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MIPS: cmpxchg: Error out on unsupported xchg() calls

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xchg() has up until now simply returned the x parameter in cases where
it is called with a pointer to a value of an unsupported size. This will
often cause the calling code to hit a failure path, presuming that the
value of x differs from the content of the memory pointed at by ptr, but
we can do better by producing a compile-time or link-time error such
that unsupported calls to xchg() are detectable earlier than runtime.

This patch does this in the same was as is already done for cmpxchg(),
using a call to a missing function annotated with __compiletime_error().

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16351/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2017-06-09 17:26:36 -07:00 committed by Ralf Baechle
parent 77299db802
commit d15dc68c11
1 changed files with 17 additions and 15 deletions
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32
arch/mips/include/asm/cmpxchg.h
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@ -24,6 +24,21 @@
# define __scbeqz "beqz"
#endif
/*
* These functions doesn't exist, so if they are called you'll either:
*
* - Get an error at compile-time due to __compiletime_error, if supported by
* your compiler.
*
* or:
*
* - Get an error at link-time due to the call to the missing function.
*/
extern void __cmpxchg_called_with_bad_pointer(void)
__compiletime_error("Bad argument size for cmpxchg");
extern unsigned long __xchg_called_with_bad_pointer(void)
__compiletime_error("Bad argument size for xchg");
#define __xchg_asm(ld, st, m, val) \
({ \
__typeof(*(m)) __ret; \
@ -89,9 +104,9 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
return __xchg_u32(ptr, x);
case 8:
return __xchg_u64(ptr, x);
default:
return __xchg_called_with_bad_pointer();
}
return x;
}
#define xchg(ptr, x) \
@ -136,19 +151,6 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
__ret; \
})
/*
* This function doesn't exist, so if it is called you'll either:
*
* - Get an error at compile-time due to __compiletime_error, if supported by
* your compiler.
*
* or:
*
* - Get an error at link-time due to the call to the missing function.
*/
extern void __cmpxchg_called_with_bad_pointer(void)
__compiletime_error("Bad argument size for cmpxchg");
#define __cmpxchg(ptr, old, new, pre_barrier, post_barrier) \
({ \
__typeof__(ptr) __ptr = (ptr); \