Commit d6d51a96 authored by Linus Walleij's avatar Linus Walleij Committed by Russell King
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ARM: 9014/2: Replace string mem* functions for KASan

Functions like memset()/memmove()/memcpy() do a lot of memory

If a bad pointer is passed to one of these functions it is important
to catch this. Compiler instrumentation cannot do this since these
functions are written in assembly.

KASan replaces these memory functions with instrumented variants.

The original functions are declared as weak symbols so that
the strong definitions in mm/kasan/kasan.c can replace them.

The original functions have aliases with a '__' prefix in their
name, so we can call the non-instrumented variant if needed.

We must use __memcpy()/__memset() in place of memcpy()/memset()
when we copy .data to RAM and when we clear .bss, because
kasan_early_init cannot be called before the initialization of
.data and .bss.

For the kernel compression and EFI libstub's custom string
libraries we need a special quirk: even if these are built
without KASan enabled, they rely on the global headers for their
custom string libraries, which means that e.g. memcpy()
will be defined to __memcpy() and we get link failures.
Since these implementations are written i C rather than
assembly we use e.g. __alias(memcpy) to redirected any
users back to the local implementation.

Cc: Andrey Ryabinin <>
Cc: Alexander Potapenko <>
Cc: Dmitry Vyukov <>
Reviewed-by: default avatarArd Biesheuvel <>
Tested-by: Ard Biesheuvel <> # QEMU/KVM/mach-virt/LPAE/8G
Tested-by: Florian Fainelli <> # Brahma SoCs
Tested-by: Ahmad Fatoum <> # i.MX6Q
Reported-by: default avatarRussell King - ARM Linux <>
Signed-off-by: default avatarAhmad Fatoum <>
Signed-off-by: default avatarAbbott Liu <>
Signed-off-by: Florian Fainelli's avatarFlorian Fainelli <>
Signed-off-by: default avatarLinus Walleij <>
Signed-off-by: default avatarRussell King <>
parent d5d44e7e
......@@ -7,6 +7,25 @@
#include <linux/string.h>
* The decompressor is built without KASan but uses the same redirects as the
* rest of the kernel when CONFIG_KASAN is enabled, defining e.g. memcpy()
* to __memcpy() but since we are not linking with the main kernel string
* library in the decompressor, that will lead to link failures.
* Undefine KASan's versions, define the wrapped functions and alias them to
* the right names so that when e.g. __memcpy() appear in the code, it will
* still be linked to this local version of memcpy().
#undef memcpy
#undef memmove
#undef memset
void *__memcpy(void *__dest, __const void *__src, size_t __n) __alias(memcpy);
void *__memmove(void *__dest, __const void *__src, size_t count) __alias(memmove);
void *__memset(void *s, int c, size_t count) __alias(memset);
void *memcpy(void *__dest, __const void *__src, size_t __n)
int i = 0;
......@@ -5,6 +5,9 @@
* We don't do inline string functions, since the
* optimised inline asm versions are not small.
* The __underscore versions of some functions are for KASan to be able
* to replace them with instrumented versions.
......@@ -15,15 +18,18 @@ extern char * strchr(const char * s, int c);
extern void * memcpy(void *, const void *, __kernel_size_t);
extern void *__memcpy(void *dest, const void *src, __kernel_size_t n);
extern void * memmove(void *, const void *, __kernel_size_t);
extern void *__memmove(void *dest, const void *src, __kernel_size_t n);
extern void * memchr(const void *, int, __kernel_size_t);
extern void * memset(void *, int, __kernel_size_t);
extern void *__memset(void *s, int c, __kernel_size_t n);
#define __HAVE_ARCH_MEMSET32
extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t);
......@@ -39,4 +45,24 @@ static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n)
return __memset64(p, v, n * 8, v >> 32);
* For files that are not instrumented (e.g. mm/slub.c) we
* must use non-instrumented versions of the mem*
* functions named __memcpy() etc. All such kernel code has
* been tagged with KASAN_SANITIZE_file.o = n, which means
* that the address sanitization argument isn't passed to the
* compiler, and __SANITIZE_ADDRESS__ is not set. As a result
* these defines kick in.
#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
#define memcpy(dst, src, len) __memcpy(dst, src, len)
#define memmove(dst, src, len) __memmove(dst, src, len)
#define memset(s, c, n) __memset(s, c, n)
#ifndef __NO_FORTIFY
#define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
......@@ -95,7 +95,7 @@ __mmap_switched:
THUMB( ldmia r4!, {r0, r1, r2, r3} )
THUMB( mov sp, r3 )
sub r2, r2, r1
bl memcpy @ copy .data to RAM
bl __memcpy @ copy .data to RAM
ARM( ldmia r4!, {r0, r1, sp} )
......@@ -103,7 +103,7 @@ __mmap_switched:
THUMB( mov sp, r3 )
sub r2, r1, r0
mov r1, #0
bl memset @ clear .bss
bl __memset @ clear .bss
ldmia r4, {r0, r1, r2, r3}
str r9, [r0] @ Save processor ID
......@@ -58,6 +58,8 @@
/* Prototype: void *memcpy(void *dest, const void *src, size_t n); */
.weak memcpy
......@@ -65,3 +67,4 @@ ENTRY(memcpy)
......@@ -24,12 +24,14 @@
* occurring in the opposite direction.
.weak memmove
UNWIND( .fnstart )
subs ip, r0, r1
cmphi r2, ip
bls memcpy
bls __memcpy
stmfd sp!, {r0, r4, lr}
UNWIND( .fnend )
......@@ -222,3 +224,4 @@ ENTRY(memmove)
18: backward_copy_shift push=24 pull=8
......@@ -13,6 +13,8 @@
.align 5
.weak memset
UNWIND( .fnstart )
......@@ -132,6 +134,7 @@ UNWIND( .fnstart )
UNWIND( .fnend )
UNWIND( .fnstart )
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