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author | Linus Torvalds <torvalds@linux-foundation.org> | 2009-07-02 12:05:10 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-07-02 12:05:10 -0700 |
commit | 43644679a1e80f53e6e0155ab75b1093ba3c0365 (patch) | |
tree | 8c06f272fe6290c9031adc7f176711af12435902 /arch/x86/include/asm | |
parent | 42ca4fb69126dd9d0e25112edca1cacf846aa5c3 (diff) | |
download | op-kernel-dev-43644679a1e80f53e6e0155ab75b1093ba3c0365.zip op-kernel-dev-43644679a1e80f53e6e0155ab75b1093ba3c0365.tar.gz |
x86: fix power-of-2 round_up/round_down macros
These macros had two bugs:
- the type of the mask was not correctly expanded to the full size of
the argument being expanded, resulting in possible loss of high bits
when mixing types.
- the alignment argument was evaluated twice, despite the macro looking
like a fancy function (but it really does need to be a macro, since
it works on arbitrary integer types)
Noticed by Peter Anvin, and with a fix that is a modification of his
suggestion (bug noticed by Yinghai Lu).
Cc: Peter Anvin <hpa@zytor.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/include/asm')
-rw-r--r-- | arch/x86/include/asm/proto.h | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h index 49fb3ec..621f56d 100644 --- a/arch/x86/include/asm/proto.h +++ b/arch/x86/include/asm/proto.h @@ -22,7 +22,14 @@ extern int reboot_force; long do_arch_prctl(struct task_struct *task, int code, unsigned long addr); -#define round_up(x, y) (((x) + (y) - 1) & ~((y) - 1)) -#define round_down(x, y) ((x) & ~((y) - 1)) +/* + * This looks more complex than it should be. But we need to + * get the type for the ~ right in round_down (it needs to be + * as wide as the result!), and we want to evaluate the macro + * arguments just once each. + */ +#define __round_mask(x,y) ((__typeof__(x))((y)-1)) +#define round_up(x,y) ((((x)-1) | __round_mask(x,y))+1) +#define round_down(x,y) ((x) & ~__round_mask(x,y)) #endif /* _ASM_X86_PROTO_H */ |