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| author | Namhyung Kim <namhyung@gmail.com> | 2010-08-11 15:37:41 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2010-08-11 08:43:49 +0200 |
| commit | 8fd49936a8cac246fc9ed85508556c82cd44cf68 (patch) | |
| tree | 95fae1020c749884691f15ac8704a35914b29ffd /arch/x86/include/asm/page.h | |
| parent | 5989cd6a1cbf86587edcc856791f960978087311 (diff) | |
| download | linux-8fd49936a8cac246fc9ed85508556c82cd44cf68.tar.gz linux-8fd49936a8cac246fc9ed85508556c82cd44cf68.tar.bz2 linux-8fd49936a8cac246fc9ed85508556c82cd44cf68.zip | |
x86: Document __phys_reloc_hide() usage in __pa_symbol()
Until all supported versions of gcc recognize
-fno-strict-overflow, we should keep the RELOC_HIDE() magic in
__pa_symbol(). Comment it.
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
LKML-Reference: <1281508661-29507-1-git-send-email-namhyung@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include/asm/page.h')
| -rw-r--r-- | arch/x86/include/asm/page.h | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h index 625c3f0e741a..8ca82839288a 100644 --- a/arch/x86/include/asm/page.h +++ b/arch/x86/include/asm/page.h @@ -37,6 +37,13 @@ static inline void copy_user_page(void *to, void *from, unsigned long vaddr, #define __pa_nodebug(x) __phys_addr_nodebug((unsigned long)(x)) /* __pa_symbol should be used for C visible symbols. This seems to be the official gcc blessed way to do such arithmetic. */ +/* + * We need __phys_reloc_hide() here because gcc may assume that there is no + * overflow during __pa() calculation and can optimize it unexpectedly. + * Newer versions of gcc provide -fno-strict-overflow switch to handle this + * case properly. Once all supported versions of gcc understand it, we can + * remove this Voodoo magic stuff. (i.e. once gcc3.x is deprecated) + */ #define __pa_symbol(x) __pa(__phys_reloc_hide((unsigned long)(x))) #define __va(x) ((void *)((unsigned long)(x)+PAGE_OFFSET)) |