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authorNamhyung Kim <namhyung@gmail.com>2010-08-11 15:37:41 +0900
committerIngo Molnar <mingo@elte.hu>2010-08-11 08:43:49 +0200
commit8fd49936a8cac246fc9ed85508556c82cd44cf68 (patch)
tree95fae1020c749884691f15ac8704a35914b29ffd /arch/x86/include/asm
parent5989cd6a1cbf86587edcc856791f960978087311 (diff)
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')
-rw-r--r--arch/x86/include/asm/page.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index 625c3f0e741..8ca82839288 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))