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fs/proc/kcore.c: allow translation of physical memory addresses

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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>
This commit is contained in:
Alexander Gordeev 2024-09-30 14:21:19 +02:00 committed by Andrew Morton
parent 76503e1fa1
commit 3d5854d75e
2 changed files with 36 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

2
arch/s390/include/asm/io.h
View file

@ -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

36
fs/proc/kcore.c
View file

@ -50,6 +50,20 @@ static struct proc_dir_entry *proc_root_kcore;
#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 kiocb *iocb, struct iov_iter *iter)
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 kiocb *iocb, struct iov_iter *iter)
}
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 kiocb *iocb, struct iov_iter *iter)
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;