in v18* - Rebase on top of next-20230613 - Minor updates
*Changes in v17* - Rebase on top of next-20230606 - Minor improvements in PAGEMAP_SCAN IOCTL patch
*Changes in v16* - Fix a corner case - Add exclusive PM_SCAN_OP_WP back
*Changes in v15* - Build fix (Add missed build fix in RESEND)
*Changes in v14* - Fix build error caused by #ifdef added at last minute in some configs
*Changes in v13* - Rebase on top of next-20230414 - Give-up on using uffd_wp_range() and write new helpers, flush tlb only once
*Changes in v12* - Update and other memory types to UFFD_FEATURE_WP_ASYNC - Rebaase on top of next-20230406 - Review updates
*Changes in v11* - Rebase on top of next-20230307 - Base patches on UFFD_FEATURE_WP_UNPOPULATED - Do a lot of cosmetic changes and review updates - Remove ENGAGE_WP + !GET operation as it can be performed with UFFDIO_WRITEPROTECT
*Changes in v10* - Add specific condition to return error if hugetlb is used with wp async - Move changes in tools/include/uapi/linux/fs.h to separate patch - Add documentation
*Changes in v9:* - Correct fault resolution for userfaultfd wp async - Fix build warnings and errors which were happening on some configs - Simplify pagemap ioctl's code
*Changes in v8:* - Update uffd async wp implementation - Improve PAGEMAP_IOCTL implementation
*Changes in v7:* - Add uffd wp async - Update the IOCTL to use uffd under the hood instead of soft-dirty flags
*Motivation* The real motivation for adding PAGEMAP_SCAN IOCTL is to emulate Windows GetWriteWatch() syscall [1]. The GetWriteWatch{} retrieves the addresses of the pages that are written to in a region of virtual memory.
This syscall is used in Windows applications and games etc. This syscall is being emulated in pretty slow manner in userspace. Our purpose is to enhance the kernel such that we translate it efficiently in a better way. Currently some out of tree hack patches are being used to efficiently emulate it in some kernels. We intend to replace those with these patches. So the whole gaming on Linux can effectively get benefit from this. It means there would be tons of users of this code.
CRIU use case [2] was mentioned by Andrei and Danylo:
Use cases for migrating sparse VMAs are binaries sanitized with ASAN, MSAN or TSAN [3]. All of these sanitizers produce sparse mappings of shadow memory [4]. Being able to migrate such binaries allows to highly reduce the amount of work needed to identify and fix post-migration crashes, which happen constantly.
Andrei's defines the following uses of this code: * it is more granular and allows us to track changed pages more effectively. The current interface can clear dirty bits for the entire process only. In addition, reading info about pages is a separate operation. It means we must freeze the process to read information about all its pages, reset dirty bits, only then we can start dumping pages. The information about pages becomes more and more outdated, while we are processing pages. The new interface solves both these downsides. First, it allows us to read pte bits and clear the soft-dirty bit atomically. It means that CRIU will not need to freeze processes to pre-dump their memory. Second, it clears soft-dirty bits for a specified region of memory. It means CRIU will have actual info about pages to the moment of dumping them. * The new interface has to be much faster because basic page filtering is happening in the kernel. With the old interface, we have to read pagemap for each page.
*Implementation Evolution (Short Summary)* From the definition of GetWriteWatch(), we feel like kernel's soft-dirty feature can be used under the hood with some additions like: * reset soft-dirty flag for only a specific region of memory instead of clearing the flag for the entire process * get and clear soft-dirty flag for a specific region atomically
So we decided to use ioctl on pagemap file to read or/and reset soft-dirty flag. But using soft-dirty flag, sometimes we get extra pages which weren't even written. They had become soft-dirty because of VMA merging and VM_SOFTDIRTY flag. This breaks the definition of GetWriteWatch(). We were able to by-pass this short coming by ignoring VM_SOFTDIRTY until David reported that mprotect etc messes up the soft-dirty flag while ignoring VM_SOFTDIRTY [5]. This wasn't happening until [6] got introduced. We discussed if we can revert these patches. But we could not reach to any conclusion. So at this point, I made couple of tries to solve this whole VM_SOFTDIRTY issue by correcting the soft-dirty implementation: * [7] Correct the bug fixed wrongly back in 2014. It had potential to cause regression. We left it behind. * [8] Keep a list of soft-dirty part of a VMA across splits and merges. I got the reply don't increase the size of the VMA by 8 bytes.
At this point, we left soft-dirty considering it is too much delicate and userfaultfd [9] seemed like the only way forward. From there onward, we have been basing soft-dirty emulation on userfaultfd wp feature where kernel resolves the faults itself when WP_ASYNC feature is used. It was straight forward to add WP_ASYNC feature in userfautlfd. Now we get only those pages dirty or written-to which are really written in reality. (PS There is another WP_UNPOPULATED userfautfd feature is required which is needed to avoid pre-faulting memory before write-protecting [9].)
All the different masks were added on the request of CRIU devs to create interface more generic and better.
[1] https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-g... [2] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com [3] https://github.com/google/sanitizers [4] https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#64-bit [5] https://lore.kernel.org/all/bfcae708-db21-04b4-0bbe-712badd03071@redhat.com [6] https://lore.kernel.org/all/20220725142048.30450-1-peterx@redhat.com/ [7] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.c... [8] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.c... [9] https://lore.kernel.org/all/20230306213925.617814-1-peterx@redhat.com [10] https://lore.kernel.org/all/20230125144529.1630917-1-mdanylo@google.com
* Original Cover letter from v8* Hello,
Note: Soft-dirty pages and pages which have been written-to are synonyms. As kernel already has soft-dirty feature inside which we have given up to use, we are using written-to terminology while using UFFD async WP under the hood.
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl: - Get the information if the pages have been written-to (PAGE_IS_WRITTEN), file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT) or swapped (PAGE_IS_SWAPPED). - Write-protect the pages (PAGEMAP_WP_ENGAGE) to start finding which pages have been written-to. - Find pages which have been written-to and write protect the pages (atomic PAGE_IS_WRITTEN + PAGEMAP_WP_ENGAGE)
It is possible to find and clear soft-dirty pages entirely in userspace. But it isn't efficient: - The mprotect and SIGSEGV handler for bookkeeping - The userfaultfd wp (synchronous) with the handler for bookkeeping
Some benchmarks can be seen here[1]. This series adds features that weren't present earlier: - There is no atomic get soft-dirty/Written-to status and clear present in the kernel. - The pages which have been written-to can not be found in accurate way. (Kernel's soft-dirty PTE bit + sof_dirty VMA bit shows more soft-dirty pages than there actually are.)
Historically, soft-dirty PTE bit tracking has been used in the CRIU project. The procfs interface is enough for finding the soft-dirty bit status and clearing the soft-dirty bit of all the pages of a process. We have the use case where we need to track the soft-dirty PTE bit for only specific pages on-demand. We need this tracking and clear mechanism of a region of memory while the process is running to emulate the getWriteWatch() syscall of Windows.
*(Moved to using UFFD instead of soft-dirtyi feature to find pages which have been written-to from v7 patch series)*: Stop using the soft-dirty flags for finding which pages have been written to. It is too delicate and wrong as it shows more soft-dirty pages than the actual soft-dirty pages. There is no interest in correcting it [2][3] as this is how the feature was written years ago. It shouldn't be updated to changed behaviour. Peter Xu has suggested using the async version of the UFFD WP [4] as it is based inherently on the PTEs.
So in this patch series, I've added a new mode to the UFFD which is asynchronous version of the write protect. When this variant of the UFFD WP is used, the page faults are resolved automatically by the kernel. The pages which have been written-to can be found by reading pagemap file (!PM_UFFD_WP). This feature can be used successfully to find which pages have been written to from the time the pages were write protected. This works just like the soft-dirty flag without showing any extra pages which aren't soft-dirty in reality.
The information related to pages if the page is file mapped, present and swapped is required for the CRIU project [5][6]. The addition of the required mask, any mask, excluded mask and return masks are also required for the CRIU project [5].
The IOCTL returns the addresses of the pages which match the specific masks. The page addresses are returned in struct page_region in a compact form. The max_pages is needed to support a use case where user only wants to get a specific number of pages. So there is no need to find all the pages of interest in the range when max_pages is specified. The IOCTL returns when the maximum number of the pages are found. The max_pages is optional. If max_pages is specified, it must be equal or greater than the vec_size. This restriction is needed to handle worse case when one page_region only contains info of one page and it cannot be compacted. This is needed to emulate the Windows getWriteWatch() syscall.
The patch series include the detailed selftest which can be used as an example for the uffd async wp test and PAGEMAP_IOCTL. It shows the interface usages as well.
[1] https://lore.kernel.org/lkml/54d4c322-cd6e-eefd-b161-2af2b56aae24@collabora.... [2] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.c... [3] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.c... [4] https://lore.kernel.org/all/Y6Hc2d+7eTKs7AiH@x1n [5] https://lore.kernel.org/all/YyiDg79flhWoMDZB@gmail.com/ [6] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com/
Regards, Muhammad Usama Anjum
Muhammad Usama Anjum (4): fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs tools headers UAPI: Update linux/fs.h with the kernel sources mm/pagemap: add documentation of PAGEMAP_SCAN IOCTL selftests: mm: add pagemap ioctl tests
Peter Xu (1): userfaultfd: UFFD_FEATURE_WP_ASYNC
Documentation/admin-guide/mm/pagemap.rst | 58 + Documentation/admin-guide/mm/userfaultfd.rst | 35 + fs/proc/task_mmu.c | 591 +++++++ fs/userfaultfd.c | 26 +- include/linux/hugetlb.h | 1 + include/linux/userfaultfd_k.h | 21 +- include/uapi/linux/fs.h | 55 + include/uapi/linux/userfaultfd.h | 9 +- mm/hugetlb.c | 34 +- mm/memory.c | 27 +- tools/include/uapi/linux/fs.h | 55 + tools/testing/selftests/mm/.gitignore | 2 + tools/testing/selftests/mm/Makefile | 3 +- tools/testing/selftests/mm/config | 1 + tools/testing/selftests/mm/pagemap_ioctl.c | 1464 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 16 files changed, 2362 insertions(+), 24 deletions(-) create mode 100644 tools/testing/selftests/mm/pagemap_ioctl.c mode change 100644 => 100755 tools/testing/selftests/mm/run_vmtests.sh
From: Peter Xu peterx@redhat.com
This patch adds a new userfaultfd-wp feature UFFD_FEATURE_WP_ASYNC, that allows userfaultfd wr-protect faults to be resolved by the kernel directly.
It can be used like a high accuracy version of soft-dirty, without vma modifications during tracking, and also with ranged support by default rather than for a whole mm when reset the protections due to existence of ioctl(UFFDIO_WRITEPROTECT).
Several goals of such a dirty tracking interface:
1. All types of memory should be supported and tracable. This is nature for soft-dirty but should mention when the context is userfaultfd, because it used to only support anon/shmem/hugetlb. The problem is for a dirty tracking purpose these three types may not be enough, and it's legal to track anything e.g. any page cache writes from mmap.
2. Protections can be applied to partial of a memory range, without vma split/merge fuss. The hope is that the tracking itself should not affect any vma layout change. It also helps when reset happens because the reset will not need mmap write lock which can block the tracee.
3. Accuracy needs to be maintained. This means we need pte markers to work on any type of VMA.
One could question that, the whole concept of async dirty tracking is not really close to fundamentally what userfaultfd used to be: it's not "a fault to be serviced by userspace" anymore. However, using userfaultfd-wp here as a framework is convenient for us in at least:
1. VM_UFFD_WP vma flag, which has a very good name to suite something like this, so we don't need VM_YET_ANOTHER_SOFT_DIRTY. Just use a new feature bit to identify from a sync version of uffd-wp registration.
2. PTE markers logic can be leveraged across the whole kernel to maintain the uffd-wp bit as long as an arch supports, this also applies to this case where uffd-wp bit will be a hint to dirty information and it will not go lost easily (e.g. when some page cache ptes got zapped).
3. Reuse ioctl(UFFDIO_WRITEPROTECT) interface for either starting or resetting a range of memory, while there's no counterpart in the old soft-dirty world, hence if this is wanted in a new design we'll need a new interface otherwise.
We can somehow understand that commonality because uffd-wp was fundamentally a similar idea of write-protecting pages just like soft-dirty.
This implementation allows WP_ASYNC to imply WP_UNPOPULATED, because so far WP_ASYNC seems to not usable if without WP_UNPOPULATE. This also gives us chance to modify impl of WP_ASYNC just in case it could be not depending on WP_UNPOPULATED anymore in the future kernels. It's also fine to imply that because both features will rely on PTE_MARKER_UFFD_WP config option, so they'll show up together (or both missing) in an UFFDIO_API probe.
vma_can_userfault() now allows any VMA if the userfaultfd registration is only about async uffd-wp. So we can track dirty for all kinds of memory including generic file systems (like XFS, EXT4 or BTRFS).
One trick worth mention in do_wp_page() is that we need to manually update vmf->orig_pte here because it can be used later with a pte_same() check - this path always has FAULT_FLAG_ORIG_PTE_VALID set in the flags.
The major defect of this approach of dirty tracking is we need to populate the pgtables when tracking starts. Soft-dirty doesn't do it like that. It's unwanted in the case where the range of memory to track is huge and unpopulated (e.g., tracking updates on a 10G file with mmap() on top, without having any page cache installed yet). One way to improve this is to allow pte markers exist for larger than PTE level for PMD+. That will not change the interface if to implemented, so we can leave that for later.
Co-developed-by: Muhammad Usama Anjum usama.anjum@collabora.com Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com Signed-off-by: Peter Xu peterx@redhat.com --- Changes in v24: - Rebase on top of next-20230710 - UFFD_FEATURE_WP_ASYNC has been defined to be (1 << 15) after the rebase
Changes in v18: - Rebase on top of next-20230613 (use ptep_get)
Changes in v17: - Rebase on top of next-20230525
Changes in v12: - Peter added the hugetlb support and revamped some other implementation - Transferred the authorship to Peter - Merge documentation to this patch
Changes in v11: - Fix return code in userfaultfd_register() and minor changes here and there - Rebase on top of next-20230307 - Base patches on UFFD_FEATURE_WP_UNPOPULATED https://lore.kernel.org/all/20230306213925.617814-1-peterx@redhat.com - UFFD_FEATURE_WP_ASYNC depends on UFFD_FEATURE_WP_UNPOPULATED to work (correctly)
Changes in v10: - Build fix - Update comments and add error condition to return error from uffd register if hugetlb pages are present when wp async flag is set
Changes in v9: - Correct the fault resolution with code contributed by Peter
Changes in v7: - Remove UFFDIO_WRITEPROTECT_MODE_ASYNC_WP and add UFFD_FEATURE_WP_ASYNC - Handle automatic page fault resolution in better way (thanks to Peter) --- Documentation/admin-guide/mm/userfaultfd.rst | 35 ++++++++++++++++++++ fs/userfaultfd.c | 26 ++++++++++++--- include/linux/userfaultfd_k.h | 21 +++++++++++- include/uapi/linux/userfaultfd.h | 9 ++++- mm/hugetlb.c | 32 ++++++++++-------- mm/memory.c | 27 +++++++++++++-- 6 files changed, 128 insertions(+), 22 deletions(-)
diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 4349a8c2b978..203e26da5f92 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -244,6 +244,41 @@ write-protected (so future writes will also result in a WP fault). These ioctls support a mode flag (``UFFDIO_COPY_MODE_WP`` or ``UFFDIO_CONTINUE_MODE_WP`` respectively) to configure the mapping this way.
+If the userfaultfd context has ``UFFD_FEATURE_WP_ASYNC`` feature bit set, +any vma registered with write-protection will work in async mode rather +than the default sync mode. + +In async mode, there will be no message generated when a write operation +happens, meanwhile the write-protection will be resolved automatically by +the kernel. It can be seen as a more accurate version of soft-dirty +tracking and it can be different in a few ways: + + - The dirty result will not be affected by vma changes (e.g. vma + merging) because the dirty is only tracked by the pte. + + - It supports range operations by default, so one can enable tracking on + any range of memory as long as page aligned. + + - Dirty information will not get lost if the pte was zapped due to + various reasons (e.g. during split of a shmem transparent huge page). + + - Due to a reverted meaning of soft-dirty (page clean when uffd-wp bit + set; dirty when uffd-wp bit cleared), it has different semantics on + some of the memory operations. For example: ``MADV_DONTNEED`` on + anonymous (or ``MADV_REMOVE`` on a file mapping) will be treated as + dirtying of memory by dropping uffd-wp bit during the procedure. + +The user app can collect the "written/dirty" status by looking up the +uffd-wp bit for the pages being interested in /proc/pagemap. + +The page will not be under track of uffd-wp async mode until the page is +explicitly write-protected by ``ioctl(UFFDIO_WRITEPROTECT)`` with the mode +flag ``UFFDIO_WRITEPROTECT_MODE_WP`` set. Trying to resolve a page fault +that was tracked by async mode userfaultfd-wp is invalid. + +When userfaultfd-wp async mode is used alone, it can be applied to all +kinds of memory. + Memory Poisioning Emulation ---------------------------
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index db57d5d4fcb7..08be70c7a57e 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -123,6 +123,11 @@ static bool userfaultfd_is_initialized(struct userfaultfd_ctx *ctx) return ctx->features & UFFD_FEATURE_INITIALIZED; }
+static bool userfaultfd_wp_async_ctx(struct userfaultfd_ctx *ctx) +{ + return ctx && (ctx->features & UFFD_FEATURE_WP_ASYNC); +} + /* * Whether WP_UNPOPULATED is enabled on the uffd context. It is only * meaningful when userfaultfd_wp()==true on the vma and when it's @@ -1318,6 +1323,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, bool basic_ioctls; unsigned long start, end, vma_end; struct vma_iterator vmi; + bool wp_async = userfaultfd_wp_async_ctx(ctx); pgoff_t pgoff;
user_uffdio_register = (struct uffdio_register __user *) arg; @@ -1392,7 +1398,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
/* check not compatible vmas */ ret = -EINVAL; - if (!vma_can_userfault(cur, vm_flags)) + if (!vma_can_userfault(cur, vm_flags, wp_async)) goto out_unlock;
/* @@ -1453,7 +1459,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, for_each_vma_range(vmi, vma, end) { cond_resched();
- BUG_ON(!vma_can_userfault(vma, vm_flags)); + BUG_ON(!vma_can_userfault(vma, vm_flags, wp_async)); BUG_ON(vma->vm_userfaultfd_ctx.ctx && vma->vm_userfaultfd_ctx.ctx != ctx); WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); @@ -1553,6 +1559,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, unsigned long start, end, vma_end; const void __user *buf = (void __user *)arg; struct vma_iterator vmi; + bool wp_async = userfaultfd_wp_async_ctx(ctx); pgoff_t pgoff;
ret = -EFAULT; @@ -1607,7 +1614,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, * provides for more strict behavior to notice * unregistration errors. */ - if (!vma_can_userfault(cur, cur->vm_flags)) + if (!vma_can_userfault(cur, cur->vm_flags, wp_async)) goto out_unlock;
found = true; @@ -1623,7 +1630,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, for_each_vma_range(vmi, vma, end) { cond_resched();
- BUG_ON(!vma_can_userfault(vma, vma->vm_flags)); + BUG_ON(!vma_can_userfault(vma, vma->vm_flags, wp_async));
/* * Nothing to do: this vma is already registered into this @@ -2005,6 +2012,11 @@ static inline int userfaultfd_poison(struct userfaultfd_ctx *ctx, unsigned long return ret; }
+bool userfaultfd_wp_async(struct vm_area_struct *vma) +{ + return userfaultfd_wp_async_ctx(vma->vm_userfaultfd_ctx.ctx); +} + static inline unsigned int uffd_ctx_features(__u64 user_features) { /* @@ -2038,6 +2050,11 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, ret = -EPERM; if ((features & UFFD_FEATURE_EVENT_FORK) && !capable(CAP_SYS_PTRACE)) goto err_out; + + /* WP_ASYNC relies on WP_UNPOPULATED, choose it unconditionally */ + if (features & UFFD_FEATURE_WP_ASYNC) + features |= UFFD_FEATURE_WP_UNPOPULATED; + /* report all available features and ioctls to userland */ uffdio_api.features = UFFD_API_FEATURES; #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR @@ -2050,6 +2067,7 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, #ifndef CONFIG_PTE_MARKER_UFFD_WP uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM; uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED; + uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC; #endif uffdio_api.ioctls = UFFD_API_IOCTLS; ret = -EFAULT; diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index ac8c6854097c..c98df391bfd8 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -161,11 +161,22 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma) }
static inline bool vma_can_userfault(struct vm_area_struct *vma, - unsigned long vm_flags) + unsigned long vm_flags, + bool wp_async) { + vm_flags &= __VM_UFFD_FLAGS; + if ((vm_flags & VM_UFFD_MINOR) && (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma))) return false; + + /* + * If wp async enabled, and WP is the only mode enabled, allow any + * memory type. + */ + if (wp_async && (vm_flags == VM_UFFD_WP)) + return true; + #ifndef CONFIG_PTE_MARKER_UFFD_WP /* * If user requested uffd-wp but not enabled pte markers for @@ -175,6 +186,8 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma, if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma)) return false; #endif + + /* By default, allow any of anon|shmem|hugetlb */ return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) || vma_is_shmem(vma); } @@ -197,6 +210,7 @@ extern int userfaultfd_unmap_prep(struct vm_area_struct *vma, extern void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf); extern bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma); +extern bool userfaultfd_wp_async(struct vm_area_struct *vma);
#else /* CONFIG_USERFAULTFD */
@@ -297,6 +311,11 @@ static inline bool userfaultfd_wp_unpopulated(struct vm_area_struct *vma) return false; }
+static inline bool userfaultfd_wp_async(struct vm_area_struct *vma) +{ + return false; +} + #endif /* CONFIG_USERFAULTFD */
static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma) diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 62151706c5a3..0dbc81015018 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -40,7 +40,8 @@ UFFD_FEATURE_EXACT_ADDRESS | \ UFFD_FEATURE_WP_HUGETLBFS_SHMEM | \ UFFD_FEATURE_WP_UNPOPULATED | \ - UFFD_FEATURE_POISON) + UFFD_FEATURE_POISON | \ + UFFD_FEATURE_WP_ASYNC) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -216,6 +217,11 @@ struct uffdio_api { * (i.e. empty ptes). This will be the default behavior for shmem * & hugetlbfs, so this flag only affects anonymous memory behavior * when userfault write-protection mode is registered. + * + * UFFD_FEATURE_WP_ASYNC indicates that userfaultfd write-protection + * asynchronous mode is supported in which the write fault is + * automatically resolved and write-protection is un-set. + * It implies UFFD_FEATURE_WP_UNPOPULATED. */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) @@ -232,6 +238,7 @@ struct uffdio_api { #define UFFD_FEATURE_WP_HUGETLBFS_SHMEM (1<<12) #define UFFD_FEATURE_WP_UNPOPULATED (1<<13) #define UFFD_FEATURE_POISON (1<<14) +#define UFFD_FEATURE_WP_ASYNC (1<<15) __u64 features;
__u64 ioctls; diff --git a/mm/hugetlb.c b/mm/hugetlb.c index e4a28ce0667f..ee88a2a6649f 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6165,21 +6165,27 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, /* Handle userfault-wp first, before trying to lock more pages */ if (userfaultfd_wp(vma) && huge_pte_uffd_wp(huge_ptep_get(ptep)) && (flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) { - struct vm_fault vmf = { - .vma = vma, - .address = haddr, - .real_address = address, - .flags = flags, - }; + if (!userfaultfd_wp_async(vma)) { + struct vm_fault vmf = { + .vma = vma, + .address = haddr, + .real_address = address, + .flags = flags, + };
- spin_unlock(ptl); - if (pagecache_folio) { - folio_unlock(pagecache_folio); - folio_put(pagecache_folio); + spin_unlock(ptl); + if (pagecache_folio) { + folio_unlock(pagecache_folio); + folio_put(pagecache_folio); + } + hugetlb_vma_unlock_read(vma); + mutex_unlock(&hugetlb_fault_mutex_table[hash]); + return handle_userfault(&vmf, VM_UFFD_WP); } - hugetlb_vma_unlock_read(vma); - mutex_unlock(&hugetlb_fault_mutex_table[hash]); - return handle_userfault(&vmf, VM_UFFD_WP); + + entry = huge_pte_clear_uffd_wp(entry); + set_huge_pte_at(mm, haddr, ptep, entry); + /* Fallthrough to CoW */ }
/* diff --git a/mm/memory.c b/mm/memory.c index 0a265ac6246e..b9f8c32ddd28 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3352,11 +3352,28 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; struct vm_area_struct *vma = vmf->vma; struct folio *folio = NULL; + pte_t pte;
if (likely(!unshare)) { if (userfaultfd_pte_wp(vma, ptep_get(vmf->pte))) { - pte_unmap_unlock(vmf->pte, vmf->ptl); - return handle_userfault(vmf, VM_UFFD_WP); + if (!userfaultfd_wp_async(vma)) { + pte_unmap_unlock(vmf->pte, vmf->ptl); + return handle_userfault(vmf, VM_UFFD_WP); + } + + /* + * Nothing needed (cache flush, TLB invalidations, + * etc.) because we're only removing the uffd-wp bit, + * which is completely invisible to the user. + */ + pte = pte_clear_uffd_wp(ptep_get(vmf->pte)); + + set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); + /* + * Update this to be prepared for following up CoW + * handling + */ + vmf->orig_pte = pte; }
/* @@ -4851,8 +4868,11 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
if (vma_is_anonymous(vmf->vma)) { if (likely(!unshare) && - userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd)) + userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd)) { + if (userfaultfd_wp_async(vmf->vma)) + goto split; return handle_userfault(vmf, VM_UFFD_WP); + } return do_huge_pmd_wp_page(vmf); }
@@ -4864,6 +4884,7 @@ static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf) } }
+split: /* COW or write-notify handled on pte level: split pmd. */ __split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL);
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl: - Get the information if the pages have been written-to (PAGE_IS_WRITTEN), file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT), swapped (PAGE_IS_SWAPPED) or page has pfn zero (PAGE_IS_PFNZERO). - Find pages which have been written-to and/or write protect the pages (atomic PM_SCAN_OP_GET + PM_SCAN_OP_WP)
This IOCTL can be extended to get information about more PTE bits. The entire address range passed by user [start, end) is scanned until either the user provided buffer is full or max_pages have been found.
Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com --- Changes in v25: - Do proper filtering on hole as well (hole got missed earlier)
Changes in v24: - Place WP markers in case of hole as well
Changes in v23: - Set vec_buf_index to 0 only when vec_buf_index is set - Return -EFAULT instead of -EINVAL if vec is NULL - Correctly return the walk ending address to the page granularity
Changes in v22: - Interface change to return walk ending address to user: - Replace [start start + len) with [start, end) - Return the ending address of the address walk in start
Changes in v21: - Abort walk instead of returning error if WP is to be performed on partial hugetlb - Changed the data types of some variables in pagemap_scan_private to long
Changes in v20: - Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
Changes in v19: - Interface changes such as renaming, return mask and WP can be used with any flags specified in masks - Internal code changes
Changes in v18: - Rebased on top of next-20230613 - ptep_get() updates - remove pmd_trans_unstable() and add ACTION_AGAIN - Review updates (Micheal)
Changes in v17: - Rebased on next-20230606 - Made make_uffd_wp_*_pte() better and minor changes
Changes in v16: - Fixed a corner case where kernel writes beyond user buffer by one element - Bring back exclusive PM_SCAN_OP_WP - Cosmetic changes
Changes in v15: - Build fix: - Use generic tlb flush function in pagemap_scan_pmd_entry() instead of using x86 specific flush function in do_pagemap_scan() - Remove #ifdef from pagemap_scan_hugetlb_entry() - Use mm instead of undefined vma->vm_mm
Changes in v14: - Fix build error caused by #ifdef added at last minute in some configs
Changes in v13: - Review updates - mmap_read_lock_killable() instead of mmap_read_lock() - Replace uffd_wp_range() with helpers which increases performance drastically for OP_WP operations by reducing the number of tlb flushing etc - Add MMU_NOTIFY_PROTECTION_VMA notification for the memory range
Changes in v12: - Add hugetlb support to cover all memory types - Merge "userfaultfd: Define dummy uffd_wp_range()" with this patch - Review updates to the code
Changes in v11: - Find written pages in a better way - Fix a corner case (thanks Paul) - Improve the code/comments - remove ENGAGE_WP + ! GET operation - shorten the commit message in favour of moving documentation to pagemap.rst
Changes in v10: - move changes in tools/include/uapi/linux/fs.h to separate patch - update commit message
Change in v8: - Correct is_pte_uffd_wp() - Improve readability and error checks - Remove some un-needed code
Changes in v7: - Rebase on top of latest next - Fix some corner cases - Base soft-dirty on the uffd wp async - Update the terminologies - Optimize the memory usage inside the ioctl --- fs/proc/task_mmu.c | 591 ++++++++++++++++++++++++++++++++++++++++ include/linux/hugetlb.h | 1 + include/uapi/linux/fs.h | 55 ++++ mm/hugetlb.c | 2 +- 4 files changed, 648 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index cfab855fe7e9..596fdfdc4387 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -19,6 +19,7 @@ #include <linux/shmem_fs.h> #include <linux/uaccess.h> #include <linux/pkeys.h> +#include <linux/minmax.h>
#include <asm/elf.h> #include <asm/tlb.h> @@ -1768,11 +1769,601 @@ static int pagemap_release(struct inode *inode, struct file *file) return 0; }
+#define PM_SCAN_REQUIRE_UFFD (1ULL << 63) + +#define PM_SCAN_FOUND_MAX_PAGES (1) +#define PM_SCAN_END_WALK (-256) + +#define PM_SCAN_BITS_ALL (PAGE_IS_WRITTEN | PAGE_IS_FILE | \ + PAGE_IS_PRESENT | PAGE_IS_SWAPPED | \ + PAGE_IS_PFNZERO) +#define PM_SCAN_OPS (PM_SCAN_OP_GET | PM_SCAN_OP_WP) +#define IS_PM_SCAN_GET(flags) (flags & PM_SCAN_OP_GET) +#define IS_PM_SCAN_WP(flags) (flags & PM_SCAN_OP_WP) + +#define PM_SCAN_FLAGS(wt, file, present, swap, pfnzero) \ + ((wt) | ((file) << 1) | ((present) << 2) | \ + ((swap) << 3) | ((pfnzero) << 4)) + +struct pagemap_scan_private { + struct page_region *vec_buf, cur_buf; + unsigned long vec_buf_len, vec_buf_index, max_pages, found_pages; + unsigned long long flags, required_mask, anyof_mask, excluded_mask, return_mask, end_addr; +}; + +static inline bool is_pte_uffd_wp(pte_t pte) +{ + return (pte_present(pte) && pte_uffd_wp(pte)) || + pte_swp_uffd_wp_any(pte); +} + +static inline void make_uffd_wp_pte(struct vm_area_struct *vma, + unsigned long addr, pte_t *pte) +{ + pte_t ptent = ptep_get(pte); + + if (pte_present(ptent)) { + pte_t old_pte; + + old_pte = ptep_modify_prot_start(vma, addr, pte); + ptent = pte_mkuffd_wp(ptent); + ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent); + } else if (is_swap_pte(ptent)) { + ptent = pte_swp_mkuffd_wp(ptent); + set_pte_at(vma->vm_mm, addr, pte, ptent); + } else { + set_pte_at(vma->vm_mm, addr, pte, + make_pte_marker(PTE_MARKER_UFFD_WP)); + } +} + +static inline bool pagemap_scan_is_file(struct vm_area_struct *vma, pte_t ptent, + unsigned long addr) +{ + struct page *page = NULL; + swp_entry_t entry; + + if (pte_present(ptent)) { + page = vm_normal_page(vma, addr, ptent); + } else { + entry = pte_to_swp_entry(ptent); + if (is_pfn_swap_entry(entry)) + page = pfn_swap_entry_to_page(entry); + } + + if (page && !PageAnon(page)) + return true; + + return false; +} + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static inline bool is_pmd_uffd_wp(pmd_t pmd) +{ + return (pmd_present(pmd) && pmd_uffd_wp(pmd)) || + (is_swap_pmd(pmd) && pmd_swp_uffd_wp(pmd)); +} + +static inline void make_uffd_wp_pmd(struct vm_area_struct *vma, + unsigned long addr, pmd_t *pmdp) +{ + pmd_t old, pmd = *pmdp; + + if (pmd_present(pmd)) { + old = pmdp_invalidate_ad(vma, addr, pmdp); + pmd = pmd_mkuffd_wp(old); + set_pmd_at(vma->vm_mm, addr, pmdp, pmd); + } else if (is_migration_entry(pmd_to_swp_entry(pmd))) { + pmd = pmd_swp_mkuffd_wp(pmd); + set_pmd_at(vma->vm_mm, addr, pmdp, pmd); + } +} +#endif + +#ifdef CONFIG_HUGETLB_PAGE +static inline bool is_huge_pte_uffd_wp(pte_t pte) +{ + return (pte_present(pte) && huge_pte_uffd_wp(pte)) || + pte_swp_uffd_wp_any(pte); +} + +static inline void make_uffd_wp_huge_pte(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, + pte_t ptent) +{ + if (is_hugetlb_entry_hwpoisoned(ptent) || is_pte_marker(ptent)) + return; + + if (is_hugetlb_entry_migration(ptent)) + set_huge_pte_at(vma->vm_mm, addr, ptep, + pte_swp_mkuffd_wp(ptent)); + else if (!huge_pte_none(ptent)) + huge_ptep_modify_prot_commit(vma, addr, ptep, ptent, + huge_pte_mkuffd_wp(ptent)); + else + set_huge_pte_at(vma->vm_mm, addr, ptep, + make_pte_marker(PTE_MARKER_UFFD_WP)); +} + +static inline bool pagemap_scan_is_huge_file(pte_t pte) +{ + if (pte_present(pte) && (!PageAnon(pte_page(pte)))) + return true; + + return false; +} +#endif + +static int pagemap_scan_test_walk(unsigned long start, unsigned long end, + struct mm_walk *walk) +{ + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + + if ((p->flags & PM_SCAN_REQUIRE_UFFD) && (!userfaultfd_wp_async(vma) || + !userfaultfd_wp_use_markers(vma))) + return -EPERM; + + if (vma->vm_flags & VM_PFNMAP) + return 1; + + return 0; +} + +static int pagemap_scan_output(unsigned long bitmap, + struct pagemap_scan_private *p, + unsigned long addr, unsigned int n_pages) +{ + struct page_region *cur_buf = &p->cur_buf; + + bitmap &= p->return_mask; + + if (cur_buf->flags == bitmap && + cur_buf->start + cur_buf->len * PAGE_SIZE == addr) { + cur_buf->len += n_pages; + p->found_pages += n_pages; + } else { + if (cur_buf->len) { + if (p->vec_buf_index >= p->vec_buf_len) { + p->end_addr = addr; + return PM_SCAN_END_WALK; + } + + memcpy(&p->vec_buf[p->vec_buf_index], cur_buf, + sizeof(*p->vec_buf)); + p->vec_buf_index++; + } + + cur_buf->start = addr; + cur_buf->len = n_pages; + cur_buf->flags = bitmap; + p->found_pages += n_pages; + } + + if (p->found_pages == p->max_pages) { + p->end_addr = addr + n_pages * PAGE_SIZE; + return PM_SCAN_FOUND_MAX_PAGES; + } + + return 0; +} + +static bool pagemap_scan_is_interesting_page(unsigned long bitmap, + struct pagemap_scan_private *p) +{ + if ((p->required_mask & bitmap) != p->required_mask) + return false; + if (p->anyof_mask && !(p->anyof_mask & bitmap)) + return false; + if (p->excluded_mask & bitmap) + return false; + + return true; +} + +static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, + unsigned long end, struct mm_walk *walk) +{ + bool is_written, flush = false, interesting = true; + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + unsigned long bitmap, addr = end; + pte_t *pte, *orig_pte, ptent; + spinlock_t *ptl; + int ret = 0; + + arch_enter_lazy_mmu_mode(); + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + ptl = pmd_trans_huge_lock(pmd, vma); + if (ptl) { + unsigned long n_pages = (end - start)/PAGE_SIZE; + + if (n_pages > p->max_pages - p->found_pages) + n_pages = p->max_pages - p->found_pages; + + is_written = !is_pmd_uffd_wp(*pmd); + + bitmap = PM_SCAN_FLAGS(is_written, false, + pmd_present(*pmd), is_swap_pmd(*pmd), + pmd_present(*pmd) && is_zero_pfn(pmd_pfn(*pmd))); + + if (IS_PM_SCAN_GET(p->flags)) + interesting = pagemap_scan_is_interesting_page(bitmap, p); + + if (interesting) { + /* + * Break huge page into small pages if the WP operation + * need to be performed is on a portion of the huge page. + */ + if (is_written && IS_PM_SCAN_WP(p->flags) && + n_pages < HPAGE_SIZE/PAGE_SIZE) { + spin_unlock(ptl); + + split_huge_pmd(vma, pmd, start); + goto process_smaller_pages; + } + + if (IS_PM_SCAN_GET(p->flags)) + ret = pagemap_scan_output(bitmap, p, start, n_pages); + + if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) { + make_uffd_wp_pmd(vma, start, pmd); + flush_tlb_range(vma, start, end); + } + } + + spin_unlock(ptl); + arch_leave_lazy_mmu_mode(); + + return ret; + } + +process_smaller_pages: +#endif + + orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl); + if (!pte) { + walk->action = ACTION_AGAIN; + return 0; + } + + for (addr = start; addr < end && !ret; pte++, addr += PAGE_SIZE) { + ptent = ptep_get(pte); + is_written = !is_pte_uffd_wp(ptent); + + bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_file(vma, ptent, addr), + pte_present(ptent), is_swap_pte(ptent), + pte_present(ptent) && is_zero_pfn(pte_pfn(ptent))); + + if (IS_PM_SCAN_GET(p->flags)) { + interesting = pagemap_scan_is_interesting_page(bitmap, p); + if (interesting) + ret = pagemap_scan_output(bitmap, p, addr, 1); + } + + if (IS_PM_SCAN_WP(p->flags) && is_written && interesting && + ret >= 0) { + make_uffd_wp_pte(vma, addr, pte); + flush = true; + } + } + + if (flush) + flush_tlb_range(vma, start, addr); + + pte_unmap_unlock(orig_pte, ptl); + arch_leave_lazy_mmu_mode(); + + cond_resched(); + return ret; +} + +#ifdef CONFIG_HUGETLB_PAGE +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask, + unsigned long start, unsigned long end, + struct mm_walk *walk) +{ + unsigned long n_pages = (end - start)/PAGE_SIZE; + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + bool is_written, interesting = true; + struct hstate *h = hstate_vma(vma); + unsigned long bitmap; + spinlock_t *ptl; + int ret = 0; + pte_t ptent; + + if (IS_PM_SCAN_WP(p->flags) && n_pages < HPAGE_SIZE/PAGE_SIZE) { + p->end_addr = start; + return -EINVAL; + } + + if (n_pages > p->max_pages - p->found_pages) + n_pages = p->max_pages - p->found_pages; + + if (IS_PM_SCAN_WP(p->flags)) { + i_mmap_lock_write(vma->vm_file->f_mapping); + ptl = huge_pte_lock(h, vma->vm_mm, ptep); + } + + ptent = huge_ptep_get(ptep); + is_written = !is_huge_pte_uffd_wp(ptent); + + bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_huge_file(ptent), + pte_present(ptent), is_swap_pte(ptent), + pte_present(ptent) && is_zero_pfn(pte_pfn(ptent))); + + if (IS_PM_SCAN_GET(p->flags)) + interesting = pagemap_scan_is_interesting_page(bitmap, p); + + if (interesting) { + /* + * Partial hugetlb page clear isn't supported + */ + if (is_written && IS_PM_SCAN_WP(p->flags) && + n_pages < HPAGE_SIZE/PAGE_SIZE) { + ret = PM_SCAN_END_WALK; + p->end_addr = start; + goto unlock_and_return; + } + + if (IS_PM_SCAN_GET(p->flags)) + ret = pagemap_scan_output(bitmap, p, start, n_pages); + + if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) { + make_uffd_wp_huge_pte(vma, start, ptep, ptent); + flush_hugetlb_tlb_range(vma, start, end); + } + } + +unlock_and_return: + if (IS_PM_SCAN_WP(p->flags)) { + spin_unlock(ptl); + i_mmap_unlock_write(vma->vm_file->f_mapping); + } + + return ret; +} +#else +#define pagemap_scan_hugetlb_entry NULL +#endif + +static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end, + int depth, struct mm_walk *walk) +{ + unsigned long n_pages = (end - addr)/PAGE_SIZE; + struct pagemap_scan_private *p = walk->private; + struct vm_area_struct *vma = walk->vma; + bool interesting = true; + unsigned long bitmap; + int ret = 0; + + if (!vma) + return 0; + + bitmap = PM_SCAN_FLAGS(false, false, false, false, false); + + if (IS_PM_SCAN_GET(p->flags)) + interesting = pagemap_scan_is_interesting_page(bitmap, p); + + if (interesting) { + if (IS_PM_SCAN_GET(p->flags)) { + if (n_pages > p->max_pages - p->found_pages) + n_pages = p->max_pages - p->found_pages; + + ret = pagemap_scan_output(bitmap, p, addr, n_pages); + } + + if (IS_PM_SCAN_WP(p->flags) && !ret && + uffd_wp_range(vma, addr, end - addr, true) < 0) + ret = -EINVAL; + } + + return ret; +} + +static const struct mm_walk_ops pagemap_scan_ops = { + .test_walk = pagemap_scan_test_walk, + .pmd_entry = pagemap_scan_pmd_entry, + .pte_hole = pagemap_scan_pte_hole, + .hugetlb_entry = pagemap_scan_hugetlb_entry, +}; + +static int pagemap_scan_args_valid(struct pm_scan_arg *arg, unsigned long start, + unsigned long end, struct page_region __user *vec) +{ + /* Detect illegal size, flags, len and masks */ + if (arg->size != sizeof(struct pm_scan_arg)) + return -EINVAL; + if (!arg->flags) + return -EINVAL; + if (arg->flags & ~PM_SCAN_OPS) + return -EINVAL; + if (!(end - start)) + return -EINVAL; + if ((arg->required_mask | arg->anyof_mask | arg->excluded_mask | + arg->return_mask) & ~PM_SCAN_BITS_ALL) + return -EINVAL; + if (!arg->required_mask && !arg->anyof_mask && + !arg->excluded_mask) + return -EINVAL; + if (!arg->return_mask) + return -EINVAL; + + /* Validate memory range */ + if (!IS_ALIGNED(start, PAGE_SIZE)) + return -EINVAL; + if (!access_ok((void __user *)start, end - start)) + return -EFAULT; + + if (IS_PM_SCAN_GET(arg->flags)) { + if (arg->vec_len == 0) + return -EINVAL; + if (!vec) + return -EFAULT; + if (!access_ok((void __user *)vec, + arg->vec_len * sizeof(struct page_region))) + return -EFAULT; + } + + if (IS_PM_SCAN_WP(arg->flags) && !IS_PM_SCAN_GET(arg->flags) && + arg->max_pages) + return -EINVAL; + + return 0; +} + +static long do_pagemap_scan(struct mm_struct *mm, unsigned long __arg) +{ + struct pm_scan_arg __user *uarg = (struct pm_scan_arg __user *)__arg; + unsigned long long start, end, walk_start, walk_end; + unsigned long empty_slots, vec_index = 0; + struct mmu_notifier_range range; + struct page_region __user *vec; + struct pagemap_scan_private p; + struct pm_scan_arg arg; + int ret = 0; + + if (copy_from_user(&arg, uarg, sizeof(arg))) + return -EFAULT; + + start = untagged_addr((unsigned long)arg.start); + end = untagged_addr((unsigned long)arg.end); + vec = (struct page_region __user *)untagged_addr((unsigned long)arg.vec); + + ret = pagemap_scan_args_valid(&arg, start, end, vec); + if (ret) + return ret; + + p.max_pages = (arg.max_pages) ? arg.max_pages : ULONG_MAX; + p.found_pages = 0; + p.required_mask = arg.required_mask; + p.anyof_mask = arg.anyof_mask; + p.excluded_mask = arg.excluded_mask; + p.return_mask = arg.return_mask; + p.flags = arg.flags; + p.flags |= ((p.required_mask | p.anyof_mask | p.excluded_mask) & + PAGE_IS_WRITTEN) ? PM_SCAN_REQUIRE_UFFD : 0; + p.cur_buf.start = p.cur_buf.len = p.cur_buf.flags = 0; + p.vec_buf = NULL; + p.vec_buf_len = PAGEMAP_WALK_SIZE >> PAGE_SHIFT; + p.vec_buf_index = 0; + p.end_addr = 0; + + /* + * Allocate smaller buffer to get output from inside the page walk + * functions and walk page range in PAGEMAP_WALK_SIZE size chunks. As + * we want to return output to user in compact form where no two + * consecutive regions should be continuous and have the same flags. + * So store the latest element in p.cur_buf between different walks and + * store the p.cur_buf at the end of the walk to the user buffer. + */ + if (IS_PM_SCAN_GET(p.flags)) { + p.vec_buf = kmalloc_array(p.vec_buf_len, sizeof(*p.vec_buf), + GFP_KERNEL); + if (!p.vec_buf) + return -ENOMEM; + } + + /* + * Protection change for the range is going to happen. + */ + if (IS_PM_SCAN_WP(p.flags)) { + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, + mm, start, end); + mmu_notifier_invalidate_range_start(&range); + } + + walk_start = walk_end = start; + while (walk_end < end && !ret) { + if (IS_PM_SCAN_GET(p.flags)) { + /* + * All data is copied to cur_buf first. When more data + * is found, we push cur_buf to vec_buf and copy new + * data to cur_buf. Subtract 1 from length as the + * index of cur_buf isn't counted in length. + */ + empty_slots = arg.vec_len - vec_index; + p.vec_buf_len = min(p.vec_buf_len, empty_slots - 1); + } + + ret = mmap_read_lock_killable(mm); + if (ret) + goto out; + + walk_end = min((walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, end); + + ret = walk_page_range(mm, walk_start, walk_end, + &pagemap_scan_ops, &p); + mmap_read_unlock(mm); + + if (ret == PM_SCAN_FOUND_MAX_PAGES || ret == PM_SCAN_END_WALK) + arg.start = p.end_addr; + + if (ret && ret != PM_SCAN_FOUND_MAX_PAGES && + ret != PM_SCAN_END_WALK) + goto out; + + if (p.vec_buf_index) { + if (copy_to_user(&vec[vec_index], p.vec_buf, + p.vec_buf_index * sizeof(*p.vec_buf))) { + /* + * Return error even though the OP succeeded + */ + ret = -EFAULT; + goto out; + } + vec_index += p.vec_buf_index; + p.vec_buf_index = 0; + } + walk_start = walk_end; + } + + if (p.cur_buf.len) { + if (copy_to_user(&vec[vec_index], &p.cur_buf, sizeof(p.cur_buf))) { + ret = -EFAULT; + goto out; + } + vec_index++; + } + + ret = vec_index; + +out: + if (!p.end_addr) + arg.start = walk_start; + if (copy_to_user(&uarg->start, &arg.start, sizeof(arg.start))) + ret = -EFAULT; + + if (IS_PM_SCAN_WP(p.flags)) + mmu_notifier_invalidate_range_end(&range); + + kfree(p.vec_buf); + return ret; +} + +static long do_pagemap_cmd(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct mm_struct *mm = file->private_data; + + switch (cmd) { + case PAGEMAP_SCAN: + return do_pagemap_scan(mm, arg); + + default: + return -EINVAL; + } +} + const struct file_operations proc_pagemap_operations = { .llseek = mem_lseek, /* borrow this */ .read = pagemap_read, .open = pagemap_open, .release = pagemap_release, + .unlocked_ioctl = do_pagemap_cmd, + .compat_ioctl = do_pagemap_cmd, }; #endif /* CONFIG_PROC_PAGE_MONITOR */
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 623e98d62df3..c44e7bde0339 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma, unsigned long cp_flags);
bool is_hugetlb_entry_migration(pte_t pte); +bool is_hugetlb_entry_hwpoisoned(pte_t pte); void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
#else /* !CONFIG_HUGETLB_PAGE */ diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index b7b56871029c..ac684d99e68f 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -305,4 +305,59 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND)
+/* Pagemap ioctl */ +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg) + +/* Bits are set in flags of the page_region and masks in pm_scan_args */ +#define PAGE_IS_WRITTEN (1 << 0) +#define PAGE_IS_FILE (1 << 1) +#define PAGE_IS_PRESENT (1 << 2) +#define PAGE_IS_SWAPPED (1 << 3) +#define PAGE_IS_PFNZERO (1 << 4) + +/* + * struct page_region - Page region with flags + * @start: Start of the region + * @len: Length of the region in pages + * @bitmap: Bits sets for the region + */ +struct page_region { + __u64 start; + __u64 len; + __u64 flags; +}; + +/* + * struct pm_scan_arg - Pagemap ioctl argument + * @size: Size of the structure + * @flags: Flags for the IOCTL + * @start: Starting address of the region + * (Ending address of the walk is also returned in it) + * @end: Ending address of the region + * @vec: Address of page_region struct array for output + * @vec_len: Length of the page_region struct array + * @max_pages: Optional max return pages + * @required_mask: Required mask - All of these bits have to be set in the PTE + * @anyof_mask: Any mask - Any of these bits are set in the PTE + * @excluded_mask: Exclude mask - None of these bits are set in the PTE + * @return_mask: Bits that are to be reported in page_region + */ +struct pm_scan_arg { + __u64 size; + __u64 flags; + __u64 start; + __u64 end; + __u64 vec; + __u64 vec_len; + __u64 max_pages; + __u64 required_mask; + __u64 anyof_mask; + __u64 excluded_mask; + __u64 return_mask; +}; + +/* Supported flags */ +#define PM_SCAN_OP_GET (1 << 0) +#define PM_SCAN_OP_WP (1 << 1) + #endif /* _UAPI_LINUX_FS_H */ diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ee88a2a6649f..f7cefdcb114c 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4981,7 +4981,7 @@ bool is_hugetlb_entry_migration(pte_t pte) return false; }
-static bool is_hugetlb_entry_hwpoisoned(pte_t pte) +bool is_hugetlb_entry_hwpoisoned(pte_t pte) { swp_entry_t swp;
On Thu, Jul 13, 2023 at 3:14 AM Muhammad Usama Anjum usama.anjum@collabora.com wrote:
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl:
- Get the information if the pages have been written-to (PAGE_IS_WRITTEN), file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT), swapped (PAGE_IS_SWAPPED) or page has pfn zero (PAGE_IS_PFNZERO).
- Find pages which have been written-to and/or write protect the pages (atomic PM_SCAN_OP_GET + PM_SCAN_OP_WP)
This IOCTL can be extended to get information about more PTE bits. The entire address range passed by user [start, end) is scanned until either the user provided buffer is full or max_pages have been found.
Reviewed-by: Andrei Vagin avagin@gmail.com
Here are a few inline comments.
Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com
Changes in v25:
- Do proper filtering on hole as well (hole got missed earlier)
Changes in v24:
- Place WP markers in case of hole as well
Changes in v23:
- Set vec_buf_index to 0 only when vec_buf_index is set
- Return -EFAULT instead of -EINVAL if vec is NULL
- Correctly return the walk ending address to the page granularity
Changes in v22:
- Interface change to return walk ending address to user:
- Replace [start start + len) with [start, end)
- Return the ending address of the address walk in start
Changes in v21:
- Abort walk instead of returning error if WP is to be performed on partial hugetlb
- Changed the data types of some variables in pagemap_scan_private to long
Changes in v20:
- Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
Changes in v19:
- Interface changes such as renaming, return mask and WP can be used with any flags specified in masks
- Internal code changes
Changes in v18:
- Rebased on top of next-20230613
- ptep_get() updates
- remove pmd_trans_unstable() and add ACTION_AGAIN
- Review updates (Micheal)
Changes in v17:
- Rebased on next-20230606
- Made make_uffd_wp_*_pte() better and minor changes
Changes in v16:
- Fixed a corner case where kernel writes beyond user buffer by one element
- Bring back exclusive PM_SCAN_OP_WP
- Cosmetic changes
Changes in v15:
- Build fix:
- Use generic tlb flush function in pagemap_scan_pmd_entry() instead of using x86 specific flush function in do_pagemap_scan()
- Remove #ifdef from pagemap_scan_hugetlb_entry()
- Use mm instead of undefined vma->vm_mm
Changes in v14:
- Fix build error caused by #ifdef added at last minute in some configs
Changes in v13:
- Review updates
- mmap_read_lock_killable() instead of mmap_read_lock()
- Replace uffd_wp_range() with helpers which increases performance drastically for OP_WP operations by reducing the number of tlb flushing etc
- Add MMU_NOTIFY_PROTECTION_VMA notification for the memory range
Changes in v12:
- Add hugetlb support to cover all memory types
- Merge "userfaultfd: Define dummy uffd_wp_range()" with this patch
- Review updates to the code
Changes in v11:
- Find written pages in a better way
- Fix a corner case (thanks Paul)
- Improve the code/comments
- remove ENGAGE_WP + ! GET operation
- shorten the commit message in favour of moving documentation to pagemap.rst
Changes in v10:
- move changes in tools/include/uapi/linux/fs.h to separate patch
- update commit message
Change in v8:
- Correct is_pte_uffd_wp()
- Improve readability and error checks
- Remove some un-needed code
Changes in v7:
- Rebase on top of latest next
- Fix some corner cases
- Base soft-dirty on the uffd wp async
- Update the terminologies
- Optimize the memory usage inside the ioctl
fs/proc/task_mmu.c | 591 ++++++++++++++++++++++++++++++++++++++++ include/linux/hugetlb.h | 1 + include/uapi/linux/fs.h | 55 ++++ mm/hugetlb.c | 2 +- 4 files changed, 648 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index cfab855fe7e9..596fdfdc4387 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -19,6 +19,7 @@ #include <linux/shmem_fs.h> #include <linux/uaccess.h> #include <linux/pkeys.h> +#include <linux/minmax.h>
#include <asm/elf.h> #include <asm/tlb.h> @@ -1768,11 +1769,601 @@ static int pagemap_release(struct inode *inode, struct file *file) return 0; }
+#define PM_SCAN_REQUIRE_UFFD (1ULL << 63)
+#define PM_SCAN_FOUND_MAX_PAGES (1) +#define PM_SCAN_END_WALK (-256)
I would add a comment to explain why one is negative and another one is positive.
+#define PM_SCAN_BITS_ALL (PAGE_IS_WRITTEN | PAGE_IS_FILE | \
PAGE_IS_PRESENT | PAGE_IS_SWAPPED | \PAGE_IS_PFNZERO)+#define PM_SCAN_OPS (PM_SCAN_OP_GET | PM_SCAN_OP_WP) +#define IS_PM_SCAN_GET(flags) (flags & PM_SCAN_OP_GET) +#define IS_PM_SCAN_WP(flags) (flags & PM_SCAN_OP_WP)
+#define PM_SCAN_FLAGS(wt, file, present, swap, pfnzero) \
((wt) | ((file) << 1) | ((present) << 2) | \((swap) << 3) | ((pfnzero) << 4))
it is better to use PAGE_IS_* constants here
+struct pagemap_scan_private {
struct page_region *vec_buf, cur_buf;unsigned long vec_buf_len, vec_buf_index, max_pages, found_pages;unsigned long long flags, required_mask, anyof_mask, excluded_mask, return_mask, end_addr;
end_addr has to be unsigned long.
+};
+static inline bool is_pte_uffd_wp(pte_t pte) +{
return (pte_present(pte) && pte_uffd_wp(pte)) ||pte_swp_uffd_wp_any(pte);+}
+static inline void make_uffd_wp_pte(struct vm_area_struct *vma,
unsigned long addr, pte_t *pte)+{
pte_t ptent = ptep_get(pte);if (pte_present(ptent)) {pte_t old_pte;old_pte = ptep_modify_prot_start(vma, addr, pte);ptent = pte_mkuffd_wp(ptent);ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);} else if (is_swap_pte(ptent)) {ptent = pte_swp_mkuffd_wp(ptent);set_pte_at(vma->vm_mm, addr, pte, ptent);} else {set_pte_at(vma->vm_mm, addr, pte,make_pte_marker(PTE_MARKER_UFFD_WP));}+}
+static inline bool pagemap_scan_is_file(struct vm_area_struct *vma, pte_t ptent,
unsigned long addr)+{
struct page *page = NULL;swp_entry_t entry;if (pte_present(ptent)) {page = vm_normal_page(vma, addr, ptent);} else {entry = pte_to_swp_entry(ptent);if (is_pfn_swap_entry(entry))page = pfn_swap_entry_to_page(entry);}if (page && !PageAnon(page))return true;return false;+}
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static inline bool is_pmd_uffd_wp(pmd_t pmd) +{
return (pmd_present(pmd) && pmd_uffd_wp(pmd)) ||(is_swap_pmd(pmd) && pmd_swp_uffd_wp(pmd));+}
+static inline void make_uffd_wp_pmd(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp)+{
pmd_t old, pmd = *pmdp;if (pmd_present(pmd)) {old = pmdp_invalidate_ad(vma, addr, pmdp);pmd = pmd_mkuffd_wp(old);set_pmd_at(vma->vm_mm, addr, pmdp, pmd);} else if (is_migration_entry(pmd_to_swp_entry(pmd))) {pmd = pmd_swp_mkuffd_wp(pmd);set_pmd_at(vma->vm_mm, addr, pmdp, pmd);}+} +#endif
+#ifdef CONFIG_HUGETLB_PAGE +static inline bool is_huge_pte_uffd_wp(pte_t pte) +{
return (pte_present(pte) && huge_pte_uffd_wp(pte)) ||pte_swp_uffd_wp_any(pte);+}
+static inline void make_uffd_wp_huge_pte(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep,pte_t ptent)+{
if (is_hugetlb_entry_hwpoisoned(ptent) || is_pte_marker(ptent))return;if (is_hugetlb_entry_migration(ptent))set_huge_pte_at(vma->vm_mm, addr, ptep,pte_swp_mkuffd_wp(ptent));else if (!huge_pte_none(ptent))huge_ptep_modify_prot_commit(vma, addr, ptep, ptent,huge_pte_mkuffd_wp(ptent));elseset_huge_pte_at(vma->vm_mm, addr, ptep,make_pte_marker(PTE_MARKER_UFFD_WP));+}
+static inline bool pagemap_scan_is_huge_file(pte_t pte) +{
if (pte_present(pte) && (!PageAnon(pte_page(pte))))return true;return false;+} +#endif
+static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
struct mm_walk *walk)+{
struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;if ((p->flags & PM_SCAN_REQUIRE_UFFD) && (!userfaultfd_wp_async(vma) ||!userfaultfd_wp_use_markers(vma)))return -EPERM;if (vma->vm_flags & VM_PFNMAP)return 1;return 0;+}
+static int pagemap_scan_output(unsigned long bitmap,
struct pagemap_scan_private *p,unsigned long addr, unsigned int n_pages)+{
struct page_region *cur_buf = &p->cur_buf;bitmap &= p->return_mask;if (cur_buf->flags == bitmap &&cur_buf->start + cur_buf->len * PAGE_SIZE == addr) {cur_buf->len += n_pages;p->found_pages += n_pages;} else {if (cur_buf->len) {if (p->vec_buf_index >= p->vec_buf_len) {p->end_addr = addr;return PM_SCAN_END_WALK;}memcpy(&p->vec_buf[p->vec_buf_index], cur_buf,sizeof(*p->vec_buf));p->vec_buf_index++;}cur_buf->start = addr;cur_buf->len = n_pages;cur_buf->flags = bitmap;p->found_pages += n_pages;}if (p->found_pages == p->max_pages) {p->end_addr = addr + n_pages * PAGE_SIZE;return PM_SCAN_FOUND_MAX_PAGES;}return 0;+}
+static bool pagemap_scan_is_interesting_page(unsigned long bitmap,
struct pagemap_scan_private *p)+{
if ((p->required_mask & bitmap) != p->required_mask)return false;if (p->anyof_mask && !(p->anyof_mask & bitmap))return false;if (p->excluded_mask & bitmap)return false;return true;+}
+static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
unsigned long end, struct mm_walk *walk)+{
bool is_written, flush = false, interesting = true;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;unsigned long bitmap, addr = end;pte_t *pte, *orig_pte, ptent;spinlock_t *ptl;int ret = 0;arch_enter_lazy_mmu_mode();+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
ptl = pmd_trans_huge_lock(pmd, vma);if (ptl) {unsigned long n_pages = (end - start)/PAGE_SIZE;if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;is_written = !is_pmd_uffd_wp(*pmd);bitmap = PM_SCAN_FLAGS(is_written, false,pmd_present(*pmd), is_swap_pmd(*pmd),pmd_present(*pmd) && is_zero_pfn(pmd_pfn(*pmd)));if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {/** Break huge page into small pages if the WP operation* need to be performed is on a portion of the huge page.*/if (is_written && IS_PM_SCAN_WP(p->flags) &&n_pages < HPAGE_SIZE/PAGE_SIZE) {spin_unlock(ptl);split_huge_pmd(vma, pmd, start);goto process_smaller_pages;}if (IS_PM_SCAN_GET(p->flags))ret = pagemap_scan_output(bitmap, p, start, n_pages);if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) {make_uffd_wp_pmd(vma, start, pmd);flush_tlb_range(vma, start, end);}}spin_unlock(ptl);arch_leave_lazy_mmu_mode();return ret;}+process_smaller_pages: +#endif
orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);if (!pte) {walk->action = ACTION_AGAIN;return 0;}for (addr = start; addr < end && !ret; pte++, addr += PAGE_SIZE) {ptent = ptep_get(pte);is_written = !is_pte_uffd_wp(ptent);bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_file(vma, ptent, addr),pte_present(ptent), is_swap_pte(ptent),pte_present(ptent) && is_zero_pfn(pte_pfn(ptent)));if (IS_PM_SCAN_GET(p->flags)) {interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting)ret = pagemap_scan_output(bitmap, p, addr, 1);}if (IS_PM_SCAN_WP(p->flags) && is_written && interesting &&ret >= 0) {make_uffd_wp_pte(vma, addr, pte);flush = true;}}if (flush)flush_tlb_range(vma, start, addr);pte_unmap_unlock(orig_pte, ptl);arch_leave_lazy_mmu_mode();cond_resched();return ret;+}
+#ifdef CONFIG_HUGETLB_PAGE +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask,
unsigned long start, unsigned long end,struct mm_walk *walk)+{
unsigned long n_pages = (end - start)/PAGE_SIZE;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;bool is_written, interesting = true;struct hstate *h = hstate_vma(vma);unsigned long bitmap;spinlock_t *ptl;int ret = 0;pte_t ptent;if (IS_PM_SCAN_WP(p->flags) && n_pages < HPAGE_SIZE/PAGE_SIZE) {p->end_addr = start;return -EINVAL;}if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;if (IS_PM_SCAN_WP(p->flags)) {i_mmap_lock_write(vma->vm_file->f_mapping);ptl = huge_pte_lock(h, vma->vm_mm, ptep);}ptent = huge_ptep_get(ptep);is_written = !is_huge_pte_uffd_wp(ptent);bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_huge_file(ptent),pte_present(ptent), is_swap_pte(ptent),pte_present(ptent) && is_zero_pfn(pte_pfn(ptent)));if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {/** Partial hugetlb page clear isn't supported*/if (is_written && IS_PM_SCAN_WP(p->flags) &&n_pages < HPAGE_SIZE/PAGE_SIZE) {ret = PM_SCAN_END_WALK;p->end_addr = start;goto unlock_and_return;}if (IS_PM_SCAN_GET(p->flags))ret = pagemap_scan_output(bitmap, p, start, n_pages);if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) {make_uffd_wp_huge_pte(vma, start, ptep, ptent);flush_hugetlb_tlb_range(vma, start, end);}}+unlock_and_return:
if (IS_PM_SCAN_WP(p->flags)) {spin_unlock(ptl);i_mmap_unlock_write(vma->vm_file->f_mapping);}return ret;+} +#else +#define pagemap_scan_hugetlb_entry NULL +#endif
+static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
int depth, struct mm_walk *walk)+{
unsigned long n_pages = (end - addr)/PAGE_SIZE;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;bool interesting = true;unsigned long bitmap;int ret = 0;if (!vma)return 0;bitmap = PM_SCAN_FLAGS(false, false, false, false, false);if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {if (IS_PM_SCAN_GET(p->flags)) {if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;ret = pagemap_scan_output(bitmap, p, addr, n_pages);}if (IS_PM_SCAN_WP(p->flags) && !ret &&uffd_wp_range(vma, addr, end - addr, true) < 0)
Why do we need to call uffd_wp_range for holes? Should we call flush_tlb_range after it?
ret = -EINVAL;}return ret;+}
+static const struct mm_walk_ops pagemap_scan_ops = {
.test_walk = pagemap_scan_test_walk,.pmd_entry = pagemap_scan_pmd_entry,.pte_hole = pagemap_scan_pte_hole,.hugetlb_entry = pagemap_scan_hugetlb_entry,+};
+static int pagemap_scan_args_valid(struct pm_scan_arg *arg, unsigned long start,
unsigned long end, struct page_region __user *vec)+{
/* Detect illegal size, flags, len and masks */if (arg->size != sizeof(struct pm_scan_arg))return -EINVAL;if (!arg->flags)return -EINVAL;if (arg->flags & ~PM_SCAN_OPS)return -EINVAL;if (!(end - start))return -EINVAL;if ((arg->required_mask | arg->anyof_mask | arg->excluded_mask |arg->return_mask) & ~PM_SCAN_BITS_ALL)return -EINVAL;if (!arg->required_mask && !arg->anyof_mask &&!arg->excluded_mask)return -EINVAL;if (!arg->return_mask)return -EINVAL;/* Validate memory range */if (!IS_ALIGNED(start, PAGE_SIZE))return -EINVAL;if (!access_ok((void __user *)start, end - start))return -EFAULT;if (IS_PM_SCAN_GET(arg->flags)) {if (arg->vec_len == 0)return -EINVAL;if (!vec)return -EFAULT;if (!access_ok((void __user *)vec,arg->vec_len * sizeof(struct page_region)))return -EFAULT;}if (IS_PM_SCAN_WP(arg->flags) && !IS_PM_SCAN_GET(arg->flags) &&arg->max_pages)return -EINVAL;return 0;+}
+static long do_pagemap_scan(struct mm_struct *mm, unsigned long __arg) +{
struct pm_scan_arg __user *uarg = (struct pm_scan_arg __user *)__arg;unsigned long long start, end, walk_start, walk_end;unsigned long empty_slots, vec_index = 0;struct mmu_notifier_range range;struct page_region __user *vec;struct pagemap_scan_private p;struct pm_scan_arg arg;int ret = 0;if (copy_from_user(&arg, uarg, sizeof(arg)))return -EFAULT;start = untagged_addr((unsigned long)arg.start);end = untagged_addr((unsigned long)arg.end);vec = (struct page_region __user *)untagged_addr((unsigned long)arg.vec);ret = pagemap_scan_args_valid(&arg, start, end, vec);if (ret)return ret;p.max_pages = (arg.max_pages) ? arg.max_pages : ULONG_MAX;p.found_pages = 0;p.required_mask = arg.required_mask;p.anyof_mask = arg.anyof_mask;p.excluded_mask = arg.excluded_mask;p.return_mask = arg.return_mask;p.flags = arg.flags;p.flags |= ((p.required_mask | p.anyof_mask | p.excluded_mask) &PAGE_IS_WRITTEN) ? PM_SCAN_REQUIRE_UFFD : 0;p.cur_buf.start = p.cur_buf.len = p.cur_buf.flags = 0;p.vec_buf = NULL;p.vec_buf_len = PAGEMAP_WALK_SIZE >> PAGE_SHIFT;p.vec_buf_index = 0;p.end_addr = 0;/** Allocate smaller buffer to get output from inside the page walk* functions and walk page range in PAGEMAP_WALK_SIZE size chunks. As* we want to return output to user in compact form where no two* consecutive regions should be continuous and have the same flags.* So store the latest element in p.cur_buf between different walks and* store the p.cur_buf at the end of the walk to the user buffer.*/if (IS_PM_SCAN_GET(p.flags)) {p.vec_buf = kmalloc_array(p.vec_buf_len, sizeof(*p.vec_buf),GFP_KERNEL);if (!p.vec_buf)return -ENOMEM;}/** Protection change for the range is going to happen.*/if (IS_PM_SCAN_WP(p.flags)) {mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,mm, start, end);mmu_notifier_invalidate_range_start(&range);}walk_start = walk_end = start;while (walk_end < end && !ret) {if (IS_PM_SCAN_GET(p.flags)) {/** All data is copied to cur_buf first. When more data* is found, we push cur_buf to vec_buf and copy new* data to cur_buf. Subtract 1 from length as the* index of cur_buf isn't counted in length.*/empty_slots = arg.vec_len - vec_index;p.vec_buf_len = min(p.vec_buf_len, empty_slots - 1);}
I still don't understand why we don't want/need to check for pending signals.
ret = mmap_read_lock_killable(mm);if (ret)goto out;walk_end = min((walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, end);ret = walk_page_range(mm, walk_start, walk_end,&pagemap_scan_ops, &p);mmap_read_unlock(mm);if (ret == PM_SCAN_FOUND_MAX_PAGES || ret == PM_SCAN_END_WALK)arg.start = p.end_addr;
nit: this check can be moved out of the loop.
if (ret && ret != PM_SCAN_FOUND_MAX_PAGES &&ret != PM_SCAN_END_WALK)goto out;if (p.vec_buf_index) {if (copy_to_user(&vec[vec_index], p.vec_buf,p.vec_buf_index * sizeof(*p.vec_buf))) {/** Return error even though the OP succeeded*/ret = -EFAULT;goto out;}vec_index += p.vec_buf_index;p.vec_buf_index = 0;}walk_start = walk_end;}if (p.cur_buf.len) {if (copy_to_user(&vec[vec_index], &p.cur_buf, sizeof(p.cur_buf))) {ret = -EFAULT;goto out;}vec_index++;}ret = vec_index;+out:
if (!p.end_addr)arg.start = walk_start;if (copy_to_user(&uarg->start, &arg.start, sizeof(arg.start)))ret = -EFAULT;if (IS_PM_SCAN_WP(p.flags))mmu_notifier_invalidate_range_end(&range);kfree(p.vec_buf);return ret;+}
+static long do_pagemap_cmd(struct file *file, unsigned int cmd,
unsigned long arg)+{
struct mm_struct *mm = file->private_data;switch (cmd) {case PAGEMAP_SCAN:return do_pagemap_scan(mm, arg);default:return -EINVAL;}+}
const struct file_operations proc_pagemap_operations = { .llseek = mem_lseek, /* borrow this */ .read = pagemap_read, .open = pagemap_open, .release = pagemap_release,
.unlocked_ioctl = do_pagemap_cmd,.compat_ioctl = do_pagemap_cmd,}; #endif /* CONFIG_PROC_PAGE_MONITOR */
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 623e98d62df3..c44e7bde0339 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma, unsigned long cp_flags);
bool is_hugetlb_entry_migration(pte_t pte); +bool is_hugetlb_entry_hwpoisoned(pte_t pte); void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
#else /* !CONFIG_HUGETLB_PAGE */ diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index b7b56871029c..ac684d99e68f 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -305,4 +305,59 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND)
+/* Pagemap ioctl */ +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg)
+/* Bits are set in flags of the page_region and masks in pm_scan_args */ +#define PAGE_IS_WRITTEN (1 << 0) +#define PAGE_IS_FILE (1 << 1) +#define PAGE_IS_PRESENT (1 << 2) +#define PAGE_IS_SWAPPED (1 << 3) +#define PAGE_IS_PFNZERO (1 << 4)
+/*
- struct page_region - Page region with flags
- @start: Start of the region
- @len: Length of the region in pages
- @bitmap: Bits sets for the region
- */
+struct page_region {
__u64 start;__u64 len;__u64 flags;+};
+/*
- struct pm_scan_arg - Pagemap ioctl argument
- @size: Size of the structure
- @flags: Flags for the IOCTL
- @start: Starting address of the region
(Ending address of the walk is also returned in it)
- @end: Ending address of the region
- @vec: Address of page_region struct array for output
- @vec_len: Length of the page_region struct array
- @max_pages: Optional max return pages
- @required_mask: Required mask - All of these bits have to be set in the PTE
- @anyof_mask: Any mask - Any of these bits are set in the PTE
- @excluded_mask: Exclude mask - None of these bits are set in the PTE
- @return_mask: Bits that are to be reported in page_region
- */
+struct pm_scan_arg {
__u64 size;__u64 flags;__u64 start;__u64 end;__u64 vec;__u64 vec_len;__u64 max_pages;__u64 required_mask;__u64 anyof_mask;__u64 excluded_mask;__u64 return_mask;+};
+/* Supported flags */ +#define PM_SCAN_OP_GET (1 << 0) +#define PM_SCAN_OP_WP (1 << 1)
#endif /* _UAPI_LINUX_FS_H */ diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ee88a2a6649f..f7cefdcb114c 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4981,7 +4981,7 @@ bool is_hugetlb_entry_migration(pte_t pte) return false; }
-static bool is_hugetlb_entry_hwpoisoned(pte_t pte) +bool is_hugetlb_entry_hwpoisoned(pte_t pte) { swp_entry_t swp;
-- 2.39.2
On 7/17/23 10:26 PM, Andrei Vagin wrote:
On Thu, Jul 13, 2023 at 3:14 AM Muhammad Usama Anjum usama.anjum@collabora.com wrote:
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl:
- Get the information if the pages have been written-to (PAGE_IS_WRITTEN), file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT), swapped (PAGE_IS_SWAPPED) or page has pfn zero (PAGE_IS_PFNZERO).
- Find pages which have been written-to and/or write protect the pages (atomic PM_SCAN_OP_GET + PM_SCAN_OP_WP)
This IOCTL can be extended to get information about more PTE bits. The entire address range passed by user [start, end) is scanned until either the user provided buffer is full or max_pages have been found.
Reviewed-by: Andrei Vagin avagin@gmail.com
Thank you.
Here are a few inline comments.
Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com
Changes in v25:
- Do proper filtering on hole as well (hole got missed earlier)
Changes in v24:
- Place WP markers in case of hole as well
Changes in v23:
- Set vec_buf_index to 0 only when vec_buf_index is set
- Return -EFAULT instead of -EINVAL if vec is NULL
- Correctly return the walk ending address to the page granularity
Changes in v22:
- Interface change to return walk ending address to user:
- Replace [start start + len) with [start, end)
- Return the ending address of the address walk in start
Changes in v21:
- Abort walk instead of returning error if WP is to be performed on partial hugetlb
- Changed the data types of some variables in pagemap_scan_private to long
Changes in v20:
- Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
Changes in v19:
- Interface changes such as renaming, return mask and WP can be used with any flags specified in masks
- Internal code changes
Changes in v18:
- Rebased on top of next-20230613
- ptep_get() updates
- remove pmd_trans_unstable() and add ACTION_AGAIN
- Review updates (Micheal)
Changes in v17:
- Rebased on next-20230606
- Made make_uffd_wp_*_pte() better and minor changes
Changes in v16:
- Fixed a corner case where kernel writes beyond user buffer by one element
- Bring back exclusive PM_SCAN_OP_WP
- Cosmetic changes
Changes in v15:
- Build fix:
- Use generic tlb flush function in pagemap_scan_pmd_entry() instead of using x86 specific flush function in do_pagemap_scan()
- Remove #ifdef from pagemap_scan_hugetlb_entry()
- Use mm instead of undefined vma->vm_mm
Changes in v14:
- Fix build error caused by #ifdef added at last minute in some configs
Changes in v13:
- Review updates
- mmap_read_lock_killable() instead of mmap_read_lock()
- Replace uffd_wp_range() with helpers which increases performance drastically for OP_WP operations by reducing the number of tlb flushing etc
- Add MMU_NOTIFY_PROTECTION_VMA notification for the memory range
Changes in v12:
- Add hugetlb support to cover all memory types
- Merge "userfaultfd: Define dummy uffd_wp_range()" with this patch
- Review updates to the code
Changes in v11:
- Find written pages in a better way
- Fix a corner case (thanks Paul)
- Improve the code/comments
- remove ENGAGE_WP + ! GET operation
- shorten the commit message in favour of moving documentation to pagemap.rst
Changes in v10:
- move changes in tools/include/uapi/linux/fs.h to separate patch
- update commit message
Change in v8:
- Correct is_pte_uffd_wp()
- Improve readability and error checks
- Remove some un-needed code
Changes in v7:
- Rebase on top of latest next
- Fix some corner cases
- Base soft-dirty on the uffd wp async
- Update the terminologies
- Optimize the memory usage inside the ioctl
fs/proc/task_mmu.c | 591 ++++++++++++++++++++++++++++++++++++++++ include/linux/hugetlb.h | 1 + include/uapi/linux/fs.h | 55 ++++ mm/hugetlb.c | 2 +- 4 files changed, 648 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index cfab855fe7e9..596fdfdc4387 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -19,6 +19,7 @@ #include <linux/shmem_fs.h> #include <linux/uaccess.h> #include <linux/pkeys.h> +#include <linux/minmax.h>
#include <asm/elf.h> #include <asm/tlb.h> @@ -1768,11 +1769,601 @@ static int pagemap_release(struct inode *inode, struct file *file) return 0; }
+#define PM_SCAN_REQUIRE_UFFD (1ULL << 63)
+#define PM_SCAN_FOUND_MAX_PAGES (1) +#define PM_SCAN_END_WALK (-256)
I would add a comment to explain why one is negative and another one is positive.
Sure. I'll add.
+#define PM_SCAN_BITS_ALL (PAGE_IS_WRITTEN | PAGE_IS_FILE | \
PAGE_IS_PRESENT | PAGE_IS_SWAPPED | \PAGE_IS_PFNZERO)+#define PM_SCAN_OPS (PM_SCAN_OP_GET | PM_SCAN_OP_WP) +#define IS_PM_SCAN_GET(flags) (flags & PM_SCAN_OP_GET) +#define IS_PM_SCAN_WP(flags) (flags & PM_SCAN_OP_WP)
+#define PM_SCAN_FLAGS(wt, file, present, swap, pfnzero) \
((wt) | ((file) << 1) | ((present) << 2) | \((swap) << 3) | ((pfnzero) << 4))it is better to use PAGE_IS_* constants here
#define PAGE_IS_PFNZERO (1 << 4) PAGE_IS_PFNZERO macro cannot be used here.
+struct pagemap_scan_private {
struct page_region *vec_buf, cur_buf;unsigned long vec_buf_len, vec_buf_index, max_pages, found_pages;unsigned long long flags, required_mask, anyof_mask, excluded_mask, return_mask, end_addr;end_addr has to be unsigned long.
Sure.
+};
+static inline bool is_pte_uffd_wp(pte_t pte) +{
return (pte_present(pte) && pte_uffd_wp(pte)) ||pte_swp_uffd_wp_any(pte);+}
+static inline void make_uffd_wp_pte(struct vm_area_struct *vma,
unsigned long addr, pte_t *pte)+{
pte_t ptent = ptep_get(pte);if (pte_present(ptent)) {pte_t old_pte;old_pte = ptep_modify_prot_start(vma, addr, pte);ptent = pte_mkuffd_wp(ptent);ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);} else if (is_swap_pte(ptent)) {ptent = pte_swp_mkuffd_wp(ptent);set_pte_at(vma->vm_mm, addr, pte, ptent);} else {set_pte_at(vma->vm_mm, addr, pte,make_pte_marker(PTE_MARKER_UFFD_WP));}+}
+static inline bool pagemap_scan_is_file(struct vm_area_struct *vma, pte_t ptent,
unsigned long addr)+{
struct page *page = NULL;swp_entry_t entry;if (pte_present(ptent)) {page = vm_normal_page(vma, addr, ptent);} else {entry = pte_to_swp_entry(ptent);if (is_pfn_swap_entry(entry))page = pfn_swap_entry_to_page(entry);}if (page && !PageAnon(page))return true;return false;+}
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static inline bool is_pmd_uffd_wp(pmd_t pmd) +{
return (pmd_present(pmd) && pmd_uffd_wp(pmd)) ||(is_swap_pmd(pmd) && pmd_swp_uffd_wp(pmd));+}
+static inline void make_uffd_wp_pmd(struct vm_area_struct *vma,
unsigned long addr, pmd_t *pmdp)+{
pmd_t old, pmd = *pmdp;if (pmd_present(pmd)) {old = pmdp_invalidate_ad(vma, addr, pmdp);pmd = pmd_mkuffd_wp(old);set_pmd_at(vma->vm_mm, addr, pmdp, pmd);} else if (is_migration_entry(pmd_to_swp_entry(pmd))) {pmd = pmd_swp_mkuffd_wp(pmd);set_pmd_at(vma->vm_mm, addr, pmdp, pmd);}+} +#endif
+#ifdef CONFIG_HUGETLB_PAGE +static inline bool is_huge_pte_uffd_wp(pte_t pte) +{
return (pte_present(pte) && huge_pte_uffd_wp(pte)) ||pte_swp_uffd_wp_any(pte);+}
+static inline void make_uffd_wp_huge_pte(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep,pte_t ptent)+{
if (is_hugetlb_entry_hwpoisoned(ptent) || is_pte_marker(ptent))return;if (is_hugetlb_entry_migration(ptent))set_huge_pte_at(vma->vm_mm, addr, ptep,pte_swp_mkuffd_wp(ptent));else if (!huge_pte_none(ptent))huge_ptep_modify_prot_commit(vma, addr, ptep, ptent,huge_pte_mkuffd_wp(ptent));elseset_huge_pte_at(vma->vm_mm, addr, ptep,make_pte_marker(PTE_MARKER_UFFD_WP));+}
+static inline bool pagemap_scan_is_huge_file(pte_t pte) +{
if (pte_present(pte) && (!PageAnon(pte_page(pte))))return true;return false;+} +#endif
+static int pagemap_scan_test_walk(unsigned long start, unsigned long end,
struct mm_walk *walk)+{
struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;if ((p->flags & PM_SCAN_REQUIRE_UFFD) && (!userfaultfd_wp_async(vma) ||!userfaultfd_wp_use_markers(vma)))return -EPERM;if (vma->vm_flags & VM_PFNMAP)return 1;return 0;+}
+static int pagemap_scan_output(unsigned long bitmap,
struct pagemap_scan_private *p,unsigned long addr, unsigned int n_pages)+{
struct page_region *cur_buf = &p->cur_buf;bitmap &= p->return_mask;if (cur_buf->flags == bitmap &&cur_buf->start + cur_buf->len * PAGE_SIZE == addr) {cur_buf->len += n_pages;p->found_pages += n_pages;} else {if (cur_buf->len) {if (p->vec_buf_index >= p->vec_buf_len) {p->end_addr = addr;return PM_SCAN_END_WALK;}memcpy(&p->vec_buf[p->vec_buf_index], cur_buf,sizeof(*p->vec_buf));p->vec_buf_index++;}cur_buf->start = addr;cur_buf->len = n_pages;cur_buf->flags = bitmap;p->found_pages += n_pages;}if (p->found_pages == p->max_pages) {p->end_addr = addr + n_pages * PAGE_SIZE;return PM_SCAN_FOUND_MAX_PAGES;}return 0;+}
+static bool pagemap_scan_is_interesting_page(unsigned long bitmap,
struct pagemap_scan_private *p)+{
if ((p->required_mask & bitmap) != p->required_mask)return false;if (p->anyof_mask && !(p->anyof_mask & bitmap))return false;if (p->excluded_mask & bitmap)return false;return true;+}
+static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start,
unsigned long end, struct mm_walk *walk)+{
bool is_written, flush = false, interesting = true;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;unsigned long bitmap, addr = end;pte_t *pte, *orig_pte, ptent;spinlock_t *ptl;int ret = 0;arch_enter_lazy_mmu_mode();+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
ptl = pmd_trans_huge_lock(pmd, vma);if (ptl) {unsigned long n_pages = (end - start)/PAGE_SIZE;if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;is_written = !is_pmd_uffd_wp(*pmd);bitmap = PM_SCAN_FLAGS(is_written, false,pmd_present(*pmd), is_swap_pmd(*pmd),pmd_present(*pmd) && is_zero_pfn(pmd_pfn(*pmd)));if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {/** Break huge page into small pages if the WP operation* need to be performed is on a portion of the huge page.*/if (is_written && IS_PM_SCAN_WP(p->flags) &&n_pages < HPAGE_SIZE/PAGE_SIZE) {spin_unlock(ptl);split_huge_pmd(vma, pmd, start);goto process_smaller_pages;}if (IS_PM_SCAN_GET(p->flags))ret = pagemap_scan_output(bitmap, p, start, n_pages);if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) {make_uffd_wp_pmd(vma, start, pmd);flush_tlb_range(vma, start, end);}}spin_unlock(ptl);arch_leave_lazy_mmu_mode();return ret;}+process_smaller_pages: +#endif
orig_pte = pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);if (!pte) {walk->action = ACTION_AGAIN;return 0;}for (addr = start; addr < end && !ret; pte++, addr += PAGE_SIZE) {ptent = ptep_get(pte);is_written = !is_pte_uffd_wp(ptent);bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_file(vma, ptent, addr),pte_present(ptent), is_swap_pte(ptent),pte_present(ptent) && is_zero_pfn(pte_pfn(ptent)));if (IS_PM_SCAN_GET(p->flags)) {interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting)ret = pagemap_scan_output(bitmap, p, addr, 1);}if (IS_PM_SCAN_WP(p->flags) && is_written && interesting &&ret >= 0) {make_uffd_wp_pte(vma, addr, pte);flush = true;}}if (flush)flush_tlb_range(vma, start, addr);pte_unmap_unlock(orig_pte, ptl);arch_leave_lazy_mmu_mode();cond_resched();return ret;+}
+#ifdef CONFIG_HUGETLB_PAGE +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask,
unsigned long start, unsigned long end,struct mm_walk *walk)+{
unsigned long n_pages = (end - start)/PAGE_SIZE;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;bool is_written, interesting = true;struct hstate *h = hstate_vma(vma);unsigned long bitmap;spinlock_t *ptl;int ret = 0;pte_t ptent;if (IS_PM_SCAN_WP(p->flags) && n_pages < HPAGE_SIZE/PAGE_SIZE) {p->end_addr = start;return -EINVAL;}if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;if (IS_PM_SCAN_WP(p->flags)) {i_mmap_lock_write(vma->vm_file->f_mapping);ptl = huge_pte_lock(h, vma->vm_mm, ptep);}ptent = huge_ptep_get(ptep);is_written = !is_huge_pte_uffd_wp(ptent);bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_huge_file(ptent),pte_present(ptent), is_swap_pte(ptent),pte_present(ptent) && is_zero_pfn(pte_pfn(ptent)));if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {/** Partial hugetlb page clear isn't supported*/if (is_written && IS_PM_SCAN_WP(p->flags) &&n_pages < HPAGE_SIZE/PAGE_SIZE) {ret = PM_SCAN_END_WALK;p->end_addr = start;goto unlock_and_return;}if (IS_PM_SCAN_GET(p->flags))ret = pagemap_scan_output(bitmap, p, start, n_pages);if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) {make_uffd_wp_huge_pte(vma, start, ptep, ptent);flush_hugetlb_tlb_range(vma, start, end);}}+unlock_and_return:
if (IS_PM_SCAN_WP(p->flags)) {spin_unlock(ptl);i_mmap_unlock_write(vma->vm_file->f_mapping);}return ret;+} +#else +#define pagemap_scan_hugetlb_entry NULL +#endif
+static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
int depth, struct mm_walk *walk)+{
unsigned long n_pages = (end - addr)/PAGE_SIZE;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;bool interesting = true;unsigned long bitmap;int ret = 0;if (!vma)return 0;bitmap = PM_SCAN_FLAGS(false, false, false, false, false);if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {if (IS_PM_SCAN_GET(p->flags)) {if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;ret = pagemap_scan_output(bitmap, p, addr, n_pages);}if (IS_PM_SCAN_WP(p->flags) && !ret &&uffd_wp_range(vma, addr, end - addr, true) < 0)Why do we need to call uffd_wp_range for holes? Should we call flush_tlb_range after it?
ret = -EINVAL;}return ret;+}
+static const struct mm_walk_ops pagemap_scan_ops = {
.test_walk = pagemap_scan_test_walk,.pmd_entry = pagemap_scan_pmd_entry,.pte_hole = pagemap_scan_pte_hole,.hugetlb_entry = pagemap_scan_hugetlb_entry,+};
+static int pagemap_scan_args_valid(struct pm_scan_arg *arg, unsigned long start,
unsigned long end, struct page_region __user *vec)+{
/* Detect illegal size, flags, len and masks */if (arg->size != sizeof(struct pm_scan_arg))return -EINVAL;if (!arg->flags)return -EINVAL;if (arg->flags & ~PM_SCAN_OPS)return -EINVAL;if (!(end - start))return -EINVAL;if ((arg->required_mask | arg->anyof_mask | arg->excluded_mask |arg->return_mask) & ~PM_SCAN_BITS_ALL)return -EINVAL;if (!arg->required_mask && !arg->anyof_mask &&!arg->excluded_mask)return -EINVAL;if (!arg->return_mask)return -EINVAL;/* Validate memory range */if (!IS_ALIGNED(start, PAGE_SIZE))return -EINVAL;if (!access_ok((void __user *)start, end - start))return -EFAULT;if (IS_PM_SCAN_GET(arg->flags)) {if (arg->vec_len == 0)return -EINVAL;if (!vec)return -EFAULT;if (!access_ok((void __user *)vec,arg->vec_len * sizeof(struct page_region)))return -EFAULT;}if (IS_PM_SCAN_WP(arg->flags) && !IS_PM_SCAN_GET(arg->flags) &&arg->max_pages)return -EINVAL;return 0;+}
+static long do_pagemap_scan(struct mm_struct *mm, unsigned long __arg) +{
struct pm_scan_arg __user *uarg = (struct pm_scan_arg __user *)__arg;unsigned long long start, end, walk_start, walk_end;unsigned long empty_slots, vec_index = 0;struct mmu_notifier_range range;struct page_region __user *vec;struct pagemap_scan_private p;struct pm_scan_arg arg;int ret = 0;if (copy_from_user(&arg, uarg, sizeof(arg)))return -EFAULT;start = untagged_addr((unsigned long)arg.start);end = untagged_addr((unsigned long)arg.end);vec = (struct page_region __user *)untagged_addr((unsigned long)arg.vec);ret = pagemap_scan_args_valid(&arg, start, end, vec);if (ret)return ret;p.max_pages = (arg.max_pages) ? arg.max_pages : ULONG_MAX;p.found_pages = 0;p.required_mask = arg.required_mask;p.anyof_mask = arg.anyof_mask;p.excluded_mask = arg.excluded_mask;p.return_mask = arg.return_mask;p.flags = arg.flags;p.flags |= ((p.required_mask | p.anyof_mask | p.excluded_mask) &PAGE_IS_WRITTEN) ? PM_SCAN_REQUIRE_UFFD : 0;p.cur_buf.start = p.cur_buf.len = p.cur_buf.flags = 0;p.vec_buf = NULL;p.vec_buf_len = PAGEMAP_WALK_SIZE >> PAGE_SHIFT;p.vec_buf_index = 0;p.end_addr = 0;/** Allocate smaller buffer to get output from inside the page walk* functions and walk page range in PAGEMAP_WALK_SIZE size chunks. As* we want to return output to user in compact form where no two* consecutive regions should be continuous and have the same flags.* So store the latest element in p.cur_buf between different walks and* store the p.cur_buf at the end of the walk to the user buffer.*/if (IS_PM_SCAN_GET(p.flags)) {p.vec_buf = kmalloc_array(p.vec_buf_len, sizeof(*p.vec_buf),GFP_KERNEL);if (!p.vec_buf)return -ENOMEM;}/** Protection change for the range is going to happen.*/if (IS_PM_SCAN_WP(p.flags)) {mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,mm, start, end);mmu_notifier_invalidate_range_start(&range);}walk_start = walk_end = start;while (walk_end < end && !ret) {if (IS_PM_SCAN_GET(p.flags)) {/** All data is copied to cur_buf first. When more data* is found, we push cur_buf to vec_buf and copy new* data to cur_buf. Subtract 1 from length as the* index of cur_buf isn't counted in length.*/empty_slots = arg.vec_len - vec_index;p.vec_buf_len = min(p.vec_buf_len, empty_slots - 1);}I still don't understand why we don't want/need to check for pending signals.
We haven't added it as other existing code such as mincore() and pagemap_read() don't have it either. Also mmap_read_lock_killable would return error if there is some critical single pending.
ret = mmap_read_lock_killable(mm);if (ret)goto out;walk_end = min((walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, end);ret = walk_page_range(mm, walk_start, walk_end,&pagemap_scan_ops, &p);mmap_read_unlock(mm);if (ret == PM_SCAN_FOUND_MAX_PAGES || ret == PM_SCAN_END_WALK)arg.start = p.end_addr;nit: this check can be moved out of the loop.
No, ret could get replaced by error if copy_to_user() fails. So we have to do this before that.
if (ret && ret != PM_SCAN_FOUND_MAX_PAGES &&ret != PM_SCAN_END_WALK)goto out;if (p.vec_buf_index) {if (copy_to_user(&vec[vec_index], p.vec_buf,p.vec_buf_index * sizeof(*p.vec_buf))) {/** Return error even though the OP succeeded*/ret = -EFAULT;goto out;}vec_index += p.vec_buf_index;p.vec_buf_index = 0;}walk_start = walk_end;}if (p.cur_buf.len) {if (copy_to_user(&vec[vec_index], &p.cur_buf, sizeof(p.cur_buf))) {ret = -EFAULT;goto out;}vec_index++;}ret = vec_index;+out:
if (!p.end_addr)arg.start = walk_start;if (copy_to_user(&uarg->start, &arg.start, sizeof(arg.start)))ret = -EFAULT;if (IS_PM_SCAN_WP(p.flags))mmu_notifier_invalidate_range_end(&range);kfree(p.vec_buf);return ret;+}
+static long do_pagemap_cmd(struct file *file, unsigned int cmd,
unsigned long arg)+{
struct mm_struct *mm = file->private_data;switch (cmd) {case PAGEMAP_SCAN:return do_pagemap_scan(mm, arg);default:return -EINVAL;}+}
const struct file_operations proc_pagemap_operations = { .llseek = mem_lseek, /* borrow this */ .read = pagemap_read, .open = pagemap_open, .release = pagemap_release,
.unlocked_ioctl = do_pagemap_cmd,.compat_ioctl = do_pagemap_cmd,}; #endif /* CONFIG_PROC_PAGE_MONITOR */
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 623e98d62df3..c44e7bde0339 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -259,6 +259,7 @@ long hugetlb_change_protection(struct vm_area_struct *vma, unsigned long cp_flags);
bool is_hugetlb_entry_migration(pte_t pte); +bool is_hugetlb_entry_hwpoisoned(pte_t pte); void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
#else /* !CONFIG_HUGETLB_PAGE */ diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index b7b56871029c..ac684d99e68f 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -305,4 +305,59 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND)
+/* Pagemap ioctl */ +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg)
+/* Bits are set in flags of the page_region and masks in pm_scan_args */ +#define PAGE_IS_WRITTEN (1 << 0) +#define PAGE_IS_FILE (1 << 1) +#define PAGE_IS_PRESENT (1 << 2) +#define PAGE_IS_SWAPPED (1 << 3) +#define PAGE_IS_PFNZERO (1 << 4)
+/*
- struct page_region - Page region with flags
- @start: Start of the region
- @len: Length of the region in pages
- @bitmap: Bits sets for the region
- */
+struct page_region {
__u64 start;__u64 len;__u64 flags;+};
+/*
- struct pm_scan_arg - Pagemap ioctl argument
- @size: Size of the structure
- @flags: Flags for the IOCTL
- @start: Starting address of the region
(Ending address of the walk is also returned in it)
- @end: Ending address of the region
- @vec: Address of page_region struct array for output
- @vec_len: Length of the page_region struct array
- @max_pages: Optional max return pages
- @required_mask: Required mask - All of these bits have to be set in the PTE
- @anyof_mask: Any mask - Any of these bits are set in the PTE
- @excluded_mask: Exclude mask - None of these bits are set in the PTE
- @return_mask: Bits that are to be reported in page_region
- */
+struct pm_scan_arg {
__u64 size;__u64 flags;__u64 start;__u64 end;__u64 vec;__u64 vec_len;__u64 max_pages;__u64 required_mask;__u64 anyof_mask;__u64 excluded_mask;__u64 return_mask;+};
+/* Supported flags */ +#define PM_SCAN_OP_GET (1 << 0) +#define PM_SCAN_OP_WP (1 << 1)
#endif /* _UAPI_LINUX_FS_H */ diff --git a/mm/hugetlb.c b/mm/hugetlb.c index ee88a2a6649f..f7cefdcb114c 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4981,7 +4981,7 @@ bool is_hugetlb_entry_migration(pte_t pte) return false; }
-static bool is_hugetlb_entry_hwpoisoned(pte_t pte) +bool is_hugetlb_entry_hwpoisoned(pte_t pte) { swp_entry_t swp;
-- 2.39.2
On Tue, Jul 18, 2023 at 1:18 AM Muhammad Usama Anjum usama.anjum@collabora.com wrote:
On 7/17/23 10:26 PM, Andrei Vagin wrote:
On Thu, Jul 13, 2023 at 3:14 AM Muhammad Usama Anjum usama.anjum@collabora.com wrote:
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl:
- Get the information if the pages have been written-to (PAGE_IS_WRITTEN), file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT), swapped (PAGE_IS_SWAPPED) or page has pfn zero (PAGE_IS_PFNZERO).
- Find pages which have been written-to and/or write protect the pages (atomic PM_SCAN_OP_GET + PM_SCAN_OP_WP)
This IOCTL can be extended to get information about more PTE bits. The entire address range passed by user [start, end) is scanned until either the user provided buffer is full or max_pages have been found.
Reviewed-by: Andrei Vagin avagin@gmail.com
Thank you.
<snip>
+#ifdef CONFIG_HUGETLB_PAGE +static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask,
unsigned long start, unsigned long end,struct mm_walk *walk)+{
unsigned long n_pages = (end - start)/PAGE_SIZE;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;bool is_written, interesting = true;struct hstate *h = hstate_vma(vma);unsigned long bitmap;spinlock_t *ptl;int ret = 0;pte_t ptent;if (IS_PM_SCAN_WP(p->flags) && n_pages < HPAGE_SIZE/PAGE_SIZE) {p->end_addr = start;return -EINVAL;}if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;if (IS_PM_SCAN_WP(p->flags)) {i_mmap_lock_write(vma->vm_file->f_mapping);ptl = huge_pte_lock(h, vma->vm_mm, ptep);}ptent = huge_ptep_get(ptep);is_written = !is_huge_pte_uffd_wp(ptent);bitmap = PM_SCAN_FLAGS(is_written, pagemap_scan_is_huge_file(ptent),pte_present(ptent), is_swap_pte(ptent),pte_present(ptent) && is_zero_pfn(pte_pfn(ptent)));if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {/** Partial hugetlb page clear isn't supported*/if (is_written && IS_PM_SCAN_WP(p->flags) &&n_pages < HPAGE_SIZE/PAGE_SIZE) {ret = PM_SCAN_END_WALK;p->end_addr = start;goto unlock_and_return;}if (IS_PM_SCAN_GET(p->flags))ret = pagemap_scan_output(bitmap, p, start, n_pages);if (IS_PM_SCAN_WP(p->flags) && is_written && ret >= 0) {make_uffd_wp_huge_pte(vma, start, ptep, ptent);flush_hugetlb_tlb_range(vma, start, end);}}+unlock_and_return:
if (IS_PM_SCAN_WP(p->flags)) {spin_unlock(ptl);i_mmap_unlock_write(vma->vm_file->f_mapping);}return ret;+} +#else +#define pagemap_scan_hugetlb_entry NULL +#endif
+static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
int depth, struct mm_walk *walk)+{
unsigned long n_pages = (end - addr)/PAGE_SIZE;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;bool interesting = true;unsigned long bitmap;int ret = 0;if (!vma)return 0;bitmap = PM_SCAN_FLAGS(false, false, false, false, false);if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {if (IS_PM_SCAN_GET(p->flags)) {if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;ret = pagemap_scan_output(bitmap, p, addr, n_pages);}if (IS_PM_SCAN_WP(p->flags) && !ret &&uffd_wp_range(vma, addr, end - addr, true) < 0)Why do we need to call uffd_wp_range for holes? Should we call flush_tlb_range after it?
Did you skip this question?
ret = -EINVAL;}return ret;+}
+static const struct mm_walk_ops pagemap_scan_ops = {
.test_walk = pagemap_scan_test_walk,.pmd_entry = pagemap_scan_pmd_entry,.pte_hole = pagemap_scan_pte_hole,.hugetlb_entry = pagemap_scan_hugetlb_entry,+};
+static int pagemap_scan_args_valid(struct pm_scan_arg *arg, unsigned long start,
unsigned long end, struct page_region __user *vec)+{
/* Detect illegal size, flags, len and masks */if (arg->size != sizeof(struct pm_scan_arg))return -EINVAL;if (!arg->flags)return -EINVAL;if (arg->flags & ~PM_SCAN_OPS)return -EINVAL;if (!(end - start))return -EINVAL;if ((arg->required_mask | arg->anyof_mask | arg->excluded_mask |arg->return_mask) & ~PM_SCAN_BITS_ALL)return -EINVAL;if (!arg->required_mask && !arg->anyof_mask &&!arg->excluded_mask)return -EINVAL;if (!arg->return_mask)return -EINVAL;/* Validate memory range */if (!IS_ALIGNED(start, PAGE_SIZE))return -EINVAL;if (!access_ok((void __user *)start, end - start))return -EFAULT;if (IS_PM_SCAN_GET(arg->flags)) {if (arg->vec_len == 0)return -EINVAL;if (!vec)return -EFAULT;if (!access_ok((void __user *)vec,arg->vec_len * sizeof(struct page_region)))return -EFAULT;}if (IS_PM_SCAN_WP(arg->flags) && !IS_PM_SCAN_GET(arg->flags) &&arg->max_pages)return -EINVAL;return 0;+}
+static long do_pagemap_scan(struct mm_struct *mm, unsigned long __arg) +{
struct pm_scan_arg __user *uarg = (struct pm_scan_arg __user *)__arg;unsigned long long start, end, walk_start, walk_end;unsigned long empty_slots, vec_index = 0;struct mmu_notifier_range range;struct page_region __user *vec;struct pagemap_scan_private p;struct pm_scan_arg arg;int ret = 0;if (copy_from_user(&arg, uarg, sizeof(arg)))return -EFAULT;start = untagged_addr((unsigned long)arg.start);end = untagged_addr((unsigned long)arg.end);vec = (struct page_region __user *)untagged_addr((unsigned long)arg.vec);ret = pagemap_scan_args_valid(&arg, start, end, vec);if (ret)return ret;p.max_pages = (arg.max_pages) ? arg.max_pages : ULONG_MAX;p.found_pages = 0;p.required_mask = arg.required_mask;p.anyof_mask = arg.anyof_mask;p.excluded_mask = arg.excluded_mask;p.return_mask = arg.return_mask;p.flags = arg.flags;p.flags |= ((p.required_mask | p.anyof_mask | p.excluded_mask) &PAGE_IS_WRITTEN) ? PM_SCAN_REQUIRE_UFFD : 0;p.cur_buf.start = p.cur_buf.len = p.cur_buf.flags = 0;p.vec_buf = NULL;p.vec_buf_len = PAGEMAP_WALK_SIZE >> PAGE_SHIFT;p.vec_buf_index = 0;p.end_addr = 0;/** Allocate smaller buffer to get output from inside the page walk* functions and walk page range in PAGEMAP_WALK_SIZE size chunks. As* we want to return output to user in compact form where no two* consecutive regions should be continuous and have the same flags.* So store the latest element in p.cur_buf between different walks and* store the p.cur_buf at the end of the walk to the user buffer.*/if (IS_PM_SCAN_GET(p.flags)) {p.vec_buf = kmalloc_array(p.vec_buf_len, sizeof(*p.vec_buf),GFP_KERNEL);if (!p.vec_buf)return -ENOMEM;}/** Protection change for the range is going to happen.*/if (IS_PM_SCAN_WP(p.flags)) {mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,mm, start, end);mmu_notifier_invalidate_range_start(&range);}walk_start = walk_end = start;while (walk_end < end && !ret) {if (IS_PM_SCAN_GET(p.flags)) {/** All data is copied to cur_buf first. When more data* is found, we push cur_buf to vec_buf and copy new* data to cur_buf. Subtract 1 from length as the* index of cur_buf isn't counted in length.*/empty_slots = arg.vec_len - vec_index;p.vec_buf_len = min(p.vec_buf_len, empty_slots - 1);}I still don't understand why we don't want/need to check for pending signals.
We haven't added it as other existing code such as mincore() and
It doesn't convince me. There should be reasons to do or not to do certain things. We can't say how long this loop can be running, so it is the reason why we can want to check pending signals.
pagemap_read() don't have it either.
I already explained that this case is different, because the size of the output buffer is limited for pagemap_read.
Also mmap_read_lock_killable would return error if there is some critical single pending.\
It isn't completely true. It doesn't return errors in the fast path when it takes the lock right away. It checks signals only when it needs to wait for the lock.
ret = mmap_read_lock_killable(mm);if (ret)goto out;walk_end = min((walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, end);ret = walk_page_range(mm, walk_start, walk_end,&pagemap_scan_ops, &p);mmap_read_unlock(mm);if (ret == PM_SCAN_FOUND_MAX_PAGES || ret == PM_SCAN_END_WALK)arg.start = p.end_addr;nit: this check can be moved out of the loop.
No, ret could get replaced by error if copy_to_user() fails. So we have to do this before that.
If we fail to copy a vector, it is a fatal error and it probably doesn't matter what end address has been there. It is up to you to leave it here or not.
if (ret && ret != PM_SCAN_FOUND_MAX_PAGES &&ret != PM_SCAN_END_WALK)goto out;if (p.vec_buf_index) {if (copy_to_user(&vec[vec_index], p.vec_buf,p.vec_buf_index * sizeof(*p.vec_buf))) {/** Return error even though the OP succeeded*/ret = -EFAULT;goto out;}vec_index += p.vec_buf_index;p.vec_buf_index = 0;}walk_start = walk_end;}if (p.cur_buf.len) {if (copy_to_user(&vec[vec_index], &p.cur_buf, sizeof(p.cur_buf))) {ret = -EFAULT;goto out;}vec_index++;}ret = vec_index;+out:
if (!p.end_addr)arg.start = walk_start;if (copy_to_user(&uarg->start, &arg.start, sizeof(arg.start)))ret = -EFAULT;if (IS_PM_SCAN_WP(p.flags))mmu_notifier_invalidate_range_end(&range);kfree(p.vec_buf);return ret;+}
Thanks, Andrei
On 7/18/23 9:08 PM, Andrei Vagin wrote: ...
+static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
int depth, struct mm_walk *walk)+{
unsigned long n_pages = (end - addr)/PAGE_SIZE;struct pagemap_scan_private *p = walk->private;struct vm_area_struct *vma = walk->vma;bool interesting = true;unsigned long bitmap;int ret = 0;if (!vma)return 0;bitmap = PM_SCAN_FLAGS(false, false, false, false, false);if (IS_PM_SCAN_GET(p->flags))interesting = pagemap_scan_is_interesting_page(bitmap, p);if (interesting) {if (IS_PM_SCAN_GET(p->flags)) {if (n_pages > p->max_pages - p->found_pages)n_pages = p->max_pages - p->found_pages;ret = pagemap_scan_output(bitmap, p, addr, n_pages);}if (IS_PM_SCAN_WP(p->flags) && !ret &&uffd_wp_range(vma, addr, end - addr, true) < 0)Why do we need to call uffd_wp_range for holes? Should we call flush_tlb_range after it?
Did you skip this question?
Sorry, missed it the first time. In case of holes, there isn't any pmd or pte. But we need to place the PTE markers indicating that this memory is WPed. So we can parse the address range from PGD ourselves and place the markers. Or we can use the uffd_wp_range(). Using uffd_wp_range() for this case seems optimal. We don't need to do flush as uffd_wp_range() flushes the range by itself.
ret = -EINVAL;}return ret;+}
+static const struct mm_walk_ops pagemap_scan_ops = {
.test_walk = pagemap_scan_test_walk,.pmd_entry = pagemap_scan_pmd_entry,.pte_hole = pagemap_scan_pte_hole,.hugetlb_entry = pagemap_scan_hugetlb_entry,+};
+static int pagemap_scan_args_valid(struct pm_scan_arg *arg, unsigned long start,
unsigned long end, struct page_region __user *vec)+{
/* Detect illegal size, flags, len and masks */if (arg->size != sizeof(struct pm_scan_arg))return -EINVAL;if (!arg->flags)return -EINVAL;if (arg->flags & ~PM_SCAN_OPS)return -EINVAL;if (!(end - start))return -EINVAL;if ((arg->required_mask | arg->anyof_mask | arg->excluded_mask |arg->return_mask) & ~PM_SCAN_BITS_ALL)return -EINVAL;if (!arg->required_mask && !arg->anyof_mask &&!arg->excluded_mask)return -EINVAL;if (!arg->return_mask)return -EINVAL;/* Validate memory range */if (!IS_ALIGNED(start, PAGE_SIZE))return -EINVAL;if (!access_ok((void __user *)start, end - start))return -EFAULT;if (IS_PM_SCAN_GET(arg->flags)) {if (arg->vec_len == 0)return -EINVAL;if (!vec)return -EFAULT;if (!access_ok((void __user *)vec,arg->vec_len * sizeof(struct page_region)))return -EFAULT;}if (IS_PM_SCAN_WP(arg->flags) && !IS_PM_SCAN_GET(arg->flags) &&arg->max_pages)return -EINVAL;return 0;+}
+static long do_pagemap_scan(struct mm_struct *mm, unsigned long __arg) +{
struct pm_scan_arg __user *uarg = (struct pm_scan_arg __user *)__arg;unsigned long long start, end, walk_start, walk_end;unsigned long empty_slots, vec_index = 0;struct mmu_notifier_range range;struct page_region __user *vec;struct pagemap_scan_private p;struct pm_scan_arg arg;int ret = 0;if (copy_from_user(&arg, uarg, sizeof(arg)))return -EFAULT;start = untagged_addr((unsigned long)arg.start);end = untagged_addr((unsigned long)arg.end);vec = (struct page_region __user *)untagged_addr((unsigned long)arg.vec);ret = pagemap_scan_args_valid(&arg, start, end, vec);if (ret)return ret;p.max_pages = (arg.max_pages) ? arg.max_pages : ULONG_MAX;p.found_pages = 0;p.required_mask = arg.required_mask;p.anyof_mask = arg.anyof_mask;p.excluded_mask = arg.excluded_mask;p.return_mask = arg.return_mask;p.flags = arg.flags;p.flags |= ((p.required_mask | p.anyof_mask | p.excluded_mask) &PAGE_IS_WRITTEN) ? PM_SCAN_REQUIRE_UFFD : 0;p.cur_buf.start = p.cur_buf.len = p.cur_buf.flags = 0;p.vec_buf = NULL;p.vec_buf_len = PAGEMAP_WALK_SIZE >> PAGE_SHIFT;p.vec_buf_index = 0;p.end_addr = 0;/** Allocate smaller buffer to get output from inside the page walk* functions and walk page range in PAGEMAP_WALK_SIZE size chunks. As* we want to return output to user in compact form where no two* consecutive regions should be continuous and have the same flags.* So store the latest element in p.cur_buf between different walks and* store the p.cur_buf at the end of the walk to the user buffer.*/if (IS_PM_SCAN_GET(p.flags)) {p.vec_buf = kmalloc_array(p.vec_buf_len, sizeof(*p.vec_buf),GFP_KERNEL);if (!p.vec_buf)return -ENOMEM;}/** Protection change for the range is going to happen.*/if (IS_PM_SCAN_WP(p.flags)) {mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,mm, start, end);mmu_notifier_invalidate_range_start(&range);}walk_start = walk_end = start;while (walk_end < end && !ret) {if (IS_PM_SCAN_GET(p.flags)) {/** All data is copied to cur_buf first. When more data* is found, we push cur_buf to vec_buf and copy new* data to cur_buf. Subtract 1 from length as the* index of cur_buf isn't counted in length.*/empty_slots = arg.vec_len - vec_index;p.vec_buf_len = min(p.vec_buf_len, empty_slots - 1);}I still don't understand why we don't want/need to check for pending signals.
We haven't added it as other existing code such as mincore() and
It doesn't convince me. There should be reasons to do or not to do certain things. We can't say how long this loop can be running, so it is the reason why we can want to check pending signals.
pagemap_read() don't have it either.
I already explained that this case is different, because the size of the output buffer is limited for pagemap_read.
Also mmap_read_lock_killable would return error if there is some critical single pending.\
It isn't completely true. It doesn't return errors in the fast path when it takes the lock right away. It checks signals only when it needs to wait for the lock.
Okay. It seems reasonable. I'll add the following at the start of the loop:
if (fatal_signal_pending(current)) return -EINTR;
ret = mmap_read_lock_killable(mm);if (ret)goto out;walk_end = min((walk_start + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK, end);ret = walk_page_range(mm, walk_start, walk_end,&pagemap_scan_ops, &p);mmap_read_unlock(mm);if (ret == PM_SCAN_FOUND_MAX_PAGES || ret == PM_SCAN_END_WALK)arg.start = p.end_addr;nit: this check can be moved out of the loop.
No, ret could get replaced by error if copy_to_user() fails. So we have to do this before that.
If we fail to copy a vector, it is a fatal error and it probably doesn't matter what end address has been there. It is up to you to leave it here or not.
Sure.
New IOCTL and macros has been added in the kernel sources. Update the tools header file as well.
Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com --- Changes in v21: - Update tools/include/uapi/linux/fs.h
Changes in v19: - Update fs.h accourding to precious patch --- tools/include/uapi/linux/fs.h | 55 +++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+)
diff --git a/tools/include/uapi/linux/fs.h b/tools/include/uapi/linux/fs.h index b7b56871029c..ac684d99e68f 100644 --- a/tools/include/uapi/linux/fs.h +++ b/tools/include/uapi/linux/fs.h @@ -305,4 +305,59 @@ typedef int __bitwise __kernel_rwf_t; #define RWF_SUPPORTED (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\ RWF_APPEND)
+/* Pagemap ioctl */ +#define PAGEMAP_SCAN _IOWR('f', 16, struct pm_scan_arg) + +/* Bits are set in flags of the page_region and masks in pm_scan_args */ +#define PAGE_IS_WRITTEN (1 << 0) +#define PAGE_IS_FILE (1 << 1) +#define PAGE_IS_PRESENT (1 << 2) +#define PAGE_IS_SWAPPED (1 << 3) +#define PAGE_IS_PFNZERO (1 << 4) + +/* + * struct page_region - Page region with flags + * @start: Start of the region + * @len: Length of the region in pages + * @bitmap: Bits sets for the region + */ +struct page_region { + __u64 start; + __u64 len; + __u64 flags; +}; + +/* + * struct pm_scan_arg - Pagemap ioctl argument + * @size: Size of the structure + * @flags: Flags for the IOCTL + * @start: Starting address of the region + * (Ending address of the walk is also returned in it) + * @end: Ending address of the region + * @vec: Address of page_region struct array for output + * @vec_len: Length of the page_region struct array + * @max_pages: Optional max return pages + * @required_mask: Required mask - All of these bits have to be set in the PTE + * @anyof_mask: Any mask - Any of these bits are set in the PTE + * @excluded_mask: Exclude mask - None of these bits are set in the PTE + * @return_mask: Bits that are to be reported in page_region + */ +struct pm_scan_arg { + __u64 size; + __u64 flags; + __u64 start; + __u64 end; + __u64 vec; + __u64 vec_len; + __u64 max_pages; + __u64 required_mask; + __u64 anyof_mask; + __u64 excluded_mask; + __u64 return_mask; +}; + +/* Supported flags */ +#define PM_SCAN_OP_GET (1 << 0) +#define PM_SCAN_OP_WP (1 << 1) + #endif /* _UAPI_LINUX_FS_H */
Add some explanation and method to use write-protection and written-to on memory range.
Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com --- Changes in v21: - Update according to changed interface
Changes in v20: - Add new flag in documentation
Changes in v19: - Improved documentatiom with punctuation marks
Changes in v16: - Update the documentation
Changes in v11: - Add more documentation
rst --- Documentation/admin-guide/mm/pagemap.rst | 58 ++++++++++++++++++++++++ 1 file changed, 58 insertions(+)
diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst index c8f380271cad..4bdad8eff009 100644 --- a/Documentation/admin-guide/mm/pagemap.rst +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -227,3 +227,61 @@ Before Linux 3.11 pagemap bits 55-60 were used for "page-shift" (which is always 12 at most architectures). Since Linux 3.11 their meaning changes after first clear of soft-dirty bits. Since Linux 4.2 they are used for flags unconditionally. + +Pagemap Scan IOCTL +================== + +The ``PAGEMAP_SCAN`` IOCTL on the pagemap file can be used to get or optionally +clear the info about page table entries. The following operations are supported +in this IOCTL: +- Get the information if the pages have been written to (``PAGE_IS_WRITTEN``), + file mapped (``PAGE_IS_FILE``), present (``PAGE_IS_PRESENT``), swapped + (``PAGE_IS_SWAPPED``) or page has pfn zero (``PAGE_IS_PFNZERO``). +- Find pages which have been written to and/or write protect the pages atomically + (atomic ``PM_SCAN_OP_GET + PM_SCAN_OP_WP``) + +The ``struct pm_scan_arg`` is used as the argument of the IOCTL. + 1. The size of the ``struct pm_scan_arg`` must be specified in the ``size`` + field. This field will be helpful in recognizing the structure if extensions + are done later. + 2. The flags can be specified in the ``flags`` field. The ``PM_SCAN_OP_GET`` + and ``PM_SCAN_OP_WP`` are the only added flags at this time. + 3. The range is specified through ``start`` and ``end``. + 4. The output buffer of ``struct page_region`` array and size is specified in + ``vec`` and ``vec_len``. + 5. The optional maximum requested pages are specified in the ``max_pages``. + 6. The masks are specified in ``required_mask``, ``anyof_mask``, + ``excluded_ mask`` and ``return_mask``. + 1. To find if ``PAGE_IS_WRITTEN`` flag is set for pages which have + ``PAGE_IS_FILE`` set and ``PAGE_IS_SWAPPED`` unset, ``required_mask`` + is set to ``PAGE_IS_FILE``, ``exclude_mask`` is set to + ``PAGE_IS_SWAPPED`` and ``return_mask`` is set to ``PAGE_IS_WRITTEN``. + The output buffer in ``vec`` and length must be specified in ``vec_len``. + 2. To find pages which have either ``PAGE_IS_FILE`` or ``PAGE_IS_SWAPPED`` + set, ``anyof_masks`` is set to ``PAGE_IS_FILE | PAGE_IS_SWAPPED``. + 3. To find written pages and engage write protect, ``PAGE_IS_WRITTEN`` is + specified in ``required_mask`` and ``return_mask``. In addition to + specifying the output buffer in ``vec`` and length in ``vec_len``, the + ``PM_SCAN_OP_WP`` is specified in ``flags`` to perform write protect + on the range as well. + +The ``PAGE_IS_WRITTEN`` flag can be considered as the better and correct +alternative of soft-dirty flag. It doesn't get affected by housekeeping chores +(VMA merging) of the kernel and hence the user can find the true soft-dirty pages +only. This IOCTL adds the atomic way to find which pages have been written and +write protect those pages again. This kind of operation is needed to efficiently +find out which pages have changed in the memory. + +To get information about which pages have been written to or optionally write +protect the pages, following must be performed first in order: + 1. The userfaultfd file descriptor is created with ``userfaultfd`` syscall. + 2. The ``UFFD_FEATURE_WP_UNPOPULATED`` and ``UFFD_FEATURE_WP_ASYNC`` features + are set by ``UFFDIO_API`` IOCTL. + 3. The memory range is registered with ``UFFDIO_REGISTER_MODE_WP`` mode + through ``UFFDIO_REGISTER`` IOCTL. + 4. Then any part of the registered memory or the whole memory region must + be write protected using ``PAGEMAP_SCAN`` IOCTL with flag ``PM_SCAN_OP_WP`` + or the ``UFFDIO_WRITEPROTECT`` IOCTL can be used. Both of these perform the + same operation. The former is better in terms of performance. + 5. Now the ``PAGEMAP_SCAN`` IOCTL can be used to either just find pages which + have been written to and/or optionally write protect the pages as well.
Add pagemap ioctl tests. Add several different types of tests to judge the correction of the interface.
Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com --- Changes in v19: - Incorporated interface changes and update tests
Changes in v18: - Rebase on top of 20230613 (Resolve conflict in Makefile) - Add temp files to .gitignore
Changes in v17: - Rebase on top of next-20230525
Changes in v16: - Added yet more tests which is a randomization test case to catch the corner cases - Add reset by exclusive PM_SCAN_OP_WP as well
Changes in v13: - Update tests and rebase Makefile
Changes in v12: - Updates and add more memory type tests
Changes in v11: - Rebase on top of next-20230216 and update tests
Chages in v7: - Add and update all test cases
Changes in v6: - Rename variables
Changes in v4: - Updated all the tests to conform to new IOCTL
Changes in v3: - Add another test to do sanity of flags
Changes in v2: - Update the tests to use the ioctl interface instead of syscall --- TAP version 13 1..92 ok 1 sanity_tests_sd memory size must be valid ok 2 sanity_tests_sd output buffer must be specified ok 3 sanity_tests_sd output buffer size must be valid ok 4 sanity_tests_sd wrong flag specified ok 5 sanity_tests_sd flag has extra bits specified ok 6 sanity_tests_sd no selection mask is specified ok 7 sanity_tests_sd no return mask is specified ok 8 sanity_tests_sd wrong return mask specified ok 9 sanity_tests_sd mixture of correct and wrong flag ok 10 sanity_tests_sd PAGEMAP_BITS_ALL cannot be specified with PM_SCAN_OP_WP ok 11 sanity_tests_sd Clear area with larger vec size ok 12 sanity_tests_sd Repeated pattern of written and non-written pages ok 13 sanity_tests_sd Repeated pattern of written and non-written pages in parts ok 14 sanity_tests_sd Repeated pattern of written and non-written pages max_pages ok 15 sanity_tests_sd only get 2 written pages and clear them as well ok 16 sanity_tests_sd Two regions ok 17 sanity_tests_sd Smaller max_pages ok 18 Smaller vec 46 50 ok 19 Page testing: all new pages must not be written (dirty) ok 20 Page testing: all pages must be written (dirty) ok 21 Page testing: all pages dirty other than first and the last one ok 22 Page testing: PM_SCAN_OP_WP ok 23 Page testing: only middle page dirty ok 24 Page testing: only two middle pages dirty ok 25 Large Page testing: all new pages must not be written (dirty) ok 26 Large Page testing: all pages must be written (dirty) ok 27 Large Page testing: all pages dirty other than first and the last one ok 28 Large Page testing: PM_SCAN_OP_WP ok 29 Large Page testing: only middle page dirty ok 30 Large Page testing: only two middle pages dirty ok 31 Huge page testing: all new pages must not be written (dirty) ok 32 Huge page testing: all pages must be written (dirty) ok 33 Huge page testing: all pages dirty other than first and the last one ok 34 Huge page testing: PM_SCAN_OP_WP ok 35 Huge page testing: only middle page dirty ok 36 Huge page testing: only two middle pages dirty ok 37 Hugetlb shmem testing: all new pages must not be written (dirty) ok 38 Hugetlb shmem testing: all pages must be written (dirty) ok 39 Hugetlb shmem testing: all pages dirty other than first and the last one ok 40 Hugetlb shmem testing: PM_SCAN_OP_WP ok 41 Hugetlb shmem testing: only middle page dirty ok 42 Hugetlb shmem testing: only two middle pages dirty ok 43 Hugetlb mem testing: all new pages must not be written (dirty) ok 44 Hugetlb mem testing: all pages must be written (dirty) ok 45 Hugetlb mem testing: all pages dirty other than first and the last one ok 46 Hugetlb mem testing: PM_SCAN_OP_WP ok 47 Hugetlb mem testing: only middle page dirty ok 48 Hugetlb mem testing: only two middle pages dirty ok 49 File memory testing: all new pages must not be written (dirty) ok 50 File memory testing: all pages must be written (dirty) ok 51 File memory testing: all pages dirty other than first and the last one ok 52 File memory testing: PM_SCAN_OP_WP ok 53 File memory testing: only middle page dirty ok 54 File memory testing: only two middle pages dirty ok 55 File anonymous memory testing: all new pages must not be written (dirty) ok 56 File anonymous memory testing: all pages must be written (dirty) ok 57 File anonymous memory testing: all pages dirty other than first and the last one ok 58 File anonymous memory testing: PM_SCAN_OP_WP ok 59 File anonymous memory testing: only middle page dirty ok 60 File anonymous memory testing: only two middle pages dirty ok 61 hpage_unit_tests all new huge page must not be written (dirty) ok 62 hpage_unit_tests all the huge page must not be written ok 63 hpage_unit_tests all the huge page must be written and clear ok 64 hpage_unit_tests only middle page written ok 65 hpage_unit_tests clear first half of huge page ok 66 hpage_unit_tests clear first half of huge page with limited buffer ok 67 hpage_unit_tests clear second half huge page ok 68 hpage_unit_tests get half huge page ok 69 hpage_unit_tests get half huge page ok 70 Test test_simple ok 71 mprotect_tests Both pages written ok 72 mprotect_tests Both pages are not written (dirty) ok 73 mprotect_tests Both pages written after remap and mprotect ok 74 mprotect_tests Clear and make the pages written ok 75 transact_test count 192 ok 76 transact_test count 0 ok 77 transact_test Extra pages 0 (0.0%), extra thread faults 0. ok 78 sanity_tests clear op can only be specified with PAGE_IS_WRITTEN ok 79 sanity_tests required_mask specified ok 80 sanity_tests anyof_mask specified ok 81 sanity_tests excluded_mask specified ok 82 sanity_tests required_mask and anyof_mask specified ok 83 sanity_tests Get sd and present pages with anyof_mask ok 84 sanity_tests Get all the pages with required_mask ok 85 sanity_tests Get sd and present pages with required_mask and anyof_mask ok 86 sanity_tests Don't get sd pages ok 87 sanity_tests Don't get present pages ok 88 sanity_tests Find written present pages with return mask ok 89 sanity_tests Memory mapped file ok 90 sanity_tests Read/write to private memory mapped file ok 91 unmapped_region_tests Get status of pages ok 92 userfaultfd_tests all new pages must not be written (dirty) # Totals: pass:92 fail:0 xfail:0 xpass:0 skip:0 error:0 --- tools/testing/selftests/mm/.gitignore | 2 + tools/testing/selftests/mm/Makefile | 3 +- tools/testing/selftests/mm/config | 1 + tools/testing/selftests/mm/pagemap_ioctl.c | 1464 ++++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 5 files changed, 1473 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/mm/pagemap_ioctl.c mode change 100644 => 100755 tools/testing/selftests/mm/run_vmtests.sh
diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore index cdc9ce4426b9..cc920c79ff1c 100644 --- a/tools/testing/selftests/mm/.gitignore +++ b/tools/testing/selftests/mm/.gitignore @@ -18,6 +18,8 @@ mremap_dontunmap mremap_test on-fault-limit transhuge-stress +pagemap_ioctl +*.tmp* protection_keys protection_keys_32 protection_keys_64 diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile index b7fce9073279..1dac4e8477e4 100644 --- a/tools/testing/selftests/mm/Makefile +++ b/tools/testing/selftests/mm/Makefile @@ -33,7 +33,7 @@ endif MAKEFLAGS += --no-builtin-rules
CFLAGS = -Wall -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) -LDLIBS = -lrt -lpthread +LDLIBS = -lrt -lpthread -lm
TEST_GEN_PROGS = cow TEST_GEN_PROGS += compaction_test @@ -60,6 +60,7 @@ TEST_GEN_PROGS += mrelease_test TEST_GEN_PROGS += mremap_dontunmap TEST_GEN_PROGS += mremap_test TEST_GEN_PROGS += on-fault-limit +TEST_GEN_PROGS += pagemap_ioctl TEST_GEN_PROGS += thuge-gen TEST_GEN_PROGS += transhuge-stress TEST_GEN_PROGS += uffd-stress diff --git a/tools/testing/selftests/mm/config b/tools/testing/selftests/mm/config index be087c4bc396..4309916f629e 100644 --- a/tools/testing/selftests/mm/config +++ b/tools/testing/selftests/mm/config @@ -1,5 +1,6 @@ CONFIG_SYSVIPC=y CONFIG_USERFAULTFD=y +CONFIG_PTE_MARKER_UFFD_WP=y CONFIG_TEST_VMALLOC=m CONFIG_DEVICE_PRIVATE=y CONFIG_TEST_HMM=m diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c new file mode 100644 index 000000000000..a2d2d9086b83 --- /dev/null +++ b/tools/testing/selftests/mm/pagemap_ioctl.c @@ -0,0 +1,1464 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include <stdio.h> +#include <fcntl.h> +#include <string.h> +#include <sys/mman.h> +#include <errno.h> +#include <malloc.h> +#include "vm_util.h" +#include "../kselftest.h" +#include <linux/types.h> +#include <linux/memfd.h> +#include <linux/userfaultfd.h> +#include <linux/fs.h> +#include <sys/ioctl.h> +#include <sys/stat.h> +#include <math.h> +#include <asm/unistd.h> +#include <pthread.h> +#include <sys/resource.h> +#include <assert.h> +#include <sys/ipc.h> +#include <sys/shm.h> + +#define PAGEMAP_BITS_ALL (PAGE_IS_WRITTEN | PAGE_IS_FILE | \ + PAGE_IS_PRESENT | PAGE_IS_SWAPPED) +#define PAGEMAP_NON_WRITTEN_BITS (PAGE_IS_FILE | PAGE_IS_PRESENT | \ + PAGE_IS_SWAPPED) + +#define TEST_ITERATIONS 100 +#define PAGEMAP "/proc/self/pagemap" +int pagemap_fd; +int uffd; +int page_size; +int hpage_size; + +static long pagemap_ioctl(void *start, int len, void *vec, int vec_len, int flag, + int max_pages, long required_mask, long anyof_mask, long excluded_mask, + long return_mask) +{ + struct pm_scan_arg arg; + + arg.start = (uintptr_t)start; + arg.end = (uintptr_t)(start + len); + arg.vec = (uintptr_t)vec; + arg.vec_len = vec_len; + arg.flags = flag; + arg.size = sizeof(struct pm_scan_arg); + arg.max_pages = max_pages; + arg.required_mask = required_mask; + arg.anyof_mask = anyof_mask; + arg.excluded_mask = excluded_mask; + arg.return_mask = return_mask; + + return ioctl(pagemap_fd, PAGEMAP_SCAN, &arg); +} + +int init_uffd(void) +{ + struct uffdio_api uffdio_api; + + uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK); + if (uffd == -1) + ksft_exit_fail_msg("uffd syscall failed\n"); + + uffdio_api.api = UFFD_API; + uffdio_api.features = UFFD_FEATURE_WP_UNPOPULATED | UFFD_FEATURE_WP_ASYNC | + UFFD_FEATURE_WP_HUGETLBFS_SHMEM; + if (ioctl(uffd, UFFDIO_API, &uffdio_api)) + ksft_exit_fail_msg("UFFDIO_API\n"); + + if (!(uffdio_api.api & UFFDIO_REGISTER_MODE_WP) || + !(uffdio_api.features & UFFD_FEATURE_WP_UNPOPULATED) || + !(uffdio_api.features & UFFD_FEATURE_WP_ASYNC) || + !(uffdio_api.features & UFFD_FEATURE_WP_HUGETLBFS_SHMEM)) + ksft_exit_fail_msg("UFFDIO_API error %llu\n", uffdio_api.api); + + return 0; +} + +int wp_init(void *lpBaseAddress, int dwRegionSize) +{ + struct uffdio_register uffdio_register; + struct uffdio_writeprotect wp; + + uffdio_register.range.start = (unsigned long)lpBaseAddress; + uffdio_register.range.len = dwRegionSize; + uffdio_register.mode = UFFDIO_REGISTER_MODE_WP; + if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register)) + ksft_exit_fail_msg("ioctl(UFFDIO_REGISTER) %d %s\n", errno, strerror(errno)); + + if (!(uffdio_register.ioctls & UFFDIO_WRITEPROTECT)) + ksft_exit_fail_msg("ioctl set is incorrect\n"); + + wp.range.start = (unsigned long)lpBaseAddress; + wp.range.len = dwRegionSize; + wp.mode = UFFDIO_WRITEPROTECT_MODE_WP; + + if (ioctl(uffd, UFFDIO_WRITEPROTECT, &wp)) + ksft_exit_fail_msg("ioctl(UFFDIO_WRITEPROTECT)\n"); + + return 0; +} + +int wp_free(void *lpBaseAddress, int dwRegionSize) +{ + struct uffdio_register uffdio_register; + + uffdio_register.range.start = (unsigned long)lpBaseAddress; + uffdio_register.range.len = dwRegionSize; + uffdio_register.mode = UFFDIO_REGISTER_MODE_WP; + if (ioctl(uffd, UFFDIO_UNREGISTER, &uffdio_register.range)) + ksft_exit_fail_msg("ioctl unregister failure\n"); + return 0; +} + +int wp_addr_range(void *lpBaseAddress, int dwRegionSize) +{ + struct uffdio_writeprotect wp; + + if (rand() % 2) { + wp.range.start = (unsigned long)lpBaseAddress; + wp.range.len = dwRegionSize; + wp.mode = UFFDIO_WRITEPROTECT_MODE_WP; + + if (ioctl(uffd, UFFDIO_WRITEPROTECT, &wp)) + ksft_exit_fail_msg("ioctl(UFFDIO_WRITEPROTECT)\n"); + } else { + if (pagemap_ioctl(lpBaseAddress, dwRegionSize, NULL, 0, PM_SCAN_OP_WP, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN) < 0) + ksft_exit_fail_msg("error %d %d %s\n", 1, errno, strerror(errno)); + } + + return 0; +} + +void *gethugetlb_mem(int size, int *shmid) +{ + char *mem; + + if (shmid) { + *shmid = shmget(2, size, SHM_HUGETLB | IPC_CREAT | SHM_R | SHM_W); + if (*shmid < 0) + return NULL; + + mem = shmat(*shmid, 0, 0); + if (mem == (char *)-1) { + shmctl(*shmid, IPC_RMID, NULL); + ksft_exit_fail_msg("Shared memory attach failure\n"); + } + } else { + mem = mmap(NULL, size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_HUGETLB | MAP_PRIVATE, -1, 0); + if (mem == MAP_FAILED) + return NULL; + } + + return mem; +} + +int userfaultfd_tests(void) +{ + int mem_size, vec_size, written, num_pages = 16; + char *mem, *vec; + + mem_size = num_pages * page_size; + mem = mmap(NULL, mem_size, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + + wp_init(mem, mem_size); + + /* Change protection of pages differently */ + mprotect(mem, mem_size/8, PROT_READ|PROT_WRITE); + mprotect(mem + 1 * mem_size/8, mem_size/8, PROT_READ); + mprotect(mem + 2 * mem_size/8, mem_size/8, PROT_READ|PROT_WRITE); + mprotect(mem + 3 * mem_size/8, mem_size/8, PROT_READ); + mprotect(mem + 4 * mem_size/8, mem_size/8, PROT_READ|PROT_WRITE); + mprotect(mem + 5 * mem_size/8, mem_size/8, PROT_NONE); + mprotect(mem + 6 * mem_size/8, mem_size/8, PROT_READ|PROT_WRITE); + mprotect(mem + 7 * mem_size/8, mem_size/8, PROT_READ); + + wp_addr_range(mem + (mem_size/16), mem_size - 2 * (mem_size/8)); + wp_addr_range(mem, mem_size); + + vec_size = mem_size/page_size; + vec = malloc(sizeof(struct page_region) * vec_size); + + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + vec_size - 2, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written == 0, "%s all new pages must not be written (dirty)\n", __func__); + + wp_free(mem, mem_size); + munmap(mem, mem_size); + free(vec); + return 0; +} + +int get_reads(struct page_region *vec, int vec_size) +{ + int i, sum = 0; + + for (i = 0; i < vec_size; i++) + sum += vec[i].len; + + return sum; +} + +int sanity_tests_sd(void) +{ + int mem_size, vec_size, ret, ret2, ret3, i, num_pages = 10, total_pages = 0; + int total_writes, total_reads, reads, count; + struct page_region *vec, *vec2; + char *mem, *m[2]; + + vec_size = 100; + mem_size = num_pages * page_size; + + vec = malloc(sizeof(struct page_region) * vec_size); + if (!vec) + ksft_exit_fail_msg("error nomem\n"); + + vec2 = malloc(sizeof(struct page_region) * vec_size); + if (!vec2) + ksft_exit_fail_msg("error nomem\n"); + + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + /* 1. wrong operation */ + ksft_test_result(pagemap_ioctl(mem, 0, vec, vec_size, PM_SCAN_OP_GET, + 0, PAGEMAP_BITS_ALL, 0, 0, PAGEMAP_BITS_ALL) < 0, + "%s memory size must be valid\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, NULL, vec_size, PM_SCAN_OP_GET, + 0, PAGEMAP_BITS_ALL, 0, 0, PAGEMAP_BITS_ALL) < 0, + "%s output buffer must be specified\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, 0, PM_SCAN_OP_GET, + 0, PAGEMAP_BITS_ALL, 0, 0, PAGEMAP_BITS_ALL) < 0, + "%s output buffer size must be valid\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, -1, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN) < 0, + "%s wrong flag specified\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, + PM_SCAN_OP_GET | PM_SCAN_OP_WP | 0xFF, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN) < 0, + "%s flag has extra bits specified\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, + 0, 0, 0, 0, PAGE_IS_WRITTEN) < 0, + "%s no selection mask is specified\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, + 0, PAGE_IS_WRITTEN, PAGE_IS_WRITTEN, 0, 0) < 0, + "%s no return mask is specified\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, + 0, PAGE_IS_WRITTEN, 0, 0, 0x1000) < 0, + "%s wrong return mask specified\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 0, 0xFFF, PAGE_IS_WRITTEN, 0, PAGE_IS_WRITTEN) < 0, + "%s mixture of correct and wrong flag\n", __func__); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 0, 0, 0, PAGEMAP_BITS_ALL, PAGE_IS_WRITTEN) >= 0, + "%s PAGEMAP_BITS_ALL can be specified with PM_SCAN_OP_WP\n", __func__); + + /* 2. Clear area with larger vec size */ + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + ksft_test_result(ret >= 0, "%s Clear area with larger vec size\n", __func__); + + /* 3. Repeated pattern of written and non-written pages */ + for (i = 0; i < mem_size; i += 2 * page_size) + mem[i]++; + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, 0, + 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == mem_size/(page_size * 2), + "%s Repeated pattern of written and non-written pages\n", __func__); + + /* 4. Repeated pattern of written and non-written pages in parts */ + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + num_pages/2 - 2, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ret2 = pagemap_ioctl(mem, mem_size, vec, 2, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, 0, 0, + PAGE_IS_WRITTEN); + if (ret2 < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret2, errno, strerror(errno)); + + ret3 = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret3 < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret3, errno, strerror(errno)); + + ksft_test_result((ret + ret3) == num_pages/2 && ret2 == 2, + "%s Repeated pattern of written and non-written pages in parts\n", + __func__); + + /* 5. Repeated pattern of written and non-written pages max_pages */ + for (i = 0; i < mem_size; i += 2 * page_size) + mem[i]++; + mem[(mem_size/page_size - 1) * page_size]++; + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + num_pages/2, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ret2 = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret2 < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret2, errno, strerror(errno)); + + ksft_test_result(ret == num_pages/2 && ret2 == 1, + "%s Repeated pattern of written and non-written pages max_pages\n", + __func__); + + /* 6. only get 2 dirty pages and clear them as well */ + vec_size = mem_size/page_size; + memset(mem, -1, mem_size); + + /* get and clear second and third pages */ + ret = pagemap_ioctl(mem + page_size, 2 * page_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 2, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ret2 = pagemap_ioctl(mem, mem_size, vec2, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret2 < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret2, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].len == 2 && + vec[0].start == (uintptr_t)(mem + page_size) && + ret2 == 2 && vec2[0].len == 1 && vec2[0].start == (uintptr_t)mem && + vec2[1].len == vec_size - 3 && + vec2[1].start == (uintptr_t)(mem + 3 * page_size), + "%s only get 2 written pages and clear them as well\n", __func__); + + wp_free(mem, mem_size); + munmap(mem, mem_size); + + /* 7. Two regions */ + m[0] = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (m[0] == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + m[1] = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (m[1] == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + + wp_init(m[0], mem_size); + wp_init(m[1], mem_size); + wp_addr_range(m[0], mem_size); + wp_addr_range(m[1], mem_size); + + memset(m[0], 'a', mem_size); + memset(m[1], 'b', mem_size); + + wp_addr_range(m[0], mem_size); + + ret = pagemap_ioctl(m[1], mem_size, vec, 1, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, 0, 0, + PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].len == mem_size/page_size, + "%s Two regions\n", __func__); + + wp_free(m[0], mem_size); + wp_free(m[1], mem_size); + munmap(m[0], mem_size); + munmap(m[1], mem_size); + + free(vec); + free(vec2); + + /* 8. Smaller vec */ + mem_size = 1050 * page_size; + vec_size = mem_size/(page_size*2); + + vec = malloc(sizeof(struct page_region) * vec_size); + if (!vec) + ksft_exit_fail_msg("error nomem\n"); + + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + for (i = 0; i < mem_size/page_size; i += 2) + mem[i * page_size]++; + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + mem_size/(page_size*5), PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + total_pages += ret; + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + mem_size/(page_size*5), PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + total_pages += ret; + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + mem_size/(page_size*5), PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + total_pages += ret; + + ksft_test_result(total_pages == mem_size/(page_size*2), "%s Smaller max_pages\n", __func__); + + free(vec); + wp_free(mem, mem_size); + munmap(mem, mem_size); + total_pages = 0; + + /* 9. Smaller vec */ + mem_size = 10000 * page_size; + vec_size = 50; + + vec = malloc(sizeof(struct page_region) * vec_size); + if (!vec) + ksft_exit_fail_msg("error nomem\n"); + + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + for (count = 0; count < TEST_ITERATIONS; count++) { + total_writes = total_reads = 0; + + for (i = 0; i < mem_size; i += page_size) { + if (rand() % 2) { + mem[i]++; + total_writes++; + } + } + + while (total_reads < total_writes) { + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, + PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + if (ret > vec_size) + break; + + reads = get_reads(vec, ret); + total_reads += reads; + } + + if (total_reads != total_writes) + break; + } + + ksft_test_result(count == TEST_ITERATIONS, "Smaller vec %d %d\n", ret, vec_size); + + free(vec); + wp_free(mem, mem_size); + munmap(mem, mem_size); + + return 0; +} + +int base_tests(char *prefix, char *mem, int mem_size, int skip) +{ + int vec_size, written; + struct page_region *vec, *vec2; + + if (skip) { + ksft_test_result_skip("%s all new pages must not be written (dirty)\n", prefix); + ksft_test_result_skip("%s all pages must be written (dirty)\n", prefix); + ksft_test_result_skip("%s all pages dirty other than first and the last one\n", + prefix); + ksft_test_result_skip("%s PM_SCAN_OP_WP\n", prefix); + ksft_test_result_skip("%s only middle page dirty\n", prefix); + ksft_test_result_skip("%s only two middle pages dirty\n", prefix); + return 0; + } + + vec_size = mem_size/page_size; + vec = malloc(sizeof(struct page_region) * vec_size); + vec2 = malloc(sizeof(struct page_region) * vec_size); + + /* 1. all new pages must be not be written (dirty) */ + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, vec_size - 2, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written == 0, "%s all new pages must not be written (dirty)\n", prefix); + + /* 2. all pages must be written */ + memset(mem, -1, mem_size); + + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, 0, 0, + PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written == 1 && vec[0].len == mem_size/page_size, + "%s all pages must be written (dirty)\n", prefix); + + /* 3. all pages dirty other than first and the last one */ + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + memset(mem + page_size, 0, mem_size - (2 * page_size)); + + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written == 1 && vec[0].len >= vec_size - 2 && vec[0].len <= vec_size, + "%s all pages dirty other than first and the last one\n", prefix); + + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written == 0, + "%s PM_SCAN_OP_WP\n", prefix); + + /* 4. only middle page dirty */ + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + mem[vec_size/2 * page_size]++; + + written = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, + 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written == 1 && vec[0].len >= 1, + "%s only middle page dirty\n", prefix); + + /* 5. only two middle pages dirty and walk over only middle pages */ + written = pagemap_ioctl(mem, mem_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + mem[vec_size/2 * page_size]++; + mem[(vec_size/2 + 1) * page_size]++; + + written = pagemap_ioctl(&mem[vec_size/2 * page_size], 2 * page_size, vec, 1, PM_SCAN_OP_GET, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written == 1 && vec[0].start == (uintptr_t)(&mem[vec_size/2 * page_size]) + && vec[0].len == 2, + "%s only two middle pages dirty\n", prefix); + + free(vec); + free(vec2); + return 0; +} + +void *gethugepage(int map_size) +{ + int ret; + char *map; + + map = memalign(hpage_size, map_size); + if (!map) + ksft_exit_fail_msg("memalign failed %d %s\n", errno, strerror(errno)); + + ret = madvise(map, map_size, MADV_HUGEPAGE); + if (ret) + return NULL; + + memset(map, 0, map_size); + + return map; +} + +int hpage_unit_tests(void) +{ + char *map; + int ret, ret2; + size_t num_pages = 10; + int map_size = hpage_size * num_pages; + int vec_size = map_size/page_size; + struct page_region *vec, *vec2; + + vec = malloc(sizeof(struct page_region) * vec_size); + vec2 = malloc(sizeof(struct page_region) * vec_size); + if (!vec || !vec2) + ksft_exit_fail_msg("malloc failed\n"); + + map = gethugepage(map_size); + if (map) { + wp_init(map, map_size); + wp_addr_range(map, map_size); + + /* 1. all new huge page must not be written (dirty) */ + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 0, "%s all new huge page must not be written (dirty)\n", + __func__); + + /* 2. all the huge page must not be written */ + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 0, "%s all the huge page must not be written\n", __func__); + + /* 3. all the huge page must be written and clear dirty as well */ + memset(map, -1, map_size); + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 0, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].start == (uintptr_t)map && + vec[0].len == vec_size && vec[0].flags == PAGE_IS_WRITTEN, + "%s all the huge page must be written and clear\n", __func__); + + /* 4. only middle page written */ + wp_free(map, map_size); + free(map); + map = gethugepage(map_size); + wp_init(map, map_size); + wp_addr_range(map, map_size); + map[vec_size/2 * page_size]++; + + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].len > 0, + "%s only middle page written\n", __func__); + + wp_free(map, map_size); + free(map); + } else { + ksft_test_result_skip("%s all new huge page must be written\n", __func__); + ksft_test_result_skip("%s all the huge page must not be written\n", __func__); + ksft_test_result_skip("%s all the huge page must be written and clear\n", __func__); + ksft_test_result_skip("%s only middle page written\n", __func__); + } + + /* 5. clear first half of huge page */ + map = gethugepage(map_size); + if (map) { + wp_init(map, map_size); + wp_addr_range(map, map_size); + + memset(map, 0, map_size); + + wp_addr_range(map, map_size/2); + + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].len == vec_size/2 && + vec[0].start == (uintptr_t)(map + map_size/2), + "%s clear first half of huge page\n", __func__); + wp_free(map, map_size); + free(map); + } else { + ksft_test_result_skip("%s clear first half of huge page\n", __func__); + } + + /* 6. clear first half of huge page with limited buffer */ + map = gethugepage(map_size); + if (map) { + wp_init(map, map_size); + wp_addr_range(map, map_size); + + memset(map, 0, map_size); + + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + vec_size/2, PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].len == vec_size/2 && + vec[0].start == (uintptr_t)(map + map_size/2), + "%s clear first half of huge page with limited buffer\n", + __func__); + wp_free(map, map_size); + free(map); + } else { + ksft_test_result_skip("%s clear first half of huge page with limited buffer\n", + __func__); + } + + /* 7. clear second half of huge page */ + map = gethugepage(map_size); + if (map) { + wp_init(map, map_size); + wp_addr_range(map, map_size); + + memset(map, -1, map_size); + + ret = pagemap_ioctl(map + map_size/2, map_size/2, vec, vec_size, + PM_SCAN_OP_GET | PM_SCAN_OP_WP, vec_size/2, PAGE_IS_WRITTEN, 0, + 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ret = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].len == vec_size/2, + "%s clear second half huge page\n", __func__); + wp_free(map, map_size); + free(map); + } else { + ksft_test_result_skip("%s clear second half huge page\n", __func__); + } + + /* 8. get half huge page */ + map = gethugepage(map_size); + if (map) { + wp_init(map, map_size); + wp_addr_range(map, map_size); + + memset(map, -1, map_size); + usleep(100); + + ret = pagemap_ioctl(map, map_size, vec, 1, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + hpage_size/(2*page_size), PAGE_IS_WRITTEN, 0, 0, + PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec[0].len == hpage_size/(2*page_size), + "%s get half huge page\n", __func__); + + ret2 = pagemap_ioctl(map, map_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN); + if (ret2 < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret2, errno, strerror(errno)); + + ksft_test_result(ret2 == 1 && vec[0].len == (map_size - hpage_size/2)/page_size, + "%s get half huge page\n", __func__); + + wp_free(map, map_size); + free(map); + } else { + ksft_test_result_skip("%s get half huge page\n", __func__); + ksft_test_result_skip("%s get half huge page\n", __func__); + } + + free(vec); + free(vec2); + return 0; +} + +int unmapped_region_tests(void) +{ + void *start = (void *)0x10000000; + int written, len = 0x00040000; + int vec_size = len / page_size; + struct page_region *vec = malloc(sizeof(struct page_region) * vec_size); + + /* 1. Get written pages */ + written = pagemap_ioctl(start, len, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGEMAP_NON_WRITTEN_BITS, 0, 0, PAGEMAP_NON_WRITTEN_BITS); + if (written < 0) + ksft_exit_fail_msg("error %d %d %s\n", written, errno, strerror(errno)); + + ksft_test_result(written >= 0, "%s Get status of pages\n", __func__); + + free(vec); + return 0; +} + +static void test_simple(void) +{ + int i; + char *map; + struct page_region vec; + + map = aligned_alloc(page_size, page_size); + if (!map) + ksft_exit_fail_msg("aligned_alloc failed\n"); + + wp_init(map, page_size); + wp_addr_range(map, page_size); + + for (i = 0 ; i < TEST_ITERATIONS; i++) { + if (pagemap_ioctl(map, page_size, &vec, 1, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN) == 1) { + ksft_print_msg("written bit was 1, but should be 0 (i=%d)\n", i); + break; + } + + wp_addr_range(map, page_size); + /* Write something to the page to get the written bit enabled on the page */ + map[0]++; + + if (pagemap_ioctl(map, page_size, &vec, 1, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN) == 0) { + ksft_print_msg("written bit was 0, but should be 1 (i=%d)\n", i); + break; + } + + wp_addr_range(map, page_size); + } + wp_free(map, page_size); + free(map); + + ksft_test_result(i == TEST_ITERATIONS, "Test %s\n", __func__); +} + +int sanity_tests(void) +{ + int mem_size, vec_size, ret, fd, i, buf_size; + struct page_region *vec; + char *mem, *fmem; + struct stat sbuf; + char *tmp_buf; + + /* 1. wrong operation */ + mem_size = 10 * page_size; + vec_size = mem_size / page_size; + + vec = malloc(sizeof(struct page_region) * vec_size); + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED || vec == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, + 0, PAGEMAP_BITS_ALL, 0, 0, PAGEMAP_BITS_ALL) >= 0, + "%s WP op can be specified with !PAGE_IS_WRITTEN\n", __func__); + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGEMAP_BITS_ALL, 0, 0, PAGEMAP_BITS_ALL) >= 0, + "%s required_mask specified\n", __func__); + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + 0, PAGEMAP_BITS_ALL, 0, PAGEMAP_BITS_ALL) >= 0, + "%s anyof_mask specified\n", __func__); + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + 0, 0, PAGEMAP_BITS_ALL, PAGEMAP_BITS_ALL) >= 0, + "%s excluded_mask specified\n", __func__); + ksft_test_result(pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGEMAP_BITS_ALL, PAGEMAP_BITS_ALL, 0, + PAGEMAP_BITS_ALL) >= 0, + "%s required_mask and anyof_mask specified\n", __func__); + wp_free(mem, mem_size); + munmap(mem, mem_size); + + /* 2. Get sd and present pages with anyof_mask */ + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + memset(mem, 0, mem_size); + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + 0, PAGEMAP_BITS_ALL, 0, PAGEMAP_BITS_ALL); + ksft_test_result(ret >= 0 && vec[0].start == (uintptr_t)mem && vec[0].len == vec_size && + vec[0].flags == (PAGE_IS_WRITTEN | PAGE_IS_PRESENT), + "%s Get sd and present pages with anyof_mask\n", __func__); + + /* 3. Get sd and present pages with required_mask */ + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGEMAP_BITS_ALL, 0, 0, PAGEMAP_BITS_ALL); + ksft_test_result(ret >= 0 && vec[0].start == (uintptr_t)mem && vec[0].len == vec_size && + vec[0].flags == (PAGE_IS_WRITTEN | PAGE_IS_PRESENT), + "%s Get all the pages with required_mask\n", __func__); + + /* 4. Get sd and present pages with required_mask and anyof_mask */ + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, PAGE_IS_PRESENT, 0, PAGEMAP_BITS_ALL); + ksft_test_result(ret >= 0 && vec[0].start == (uintptr_t)mem && vec[0].len == vec_size && + vec[0].flags == (PAGE_IS_WRITTEN | PAGE_IS_PRESENT), + "%s Get sd and present pages with required_mask and anyof_mask\n", + __func__); + + /* 5. Don't get sd pages */ + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + 0, 0, PAGE_IS_WRITTEN, PAGEMAP_BITS_ALL); + ksft_test_result(ret == 0, "%s Don't get sd pages\n", __func__); + + /* 6. Don't get present pages */ + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET, 0, + 0, 0, PAGE_IS_PRESENT, PAGEMAP_BITS_ALL); + ksft_test_result(ret == 0, "%s Don't get present pages\n", __func__); + + wp_free(mem, mem_size); + munmap(mem, mem_size); + + /* 8. Find written present pages with return mask */ + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + memset(mem, 0, mem_size); + + ret = pagemap_ioctl(mem, mem_size, vec, vec_size, PM_SCAN_OP_GET | PM_SCAN_OP_WP, 0, + 0, PAGEMAP_BITS_ALL, 0, PAGE_IS_WRITTEN); + ksft_test_result(ret >= 0 && vec[0].start == (uintptr_t)mem && vec[0].len == vec_size && + vec[0].flags == PAGE_IS_WRITTEN, + "%s Find written present pages with return mask\n", __func__); + wp_free(mem, mem_size); + munmap(mem, mem_size); + + /* 9. Memory mapped file */ + fd = open(__FILE__, O_RDONLY); + if (fd < 0) + ksft_exit_fail_msg("%s Memory mapped file\n"); + + ret = stat(__FILE__, &sbuf); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + fmem = mmap(NULL, sbuf.st_size, PROT_READ, MAP_PRIVATE, fd, 0); + if (fmem == MAP_FAILED) + ksft_exit_fail_msg("error nomem %ld %s\n", errno, strerror(errno)); + + tmp_buf = malloc(sbuf.st_size); + memcpy(tmp_buf, fmem, sbuf.st_size); + + ret = pagemap_ioctl(fmem, sbuf.st_size, vec, vec_size, PM_SCAN_OP_GET, 0, + 0, PAGEMAP_NON_WRITTEN_BITS, 0, PAGEMAP_NON_WRITTEN_BITS); + + ksft_test_result(ret >= 0 && vec[0].start == (uintptr_t)fmem && + vec[0].len == ceilf((float)sbuf.st_size/page_size) && + (vec[0].flags & PAGE_IS_FILE), + "%s Memory mapped file\n", __func__); + + munmap(fmem, sbuf.st_size); + close(fd); + + /* 10. Create and read/write to a memory mapped file */ + buf_size = page_size * 10; + + fd = open(__FILE__".tmp2", O_RDWR | O_CREAT, 0666); + if (fd < 0) + ksft_exit_fail_msg("Read/write to memory: %s\n", + strerror(errno)); + + for (i = 0; i < buf_size; i++) + if (write(fd, "c", 1) < 0) + ksft_exit_fail_msg("Create and read/write to a memory mapped file\n"); + + fmem = mmap(NULL, buf_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0); + if (fmem == MAP_FAILED) + ksft_exit_fail_msg("error nomem %ld %s\n", errno, strerror(errno)); + + wp_init(fmem, buf_size); + wp_addr_range(fmem, buf_size); + + for (i = 0; i < buf_size; i++) + fmem[i] = 'z'; + + msync(fmem, buf_size, MS_SYNC); + + ret = pagemap_ioctl(fmem, buf_size, vec, vec_size, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, PAGE_IS_PRESENT | PAGE_IS_SWAPPED | PAGE_IS_FILE, 0, + PAGEMAP_BITS_ALL); + + ksft_test_result(ret >= 0 && vec[0].start == (uintptr_t)fmem && + vec[0].len == (buf_size/page_size) && + (vec[0].flags & PAGE_IS_WRITTEN), + "%s Read/write to memory\n", __func__); + + wp_free(fmem, buf_size); + munmap(fmem, buf_size); + close(fd); + + free(vec); + return 0; +} + +int mprotect_tests(void) +{ + int ret; + char *mem, *mem2; + struct page_region vec; + int pagemap_fd = open("/proc/self/pagemap", O_RDONLY); + + if (pagemap_fd < 0) { + fprintf(stderr, "open() failed\n"); + exit(1); + } + + /* 1. Map two pages */ + mem = mmap(0, 2 * page_size, PROT_READ|PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + wp_init(mem, 2 * page_size); + wp_addr_range(mem, 2 * page_size); + + /* Populate both pages. */ + memset(mem, 1, 2 * page_size); + + ret = pagemap_ioctl(mem, 2 * page_size, &vec, 1, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, + 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec.len == 2, "%s Both pages written\n", __func__); + + /* 2. Start tracking */ + wp_addr_range(mem, 2 * page_size); + + ksft_test_result(pagemap_ioctl(mem, 2 * page_size, &vec, 1, PM_SCAN_OP_GET, 0, + PAGE_IS_WRITTEN, 0, 0, PAGE_IS_WRITTEN) == 0, + "%s Both pages are not written (dirty)\n", __func__); + + /* 3. Remap the second page */ + mem2 = mmap(mem + page_size, page_size, PROT_READ|PROT_WRITE, + MAP_PRIVATE|MAP_ANON|MAP_FIXED, -1, 0); + if (mem2 == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + wp_init(mem2, page_size); + wp_addr_range(mem2, page_size); + + /* Protect + unprotect. */ + mprotect(mem, page_size, PROT_NONE); + mprotect(mem, 2 * page_size, PROT_READ); + mprotect(mem, 2 * page_size, PROT_READ|PROT_WRITE); + + /* Modify both pages. */ + memset(mem, 2, 2 * page_size); + + /* Protect + unprotect. */ + mprotect(mem, page_size, PROT_NONE); + mprotect(mem, page_size, PROT_READ); + mprotect(mem, page_size, PROT_READ|PROT_WRITE); + + ret = pagemap_ioctl(mem, 2 * page_size, &vec, 1, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, + 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec.len == 2, + "%s Both pages written after remap and mprotect\n", __func__); + + /* 4. Clear and make the pages written */ + wp_addr_range(mem, 2 * page_size); + + memset(mem, 'A', 2 * page_size); + + ret = pagemap_ioctl(mem, 2 * page_size, &vec, 1, PM_SCAN_OP_GET, 0, PAGE_IS_WRITTEN, + 0, 0, PAGE_IS_WRITTEN); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + ksft_test_result(ret == 1 && vec.len == 2, + "%s Clear and make the pages written\n", __func__); + + wp_free(mem, 2 * page_size); + munmap(mem, 2 * page_size); + return 0; +} + +/* transact test */ +static const unsigned int nthreads = 6, pages_per_thread = 32, access_per_thread = 8; +static pthread_barrier_t start_barrier, end_barrier; +static unsigned int extra_thread_faults; +static unsigned int iter_count = 1000; +static volatile int finish; + +static ssize_t get_dirty_pages_reset(char *mem, unsigned int count, + int reset, int page_size) +{ + struct pm_scan_arg arg = {0}; + struct page_region rgns[256]; + int i, j, cnt, ret; + + arg.size = sizeof(struct pm_scan_arg); + arg.start = (uintptr_t)mem; + arg.max_pages = count; + arg.end = (uintptr_t)(mem + count * page_size); + arg.vec = (uintptr_t)rgns; + arg.vec_len = sizeof(rgns) / sizeof(*rgns); + arg.flags = PM_SCAN_OP_GET; + if (reset) + arg.flags |= PM_SCAN_OP_WP; + arg.required_mask = PAGE_IS_WRITTEN; + arg.return_mask = PAGE_IS_WRITTEN; + + ret = ioctl(pagemap_fd, PAGEMAP_SCAN, &arg); + if (ret < 0) + ksft_exit_fail_msg("ioctl failed\n"); + + cnt = 0; + for (i = 0; i < ret; ++i) { + if (rgns[i].flags != PAGE_IS_WRITTEN) + ksft_exit_fail_msg("wrong flags\n"); + + for (j = 0; j < rgns[i].len; ++j) + cnt++; + } + + return cnt; +} + +void *thread_proc(void *mem) +{ + int *m = mem; + long curr_faults, faults; + struct rusage r; + unsigned int i; + int ret; + + if (getrusage(RUSAGE_THREAD, &r)) + ksft_exit_fail_msg("getrusage\n"); + + curr_faults = r.ru_minflt; + + while (!finish) { + ret = pthread_barrier_wait(&start_barrier); + if (ret && ret != PTHREAD_BARRIER_SERIAL_THREAD) + ksft_exit_fail_msg("pthread_barrier_wait\n"); + + for (i = 0; i < access_per_thread; ++i) + __atomic_add_fetch(m + i * (0x1000 / sizeof(*m)), 1, __ATOMIC_SEQ_CST); + + ret = pthread_barrier_wait(&end_barrier); + if (ret && ret != PTHREAD_BARRIER_SERIAL_THREAD) + ksft_exit_fail_msg("pthread_barrier_wait\n"); + + if (getrusage(RUSAGE_THREAD, &r)) + ksft_exit_fail_msg("getrusage\n"); + + faults = r.ru_minflt - curr_faults; + if (faults < access_per_thread) + ksft_exit_fail_msg("faults < access_per_thread"); + + __atomic_add_fetch(&extra_thread_faults, faults - access_per_thread, + __ATOMIC_SEQ_CST); + curr_faults = r.ru_minflt; + } + + return NULL; +} + +static void transact_test(int page_size) +{ + unsigned int i, count, extra_pages; + pthread_t th; + char *mem; + int ret, c; + + if (pthread_barrier_init(&start_barrier, NULL, nthreads + 1)) + ksft_exit_fail_msg("pthread_barrier_init\n"); + + if (pthread_barrier_init(&end_barrier, NULL, nthreads + 1)) + ksft_exit_fail_msg("pthread_barrier_init\n"); + + mem = mmap(NULL, 0x1000 * nthreads * pages_per_thread, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("Error mmap %s.\n", strerror(errno)); + + wp_init(mem, 0x1000 * nthreads * pages_per_thread); + wp_addr_range(mem, 0x1000 * nthreads * pages_per_thread); + + memset(mem, 0, 0x1000 * nthreads * pages_per_thread); + + count = get_dirty_pages_reset(mem, nthreads * pages_per_thread, 1, page_size); + ksft_test_result(count > 0, "%s count %d\n", __func__, count); + count = get_dirty_pages_reset(mem, nthreads * pages_per_thread, 1, page_size); + ksft_test_result(count == 0, "%s count %d\n", __func__, count); + + finish = 0; + for (i = 0; i < nthreads; ++i) + pthread_create(&th, NULL, thread_proc, mem + 0x1000 * i * pages_per_thread); + + extra_pages = 0; + for (i = 0; i < iter_count; ++i) { + count = 0; + + ret = pthread_barrier_wait(&start_barrier); + if (ret && ret != PTHREAD_BARRIER_SERIAL_THREAD) + ksft_exit_fail_msg("pthread_barrier_wait\n"); + + count = get_dirty_pages_reset(mem, nthreads * pages_per_thread, 1, + page_size); + + ret = pthread_barrier_wait(&end_barrier); + if (ret && ret != PTHREAD_BARRIER_SERIAL_THREAD) + ksft_exit_fail_msg("pthread_barrier_wait\n"); + + if (count > nthreads * access_per_thread) + ksft_exit_fail_msg("Too big count %d expected %d, iter %d\n", + count, nthreads * access_per_thread, i); + + c = get_dirty_pages_reset(mem, nthreads * pages_per_thread, 1, page_size); + count += c; + + if (c > nthreads * access_per_thread) { + ksft_test_result_fail(" %s count > nthreads\n", __func__); + return; + } + + if (count != nthreads * access_per_thread) { + /* + * The purpose of the test is to make sure that no page updates are lost + * when the page updates and read-resetting soft dirty flags are performed + * in parallel. However, it is possible that the application will get the + * soft dirty flags twice on the two consecutive read-resets. This seems + * unavoidable as soft dirty flag is handled in software through page faults + * in kernel. While the updating the flags is supposed to be synchronized + * between page fault handling and read-reset, it is possible that + * read-reset happens after page fault PTE update but before the application + * re-executes write instruction. So read-reset gets the flag, clears write + * access and application gets page fault again for the same write. + */ + if (count < nthreads * access_per_thread) { + ksft_test_result_fail("Lost update, iter %d, %d vs %d.\n", i, count, + nthreads * access_per_thread); + return; + } + + extra_pages += count - nthreads * access_per_thread; + } + } + + pthread_barrier_wait(&start_barrier); + finish = 1; + pthread_barrier_wait(&end_barrier); + + ksft_test_result_pass("%s Extra pages %u (%.1lf%%), extra thread faults %d.\n", __func__, + extra_pages, + 100.0 * extra_pages / (iter_count * nthreads * access_per_thread), + extra_thread_faults); +} + +int main(void) +{ + int mem_size, shmid, buf_size, fd, i, ret; + char *mem, *map, *fmem; + struct stat sbuf; + + ksft_print_header(); + ksft_set_plan(92); + + page_size = getpagesize(); + hpage_size = read_pmd_pagesize(); + + pagemap_fd = open(PAGEMAP, O_RDWR); + if (pagemap_fd < 0) + return -EINVAL; + + if (init_uffd()) + ksft_exit_fail_msg("uffd init failed\n"); + + /* + * Written (dirty) PTE bit tests + */ + + /* 1. Sanity testing */ + sanity_tests_sd(); + + /* 2. Normal page testing */ + mem_size = 10 * page_size; + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + base_tests("Page testing:", mem, mem_size, 0); + + wp_free(mem, mem_size); + munmap(mem, mem_size); + + /* 3. Large page testing */ + mem_size = 512 * 10 * page_size; + mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0); + if (mem == MAP_FAILED) + ksft_exit_fail_msg("error nomem\n"); + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + base_tests("Large Page testing:", mem, mem_size, 0); + + wp_free(mem, mem_size); + munmap(mem, mem_size); + + /* 4. Huge page testing */ + map = gethugepage(hpage_size); + if (map) { + wp_init(map, hpage_size); + wp_addr_range(map, hpage_size); + base_tests("Huge page testing:", map, hpage_size, 0); + wp_free(map, hpage_size); + free(map); + } else { + base_tests("Huge page testing:", NULL, 0, 1); + } + + /* 5. Hugetlb page testing */ + mem_size = 2*1024*1024; + mem = gethugetlb_mem(mem_size, &shmid); + if (mem) { + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + base_tests("Hugetlb shmem testing:", mem, mem_size, 0); + + wp_free(mem, mem_size); + shmctl(shmid, IPC_RMID, NULL); + } else { + base_tests("Hugetlb shmem testing:", NULL, 0, 1); + } + + /* 6. Hugetlb page testing */ + mem = gethugetlb_mem(mem_size, NULL); + if (mem) { + wp_init(mem, mem_size); + wp_addr_range(mem, mem_size); + + base_tests("Hugetlb mem testing:", mem, mem_size, 0); + + wp_free(mem, mem_size); + } else { + base_tests("Hugetlb mem testing:", NULL, 0, 1); + } + + /* 7. file memory testing */ + buf_size = page_size * 10; + + fd = open(__FILE__".tmp0", O_RDWR | O_CREAT, 0777); + if (fd < 0) + ksft_exit_fail_msg("Create and read/write to a memory mapped file: %s\n", + strerror(errno)); + + for (i = 0; i < buf_size; i++) + if (write(fd, "c", 1) < 0) + ksft_exit_fail_msg("Create and read/write to a memory mapped file\n"); + + ret = stat(__FILE__".tmp0", &sbuf); + if (ret < 0) + ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno)); + + fmem = mmap(NULL, sbuf.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0); + if (fmem == MAP_FAILED) + ksft_exit_fail_msg("error nomem %ld %s\n", errno, strerror(errno)); + + wp_init(fmem, sbuf.st_size); + wp_addr_range(fmem, sbuf.st_size); + + base_tests("File memory testing:", fmem, sbuf.st_size, 0); + + wp_free(fmem, sbuf.st_size); + munmap(fmem, sbuf.st_size); + close(fd); + + /* 8. file memory testing */ + buf_size = page_size * 10; + + fd = memfd_create(__FILE__".tmp00", MFD_NOEXEC_SEAL); + if (fd < 0) + ksft_exit_fail_msg("Create and read/write to a memory mapped file: %s\n", + strerror(errno)); + + if (ftruncate(fd, buf_size)) + ksft_exit_fail_msg("Error ftruncate\n"); + + for (i = 0; i < buf_size; i++) + if (write(fd, "c", 1) < 0) + ksft_exit_fail_msg("Create and read/write to a memory mapped file\n"); + + fmem = mmap(NULL, buf_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0); + if (fmem == MAP_FAILED) + ksft_exit_fail_msg("error nomem %ld %s\n", errno, strerror(errno)); + + wp_init(fmem, buf_size); + wp_addr_range(fmem, buf_size); + + base_tests("File anonymous memory testing:", fmem, buf_size, 0); + + wp_free(fmem, buf_size); + munmap(fmem, buf_size); + close(fd); + + /* 9. Huge page tests */ + hpage_unit_tests(); + + /* 10. Iterative test */ + test_simple(); + + /* 11. Mprotect test */ + mprotect_tests(); + + /* 12. Transact test */ + transact_test(page_size); + + /* + * Other PTE bit tests + */ + + /* 1. Sanity testing */ + sanity_tests(); + + /* 2. Unmapped address test */ + unmapped_region_tests(); + + /* 3. Userfaultfd tests */ + userfaultfd_tests(); + + close(pagemap_fd); + return ksft_exit_pass(); +} diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh old mode 100644 new mode 100755 index 9666c0c171ab..cca4dd8ee45d --- a/tools/testing/selftests/mm/run_vmtests.sh +++ b/tools/testing/selftests/mm/run_vmtests.sh @@ -56,6 +56,8 @@ separated by spaces: memory protection key tests - soft_dirty test soft dirty page bit semantics +- pagemap + test pagemap_scan IOCTL - cow test copy-on-write semantics example: ./run_vmtests.sh -t "hmm mmap ksm" @@ -324,6 +326,8 @@ fi
CATEGORY="soft_dirty" run_test ./soft-dirty
+CATEGORY="pagemap" run_test ./pagemap_ioctl + # COW tests CATEGORY="cow" run_test ./cow
Tested v25 here on linux-next branch next-20230710, did not see any regressions with patch applied.
TAP version 13 1..92 ok 1 sanity_tests_sd memory size must be valid ok 2 sanity_tests_sd output buffer must be specified ok 3 sanity_tests_sd output buffer size must be valid ok 4 sanity_tests_sd wrong flag specified ok 5 sanity_tests_sd flag has extra bits specified ok 6 sanity_tests_sd no selection mask is specified ok 7 sanity_tests_sd no return mask is specified ok 8 sanity_tests_sd wrong return mask specified ok 9 sanity_tests_sd mixture of correct and wrong flag ok 10 sanity_tests_sd PAGEMAP_BITS_ALL can be specified with PM_SCAN_OP_WP ok 11 sanity_tests_sd Clear area with larger vec size ok 12 sanity_tests_sd Repeated pattern of written and non-written pages ok 13 sanity_tests_sd Repeated pattern of written and non-written pages in parts ok 14 sanity_tests_sd Repeated pattern of written and non-written pages max_pages ok 15 sanity_tests_sd only get 2 written pages and clear them as well ok 16 sanity_tests_sd Two regions ok 17 sanity_tests_sd Smaller max_pages ok 18 Smaller vec 46 50 ok 19 Page testing: all new pages must not be written (dirty) ok 20 Page testing: all pages must be written (dirty) ok 21 Page testing: all pages dirty other than first and the last one ok 22 Page testing: PM_SCAN_OP_WP ok 23 Page testing: only middle page dirty ok 24 Page testing: only two middle pages dirty ok 25 Large Page testing: all new pages must not be written (dirty) ok 26 Large Page testing: all pages must be written (dirty) ok 27 Large Page testing: all pages dirty other than first and the last one ok 28 Large Page testing: PM_SCAN_OP_WP ok 29 Large Page testing: only middle page dirty ok 30 Large Page testing: only two middle pages dirty ok 31 Huge page testing: all new pages must not be written (dirty) ok 32 Huge page testing: all pages must be written (dirty) ok 33 Huge page testing: all pages dirty other than first and the last one ok 34 Huge page testing: PM_SCAN_OP_WP ok 35 Huge page testing: only middle page dirty ok 36 Huge page testing: only two middle pages dirty ok 37 # SKIP Hugetlb shmem testing: all new pages must not be written (dirty) ok 38 # SKIP Hugetlb shmem testing: all pages must be written (dirty) ok 39 # SKIP Hugetlb shmem testing: all pages dirty other than first and the last one ok 40 # SKIP Hugetlb shmem testing: PM_SCAN_OP_WP ok 41 # SKIP Hugetlb shmem testing: only middle page dirty ok 42 # SKIP Hugetlb shmem testing: only two middle pages dirty ok 43 # SKIP Hugetlb mem testing: all new pages must not be written (dirty) ok 44 # SKIP Hugetlb mem testing: all pages must be written (dirty) ok 45 # SKIP Hugetlb mem testing: all pages dirty other than first and the last one ok 46 # SKIP Hugetlb mem testing: PM_SCAN_OP_WP ok 47 # SKIP Hugetlb mem testing: only middle page dirty ok 48 # SKIP Hugetlb mem testing: only two middle pages dirty ok 49 File memory testing: all new pages must not be written (dirty) ok 50 File memory testing: all pages must be written (dirty) ok 51 File memory testing: all pages dirty other than first and the last one ok 52 File memory testing: PM_SCAN_OP_WP ok 53 File memory testing: only middle page dirty ok 54 File memory testing: only two middle pages dirty ok 55 File anonymous memory testing: all new pages must not be written (dirty) ok 56 File anonymous memory testing: all pages must be written (dirty) ok 57 File anonymous memory testing: all pages dirty other than first and the last one ok 58 File anonymous memory testing: PM_SCAN_OP_WP ok 59 File anonymous memory testing: only middle page dirty ok 60 File anonymous memory testing: only two middle pages dirty ok 61 hpage_unit_tests all new huge page must not be written (dirty) ok 62 hpage_unit_tests all the huge page must not be written ok 63 hpage_unit_tests all the huge page must be written and clear ok 64 hpage_unit_tests only middle page written ok 65 hpage_unit_tests clear first half of huge page ok 66 hpage_unit_tests clear first half of huge page with limited buffer ok 67 hpage_unit_tests clear second half huge page ok 68 hpage_unit_tests get half huge page ok 69 hpage_unit_tests get half huge page ok 70 Test test_simple ok 71 mprotect_tests Both pages written ok 72 mprotect_tests Both pages are not written (dirty) ok 73 mprotect_tests Both pages written after remap and mprotect ok 74 mprotect_tests Clear and make the pages written ok 75 transact_test count 192 ok 76 transact_test count 0 ok 77 transact_test Extra pages 130 (0.3%), extra thread faults 141. ok 78 sanity_tests WP op can be specified with !PAGE_IS_WRITTEN ok 79 sanity_tests required_mask specified ok 80 sanity_tests anyof_mask specified ok 81 sanity_tests excluded_mask specified ok 82 sanity_tests required_mask and anyof_mask specified ok 83 sanity_tests Get sd and present pages with anyof_mask ok 84 sanity_tests Get all the pages with required_mask ok 85 sanity_tests Get sd and present pages with required_mask and anyof_mask ok 86 sanity_tests Don't get sd pages ok 87 sanity_tests Don't get present pages ok 88 sanity_tests Find written present pages with return mask ok 89 sanity_tests Memory mapped file ok 90 sanity_tests Read/write to memory ok 91 unmapped_region_tests Get status of pages ok 92 userfaultfd_tests all new pages must not be written (dirty) # Totals: pass:80 fail:0 xfail:0 xpass:0 skip:12 error:0
On 7/13/23 07:14, Muhammad Usama Anjum wrote:
*Changes in v25*:
- Do proper filtering on hole as well (hole got missed earlier)
*Changes in v24*:
- Rebase on top of next-20230710
- Place WP markers in case of hole as well
*Changes in v23*:
- Set vec_buf_index in loop only when vec_buf_index is set
- Return -EFAULT instead of -EINVAL if vec is NULL
- Correctly return the walk ending address to the page granularity
*Changes in v22*:
- Interface change:
- Replace [start start + len) with [start, end)
- Return the ending address of the address walk in start
*Changes in v21*:
- Abort walk instead of returning error if WP is to be performed on partial hugetlb
*Changes in v20*
- Correct PAGE_IS_FILE and add PAGE_IS_PFNZERO
*Changes in v19*
- Minor changes and interface updates
*Changes in v18*
- Rebase on top of next-20230613
- Minor updates
*Changes in v17*
- Rebase on top of next-20230606
- Minor improvements in PAGEMAP_SCAN IOCTL patch
*Changes in v16*
- Fix a corner case
- Add exclusive PM_SCAN_OP_WP back
*Changes in v15*
- Build fix (Add missed build fix in RESEND)
*Changes in v14*
- Fix build error caused by #ifdef added at last minute in some configs
*Changes in v13*
- Rebase on top of next-20230414
- Give-up on using uffd_wp_range() and write new helpers, flush tlb only once
*Changes in v12*
- Update and other memory types to UFFD_FEATURE_WP_ASYNC
- Rebaase on top of next-20230406
- Review updates
*Changes in v11*
- Rebase on top of next-20230307
- Base patches on UFFD_FEATURE_WP_UNPOPULATED
- Do a lot of cosmetic changes and review updates
- Remove ENGAGE_WP + !GET operation as it can be performed with UFFDIO_WRITEPROTECT
*Changes in v10*
- Add specific condition to return error if hugetlb is used with wp async
- Move changes in tools/include/uapi/linux/fs.h to separate patch
- Add documentation
*Changes in v9:*
- Correct fault resolution for userfaultfd wp async
- Fix build warnings and errors which were happening on some configs
- Simplify pagemap ioctl's code
*Changes in v8:*
- Update uffd async wp implementation
- Improve PAGEMAP_IOCTL implementation
*Changes in v7:*
- Add uffd wp async
- Update the IOCTL to use uffd under the hood instead of soft-dirty flags
*Motivation* The real motivation for adding PAGEMAP_SCAN IOCTL is to emulate Windows GetWriteWatch() syscall [1]. The GetWriteWatch{} retrieves the addresses of the pages that are written to in a region of virtual memory.
This syscall is used in Windows applications and games etc. This syscall is being emulated in pretty slow manner in userspace. Our purpose is to enhance the kernel such that we translate it efficiently in a better way. Currently some out of tree hack patches are being used to efficiently emulate it in some kernels. We intend to replace those with these patches. So the whole gaming on Linux can effectively get benefit from this. It means there would be tons of users of this code.
CRIU use case [2] was mentioned by Andrei and Danylo:
Use cases for migrating sparse VMAs are binaries sanitized with ASAN, MSAN or TSAN [3]. All of these sanitizers produce sparse mappings of shadow memory [4]. Being able to migrate such binaries allows to highly reduce the amount of work needed to identify and fix post-migration crashes, which happen constantly.
Andrei's defines the following uses of this code:
- it is more granular and allows us to track changed pages more effectively. The current interface can clear dirty bits for the entire process only. In addition, reading info about pages is a separate operation. It means we must freeze the process to read information about all its pages, reset dirty bits, only then we can start dumping pages. The information about pages becomes more and more outdated, while we are processing pages. The new interface solves both these downsides. First, it allows us to read pte bits and clear the soft-dirty bit atomically. It means that CRIU will not need to freeze processes to pre-dump their memory. Second, it clears soft-dirty bits for a specified region of memory. It means CRIU will have actual info about pages to the moment of dumping them.
- The new interface has to be much faster because basic page filtering is happening in the kernel. With the old interface, we have to read pagemap for each page.
*Implementation Evolution (Short Summary)* From the definition of GetWriteWatch(), we feel like kernel's soft-dirty feature can be used under the hood with some additions like:
- reset soft-dirty flag for only a specific region of memory instead of
clearing the flag for the entire process
- get and clear soft-dirty flag for a specific region atomically
So we decided to use ioctl on pagemap file to read or/and reset soft-dirty flag. But using soft-dirty flag, sometimes we get extra pages which weren't even written. They had become soft-dirty because of VMA merging and VM_SOFTDIRTY flag. This breaks the definition of GetWriteWatch(). We were able to by-pass this short coming by ignoring VM_SOFTDIRTY until David reported that mprotect etc messes up the soft-dirty flag while ignoring VM_SOFTDIRTY [5]. This wasn't happening until [6] got introduced. We discussed if we can revert these patches. But we could not reach to any conclusion. So at this point, I made couple of tries to solve this whole VM_SOFTDIRTY issue by correcting the soft-dirty implementation:
- [7] Correct the bug fixed wrongly back in 2014. It had potential to cause
regression. We left it behind.
- [8] Keep a list of soft-dirty part of a VMA across splits and merges. I
got the reply don't increase the size of the VMA by 8 bytes.
At this point, we left soft-dirty considering it is too much delicate and userfaultfd [9] seemed like the only way forward. From there onward, we have been basing soft-dirty emulation on userfaultfd wp feature where kernel resolves the faults itself when WP_ASYNC feature is used. It was straight forward to add WP_ASYNC feature in userfautlfd. Now we get only those pages dirty or written-to which are really written in reality. (PS There is another WP_UNPOPULATED userfautfd feature is required which is needed to avoid pre-faulting memory before write-protecting [9].)
All the different masks were added on the request of CRIU devs to create interface more generic and better.
[1] https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-g... [2] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com [3] https://github.com/google/sanitizers [4] https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#64-bit [5] https://lore.kernel.org/all/bfcae708-db21-04b4-0bbe-712badd03071@redhat.com [6] https://lore.kernel.org/all/20220725142048.30450-1-peterx@redhat.com/ [7] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.c... [8] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.c... [9] https://lore.kernel.org/all/20230306213925.617814-1-peterx@redhat.com [10] https://lore.kernel.org/all/20230125144529.1630917-1-mdanylo@google.com
- Original Cover letter from v8*
Hello,
Note: Soft-dirty pages and pages which have been written-to are synonyms. As kernel already has soft-dirty feature inside which we have given up to use, we are using written-to terminology while using UFFD async WP under the hood.
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl:
- Get the information if the pages have been written-to (PAGE_IS_WRITTEN), file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT) or swapped (PAGE_IS_SWAPPED).
- Write-protect the pages (PAGEMAP_WP_ENGAGE) to start finding which pages have been written-to.
- Find pages which have been written-to and write protect the pages (atomic PAGE_IS_WRITTEN + PAGEMAP_WP_ENGAGE)
It is possible to find and clear soft-dirty pages entirely in userspace. But it isn't efficient:
- The mprotect and SIGSEGV handler for bookkeeping
- The userfaultfd wp (synchronous) with the handler for bookkeeping
Some benchmarks can be seen here[1]. This series adds features that weren't present earlier:
- There is no atomic get soft-dirty/Written-to status and clear present in the kernel.
- The pages which have been written-to can not be found in accurate way. (Kernel's soft-dirty PTE bit + sof_dirty VMA bit shows more soft-dirty pages than there actually are.)
Historically, soft-dirty PTE bit tracking has been used in the CRIU project. The procfs interface is enough for finding the soft-dirty bit status and clearing the soft-dirty bit of all the pages of a process. We have the use case where we need to track the soft-dirty PTE bit for only specific pages on-demand. We need this tracking and clear mechanism of a region of memory while the process is running to emulate the getWriteWatch() syscall of Windows.
*(Moved to using UFFD instead of soft-dirtyi feature to find pages which have been written-to from v7 patch series)*: Stop using the soft-dirty flags for finding which pages have been written to. It is too delicate and wrong as it shows more soft-dirty pages than the actual soft-dirty pages. There is no interest in correcting it [2][3] as this is how the feature was written years ago. It shouldn't be updated to changed behaviour. Peter Xu has suggested using the async version of the UFFD WP [4] as it is based inherently on the PTEs.
So in this patch series, I've added a new mode to the UFFD which is asynchronous version of the write protect. When this variant of the UFFD WP is used, the page faults are resolved automatically by the kernel. The pages which have been written-to can be found by reading pagemap file (!PM_UFFD_WP). This feature can be used successfully to find which pages have been written to from the time the pages were write protected. This works just like the soft-dirty flag without showing any extra pages which aren't soft-dirty in reality.
The information related to pages if the page is file mapped, present and swapped is required for the CRIU project [5][6]. The addition of the required mask, any mask, excluded mask and return masks are also required for the CRIU project [5].
The IOCTL returns the addresses of the pages which match the specific masks. The page addresses are returned in struct page_region in a compact form. The max_pages is needed to support a use case where user only wants to get a specific number of pages. So there is no need to find all the pages of interest in the range when max_pages is specified. The IOCTL returns when the maximum number of the pages are found. The max_pages is optional. If max_pages is specified, it must be equal or greater than the vec_size. This restriction is needed to handle worse case when one page_region only contains info of one page and it cannot be compacted. This is needed to emulate the Windows getWriteWatch() syscall.
The patch series include the detailed selftest which can be used as an example for the uffd async wp test and PAGEMAP_IOCTL. It shows the interface usages as well.
[1] https://lore.kernel.org/lkml/54d4c322-cd6e-eefd-b161-2af2b56aae24@collabora.... [2] https://lore.kernel.org/all/20221220162606.1595355-1-usama.anjum@collabora.c... [3] https://lore.kernel.org/all/20221122115007.2787017-1-usama.anjum@collabora.c... [4] https://lore.kernel.org/all/Y6Hc2d+7eTKs7AiH@x1n [5] https://lore.kernel.org/all/YyiDg79flhWoMDZB@gmail.com/ [6] https://lore.kernel.org/all/20221014134802.1361436-1-mdanylo@google.com/
Regards, Muhammad Usama Anjum
Muhammad Usama Anjum (4): fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs tools headers UAPI: Update linux/fs.h with the kernel sources mm/pagemap: add documentation of PAGEMAP_SCAN IOCTL selftests: mm: add pagemap ioctl tests
Peter Xu (1): userfaultfd: UFFD_FEATURE_WP_ASYNC
Documentation/admin-guide/mm/pagemap.rst | 58 + Documentation/admin-guide/mm/userfaultfd.rst | 35 + fs/proc/task_mmu.c | 591 +++++++ fs/userfaultfd.c | 26 +- include/linux/hugetlb.h | 1 + include/linux/userfaultfd_k.h | 21 +- include/uapi/linux/fs.h | 55 + include/uapi/linux/userfaultfd.h | 9 +- mm/hugetlb.c | 34 +- mm/memory.c | 27 +- tools/include/uapi/linux/fs.h | 55 + tools/testing/selftests/mm/.gitignore | 2 + tools/testing/selftests/mm/Makefile | 3 +- tools/testing/selftests/mm/config | 1 + tools/testing/selftests/mm/pagemap_ioctl.c | 1464 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 16 files changed, 2362 insertions(+), 24 deletions(-) create mode 100644 tools/testing/selftests/mm/pagemap_ioctl.c mode change 100644 => 100755 tools/testing/selftests/mm/run_vmtests.sh
linux-kselftest-mirror@lists.linaro.org
-
Andrei Vagin -
Muhammad Usama Anjum -
Rogerio Alves