The patch titled Subject: fs/proc/kcore.c: allow translation of physical memory addresses has been added to the -mm mm-hotfixes-unstable branch. Its filename is fs-proc-kcorec-allow-translation-of-physical-memory-addresses.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Alexander Gordeev agordeev@linux.ibm.com Subject: fs/proc/kcore.c: allow translation of physical memory addresses Date: Mon, 30 Sep 2024 14:21:19 +0200

When /proc/kcore is read an attempt to read the first two pages results in HW-specific page swap on s390 and another (so called prefix) pages are accessed instead. That leads to a wrong read.

Allow architecture-specific translation of memory addresses using kc_xlate_dev_mem_ptr() and kc_unxlate_dev_mem_ptr() callbacks similarily to /dev/mem xlate_dev_mem_ptr() and unxlate_dev_mem_ptr() callbacks. That way an architecture can deal with specific physical memory ranges.

Re-use the existing /dev/mem callback implementation on s390, which handles the described prefix pages swapping correctly.

For other architectures the default callback is basically NOP. It is expected the condition (vaddr == __va(__pa(vaddr))) always holds true for KCORE_RAM memory type.

Link: https://lkml.kernel.org/r/20240930122119.1651546-1-agordeev@linux.ibm.com Signed-off-by: Alexander Gordeev agordeev@linux.ibm.com Suggested-by: Heiko Carstens hca@linux.ibm.com Cc: Vasily Gorbik gor@linux.ibm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

arch/s390/include/asm/io.h | 2 + fs/proc/kcore.c | 36 +++++++++++++++++++++++++++++++++-- 2 files changed, 36 insertions(+), 2 deletions(-)

--- a/arch/s390/include/asm/io.h~fs-proc-kcorec-allow-translation-of-physical-memory-addresses +++ a/arch/s390/include/asm/io.h @@ -16,8 +16,10 @@ #include <asm/pci_io.h>

#define xlate_dev_mem_ptr xlate_dev_mem_ptr +#define kc_xlate_dev_mem_ptr xlate_dev_mem_ptr void *xlate_dev_mem_ptr(phys_addr_t phys); #define unxlate_dev_mem_ptr unxlate_dev_mem_ptr +#define kc_unxlate_dev_mem_ptr unxlate_dev_mem_ptr void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr);

#define IO_SPACE_LIMIT 0 --- a/fs/proc/kcore.c~fs-proc-kcorec-allow-translation-of-physical-memory-addresses +++ a/fs/proc/kcore.c @@ -50,6 +50,20 @@ static struct proc_dir_entry *proc_root_ #define kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET) #endif

+#ifndef kc_xlate_dev_mem_ptr +#define kc_xlate_dev_mem_ptr kc_xlate_dev_mem_ptr +static inline void *kc_xlate_dev_mem_ptr(phys_addr_t phys) +{ + return __va(phys); +} +#endif +#ifndef kc_unxlate_dev_mem_ptr +#define kc_unxlate_dev_mem_ptr kc_unxlate_dev_mem_ptr +static inline void kc_unxlate_dev_mem_ptr(phys_addr_t phys, void *virt) +{ +} +#endif + static LIST_HEAD(kclist_head); static DECLARE_RWSEM(kclist_lock); static int kcore_need_update = 1; @@ -471,6 +485,8 @@ static ssize_t read_kcore_iter(struct ki while (buflen) { struct page *page; unsigned long pfn; + phys_addr_t phys; + void *__start;

/* * If this is the first iteration or the address is not within @@ -537,7 +553,8 @@ static ssize_t read_kcore_iter(struct ki } break; case KCORE_RAM: - pfn = __pa(start) >> PAGE_SHIFT; + phys = __pa(start); + pfn = phys >> PAGE_SHIFT; page = pfn_to_online_page(pfn);

/* @@ -557,13 +574,28 @@ static ssize_t read_kcore_iter(struct ki fallthrough; case KCORE_VMEMMAP: case KCORE_TEXT: + if (m->type == KCORE_RAM) { + __start = kc_xlate_dev_mem_ptr(phys); + if (!__start) { + ret = -ENOMEM; + if (iov_iter_zero(tsz, iter) != tsz) + ret = -EFAULT; + goto out; + } + } else { + __start = (void *)start; + } + /* * Sadly we must use a bounce buffer here to be able to * make use of copy_from_kernel_nofault(), as these * memory regions might not always be mapped on all * architectures. */ - if (copy_from_kernel_nofault(buf, (void *)start, tsz)) { + ret = copy_from_kernel_nofault(buf, __start, tsz); + if (m->type == KCORE_RAM) + kc_unxlate_dev_mem_ptr(phys, __start); + if (ret) { if (iov_iter_zero(tsz, iter) != tsz) { ret = -EFAULT; goto out; _

Patches currently in -mm which might be from agordeev@linux.ibm.com are

fs-proc-kcorec-allow-translation-of-physical-memory-addresses.patch