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/fs-proc-kcorec-allow-translation-of-physical-memory-addresses.patch
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@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx
Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Suggested-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxxxxx are
fs-proc-kcorec-allow-translation-of-physical-memory-addresses.patch
