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ARM: avoid unwanted GCC memset()/memcpy() optimisations for IO variants

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We don't want GCC optimising our memset_io(), memcpy_fromio() or
memcpy_toio() variants, so we must not call one of the standard
functions.  Provide a separate name for our assembly memcpy() and
memset() functions, and use that instead, thereby bypassing GCC's
ability to optimise these operations.

GCCs optimisation may introduce unaligned accesses which are invalid
for device mappings.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2015-07-03 15:22:54 +01:00
parent 9ab79bb22c
commit 1bd46782d0
4 changed files with 16 additions and 3 deletions
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9
arch/arm/include/asm/io.h
View file

@ -316,21 +316,24 @@ extern void _memset_io(volatile void __iomem *, int, size_t);
static inline void memset_io(volatile void __iomem *dst, unsigned c,
size_t count)
{
memset((void __force *)dst, c, count);
extern void mmioset(void *, unsigned int, size_t);
mmioset((void __force *)dst, c, count);
}
#define memset_io(dst,c,count) memset_io(dst,c,count)
static inline void memcpy_fromio(void *to, const volatile void __iomem *from,
size_t count)
{
memcpy(to, (const void __force *)from, count);
extern void mmiocpy(void *, const void *, size_t);
mmiocpy(to, (const void __force *)from, count);
}
#define memcpy_fromio(to,from,count) memcpy_fromio(to,from,count)
static inline void memcpy_toio(volatile void __iomem *to, const void *from,
size_t count)
{
memcpy((void __force *)to, from, count);
extern void mmiocpy(void *, const void *, size_t);
mmiocpy((void __force *)to, from, count);
}
#define memcpy_toio(to,from,count) memcpy_toio(to,from,count)

6
arch/arm/kernel/armksyms.c
View file

@ -50,6 +50,9 @@ extern void __aeabi_ulcmp(void);
extern void fpundefinstr(void);
void mmioset(void *, unsigned int, size_t);
void mmiocpy(void *, const void *, size_t);
/* platform dependent support */
EXPORT_SYMBOL(arm_delay_ops);
@ -88,6 +91,9 @@ EXPORT_SYMBOL(memmove);
EXPORT_SYMBOL(memchr);
EXPORT_SYMBOL(__memzero);
EXPORT_SYMBOL(mmioset);
EXPORT_SYMBOL(mmiocpy);
#ifdef CONFIG_MMU
EXPORT_SYMBOL(copy_page);

2
arch/arm/lib/memcpy.S
View file

@ -61,8 +61,10 @@
/* Prototype: void *memcpy(void *dest, const void *src, size_t n); */
ENTRY(mmiocpy)
ENTRY(memcpy)
#include "copy_template.S"
ENDPROC(memcpy)
ENDPROC(mmiocpy)

2
arch/arm/lib/memset.S
View file

@ -16,6 +16,7 @@
.text
.align 5
ENTRY(mmioset)
ENTRY(memset)
UNWIND( .fnstart )
ands r3, r0, #3 @ 1 unaligned?
@ -133,3 +134,4 @@ UNWIND( .fnstart )
b 1b
UNWIND( .fnend )
ENDPROC(memset)
ENDPROC(mmioset)