Patch "kmemcheck: rip it out" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

kmemcheck: rip it out

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kmemcheck-rip-it-out.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 4675ff05de2d76d167336b368bd07f3fef6ed5a6 Mon Sep 17 00:00:00 2001

From: "Levin, Alexander (Sasha Levin)" alexander.levin@verizon.com Date: Wed, 15 Nov 2017 17:36:02 -0800 Subject: kmemcheck: rip it out

From: Levin, Alexander (Sasha Levin) alexander.levin@verizon.com

commit 4675ff05de2d76d167336b368bd07f3fef6ed5a6 upstream.

Fix up makefiles, remove references, and git rm kmemcheck.

Link: http://lkml.kernel.org/r/20171007030159.22241-4-alexander.levin@verizon.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Vegard Nossum vegardno@ifi.uio.no Cc: Pekka Enberg penberg@kernel.org Cc: Michal Hocko mhocko@kernel.org Cc: Eric W. Biederman ebiederm@xmission.com Cc: Alexander Potapenko glider@google.com Cc: Tim Hansen devtimhansen@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- Documentation/admin-guide/kernel-parameters.txt | 7 Documentation/dev-tools/index.rst | 1 Documentation/dev-tools/kmemcheck.rst | 733 ------------------------ MAINTAINERS | 10 arch/x86/Kconfig | 3 arch/x86/include/asm/kmemcheck.h | 42 - arch/x86/include/asm/string_32.h | 9 arch/x86/include/asm/string_64.h | 8 arch/x86/kernel/cpu/intel.c | 15 arch/x86/mm/Makefile | 2 arch/x86/mm/init.c | 5 arch/x86/mm/kmemcheck/Makefile | 1 arch/x86/mm/kmemcheck/error.c | 227 ------- arch/x86/mm/kmemcheck/error.h | 15 arch/x86/mm/kmemcheck/kmemcheck.c | 658 --------------------- arch/x86/mm/kmemcheck/opcode.c | 106 --- arch/x86/mm/kmemcheck/opcode.h | 9 arch/x86/mm/kmemcheck/pte.c | 22 arch/x86/mm/kmemcheck/pte.h | 10 arch/x86/mm/kmemcheck/selftest.c | 70 -- arch/x86/mm/kmemcheck/selftest.h | 6 arch/x86/mm/kmemcheck/shadow.c | 173 ----- arch/x86/mm/kmemcheck/shadow.h | 18 include/linux/interrupt.h | 15 include/linux/kmemcheck.h | 171 ----- kernel/softirq.c | 10 kernel/sysctl.c | 10 lib/Kconfig.debug | 6 lib/Kconfig.kmemcheck | 94 --- mm/Kconfig.debug | 1 mm/Makefile | 2 mm/kmemcheck.c | 125 ---- mm/slub.c | 5 scripts/kernel-doc | 2 tools/include/linux/kmemcheck.h | 8 35 files changed, 7 insertions(+), 2592 deletions(-)

--- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1841,13 +1841,6 @@ Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, the default is off.

- kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode - Valid arguments: 0, 1, 2 - kmemcheck=0 (disabled) - kmemcheck=1 (enabled) - kmemcheck=2 (one-shot mode) - Default: 2 (one-shot mode) - kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. Default is 0 (don't ignore, but inject #GP)

--- a/Documentation/dev-tools/index.rst +++ b/Documentation/dev-tools/index.rst @@ -21,7 +21,6 @@ whole; patches welcome! kasan ubsan kmemleak - kmemcheck gdb-kernel-debugging kgdb kselftest --- a/Documentation/dev-tools/kmemcheck.rst +++ /dev/null @@ -1,733 +0,0 @@ -Getting started with kmemcheck -============================== - -Vegard Nossum vegardno@ifi.uio.no - - -Introduction ------------- - -kmemcheck is a debugging feature for the Linux Kernel. More specifically, it -is a dynamic checker that detects and warns about some uses of uninitialized -memory. - -Userspace programmers might be familiar with Valgrind's memcheck. The main -difference between memcheck and kmemcheck is that memcheck works for userspace -programs only, and kmemcheck works for the kernel only. The implementations -are of course vastly different. Because of this, kmemcheck is not as accurate -as memcheck, but it turns out to be good enough in practice to discover real -programmer errors that the compiler is not able to find through static -analysis. - -Enabling kmemcheck on a kernel will probably slow it down to the extent that -the machine will not be usable for normal workloads such as e.g. an -interactive desktop. kmemcheck will also cause the kernel to use about twice -as much memory as normal. For this reason, kmemcheck is strictly a debugging -feature. - - -Downloading ------------ - -As of version 2.6.31-rc1, kmemcheck is included in the mainline kernel. - - -Configuring and compiling -------------------------- - -kmemcheck only works for the x86 (both 32- and 64-bit) platform. A number of -configuration variables must have specific settings in order for the kmemcheck -menu to even appear in "menuconfig". These are: - -- ``CONFIG_CC_OPTIMIZE_FOR_SIZE=n`` - This option is located under "General setup" / "Optimize for size". - - Without this, gcc will use certain optimizations that usually lead to - false positive warnings from kmemcheck. An example of this is a 16-bit - field in a struct, where gcc may load 32 bits, then discard the upper - 16 bits. kmemcheck sees only the 32-bit load, and may trigger a - warning for the upper 16 bits (if they're uninitialized). - -- ``CONFIG_SLAB=y`` or ``CONFIG_SLUB=y`` - This option is located under "General setup" / "Choose SLAB - allocator". - -- ``CONFIG_FUNCTION_TRACER=n`` - This option is located under "Kernel hacking" / "Tracers" / "Kernel - Function Tracer" - - When function tracing is compiled in, gcc emits a call to another - function at the beginning of every function. This means that when the - page fault handler is called, the ftrace framework will be called - before kmemcheck has had a chance to handle the fault. If ftrace then - modifies memory that was tracked by kmemcheck, the result is an - endless recursive page fault. - -- ``CONFIG_DEBUG_PAGEALLOC=n`` - This option is located under "Kernel hacking" / "Memory Debugging" - / "Debug page memory allocations". - -In addition, I highly recommend turning on ``CONFIG_DEBUG_INFO=y``. This is also -located under "Kernel hacking". With this, you will be able to get line number -information from the kmemcheck warnings, which is extremely valuable in -debugging a problem. This option is not mandatory, however, because it slows -down the compilation process and produces a much bigger kernel image. - -Now the kmemcheck menu should be visible (under "Kernel hacking" / "Memory -Debugging" / "kmemcheck: trap use of uninitialized memory"). Here follows -a description of the kmemcheck configuration variables: - -- ``CONFIG_KMEMCHECK`` - This must be enabled in order to use kmemcheck at all... - -- ``CONFIG_KMEMCHECK_``[``DISABLED`` | ``ENABLED`` | ``ONESHOT``]``_BY_DEFAULT`` - This option controls the status of kmemcheck at boot-time. "Enabled" - will enable kmemcheck right from the start, "disabled" will boot the - kernel as normal (but with the kmemcheck code compiled in, so it can - be enabled at run-time after the kernel has booted), and "one-shot" is - a special mode which will turn kmemcheck off automatically after - detecting the first use of uninitialized memory. - - If you are using kmemcheck to actively debug a problem, then you - probably want to choose "enabled" here. - - The one-shot mode is mostly useful in automated test setups because it - can prevent floods of warnings and increase the chances of the machine - surviving in case something is really wrong. In other cases, the one- - shot mode could actually be counter-productive because it would turn - itself off at the very first error -- in the case of a false positive - too -- and this would come in the way of debugging the specific - problem you were interested in. - - If you would like to use your kernel as normal, but with a chance to - enable kmemcheck in case of some problem, it might be a good idea to - choose "disabled" here. When kmemcheck is disabled, most of the run- - time overhead is not incurred, and the kernel will be almost as fast - as normal. - -- ``CONFIG_KMEMCHECK_QUEUE_SIZE`` - Select the maximum number of error reports to store in an internal - (fixed-size) buffer. Since errors can occur virtually anywhere and in - any context, we need a temporary storage area which is guaranteed not - to generate any other page faults when accessed. The queue will be - emptied as soon as a tasklet may be scheduled. If the queue is full, - new error reports will be lost. - - The default value of 64 is probably fine. If some code produces more - than 64 errors within an irqs-off section, then the code is likely to - produce many, many more, too, and these additional reports seldom give - any more information (the first report is usually the most valuable - anyway). - - This number might have to be adjusted if you are not using serial - console or similar to capture the kernel log. If you are using the - "dmesg" command to save the log, then getting a lot of kmemcheck - warnings might overflow the kernel log itself, and the earlier reports - will get lost in that way instead. Try setting this to 10 or so on - such a setup. - -- ``CONFIG_KMEMCHECK_SHADOW_COPY_SHIFT`` - Select the number of shadow bytes to save along with each entry of the - error-report queue. These bytes indicate what parts of an allocation - are initialized, uninitialized, etc. and will be displayed when an - error is detected to help the debugging of a particular problem. - - The number entered here is actually the logarithm of the number of - bytes that will be saved. So if you pick for example 5 here, kmemcheck - will save 2^5 = 32 bytes. - - The default value should be fine for debugging most problems. It also - fits nicely within 80 columns. - -- ``CONFIG_KMEMCHECK_PARTIAL_OK`` - This option (when enabled) works around certain GCC optimizations that - produce 32-bit reads from 16-bit variables where the upper 16 bits are - thrown away afterwards. - - The default value (enabled) is recommended. This may of course hide - some real errors, but disabling it would probably produce a lot of - false positives. - -- ``CONFIG_KMEMCHECK_BITOPS_OK`` - This option silences warnings that would be generated for bit-field - accesses where not all the bits are initialized at the same time. This - may also hide some real bugs. - - This option is probably obsolete, or it should be replaced with - the kmemcheck-/bitfield-annotations for the code in question. The - default value is therefore fine. - -Now compile the kernel as usual. - - -How to use ----------- - -Booting -~~~~~~~ - -First some information about the command-line options. There is only one -option specific to kmemcheck, and this is called "kmemcheck". It can be used -to override the default mode as chosen by the ``CONFIG_KMEMCHECK_*_BY_DEFAULT`` -option. Its possible settings are: - -- ``kmemcheck=0`` (disabled) -- ``kmemcheck=1`` (enabled) -- ``kmemcheck=2`` (one-shot mode) - -If SLUB debugging has been enabled in the kernel, it may take precedence over -kmemcheck in such a way that the slab caches which are under SLUB debugging -will not be tracked by kmemcheck. In order to ensure that this doesn't happen -(even though it shouldn't by default), use SLUB's boot option ``slub_debug``, -like this: ``slub_debug=-`` - -In fact, this option may also be used for fine-grained control over SLUB vs. -kmemcheck. For example, if the command line includes -``kmemcheck=1 slub_debug=,dentry``, then SLUB debugging will be used only -for the "dentry" slab cache, and with kmemcheck tracking all the other -caches. This is advanced usage, however, and is not generally recommended. - - -Run-time enable/disable -~~~~~~~~~~~~~~~~~~~~~~~ - -When the kernel has booted, it is possible to enable or disable kmemcheck at -run-time. WARNING: This feature is still experimental and may cause false -positive warnings to appear. Therefore, try not to use this. If you find that -it doesn't work properly (e.g. you see an unreasonable amount of warnings), I -will be happy to take bug reports. - -Use the file ``/proc/sys/kernel/kmemcheck`` for this purpose, e.g.:: - - $ echo 0 > /proc/sys/kernel/kmemcheck # disables kmemcheck - -The numbers are the same as for the ``kmemcheck=`` command-line option. - - -Debugging -~~~~~~~~~ - -A typical report will look something like this:: - - WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (ffff88003e4a2024) - 80000000000000000000000000000000000000000088ffff0000000000000000 - i i i i u u u u i i i i i i i i u u u u u u u u u u u u u u u u - ^ - - Pid: 1856, comm: ntpdate Not tainted 2.6.29-rc5 #264 945P-A - RIP: 0010:[<ffffffff8104ede8>] [<ffffffff8104ede8>] __dequeue_signal+0xc8/0x190 - RSP: 0018:ffff88003cdf7d98 EFLAGS: 00210002 - RAX: 0000000000000030 RBX: ffff88003d4ea968 RCX: 0000000000000009 - RDX: ffff88003e5d6018 RSI: ffff88003e5d6024 RDI: ffff88003cdf7e84 - RBP: ffff88003cdf7db8 R08: ffff88003e5d6000 R09: 0000000000000000 - R10: 0000000000000080 R11: 0000000000000000 R12: 000000000000000e - R13: ffff88003cdf7e78 R14: ffff88003d530710 R15: ffff88003d5a98c8 - FS: 0000000000000000(0000) GS:ffff880001982000(0063) knlGS:00000 - CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033 - CR2: ffff88003f806ea0 CR3: 000000003c036000 CR4: 00000000000006a0 - DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 - DR3: 0000000000000000 DR6: 00000000ffff4ff0 DR7: 0000000000000400 - [<ffffffff8104f04e>] dequeue_signal+0x8e/0x170 - [<ffffffff81050bd8>] get_signal_to_deliver+0x98/0x390 - [<ffffffff8100b87d>] do_notify_resume+0xad/0x7d0 - [<ffffffff8100c7b5>] int_signal+0x12/0x17 - [<ffffffffffffffff>] 0xffffffffffffffff - -The single most valuable information in this report is the RIP (or EIP on 32- -bit) value. This will help us pinpoint exactly which instruction that caused -the warning. - -If your kernel was compiled with ``CONFIG_DEBUG_INFO=y``, then all we have to do -is give this address to the addr2line program, like this:: - - $ addr2line -e vmlinux -i ffffffff8104ede8 - arch/x86/include/asm/string_64.h:12 - include/asm-generic/siginfo.h:287 - kernel/signal.c:380 - kernel/signal.c:410 - -The "``-e vmlinux``" tells addr2line which file to look in. **IMPORTANT:** -This must be the vmlinux of the kernel that produced the warning in the -first place! If not, the line number information will almost certainly be -wrong. - -The "``-i``" tells addr2line to also print the line numbers of inlined -functions. In this case, the flag was very important, because otherwise, -it would only have printed the first line, which is just a call to -``memcpy()``, which could be called from a thousand places in the kernel, and -is therefore not very useful. These inlined functions would not show up in -the stack trace above, simply because the kernel doesn't load the extra -debugging information. This technique can of course be used with ordinary -kernel oopses as well. - -In this case, it's the caller of ``memcpy()`` that is interesting, and it can be -found in ``include/asm-generic/siginfo.h``, line 287:: - - 281 static inline void copy_siginfo(struct siginfo *to, struct siginfo *from) - 282 { - 283 if (from->si_code < 0) - 284 memcpy(to, from, sizeof(*to)); - 285 else - 286 /* _sigchld is currently the largest know union member */ - 287 memcpy(to, from, __ARCH_SI_PREAMBLE_SIZE + sizeof(from->_sifields._sigchld)); - 288 } - -Since this was a read (kmemcheck usually warns about reads only, though it can -warn about writes to unallocated or freed memory as well), it was probably the -"from" argument which contained some uninitialized bytes. Following the chain -of calls, we move upwards to see where "from" was allocated or initialized, -``kernel/signal.c``, line 380:: - - 359 static void collect_signal(int sig, struct sigpending *list, siginfo_t *info) - 360 { - ... - 367 list_for_each_entry(q, &list->list, list) { - 368 if (q->info.si_signo == sig) { - 369 if (first) - 370 goto still_pending; - 371 first = q; - ... - 377 if (first) { - 378 still_pending: - 379 list_del_init(&first->list); - 380 copy_siginfo(info, &first->info); - 381 __sigqueue_free(first); - ... - 392 } - 393 } - -Here, it is ``&first->info`` that is being passed on to ``copy_siginfo()``. The -variable ``first`` was found on a list -- passed in as the second argument to -``collect_signal()``. We continue our journey through the stack, to figure out -where the item on "list" was allocated or initialized. We move to line 410:: - - 395 static int __dequeue_signal(struct sigpending *pending, sigset_t *mask, - 396 siginfo_t *info) - 397 { - ... - 410 collect_signal(sig, pending, info); - ... - 414 } - -Now we need to follow the ``pending`` pointer, since that is being passed on to -``collect_signal()`` as ``list``. At this point, we've run out of lines from the -"addr2line" output. Not to worry, we just paste the next addresses from the -kmemcheck stack dump, i.e.:: - - [<ffffffff8104f04e>] dequeue_signal+0x8e/0x170 - [<ffffffff81050bd8>] get_signal_to_deliver+0x98/0x390 - [<ffffffff8100b87d>] do_notify_resume+0xad/0x7d0 - [<ffffffff8100c7b5>] int_signal+0x12/0x17 - - $ addr2line -e vmlinux -i ffffffff8104f04e ffffffff81050bd8 \ - ffffffff8100b87d ffffffff8100c7b5 - kernel/signal.c:446 - kernel/signal.c:1806 - arch/x86/kernel/signal.c:805 - arch/x86/kernel/signal.c:871 - arch/x86/kernel/entry_64.S:694 - -Remember that since these addresses were found on the stack and not as the -RIP value, they actually point to the _next_ instruction (they are return -addresses). This becomes obvious when we look at the code for line 446:: - - 422 int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info) - 423 { - ... - 431 signr = __dequeue_signal(&tsk->signal->shared_pending, - 432 mask, info); - 433 /* - 434 * itimer signal ? - 435 * - 436 * itimers are process shared and we restart periodic - 437 * itimers in the signal delivery path to prevent DoS - 438 * attacks in the high resolution timer case. This is - 439 * compliant with the old way of self restarting - 440 * itimers, as the SIGALRM is a legacy signal and only - 441 * queued once. Changing the restart behaviour to - 442 * restart the timer in the signal dequeue path is - 443 * reducing the timer noise on heavy loaded !highres - 444 * systems too. - 445 */ - 446 if (unlikely(signr == SIGALRM)) { - ... - 489 } - -So instead of looking at 446, we should be looking at 431, which is the line -that executes just before 446. Here we see that what we are looking for is -``&tsk->signal->shared_pending``. - -Our next task is now to figure out which function that puts items on this -``shared_pending`` list. A crude, but efficient tool, is ``git grep``:: - - $ git grep -n 'shared_pending' kernel/ - ... - kernel/signal.c:828: pending = group ? &t->signal->shared_pending : &t->pending; - kernel/signal.c:1339: pending = group ? &t->signal->shared_pending : &t->pending; - ... - -There were more results, but none of them were related to list operations, -and these were the only assignments. We inspect the line numbers more closely -and find that this is indeed where items are being added to the list:: - - 816 static int send_signal(int sig, struct siginfo *info, struct task_struct *t, - 817 int group) - 818 { - ... - 828 pending = group ? &t->signal->shared_pending : &t->pending; - ... - 851 q = __sigqueue_alloc(t, GFP_ATOMIC, (sig < SIGRTMIN && - 852 (is_si_special(info) || - 853 info->si_code >= 0))); - 854 if (q) { - 855 list_add_tail(&q->list, &pending->list); - ... - 890 } - -and:: - - 1309 int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group) - 1310 { - .... - 1339 pending = group ? &t->signal->shared_pending : &t->pending; - 1340 list_add_tail(&q->list, &pending->list); - .... - 1347 } - -In the first case, the list element we are looking for, ``q``, is being -returned from the function ``__sigqueue_alloc()``, which looks like an -allocation function. Let's take a look at it:: - - 187 static struct sigqueue *__sigqueue_alloc(struct task_struct *t, gfp_t flags, - 188 int override_rlimit) - 189 { - 190 struct sigqueue *q = NULL; - 191 struct user_struct *user; - 192 - 193 /* - 194 * We won't get problems with the target's UID changing under us - 195 * because changing it requires RCU be used, and if t != current, the - 196 * caller must be holding the RCU readlock (by way of a spinlock) and - 197 * we use RCU protection here - 198 */ - 199 user = get_uid(__task_cred(t)->user); - 200 atomic_inc(&user->sigpending); - 201 if (override_rlimit || - 202 atomic_read(&user->sigpending) <= - 203 t->signal->rlim[RLIMIT_SIGPENDING].rlim_cur) - 204 q = kmem_cache_alloc(sigqueue_cachep, flags); - 205 if (unlikely(q == NULL)) { - 206 atomic_dec(&user->sigpending); - 207 free_uid(user); - 208 } else { - 209 INIT_LIST_HEAD(&q->list); - 210 q->flags = 0; - 211 q->user = user; - 212 } - 213 - 214 return q; - 215 } - -We see that this function initializes ``q->list``, ``q->flags``, and -``q->user``. It seems that now is the time to look at the definition of -``struct sigqueue``, e.g.:: - - 14 struct sigqueue { - 15 struct list_head list; - 16 int flags; - 17 siginfo_t info; - 18 struct user_struct *user; - 19 }; - -And, you might remember, it was a ``memcpy()`` on ``&first->info`` that -caused the warning, so this makes perfect sense. It also seems reasonable -to assume that it is the caller of ``__sigqueue_alloc()`` that has the -responsibility of filling out (initializing) this member. - -But just which fields of the struct were uninitialized? Let's look at -kmemcheck's report again:: - - WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (ffff88003e4a2024) - 80000000000000000000000000000000000000000088ffff0000000000000000 - i i i i u u u u i i i i i i i i u u u u u u u u u u u u u u u u - ^ - -These first two lines are the memory dump of the memory object itself, and -the shadow bytemap, respectively. The memory object itself is in this case -``&first->info``. Just beware that the start of this dump is NOT the start -of the object itself! The position of the caret (^) corresponds with the -address of the read (ffff88003e4a2024). - -The shadow bytemap dump legend is as follows: - -- i: initialized -- u: uninitialized -- a: unallocated (memory has been allocated by the slab layer, but has not - yet been handed off to anybody) -- f: freed (memory has been allocated by the slab layer, but has been freed - by the previous owner) - -In order to figure out where (relative to the start of the object) the -uninitialized memory was located, we have to look at the disassembly. For -that, we'll need the RIP address again:: - - RIP: 0010:[<ffffffff8104ede8>] [<ffffffff8104ede8>] __dequeue_signal+0xc8/0x190 - - $ objdump -d --no-show-raw-insn vmlinux | grep -C 8 ffffffff8104ede8: - ffffffff8104edc8: mov %r8,0x8(%r8) - ffffffff8104edcc: test %r10d,%r10d - ffffffff8104edcf: js ffffffff8104ee88 <__dequeue_signal+0x168> - ffffffff8104edd5: mov %rax,%rdx - ffffffff8104edd8: mov $0xc,%ecx - ffffffff8104eddd: mov %r13,%rdi - ffffffff8104ede0: mov $0x30,%eax - ffffffff8104ede5: mov %rdx,%rsi - ffffffff8104ede8: rep movsl %ds:(%rsi),%es:(%rdi) - ffffffff8104edea: test $0x2,%al - ffffffff8104edec: je ffffffff8104edf0 <__dequeue_signal+0xd0> - ffffffff8104edee: movsw %ds:(%rsi),%es:(%rdi) - ffffffff8104edf0: test $0x1,%al - ffffffff8104edf2: je ffffffff8104edf5 <__dequeue_signal+0xd5> - ffffffff8104edf4: movsb %ds:(%rsi),%es:(%rdi) - ffffffff8104edf5: mov %r8,%rdi - ffffffff8104edf8: callq ffffffff8104de60 <__sigqueue_free> - -As expected, it's the "``rep movsl``" instruction from the ``memcpy()`` -that causes the warning. We know about ``REP MOVSL`` that it uses the register -``RCX`` to count the number of remaining iterations. By taking a look at the -register dump again (from the kmemcheck report), we can figure out how many -bytes were left to copy:: - - RAX: 0000000000000030 RBX: ffff88003d4ea968 RCX: 0000000000000009 - -By looking at the disassembly, we also see that ``%ecx`` is being loaded -with the value ``$0xc`` just before (ffffffff8104edd8), so we are very -lucky. Keep in mind that this is the number of iterations, not bytes. And -since this is a "long" operation, we need to multiply by 4 to get the -number of bytes. So this means that the uninitialized value was encountered -at 4 * (0xc - 0x9) = 12 bytes from the start of the object. - -We can now try to figure out which field of the "``struct siginfo``" that -was not initialized. This is the beginning of the struct:: - - 40 typedef struct siginfo { - 41 int si_signo; - 42 int si_errno; - 43 int si_code; - 44 - 45 union { - .. - 92 } _sifields; - 93 } siginfo_t; - -On 64-bit, the int is 4 bytes long, so it must the union member that has -not been initialized. We can verify this using gdb:: - - $ gdb vmlinux - ... - (gdb) p &((struct siginfo *) 0)->_sifields - $1 = (union {...} *) 0x10 - -Actually, it seems that the union member is located at offset 0x10 -- which -means that gcc has inserted 4 bytes of padding between the members ``si_code`` -and ``_sifields``. We can now get a fuller picture of the memory dump:: - - _----------------------------=> si_code - / _--------------------=> (padding) - | / _------------=> _sifields(._kill._pid) - | | / _----=> _sifields(._kill._uid) - | | | / - -------|-------|-------|-------| - 80000000000000000000000000000000000000000088ffff0000000000000000 - i i i i u u u u i i i i i i i i u u u u u u u u u u u u u u u u - -This allows us to realize another important fact: ``si_code`` contains the -value 0x80. Remember that x86 is little endian, so the first 4 bytes -"80000000" are really the number 0x00000080. With a bit of research, we -find that this is actually the constant ``SI_KERNEL`` defined in -``include/asm-generic/siginfo.h``:: - - 144 #define SI_KERNEL 0x80 /* sent by the kernel from somewhere */ - -This macro is used in exactly one place in the x86 kernel: In ``send_signal()`` -in ``kernel/signal.c``:: - - 816 static int send_signal(int sig, struct siginfo *info, struct task_struct *t, - 817 int group) - 818 { - ... - 828 pending = group ? &t->signal->shared_pending : &t->pending; - ... - 851 q = __sigqueue_alloc(t, GFP_ATOMIC, (sig < SIGRTMIN && - 852 (is_si_special(info) || - 853 info->si_code >= 0))); - 854 if (q) { - 855 list_add_tail(&q->list, &pending->list); - 856 switch ((unsigned long) info) { - ... - 865 case (unsigned long) SEND_SIG_PRIV: - 866 q->info.si_signo = sig; - 867 q->info.si_errno = 0; - 868 q->info.si_code = SI_KERNEL; - 869 q->info.si_pid = 0; - 870 q->info.si_uid = 0; - 871 break; - ... - 890 } - -Not only does this match with the ``.si_code`` member, it also matches the place -we found earlier when looking for where siginfo_t objects are enqueued on the -``shared_pending`` list. - -So to sum up: It seems that it is the padding introduced by the compiler -between two struct fields that is uninitialized, and this gets reported when -we do a ``memcpy()`` on the struct. This means that we have identified a false -positive warning. - -Normally, kmemcheck will not report uninitialized accesses in ``memcpy()`` calls -when both the source and destination addresses are tracked. (Instead, we copy -the shadow bytemap as well). In this case, the destination address clearly -was not tracked. We can dig a little deeper into the stack trace from above:: - - arch/x86/kernel/signal.c:805 - arch/x86/kernel/signal.c:871 - arch/x86/kernel/entry_64.S:694 - -And we clearly see that the destination siginfo object is located on the -stack:: - - 782 static void do_signal(struct pt_regs *regs) - 783 { - 784 struct k_sigaction ka; - 785 siginfo_t info; - ... - 804 signr = get_signal_to_deliver(&info, &ka, regs, NULL); - ... - 854 } - -And this ``&info`` is what eventually gets passed to ``copy_siginfo()`` as the -destination argument. - -Now, even though we didn't find an actual error here, the example is still a -good one, because it shows how one would go about to find out what the report -was all about. - - -Annotating false positives -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -There are a few different ways to make annotations in the source code that -will keep kmemcheck from checking and reporting certain allocations. Here -they are: - -- ``__GFP_NOTRACK_FALSE_POSITIVE`` - This flag can be passed to ``kmalloc()`` or ``kmem_cache_alloc()`` - (therefore also to other functions that end up calling one of - these) to indicate that the allocation should not be tracked - because it would lead to a false positive report. This is a "big - hammer" way of silencing kmemcheck; after all, even if the false - positive pertains to particular field in a struct, for example, we - will now lose the ability to find (real) errors in other parts of - the same struct. - - Example:: - - /* No warnings will ever trigger on accessing any part of x */ - x = kmalloc(sizeof *x, GFP_KERNEL | __GFP_NOTRACK_FALSE_POSITIVE); - -- ``kmemcheck_bitfield_begin(name)``/``kmemcheck_bitfield_end(name)`` and - ``kmemcheck_annotate_bitfield(ptr, name)`` - The first two of these three macros can be used inside struct - definitions to signal, respectively, the beginning and end of a - bitfield. Additionally, this will assign the bitfield a name, which - is given as an argument to the macros. - - Having used these markers, one can later use - kmemcheck_annotate_bitfield() at the point of allocation, to indicate - which parts of the allocation is part of a bitfield. - - Example:: - - struct foo { - int x; - - kmemcheck_bitfield_begin(flags); - int flag_a:1; - int flag_b:1; - kmemcheck_bitfield_end(flags); - - int y; - }; - - struct foo *x = kmalloc(sizeof *x); - - /* No warnings will trigger on accessing the bitfield of x */ - kmemcheck_annotate_bitfield(x, flags); - - Note that ``kmemcheck_annotate_bitfield()`` can be used even before the - return value of ``kmalloc()`` is checked -- in other words, passing NULL - as the first argument is legal (and will do nothing). - - -Reporting errors ----------------- - -As we have seen, kmemcheck will produce false positive reports. Therefore, it -is not very wise to blindly post kmemcheck warnings to mailing lists and -maintainers. Instead, I encourage maintainers and developers to find errors -in their own code. If you get a warning, you can try to work around it, try -to figure out if it's a real error or not, or simply ignore it. Most -developers know their own code and will quickly and efficiently determine the -root cause of a kmemcheck report. This is therefore also the most efficient -way to work with kmemcheck. - -That said, we (the kmemcheck maintainers) will always be on the lookout for -false positives that we can annotate and silence. So whatever you find, -please drop us a note privately! Kernel configs and steps to reproduce (if -available) are of course a great help too. - -Happy hacking! - - -Technical description ---------------------- - -kmemcheck works by marking memory pages non-present. This means that whenever -somebody attempts to access the page, a page fault is generated. The page -fault handler notices that the page was in fact only hidden, and so it calls -on the kmemcheck code to make further investigations. - -When the investigations are completed, kmemcheck "shows" the page by marking -it present (as it would be under normal circumstances). This way, the -interrupted code can continue as usual. - -But after the instruction has been executed, we should hide the page again, so -that we can catch the next access too! Now kmemcheck makes use of a debugging -feature of the processor, namely single-stepping. When the processor has -finished the one instruction that generated the memory access, a debug -exception is raised. From here, we simply hide the page again and continue -execution, this time with the single-stepping feature turned off. - -kmemcheck requires some assistance from the memory allocator in order to work. -The memory allocator needs to - - 1. Tell kmemcheck about newly allocated pages and pages that are about to - be freed. This allows kmemcheck to set up and tear down the shadow memory - for the pages in question. The shadow memory stores the status of each - byte in the allocation proper, e.g. whether it is initialized or - uninitialized. - - 2. Tell kmemcheck which parts of memory should be marked uninitialized. - There are actually a few more states, such as "not yet allocated" and - "recently freed". - -If a slab cache is set up using the SLAB_NOTRACK flag, it will never return -memory that can take page faults because of kmemcheck. - -If a slab cache is NOT set up using the SLAB_NOTRACK flag, callers can still -request memory with the __GFP_NOTRACK or __GFP_NOTRACK_FALSE_POSITIVE flags. -This does not prevent the page faults from occurring, however, but marks the -object in question as being initialized so that no warnings will ever be -produced for this object. - -Currently, the SLAB and SLUB allocators are supported by kmemcheck. --- a/MAINTAINERS +++ b/MAINTAINERS @@ -7670,16 +7670,6 @@ F: include/linux/kdb.h F: include/linux/kgdb.h F: kernel/debug/

-KMEMCHECK -M: Vegard Nossum vegardno@ifi.uio.no -M: Pekka Enberg penberg@kernel.org -S: Maintained -F: Documentation/dev-tools/kmemcheck.rst -F: arch/x86/include/asm/kmemcheck.h -F: arch/x86/mm/kmemcheck/ -F: include/linux/kmemcheck.h -F: mm/kmemcheck.c - KMEMLEAK M: Catalin Marinas catalin.marinas@arm.com S: Maintained --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -111,7 +111,6 @@ config X86 select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_KASAN if X86_64 select HAVE_ARCH_KGDB - select HAVE_ARCH_KMEMCHECK select HAVE_ARCH_MMAP_RND_BITS if MMU select HAVE_ARCH_MMAP_RND_COMPAT_BITS if MMU && COMPAT select HAVE_ARCH_COMPAT_MMAP_BASES if MMU && COMPAT @@ -1443,7 +1442,7 @@ config ARCH_DMA_ADDR_T_64BIT

config X86_DIRECT_GBPAGES def_bool y - depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK + depends on X86_64 && !DEBUG_PAGEALLOC ---help--- Certain kernel features effectively disable kernel linear 1 GB mappings (even if the CPU otherwise --- a/arch/x86/include/asm/kmemcheck.h +++ b/arch/x86/include/asm/kmemcheck.h @@ -1,43 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef ASM_X86_KMEMCHECK_H -#define ASM_X86_KMEMCHECK_H - -#include <linux/types.h> -#include <asm/ptrace.h> - -#ifdef CONFIG_KMEMCHECK -bool kmemcheck_active(struct pt_regs *regs); - -void kmemcheck_show(struct pt_regs *regs); -void kmemcheck_hide(struct pt_regs *regs); - -bool kmemcheck_fault(struct pt_regs *regs, - unsigned long address, unsigned long error_code); -bool kmemcheck_trap(struct pt_regs *regs); -#else -static inline bool kmemcheck_active(struct pt_regs *regs) -{ - return false; -} - -static inline void kmemcheck_show(struct pt_regs *regs) -{ -} - -static inline void kmemcheck_hide(struct pt_regs *regs) -{ -} - -static inline bool kmemcheck_fault(struct pt_regs *regs, - unsigned long address, unsigned long error_code) -{ - return false; -} - -static inline bool kmemcheck_trap(struct pt_regs *regs) -{ - return false; -} -#endif /* CONFIG_KMEMCHECK */ - -#endif --- a/arch/x86/include/asm/string_32.h +++ b/arch/x86/include/asm/string_32.h @@ -179,8 +179,6 @@ static inline void *__memcpy3d(void *to, * No 3D Now! */

-#ifndef CONFIG_KMEMCHECK - #if (__GNUC__ >= 4) #define memcpy(t, f, n) __builtin_memcpy(t, f, n) #else @@ -189,13 +187,6 @@ static inline void *__memcpy3d(void *to, ? __constant_memcpy((t), (f), (n)) \ : __memcpy((t), (f), (n))) #endif -#else -/* - * kmemcheck becomes very happy if we use the REP instructions unconditionally, - * because it means that we know both memory operands in advance. - */ -#define memcpy(t, f, n) __memcpy((t), (f), (n)) -#endif

#endif #endif /* !CONFIG_FORTIFY_SOURCE */ --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -33,7 +33,6 @@ extern void *memcpy(void *to, const void extern void *__memcpy(void *to, const void *from, size_t len);

#ifndef CONFIG_FORTIFY_SOURCE -#ifndef CONFIG_KMEMCHECK #if (__GNUC__ == 4 && __GNUC_MINOR__ < 3) || __GNUC__ < 4 #define memcpy(dst, src, len) \ ({ \ @@ -46,13 +45,6 @@ extern void *__memcpy(void *to, const vo __ret; \ }) #endif -#else -/* - * kmemcheck becomes very happy if we use the REP instructions unconditionally, - * because it means that we know both memory operands in advance. - */ -#define memcpy(dst, src, len) __inline_memcpy((dst), (src), (len)) -#endif #endif /* !CONFIG_FORTIFY_SOURCE */

#define __HAVE_ARCH_MEMSET --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -250,21 +250,6 @@ static void early_init_intel(struct cpui if (c->x86 == 6 && c->x86_model < 15) clear_cpu_cap(c, X86_FEATURE_PAT);

-#ifdef CONFIG_KMEMCHECK - /* - * P4s have a "fast strings" feature which causes single- - * stepping REP instructions to only generate a #DB on - * cache-line boundaries. - * - * Ingo Molnar reported a Pentium D (model 6) and a Xeon - * (model 2) with the same problem. - */ - if (c->x86 == 15) - if (msr_clear_bit(MSR_IA32_MISC_ENABLE, - MSR_IA32_MISC_ENABLE_FAST_STRING_BIT) > 0) - pr_info("kmemcheck: Disabling fast string operations\n"); -#endif - /* * If fast string is not enabled in IA32_MISC_ENABLE for any reason, * clear the fast string and enhanced fast string CPU capabilities. --- a/arch/x86/mm/Makefile +++ b/arch/x86/mm/Makefile @@ -29,8 +29,6 @@ obj-$(CONFIG_X86_PTDUMP) += debug_pageta

obj-$(CONFIG_HIGHMEM) += highmem_32.o

-obj-$(CONFIG_KMEMCHECK) += kmemcheck/ - KASAN_SANITIZE_kasan_init_$(BITS).o := n obj-$(CONFIG_KASAN) += kasan_init_$(BITS).o

--- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -170,12 +170,11 @@ static void enable_global_pages(void) static void __init probe_page_size_mask(void) { /* - * For CONFIG_KMEMCHECK or pagealloc debugging, identity mapping will - * use small pages. + * For pagealloc debugging, identity mapping will use small pages. * This will simplify cpa(), which otherwise needs to support splitting * large pages into small in interrupt context, etc. */ - if (boot_cpu_has(X86_FEATURE_PSE) && !debug_pagealloc_enabled() && !IS_ENABLED(CONFIG_KMEMCHECK)) + if (boot_cpu_has(X86_FEATURE_PSE) && !debug_pagealloc_enabled()) page_size_mask |= 1 << PG_LEVEL_2M; else direct_gbpages = 0; --- a/arch/x86/mm/kmemcheck/Makefile +++ /dev/null @@ -1 +0,0 @@ -obj-y := error.o kmemcheck.o opcode.o pte.o selftest.o shadow.o --- a/arch/x86/mm/kmemcheck/error.c +++ b/arch/x86/mm/kmemcheck/error.c @@ -1,228 +1 @@ // SPDX-License-Identifier: GPL-2.0 -#include <linux/interrupt.h> -#include <linux/kdebug.h> -#include <linux/kmemcheck.h> -#include <linux/kernel.h> -#include <linux/types.h> -#include <linux/ptrace.h> -#include <linux/stacktrace.h> -#include <linux/string.h> - -#include "error.h" -#include "shadow.h" - -enum kmemcheck_error_type { - KMEMCHECK_ERROR_INVALID_ACCESS, - KMEMCHECK_ERROR_BUG, -}; - -#define SHADOW_COPY_SIZE (1 << CONFIG_KMEMCHECK_SHADOW_COPY_SHIFT) - -struct kmemcheck_error { - enum kmemcheck_error_type type; - - union { - /* KMEMCHECK_ERROR_INVALID_ACCESS */ - struct { - /* Kind of access that caused the error */ - enum kmemcheck_shadow state; - /* Address and size of the erroneous read */ - unsigned long address; - unsigned int size; - }; - }; - - struct pt_regs regs; - struct stack_trace trace; - unsigned long trace_entries[32]; - - /* We compress it to a char. */ - unsigned char shadow_copy[SHADOW_COPY_SIZE]; - unsigned char memory_copy[SHADOW_COPY_SIZE]; -}; - -/* - * Create a ring queue of errors to output. We can't call printk() directly - * from the kmemcheck traps, since this may call the console drivers and - * result in a recursive fault. - */ -static struct kmemcheck_error error_fifo[CONFIG_KMEMCHECK_QUEUE_SIZE]; -static unsigned int error_count; -static unsigned int error_rd; -static unsigned int error_wr; -static unsigned int error_missed_count; - -static struct kmemcheck_error *error_next_wr(void) -{ - struct kmemcheck_error *e; - - if (error_count == ARRAY_SIZE(error_fifo)) { - ++error_missed_count; - return NULL; - } - - e = &error_fifo[error_wr]; - if (++error_wr == ARRAY_SIZE(error_fifo)) - error_wr = 0; - ++error_count; - return e; -} - -static struct kmemcheck_error *error_next_rd(void) -{ - struct kmemcheck_error *e; - - if (error_count == 0) - return NULL; - - e = &error_fifo[error_rd]; - if (++error_rd == ARRAY_SIZE(error_fifo)) - error_rd = 0; - --error_count; - return e; -} - -void kmemcheck_error_recall(void) -{ - static const char *desc[] = { - [KMEMCHECK_SHADOW_UNALLOCATED] = "unallocated", - [KMEMCHECK_SHADOW_UNINITIALIZED] = "uninitialized", - [KMEMCHECK_SHADOW_INITIALIZED] = "initialized", - [KMEMCHECK_SHADOW_FREED] = "freed", - }; - - static const char short_desc[] = { - [KMEMCHECK_SHADOW_UNALLOCATED] = 'a', - [KMEMCHECK_SHADOW_UNINITIALIZED] = 'u', - [KMEMCHECK_SHADOW_INITIALIZED] = 'i', - [KMEMCHECK_SHADOW_FREED] = 'f', - }; - - struct kmemcheck_error *e; - unsigned int i; - - e = error_next_rd(); - if (!e) - return; - - switch (e->type) { - case KMEMCHECK_ERROR_INVALID_ACCESS: - printk(KERN_WARNING "WARNING: kmemcheck: Caught %d-bit read from %s memory (%p)\n", - 8 * e->size, e->state < ARRAY_SIZE(desc) ? - desc[e->state] : "(invalid shadow state)", - (void *) e->address); - - printk(KERN_WARNING); - for (i = 0; i < SHADOW_COPY_SIZE; ++i) - printk(KERN_CONT "%02x", e->memory_copy[i]); - printk(KERN_CONT "\n"); - - printk(KERN_WARNING); - for (i = 0; i < SHADOW_COPY_SIZE; ++i) { - if (e->shadow_copy[i] < ARRAY_SIZE(short_desc)) - printk(KERN_CONT " %c", short_desc[e->shadow_copy[i]]); - else - printk(KERN_CONT " ?"); - } - printk(KERN_CONT "\n"); - printk(KERN_WARNING "%*c\n", 2 + 2 - * (int) (e->address & (SHADOW_COPY_SIZE - 1)), '^'); - break; - case KMEMCHECK_ERROR_BUG: - printk(KERN_EMERG "ERROR: kmemcheck: Fatal error\n"); - break; - } - - __show_regs(&e->regs, 1); - print_stack_trace(&e->trace, 0); -} - -static void do_wakeup(unsigned long data) -{ - while (error_count > 0) - kmemcheck_error_recall(); - - if (error_missed_count > 0) { - printk(KERN_WARNING "kmemcheck: Lost %d error reports because " - "the queue was too small\n", error_missed_count); - error_missed_count = 0; - } -} - -static DECLARE_TASKLET(kmemcheck_tasklet, &do_wakeup, 0); - -/* - * Save the context of an error report. - */ -void kmemcheck_error_save(enum kmemcheck_shadow state, - unsigned long address, unsigned int size, struct pt_regs *regs) -{ - static unsigned long prev_ip; - - struct kmemcheck_error *e; - void *shadow_copy; - void *memory_copy; - - /* Don't report several adjacent errors from the same EIP. */ - if (regs->ip == prev_ip) - return; - prev_ip = regs->ip; - - e = error_next_wr(); - if (!e) - return; - - e->type = KMEMCHECK_ERROR_INVALID_ACCESS; - - e->state = state; - e->address = address; - e->size = size; - - /* Save regs */ - memcpy(&e->regs, regs, sizeof(*regs)); - - /* Save stack trace */ - e->trace.nr_entries = 0; - e->trace.entries = e->trace_entries; - e->trace.max_entries = ARRAY_SIZE(e->trace_entries); - e->trace.skip = 0; - save_stack_trace_regs(regs, &e->trace); - - /* Round address down to nearest 16 bytes */ - shadow_copy = kmemcheck_shadow_lookup(address - & ~(SHADOW_COPY_SIZE - 1)); - BUG_ON(!shadow_copy); - - memcpy(e->shadow_copy, shadow_copy, SHADOW_COPY_SIZE); - - kmemcheck_show_addr(address); - memory_copy = (void *) (address & ~(SHADOW_COPY_SIZE - 1)); - memcpy(e->memory_copy, memory_copy, SHADOW_COPY_SIZE); - kmemcheck_hide_addr(address); - - tasklet_hi_schedule_first(&kmemcheck_tasklet); -} - -/* - * Save the context of a kmemcheck bug. - */ -void kmemcheck_error_save_bug(struct pt_regs *regs) -{ - struct kmemcheck_error *e; - - e = error_next_wr(); - if (!e) - return; - - e->type = KMEMCHECK_ERROR_BUG; - - memcpy(&e->regs, regs, sizeof(*regs)); - - e->trace.nr_entries = 0; - e->trace.entries = e->trace_entries; - e->trace.max_entries = ARRAY_SIZE(e->trace_entries); - e->trace.skip = 1; - save_stack_trace(&e->trace); - - tasklet_hi_schedule_first(&kmemcheck_tasklet); -} --- a/arch/x86/mm/kmemcheck/error.h +++ b/arch/x86/mm/kmemcheck/error.h @@ -1,16 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef ARCH__X86__MM__KMEMCHECK__ERROR_H -#define ARCH__X86__MM__KMEMCHECK__ERROR_H - -#include <linux/ptrace.h> - -#include "shadow.h" - -void kmemcheck_error_save(enum kmemcheck_shadow state, - unsigned long address, unsigned int size, struct pt_regs *regs); - -void kmemcheck_error_save_bug(struct pt_regs *regs); - -void kmemcheck_error_recall(void); - -#endif --- a/arch/x86/mm/kmemcheck/kmemcheck.c +++ /dev/null @@ -1,658 +0,0 @@ -/** - * kmemcheck - a heavyweight memory checker for the linux kernel - * Copyright (C) 2007, 2008 Vegard Nossum vegardno@ifi.uio.no - * (With a lot of help from Ingo Molnar and Pekka Enberg.) - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License (version 2) as - * published by the Free Software Foundation. - */ - -#include <linux/init.h> -#include <linux/interrupt.h> -#include <linux/kallsyms.h> -#include <linux/kernel.h> -#include <linux/kmemcheck.h> -#include <linux/mm.h> -#include <linux/page-flags.h> -#include <linux/percpu.h> -#include <linux/ptrace.h> -#include <linux/string.h> -#include <linux/types.h> - -#include <asm/cacheflush.h> -#include <asm/kmemcheck.h> -#include <asm/pgtable.h> -#include <asm/tlbflush.h> - -#include "error.h" -#include "opcode.h" -#include "pte.h" -#include "selftest.h" -#include "shadow.h" - - -#ifdef CONFIG_KMEMCHECK_DISABLED_BY_DEFAULT -# define KMEMCHECK_ENABLED 0 -#endif - -#ifdef CONFIG_KMEMCHECK_ENABLED_BY_DEFAULT -# define KMEMCHECK_ENABLED 1 -#endif - -#ifdef CONFIG_KMEMCHECK_ONESHOT_BY_DEFAULT -# define KMEMCHECK_ENABLED 2 -#endif - -int kmemcheck_enabled = KMEMCHECK_ENABLED; - -int __init kmemcheck_init(void) -{ -#ifdef CONFIG_SMP - /* - * Limit SMP to use a single CPU. We rely on the fact that this code - * runs before SMP is set up. - */ - if (setup_max_cpus > 1) { - printk(KERN_INFO - "kmemcheck: Limiting number of CPUs to 1.\n"); - setup_max_cpus = 1; - } -#endif - - if (!kmemcheck_selftest()) { - printk(KERN_INFO "kmemcheck: self-tests failed; disabling\n"); - kmemcheck_enabled = 0; - return -EINVAL; - } - - printk(KERN_INFO "kmemcheck: Initialized\n"); - return 0; -} - -early_initcall(kmemcheck_init); - -/* - * We need to parse the kmemcheck= option before any memory is allocated. - */ -static int __init param_kmemcheck(char *str) -{ - int val; - int ret; - - if (!str) - return -EINVAL; - - ret = kstrtoint(str, 0, &val); - if (ret) - return ret; - kmemcheck_enabled = val; - return 0; -} - -early_param("kmemcheck", param_kmemcheck); - -int kmemcheck_show_addr(unsigned long address) -{ - pte_t *pte; - - pte = kmemcheck_pte_lookup(address); - if (!pte) - return 0; - - set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); - __flush_tlb_one(address); - return 1; -} - -int kmemcheck_hide_addr(unsigned long address) -{ - pte_t *pte; - - pte = kmemcheck_pte_lookup(address); - if (!pte) - return 0; - - set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT)); - __flush_tlb_one(address); - return 1; -} - -struct kmemcheck_context { - bool busy; - int balance; - - /* - * There can be at most two memory operands to an instruction, but - * each address can cross a page boundary -- so we may need up to - * four addresses that must be hidden/revealed for each fault. - */ - unsigned long addr[4]; - unsigned long n_addrs; - unsigned long flags; - - /* Data size of the instruction that caused a fault. */ - unsigned int size; -}; - -static DEFINE_PER_CPU(struct kmemcheck_context, kmemcheck_context); - -bool kmemcheck_active(struct pt_regs *regs) -{ - struct kmemcheck_context *data = this_cpu_ptr(&kmemcheck_context); - - return data->balance > 0; -} - -/* Save an address that needs to be shown/hidden */ -static void kmemcheck_save_addr(unsigned long addr) -{ - struct kmemcheck_context *data = this_cpu_ptr(&kmemcheck_context); - - BUG_ON(data->n_addrs >= ARRAY_SIZE(data->addr)); - data->addr[data->n_addrs++] = addr; -} - -static unsigned int kmemcheck_show_all(void) -{ - struct kmemcheck_context *data = this_cpu_ptr(&kmemcheck_context); - unsigned int i; - unsigned int n; - - n = 0; - for (i = 0; i < data->n_addrs; ++i) - n += kmemcheck_show_addr(data->addr[i]); - - return n; -} - -static unsigned int kmemcheck_hide_all(void) -{ - struct kmemcheck_context *data = this_cpu_ptr(&kmemcheck_context); - unsigned int i; - unsigned int n; - - n = 0; - for (i = 0; i < data->n_addrs; ++i) - n += kmemcheck_hide_addr(data->addr[i]); - - return n; -} - -/* - * Called from the #PF handler. - */ -void kmemcheck_show(struct pt_regs *regs) -{ - struct kmemcheck_context *data = this_cpu_ptr(&kmemcheck_context); - - BUG_ON(!irqs_disabled()); - - if (unlikely(data->balance != 0)) { - kmemcheck_show_all(); - kmemcheck_error_save_bug(regs); - data->balance = 0; - return; - } - - /* - * None of the addresses actually belonged to kmemcheck. Note that - * this is not an error. - */ - if (kmemcheck_show_all() == 0) - return; - - ++data->balance; - - /* - * The IF needs to be cleared as well, so that the faulting - * instruction can run "uninterrupted". Otherwise, we might take - * an interrupt and start executing that before we've had a chance - * to hide the page again. - * - * NOTE: In the rare case of multiple faults, we must not override - * the original flags: - */ - if (!(regs->flags & X86_EFLAGS_TF)) - data->flags = regs->flags; - - regs->flags |= X86_EFLAGS_TF; - regs->flags &= ~X86_EFLAGS_IF; -} - -/* - * Called from the #DB handler. - */ -void kmemcheck_hide(struct pt_regs *regs) -{ - struct kmemcheck_context *data = this_cpu_ptr(&kmemcheck_context); - int n; - - BUG_ON(!irqs_disabled()); - - if (unlikely(data->balance != 1)) { - kmemcheck_show_all(); - kmemcheck_error_save_bug(regs); - data->n_addrs = 0; - data->balance = 0; - - if (!(data->flags & X86_EFLAGS_TF)) - regs->flags &= ~X86_EFLAGS_TF; - if (data->flags & X86_EFLAGS_IF) - regs->flags |= X86_EFLAGS_IF; - return; - } - - if (kmemcheck_enabled) - n = kmemcheck_hide_all(); - else - n = kmemcheck_show_all(); - - if (n == 0) - return; - - --data->balance; - - data->n_addrs = 0; - - if (!(data->flags & X86_EFLAGS_TF)) - regs->flags &= ~X86_EFLAGS_TF; - if (data->flags & X86_EFLAGS_IF) - regs->flags |= X86_EFLAGS_IF; -} - -void kmemcheck_show_pages(struct page *p, unsigned int n) -{ - unsigned int i; - - for (i = 0; i < n; ++i) { - unsigned long address; - pte_t *pte; - unsigned int level; - - address = (unsigned long) page_address(&p[i]); - pte = lookup_address(address, &level); - BUG_ON(!pte); - BUG_ON(level != PG_LEVEL_4K); - - set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); - set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_HIDDEN)); - __flush_tlb_one(address); - } -} - -bool kmemcheck_page_is_tracked(struct page *p) -{ - /* This will also check the "hidden" flag of the PTE. */ - return kmemcheck_pte_lookup((unsigned long) page_address(p)); -} - -void kmemcheck_hide_pages(struct page *p, unsigned int n) -{ - unsigned int i; - - for (i = 0; i < n; ++i) { - unsigned long address; - pte_t *pte; - unsigned int level; - - address = (unsigned long) page_address(&p[i]); - pte = lookup_address(address, &level); - BUG_ON(!pte); - BUG_ON(level != PG_LEVEL_4K); - - set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT)); - set_pte(pte, __pte(pte_val(*pte) | _PAGE_HIDDEN)); - __flush_tlb_one(address); - } -} - -/* Access may NOT cross page boundary */ -static void kmemcheck_read_strict(struct pt_regs *regs, - unsigned long addr, unsigned int size) -{ - void *shadow; - enum kmemcheck_shadow status; - - shadow = kmemcheck_shadow_lookup(addr); - if (!shadow) - return; - - kmemcheck_save_addr(addr); - status = kmemcheck_shadow_test(shadow, size); - if (status == KMEMCHECK_SHADOW_INITIALIZED) - return; - - if (kmemcheck_enabled) - kmemcheck_error_save(status, addr, size, regs); - - if (kmemcheck_enabled == 2) - kmemcheck_enabled = 0; - - /* Don't warn about it again. */ - kmemcheck_shadow_set(shadow, size); -} - -bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size) -{ - enum kmemcheck_shadow status; - void *shadow; - - shadow = kmemcheck_shadow_lookup(addr); - if (!shadow) - return true; - - status = kmemcheck_shadow_test_all(shadow, size); - - return status == KMEMCHECK_SHADOW_INITIALIZED; -} - -/* Access may cross page boundary */ -static void kmemcheck_read(struct pt_regs *regs, - unsigned long addr, unsigned int size) -{ - unsigned long page = addr & PAGE_MASK; - unsigned long next_addr = addr + size - 1; - unsigned long next_page = next_addr & PAGE_MASK; - - if (likely(page == next_page)) { - kmemcheck_read_strict(regs, addr, size); - return; - } - - /* - * What we do is basically to split the access across the - * two pages and handle each part separately. Yes, this means - * that we may now see reads that are 3 + 5 bytes, for - * example (and if both are uninitialized, there will be two - * reports), but it makes the code a lot simpler. - */ - kmemcheck_read_strict(regs, addr, next_page - addr); - kmemcheck_read_strict(regs, next_page, next_addr - next_page); -} - -static void kmemcheck_write_strict(struct pt_regs *regs, - unsigned long addr, unsigned int size) -{ - void *shadow; - - shadow = kmemcheck_shadow_lookup(addr); - if (!shadow) - return; - - kmemcheck_save_addr(addr); - kmemcheck_shadow_set(shadow, size); -} - -static void kmemcheck_write(struct pt_regs *regs, - unsigned long addr, unsigned int size) -{ - unsigned long page = addr & PAGE_MASK; - unsigned long next_addr = addr + size - 1; - unsigned long next_page = next_addr & PAGE_MASK; - - if (likely(page == next_page)) { - kmemcheck_write_strict(regs, addr, size); - return; - } - - /* See comment in kmemcheck_read(). */ - kmemcheck_write_strict(regs, addr, next_page - addr); - kmemcheck_write_strict(regs, next_page, next_addr - next_page); -} - -/* - * Copying is hard. We have two addresses, each of which may be split across - * a page (and each page will have different shadow addresses). - */ -static void kmemcheck_copy(struct pt_regs *regs, - unsigned long src_addr, unsigned long dst_addr, unsigned int size) -{ - uint8_t shadow[8]; - enum kmemcheck_shadow status; - - unsigned long page; - unsigned long next_addr; - unsigned long next_page; - - uint8_t *x; - unsigned int i; - unsigned int n; - - BUG_ON(size > sizeof(shadow)); - - page = src_addr & PAGE_MASK; - next_addr = src_addr + size - 1; - next_page = next_addr & PAGE_MASK; - - if (likely(page == next_page)) { - /* Same page */ - x = kmemcheck_shadow_lookup(src_addr); - if (x) { - kmemcheck_save_addr(src_addr); - for (i = 0; i < size; ++i) - shadow[i] = x[i]; - } else { - for (i = 0; i < size; ++i) - shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; - } - } else { - n = next_page - src_addr; - BUG_ON(n > sizeof(shadow)); - - /* First page */ - x = kmemcheck_shadow_lookup(src_addr); - if (x) { - kmemcheck_save_addr(src_addr); - for (i = 0; i < n; ++i) - shadow[i] = x[i]; - } else { - /* Not tracked */ - for (i = 0; i < n; ++i) - shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; - } - - /* Second page */ - x = kmemcheck_shadow_lookup(next_page); - if (x) { - kmemcheck_save_addr(next_page); - for (i = n; i < size; ++i) - shadow[i] = x[i - n]; - } else { - /* Not tracked */ - for (i = n; i < size; ++i) - shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; - } - } - - page = dst_addr & PAGE_MASK; - next_addr = dst_addr + size - 1; - next_page = next_addr & PAGE_MASK; - - if (likely(page == next_page)) { - /* Same page */ - x = kmemcheck_shadow_lookup(dst_addr); - if (x) { - kmemcheck_save_addr(dst_addr); - for (i = 0; i < size; ++i) { - x[i] = shadow[i]; - shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; - } - } - } else { - n = next_page - dst_addr; - BUG_ON(n > sizeof(shadow)); - - /* First page */ - x = kmemcheck_shadow_lookup(dst_addr); - if (x) { - kmemcheck_save_addr(dst_addr); - for (i = 0; i < n; ++i) { - x[i] = shadow[i]; - shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; - } - } - - /* Second page */ - x = kmemcheck_shadow_lookup(next_page); - if (x) { - kmemcheck_save_addr(next_page); - for (i = n; i < size; ++i) { - x[i - n] = shadow[i]; - shadow[i] = KMEMCHECK_SHADOW_INITIALIZED; - } - } - } - - status = kmemcheck_shadow_test(shadow, size); - if (status == KMEMCHECK_SHADOW_INITIALIZED) - return; - - if (kmemcheck_enabled) - kmemcheck_error_save(status, src_addr, size, regs); - - if (kmemcheck_enabled == 2) - kmemcheck_enabled = 0; -} - -enum kmemcheck_method { - KMEMCHECK_READ, - KMEMCHECK_WRITE, -}; - -static void kmemcheck_access(struct pt_regs *regs, - unsigned long fallback_address, enum kmemcheck_method fallback_method) -{ - const uint8_t *insn; - const uint8_t *insn_primary; - unsigned int size; - - struct kmemcheck_context *data = this_cpu_ptr(&kmemcheck_context); - - /* Recursive fault -- ouch. */ - if (data->busy) { - kmemcheck_show_addr(fallback_address); - kmemcheck_error_save_bug(regs); - return; - } - - data->busy = true; - - insn = (const uint8_t *) regs->ip; - insn_primary = kmemcheck_opcode_get_primary(insn); - - kmemcheck_opcode_decode(insn, &size); - - switch (insn_primary[0]) { -#ifdef CONFIG_KMEMCHECK_BITOPS_OK - /* AND, OR, XOR */ - /* - * Unfortunately, these instructions have to be excluded from - * our regular checking since they access only some (and not - * all) bits. This clears out "bogus" bitfield-access warnings. - */ - case 0x80: - case 0x81: - case 0x82: - case 0x83: - switch ((insn_primary[1] >> 3) & 7) { - /* OR */ - case 1: - /* AND */ - case 4: - /* XOR */ - case 6: - kmemcheck_write(regs, fallback_address, size); - goto out; - - /* ADD */ - case 0: - /* ADC */ - case 2: - /* SBB */ - case 3: - /* SUB */ - case 5: - /* CMP */ - case 7: - break; - } - break; -#endif - - /* MOVS, MOVSB, MOVSW, MOVSD */ - case 0xa4: - case 0xa5: - /* - * These instructions are special because they take two - * addresses, but we only get one page fault. - */ - kmemcheck_copy(regs, regs->si, regs->di, size); - goto out; - - /* CMPS, CMPSB, CMPSW, CMPSD */ - case 0xa6: - case 0xa7: - kmemcheck_read(regs, regs->si, size); - kmemcheck_read(regs, regs->di, size); - goto out; - } - - /* - * If the opcode isn't special in any way, we use the data from the - * page fault handler to determine the address and type of memory - * access. - */ - switch (fallback_method) { - case KMEMCHECK_READ: - kmemcheck_read(regs, fallback_address, size); - goto out; - case KMEMCHECK_WRITE: - kmemcheck_write(regs, fallback_address, size); - goto out; - } - -out: - data->busy = false; -} - -bool kmemcheck_fault(struct pt_regs *regs, unsigned long address, - unsigned long error_code) -{ - pte_t *pte; - - /* - * XXX: Is it safe to assume that memory accesses from virtual 86 - * mode or non-kernel code segments will _never_ access kernel - * memory (e.g. tracked pages)? For now, we need this to avoid - * invoking kmemcheck for PnP BIOS calls. - */ - if (regs->flags & X86_VM_MASK) - return false; - if (regs->cs != __KERNEL_CS) - return false; - - pte = kmemcheck_pte_lookup(address); - if (!pte) - return false; - - WARN_ON_ONCE(in_nmi()); - - if (error_code & 2) - kmemcheck_access(regs, address, KMEMCHECK_WRITE); - else - kmemcheck_access(regs, address, KMEMCHECK_READ); - - kmemcheck_show(regs); - return true; -} - -bool kmemcheck_trap(struct pt_regs *regs) -{ - if (!kmemcheck_active(regs)) - return false; - - /* We're done. */ - kmemcheck_hide(regs); - return true; -} --- a/arch/x86/mm/kmemcheck/opcode.c +++ b/arch/x86/mm/kmemcheck/opcode.c @@ -1,107 +1 @@ // SPDX-License-Identifier: GPL-2.0 -#include <linux/types.h> - -#include "opcode.h" - -static bool opcode_is_prefix(uint8_t b) -{ - return - /* Group 1 */ - b == 0xf0 || b == 0xf2 || b == 0xf3 - /* Group 2 */ - || b == 0x2e || b == 0x36 || b == 0x3e || b == 0x26 - || b == 0x64 || b == 0x65 - /* Group 3 */ - || b == 0x66 - /* Group 4 */ - || b == 0x67; -} - -#ifdef CONFIG_X86_64 -static bool opcode_is_rex_prefix(uint8_t b) -{ - return (b & 0xf0) == 0x40; -} -#else -static bool opcode_is_rex_prefix(uint8_t b) -{ - return false; -} -#endif - -#define REX_W (1 << 3) - -/* - * This is a VERY crude opcode decoder. We only need to find the size of the - * load/store that caused our #PF and this should work for all the opcodes - * that we care about. Moreover, the ones who invented this instruction set - * should be shot. - */ -void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size) -{ - /* Default operand size */ - int operand_size_override = 4; - - /* prefixes */ - for (; opcode_is_prefix(*op); ++op) { - if (*op == 0x66) - operand_size_override = 2; - } - - /* REX prefix */ - if (opcode_is_rex_prefix(*op)) { - uint8_t rex = *op; - - ++op; - if (rex & REX_W) { - switch (*op) { - case 0x63: - *size = 4; - return; - case 0x0f: - ++op; - - switch (*op) { - case 0xb6: - case 0xbe: - *size = 1; - return; - case 0xb7: - case 0xbf: - *size = 2; - return; - } - - break; - } - - *size = 8; - return; - } - } - - /* escape opcode */ - if (*op == 0x0f) { - ++op; - - /* - * This is move with zero-extend and sign-extend, respectively; - * we don't have to think about 0xb6/0xbe, because this is - * already handled in the conditional below. - */ - if (*op == 0xb7 || *op == 0xbf) - operand_size_override = 2; - } - - *size = (*op & 1) ? operand_size_override : 1; -} - -const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op) -{ - /* skip prefixes */ - while (opcode_is_prefix(*op)) - ++op; - if (opcode_is_rex_prefix(*op)) - ++op; - return op; -} --- a/arch/x86/mm/kmemcheck/opcode.h +++ b/arch/x86/mm/kmemcheck/opcode.h @@ -1,10 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef ARCH__X86__MM__KMEMCHECK__OPCODE_H -#define ARCH__X86__MM__KMEMCHECK__OPCODE_H - -#include <linux/types.h> - -void kmemcheck_opcode_decode(const uint8_t *op, unsigned int *size); -const uint8_t *kmemcheck_opcode_get_primary(const uint8_t *op); - -#endif --- a/arch/x86/mm/kmemcheck/pte.c +++ b/arch/x86/mm/kmemcheck/pte.c @@ -1,23 +1 @@ // SPDX-License-Identifier: GPL-2.0 -#include <linux/mm.h> - -#include <asm/pgtable.h> - -#include "pte.h" - -pte_t *kmemcheck_pte_lookup(unsigned long address) -{ - pte_t *pte; - unsigned int level; - - pte = lookup_address(address, &level); - if (!pte) - return NULL; - if (level != PG_LEVEL_4K) - return NULL; - if (!pte_hidden(*pte)) - return NULL; - - return pte; -} - --- a/arch/x86/mm/kmemcheck/pte.h +++ b/arch/x86/mm/kmemcheck/pte.h @@ -1,11 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef ARCH__X86__MM__KMEMCHECK__PTE_H -#define ARCH__X86__MM__KMEMCHECK__PTE_H - -#include <linux/mm.h> - -#include <asm/pgtable.h> - -pte_t *kmemcheck_pte_lookup(unsigned long address); - -#endif --- a/arch/x86/mm/kmemcheck/selftest.c +++ b/arch/x86/mm/kmemcheck/selftest.c @@ -1,71 +1 @@ // SPDX-License-Identifier: GPL-2.0 -#include <linux/bug.h> -#include <linux/kernel.h> - -#include "opcode.h" -#include "selftest.h" - -struct selftest_opcode { - unsigned int expected_size; - const uint8_t *insn; - const char *desc; -}; - -static const struct selftest_opcode selftest_opcodes[] = { - /* REP MOVS */ - {1, "\xf3\xa4", "rep movsb <mem8>, <mem8>"}, - {4, "\xf3\xa5", "rep movsl <mem32>, <mem32>"}, - - /* MOVZX / MOVZXD */ - {1, "\x66\x0f\xb6\x51\xf8", "movzwq <mem8>, <reg16>"}, - {1, "\x0f\xb6\x51\xf8", "movzwq <mem8>, <reg32>"}, - - /* MOVSX / MOVSXD */ - {1, "\x66\x0f\xbe\x51\xf8", "movswq <mem8>, <reg16>"}, - {1, "\x0f\xbe\x51\xf8", "movswq <mem8>, <reg32>"}, - -#ifdef CONFIG_X86_64 - /* MOVZX / MOVZXD */ - {1, "\x49\x0f\xb6\x51\xf8", "movzbq <mem8>, <reg64>"}, - {2, "\x49\x0f\xb7\x51\xf8", "movzbq <mem16>, <reg64>"}, - - /* MOVSX / MOVSXD */ - {1, "\x49\x0f\xbe\x51\xf8", "movsbq <mem8>, <reg64>"}, - {2, "\x49\x0f\xbf\x51\xf8", "movsbq <mem16>, <reg64>"}, - {4, "\x49\x63\x51\xf8", "movslq <mem32>, <reg64>"}, -#endif -}; - -static bool selftest_opcode_one(const struct selftest_opcode *op) -{ - unsigned size; - - kmemcheck_opcode_decode(op->insn, &size); - - if (size == op->expected_size) - return true; - - printk(KERN_WARNING "kmemcheck: opcode %s: expected size %d, got %d\n", - op->desc, op->expected_size, size); - return false; -} - -static bool selftest_opcodes_all(void) -{ - bool pass = true; - unsigned int i; - - for (i = 0; i < ARRAY_SIZE(selftest_opcodes); ++i) - pass = pass && selftest_opcode_one(&selftest_opcodes[i]); - - return pass; -} - -bool kmemcheck_selftest(void) -{ - bool pass = true; - - pass = pass && selftest_opcodes_all(); - - return pass; -} --- a/arch/x86/mm/kmemcheck/selftest.h +++ b/arch/x86/mm/kmemcheck/selftest.h @@ -1,7 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef ARCH_X86_MM_KMEMCHECK_SELFTEST_H -#define ARCH_X86_MM_KMEMCHECK_SELFTEST_H - -bool kmemcheck_selftest(void); - -#endif --- a/arch/x86/mm/kmemcheck/shadow.c +++ /dev/null @@ -1,173 +0,0 @@ -#include <linux/kmemcheck.h> -#include <linux/export.h> -#include <linux/mm.h> - -#include <asm/page.h> -#include <asm/pgtable.h> - -#include "pte.h" -#include "shadow.h" - -/* - * Return the shadow address for the given address. Returns NULL if the - * address is not tracked. - * - * We need to be extremely careful not to follow any invalid pointers, - * because this function can be called for *any* possible address. - */ -void *kmemcheck_shadow_lookup(unsigned long address) -{ - pte_t *pte; - struct page *page; - - if (!virt_addr_valid(address)) - return NULL; - - pte = kmemcheck_pte_lookup(address); - if (!pte) - return NULL; - - page = virt_to_page(address); - if (!page->shadow) - return NULL; - return page->shadow + (address & (PAGE_SIZE - 1)); -} - -static void mark_shadow(void *address, unsigned int n, - enum kmemcheck_shadow status) -{ - unsigned long addr = (unsigned long) address; - unsigned long last_addr = addr + n - 1; - unsigned long page = addr & PAGE_MASK; - unsigned long last_page = last_addr & PAGE_MASK; - unsigned int first_n; - void *shadow; - - /* If the memory range crosses a page boundary, stop there. */ - if (page == last_page) - first_n = n; - else - first_n = page + PAGE_SIZE - addr; - - shadow = kmemcheck_shadow_lookup(addr); - if (shadow) - memset(shadow, status, first_n); - - addr += first_n; - n -= first_n; - - /* Do full-page memset()s. */ - while (n >= PAGE_SIZE) { - shadow = kmemcheck_shadow_lookup(addr); - if (shadow) - memset(shadow, status, PAGE_SIZE); - - addr += PAGE_SIZE; - n -= PAGE_SIZE; - } - - /* Do the remaining page, if any. */ - if (n > 0) { - shadow = kmemcheck_shadow_lookup(addr); - if (shadow) - memset(shadow, status, n); - } -} - -void kmemcheck_mark_unallocated(void *address, unsigned int n) -{ - mark_shadow(address, n, KMEMCHECK_SHADOW_UNALLOCATED); -} - -void kmemcheck_mark_uninitialized(void *address, unsigned int n) -{ - mark_shadow(address, n, KMEMCHECK_SHADOW_UNINITIALIZED); -} - -/* - * Fill the shadow memory of the given address such that the memory at that - * address is marked as being initialized. - */ -void kmemcheck_mark_initialized(void *address, unsigned int n) -{ - mark_shadow(address, n, KMEMCHECK_SHADOW_INITIALIZED); -} -EXPORT_SYMBOL_GPL(kmemcheck_mark_initialized); - -void kmemcheck_mark_freed(void *address, unsigned int n) -{ - mark_shadow(address, n, KMEMCHECK_SHADOW_FREED); -} - -void kmemcheck_mark_unallocated_pages(struct page *p, unsigned int n) -{ - unsigned int i; - - for (i = 0; i < n; ++i) - kmemcheck_mark_unallocated(page_address(&p[i]), PAGE_SIZE); -} - -void kmemcheck_mark_uninitialized_pages(struct page *p, unsigned int n) -{ - unsigned int i; - - for (i = 0; i < n; ++i) - kmemcheck_mark_uninitialized(page_address(&p[i]), PAGE_SIZE); -} - -void kmemcheck_mark_initialized_pages(struct page *p, unsigned int n) -{ - unsigned int i; - - for (i = 0; i < n; ++i) - kmemcheck_mark_initialized(page_address(&p[i]), PAGE_SIZE); -} - -enum kmemcheck_shadow kmemcheck_shadow_test(void *shadow, unsigned int size) -{ -#ifdef CONFIG_KMEMCHECK_PARTIAL_OK - uint8_t *x; - unsigned int i; - - x = shadow; - - /* - * Make sure _some_ bytes are initialized. Gcc frequently generates - * code to access neighboring bytes. - */ - for (i = 0; i < size; ++i) { - if (x[i] == KMEMCHECK_SHADOW_INITIALIZED) - return x[i]; - } - - return x[0]; -#else - return kmemcheck_shadow_test_all(shadow, size); -#endif -} - -enum kmemcheck_shadow kmemcheck_shadow_test_all(void *shadow, unsigned int size) -{ - uint8_t *x; - unsigned int i; - - x = shadow; - - /* All bytes must be initialized. */ - for (i = 0; i < size; ++i) { - if (x[i] != KMEMCHECK_SHADOW_INITIALIZED) - return x[i]; - } - - return x[0]; -} - -void kmemcheck_shadow_set(void *shadow, unsigned int size) -{ - uint8_t *x; - unsigned int i; - - x = shadow; - for (i = 0; i < size; ++i) - x[i] = KMEMCHECK_SHADOW_INITIALIZED; -} --- a/arch/x86/mm/kmemcheck/shadow.h +++ b/arch/x86/mm/kmemcheck/shadow.h @@ -1,19 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef ARCH__X86__MM__KMEMCHECK__SHADOW_H -#define ARCH__X86__MM__KMEMCHECK__SHADOW_H - -enum kmemcheck_shadow { - KMEMCHECK_SHADOW_UNALLOCATED, - KMEMCHECK_SHADOW_UNINITIALIZED, - KMEMCHECK_SHADOW_INITIALIZED, - KMEMCHECK_SHADOW_FREED, -}; - -void *kmemcheck_shadow_lookup(unsigned long address); - -enum kmemcheck_shadow kmemcheck_shadow_test(void *shadow, unsigned int size); -enum kmemcheck_shadow kmemcheck_shadow_test_all(void *shadow, - unsigned int size); -void kmemcheck_shadow_set(void *shadow, unsigned int size); - -#endif --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -594,21 +594,6 @@ static inline void tasklet_hi_schedule(s __tasklet_hi_schedule(t); }

-extern void __tasklet_hi_schedule_first(struct tasklet_struct *t); - -/* - * This version avoids touching any other tasklets. Needed for kmemcheck - * in order not to take any page faults while enqueueing this tasklet; - * consider VERY carefully whether you really need this or - * tasklet_hi_schedule()... - */ -static inline void tasklet_hi_schedule_first(struct tasklet_struct *t) -{ - if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) - __tasklet_hi_schedule_first(t); -} - - static inline void tasklet_disable_nosync(struct tasklet_struct *t) { atomic_inc(&t->count); --- a/include/linux/kmemcheck.h +++ b/include/linux/kmemcheck.h @@ -1,172 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef LINUX_KMEMCHECK_H -#define LINUX_KMEMCHECK_H - -#include <linux/mm_types.h> -#include <linux/types.h> - -#ifdef CONFIG_KMEMCHECK -extern int kmemcheck_enabled; - -/* The slab-related functions. */ -void kmemcheck_alloc_shadow(struct page *page, int order, gfp_t flags, int node); -void kmemcheck_free_shadow(struct page *page, int order); -void kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object, - size_t size); -void kmemcheck_slab_free(struct kmem_cache *s, void *object, size_t size); - -void kmemcheck_pagealloc_alloc(struct page *p, unsigned int order, - gfp_t gfpflags); - -void kmemcheck_show_pages(struct page *p, unsigned int n); -void kmemcheck_hide_pages(struct page *p, unsigned int n); - -bool kmemcheck_page_is_tracked(struct page *p); - -void kmemcheck_mark_unallocated(void *address, unsigned int n); -void kmemcheck_mark_uninitialized(void *address, unsigned int n); -void kmemcheck_mark_initialized(void *address, unsigned int n); -void kmemcheck_mark_freed(void *address, unsigned int n); - -void kmemcheck_mark_unallocated_pages(struct page *p, unsigned int n); -void kmemcheck_mark_uninitialized_pages(struct page *p, unsigned int n); -void kmemcheck_mark_initialized_pages(struct page *p, unsigned int n); - -int kmemcheck_show_addr(unsigned long address); -int kmemcheck_hide_addr(unsigned long address); - -bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size); - -/* - * Bitfield annotations - * - * How to use: If you have a struct using bitfields, for example - * - * struct a { - * int x:8, y:8; - * }; - * - * then this should be rewritten as - * - * struct a { - * kmemcheck_bitfield_begin(flags); - * int x:8, y:8; - * kmemcheck_bitfield_end(flags); - * }; - * - * Now the "flags_begin" and "flags_end" members may be used to refer to the - * beginning and end, respectively, of the bitfield (and things like - * &x.flags_begin is allowed). As soon as the struct is allocated, the bit- - * fields should be annotated: - * - * struct a *a = kmalloc(sizeof(struct a), GFP_KERNEL); - * kmemcheck_annotate_bitfield(a, flags); - */ -#define kmemcheck_bitfield_begin(name) \ - int name##_begin[0]; - -#define kmemcheck_bitfield_end(name) \ - int name##_end[0]; - -#define kmemcheck_annotate_bitfield(ptr, name) \ - do { \ - int _n; \ - \ - if (!ptr) \ - break; \ - \ - _n = (long) &((ptr)->name##_end) \ - - (long) &((ptr)->name##_begin); \ - BUILD_BUG_ON(_n < 0); \ - \ - kmemcheck_mark_initialized(&((ptr)->name##_begin), _n); \ - } while (0) - -#define kmemcheck_annotate_variable(var) \ - do { \ - kmemcheck_mark_initialized(&(var), sizeof(var)); \ - } while (0) \ - -#else -#define kmemcheck_enabled 0 - -static inline void -kmemcheck_alloc_shadow(struct page *page, int order, gfp_t flags, int node) -{ -} - -static inline void -kmemcheck_free_shadow(struct page *page, int order) -{ -} - -static inline void -kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object, - size_t size) -{ -} - -static inline void kmemcheck_slab_free(struct kmem_cache *s, void *object, - size_t size) -{ -} - -static inline void kmemcheck_pagealloc_alloc(struct page *p, - unsigned int order, gfp_t gfpflags) -{ -} - -static inline bool kmemcheck_page_is_tracked(struct page *p) -{ - return false; -} - -static inline void kmemcheck_mark_unallocated(void *address, unsigned int n) -{ -} - -static inline void kmemcheck_mark_uninitialized(void *address, unsigned int n) -{ -} - -static inline void kmemcheck_mark_initialized(void *address, unsigned int n) -{ -} - -static inline void kmemcheck_mark_freed(void *address, unsigned int n) -{ -} - -static inline void kmemcheck_mark_unallocated_pages(struct page *p, - unsigned int n) -{ -} - -static inline void kmemcheck_mark_uninitialized_pages(struct page *p, - unsigned int n) -{ -} - -static inline void kmemcheck_mark_initialized_pages(struct page *p, - unsigned int n) -{ -} - -static inline bool kmemcheck_is_obj_initialized(unsigned long addr, size_t size) -{ - return true; -} - -#define kmemcheck_bitfield_begin(name) -#define kmemcheck_bitfield_end(name) -#define kmemcheck_annotate_bitfield(ptr, name) \ - do { \ - } while (0) - -#define kmemcheck_annotate_variable(var) \ - do { \ - } while (0) - -#endif /* CONFIG_KMEMCHECK */ - -#endif /* LINUX_KMEMCHECK_H */ --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -486,16 +486,6 @@ void __tasklet_hi_schedule(struct taskle } EXPORT_SYMBOL(__tasklet_hi_schedule);

-void __tasklet_hi_schedule_first(struct tasklet_struct *t) -{ - BUG_ON(!irqs_disabled()); - - t->next = __this_cpu_read(tasklet_hi_vec.head); - __this_cpu_write(tasklet_hi_vec.head, t); - __raise_softirq_irqoff(HI_SOFTIRQ); -} -EXPORT_SYMBOL(__tasklet_hi_schedule_first); - static __latent_entropy void tasklet_action(struct softirq_action *a) { struct tasklet_struct *list; --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -30,7 +30,6 @@ #include <linux/proc_fs.h> #include <linux/security.h> #include <linux/ctype.h> -#include <linux/kmemcheck.h> #include <linux/kmemleak.h> #include <linux/fs.h> #include <linux/init.h> @@ -1174,15 +1173,6 @@ static struct ctl_table kern_table[] = { .extra2 = &one_thousand, }, #endif -#ifdef CONFIG_KMEMCHECK - { - .procname = "kmemcheck", - .data = &kmemcheck_enabled, - .maxlen = sizeof(int), - .mode = 0644, - .proc_handler = proc_dointvec, - }, -#endif { .procname = "panic_on_warn", .data = &panic_on_warn, --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -504,7 +504,7 @@ config DEBUG_OBJECTS_ENABLE_DEFAULT

config DEBUG_SLAB bool "Debug slab memory allocations" - depends on DEBUG_KERNEL && SLAB && !KMEMCHECK + depends on DEBUG_KERNEL && SLAB help Say Y here to have the kernel do limited verification on memory allocation as well as poisoning memory on free to catch use of freed @@ -516,7 +516,7 @@ config DEBUG_SLAB_LEAK

config SLUB_DEBUG_ON bool "SLUB debugging on by default" - depends on SLUB && SLUB_DEBUG && !KMEMCHECK + depends on SLUB && SLUB_DEBUG default n help Boot with debugging on by default. SLUB boots by default with @@ -730,8 +730,6 @@ config DEBUG_STACKOVERFLOW

If in doubt, say "N".

-source "lib/Kconfig.kmemcheck" - source "lib/Kconfig.kasan"

endmenu # "Memory Debugging" --- a/lib/Kconfig.kmemcheck +++ /dev/null @@ -1,94 +0,0 @@ -config HAVE_ARCH_KMEMCHECK - bool - -if HAVE_ARCH_KMEMCHECK - -menuconfig KMEMCHECK - bool "kmemcheck: trap use of uninitialized memory" - depends on DEBUG_KERNEL - depends on !X86_USE_3DNOW - depends on SLUB || SLAB - depends on !CC_OPTIMIZE_FOR_SIZE - depends on !FUNCTION_TRACER - select FRAME_POINTER - select STACKTRACE - default n - help - This option enables tracing of dynamically allocated kernel memory - to see if memory is used before it has been given an initial value. - Be aware that this requires half of your memory for bookkeeping and - will insert extra code at *every* read and write to tracked memory - thus slow down the kernel code (but user code is unaffected). - - The kernel may be started with kmemcheck=0 or kmemcheck=1 to disable - or enable kmemcheck at boot-time. If the kernel is started with - kmemcheck=0, the large memory and CPU overhead is not incurred. - -choice - prompt "kmemcheck: default mode at boot" - depends on KMEMCHECK - default KMEMCHECK_ONESHOT_BY_DEFAULT - help - This option controls the default behaviour of kmemcheck when the - kernel boots and no kmemcheck= parameter is given. - -config KMEMCHECK_DISABLED_BY_DEFAULT - bool "disabled" - depends on KMEMCHECK - -config KMEMCHECK_ENABLED_BY_DEFAULT - bool "enabled" - depends on KMEMCHECK - -config KMEMCHECK_ONESHOT_BY_DEFAULT - bool "one-shot" - depends on KMEMCHECK - help - In one-shot mode, only the first error detected is reported before - kmemcheck is disabled. - -endchoice - -config KMEMCHECK_QUEUE_SIZE - int "kmemcheck: error queue size" - depends on KMEMCHECK - default 64 - help - Select the maximum number of errors to store in the queue. Since - errors can occur virtually anywhere and in any context, we need a - temporary storage area which is guarantueed not to generate any - other faults. The queue will be emptied as soon as a tasklet may - be scheduled. If the queue is full, new error reports will be - lost. - -config KMEMCHECK_SHADOW_COPY_SHIFT - int "kmemcheck: shadow copy size (5 => 32 bytes, 6 => 64 bytes)" - depends on KMEMCHECK - range 2 8 - default 5 - help - Select the number of shadow bytes to save along with each entry of - the queue. These bytes indicate what parts of an allocation are - initialized, uninitialized, etc. and will be displayed when an - error is detected to help the debugging of a particular problem. - -config KMEMCHECK_PARTIAL_OK - bool "kmemcheck: allow partially uninitialized memory" - depends on KMEMCHECK - default y - help - This option works around certain GCC optimizations that produce - 32-bit reads from 16-bit variables where the upper 16 bits are - thrown away afterwards. This may of course also hide some real - bugs. - -config KMEMCHECK_BITOPS_OK - bool "kmemcheck: allow bit-field manipulation" - depends on KMEMCHECK - default n - help - This option silences warnings that would be generated for bit-field - accesses where not all the bits are initialized at the same time. - This may also hide some real bugs. - -endif --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -11,7 +11,6 @@ config DEBUG_PAGEALLOC bool "Debug page memory allocations" depends on DEBUG_KERNEL depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC - depends on !KMEMCHECK select PAGE_EXTENSION select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC ---help--- --- a/mm/Makefile +++ b/mm/Makefile @@ -17,7 +17,6 @@ KCOV_INSTRUMENT_slub.o := n KCOV_INSTRUMENT_page_alloc.o := n KCOV_INSTRUMENT_debug-pagealloc.o := n KCOV_INSTRUMENT_kmemleak.o := n -KCOV_INSTRUMENT_kmemcheck.o := n KCOV_INSTRUMENT_memcontrol.o := n KCOV_INSTRUMENT_mmzone.o := n KCOV_INSTRUMENT_vmstat.o := n @@ -70,7 +69,6 @@ obj-$(CONFIG_KSM) += ksm.o obj-$(CONFIG_PAGE_POISONING) += page_poison.o obj-$(CONFIG_SLAB) += slab.o obj-$(CONFIG_SLUB) += slub.o -obj-$(CONFIG_KMEMCHECK) += kmemcheck.o obj-$(CONFIG_KASAN) += kasan/ obj-$(CONFIG_FAILSLAB) += failslab.o obj-$(CONFIG_MEMORY_HOTPLUG) += memory_hotplug.o --- a/mm/kmemcheck.c +++ b/mm/kmemcheck.c @@ -1,126 +1 @@ // SPDX-License-Identifier: GPL-2.0 -#include <linux/gfp.h> -#include <linux/mm_types.h> -#include <linux/mm.h> -#include <linux/slab.h> -#include "slab.h" -#include <linux/kmemcheck.h> - -void kmemcheck_alloc_shadow(struct page *page, int order, gfp_t flags, int node) -{ - struct page *shadow; - int pages; - int i; - - pages = 1 << order; - - /* - * With kmemcheck enabled, we need to allocate a memory area for the - * shadow bits as well. - */ - shadow = alloc_pages_node(node, flags, order); - if (!shadow) { - if (printk_ratelimit()) - pr_err("kmemcheck: failed to allocate shadow bitmap\n"); - return; - } - - for(i = 0; i < pages; ++i) - page[i].shadow = page_address(&shadow[i]); - - /* - * Mark it as non-present for the MMU so that our accesses to - * this memory will trigger a page fault and let us analyze - * the memory accesses. - */ - kmemcheck_hide_pages(page, pages); -} - -void kmemcheck_free_shadow(struct page *page, int order) -{ - struct page *shadow; - int pages; - int i; - - if (!kmemcheck_page_is_tracked(page)) - return; - - pages = 1 << order; - - kmemcheck_show_pages(page, pages); - - shadow = virt_to_page(page[0].shadow); - - for(i = 0; i < pages; ++i) - page[i].shadow = NULL; - - __free_pages(shadow, order); -} - -void kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object, - size_t size) -{ - if (unlikely(!object)) /* Skip object if allocation failed */ - return; - - /* - * Has already been memset(), which initializes the shadow for us - * as well. - */ - if (gfpflags & __GFP_ZERO) - return; - - /* No need to initialize the shadow of a non-tracked slab. */ - if (s->flags & SLAB_NOTRACK) - return; - - if (!kmemcheck_enabled || gfpflags & __GFP_NOTRACK) { - /* - * Allow notracked objects to be allocated from - * tracked caches. Note however that these objects - * will still get page faults on access, they just - * won't ever be flagged as uninitialized. If page - * faults are not acceptable, the slab cache itself - * should be marked NOTRACK. - */ - kmemcheck_mark_initialized(object, size); - } else if (!s->ctor) { - /* - * New objects should be marked uninitialized before - * they're returned to the called. - */ - kmemcheck_mark_uninitialized(object, size); - } -} - -void kmemcheck_slab_free(struct kmem_cache *s, void *object, size_t size) -{ - /* TODO: RCU freeing is unsupported for now; hide false positives. */ - if (!s->ctor && !(s->flags & SLAB_TYPESAFE_BY_RCU)) - kmemcheck_mark_freed(object, size); -} - -void kmemcheck_pagealloc_alloc(struct page *page, unsigned int order, - gfp_t gfpflags) -{ - int pages; - - if (gfpflags & (__GFP_HIGHMEM | __GFP_NOTRACK)) - return; - - pages = 1 << order; - - /* - * NOTE: We choose to track GFP_ZERO pages too; in fact, they - * can become uninitialized by copying uninitialized memory - * into them. - */ - - /* XXX: Can use zone->node for node? */ - kmemcheck_alloc_shadow(page, order, gfpflags, -1); - - if (gfpflags & __GFP_ZERO) - kmemcheck_mark_initialized_pages(page, pages); - else - kmemcheck_mark_uninitialized_pages(page, pages); -} --- a/mm/slub.c +++ b/mm/slub.c @@ -1369,7 +1369,7 @@ static inline void *slab_free_hook(struc * So in order to make the debug calls that expect irqs to be * disabled we need to disable interrupts temporarily. */ -#if defined(CONFIG_KMEMCHECK) || defined(CONFIG_LOCKDEP) +#ifdef CONFIG_LOCKDEP { unsigned long flags;

@@ -1397,8 +1397,7 @@ static inline void slab_free_freelist_ho * Compiler cannot detect this function can be removed if slab_free_hook() * evaluates to nothing. Thus, catch all relevant config debug options here. */ -#if defined(CONFIG_KMEMCHECK) || \ - defined(CONFIG_LOCKDEP) || \ +#if defined(CONFIG_LOCKDEP) || \ defined(CONFIG_DEBUG_KMEMLEAK) || \ defined(CONFIG_DEBUG_OBJECTS_FREE) || \ defined(CONFIG_KASAN) --- a/scripts/kernel-doc +++ b/scripts/kernel-doc @@ -2182,8 +2182,6 @@ sub dump_struct($$) { # strip comments: $members =~ s//*.*?*///gos; $nested =~ s//*.*?*///gos; - # strip kmemcheck_bitfield_{begin,end}.*; - $members =~ s/kmemcheck_bitfield_.*?;//gos; # strip attributes $members =~ s/__attribute__\s*(([a-z,_*\s()]*))//i; $members =~ s/__aligned\s*([^;]*)//gos; --- a/tools/include/linux/kmemcheck.h +++ b/tools/include/linux/kmemcheck.h @@ -1,9 +1 @@ /* SPDX-License-Identifier: GPL-2.0 */ -#ifndef _LIBLOCKDEP_LINUX_KMEMCHECK_H_ -#define _LIBLOCKDEP_LINUX_KMEMCHECK_H_ - -static inline void kmemcheck_mark_initialized(void *address, unsigned int n) -{ -} - -#endif

Patches currently in stable-queue which might be from alexander.levin@verizon.com are

queue-4.14/kmemcheck-remove-annotations.patch queue-4.14/kmemcheck-remove-whats-left-of-notrack-flags.patch queue-4.14/kmemcheck-stop-using-gfp_notrack-and-slab_notrack.patch queue-4.14/kmemcheck-rip-it-out.patch