Messages in this thread Patch in this message | | | Date | Sun, 1 Sep 2002 11:42:42 +0200 | From | Andi Kleen <> | Subject | [PATCH] Fix RELOC_HIDE miscompilation |
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[resend due to mailer problems]
RELOC_HIDE got miscompiled on gcc3.1/x86-64 in the access to softirq.c's per cpu variables. This patch fixes the problem.
Clearly to hide the relocation the addition needs to be done after the value obfuscation, not before.
I don't know if it triggers on other architectures (x86-64 is especially stressf here because it has negative kernel addresses), but seems like the right thing to do.
Also does the arithmetic in unsigned long to avoid undue assumptions of the comp for pointers.
-Andi
--- linux/include/linux/compiler.h-o Sun Apr 14 21:18:44 2002 +++ linux/include/linux/compiler.h Sun Sep 1 02:52:31 2002 @@ -16,7 +16,7 @@ /* This macro obfuscates arithmetic on a variable address so that gcc shouldn't recognize the original var, and make assumptions about it */ #define RELOC_HIDE(ptr, off) \ - ({ __typeof__(ptr) __ptr; \ - __asm__ ("" : "=g"(__ptr) : "0"((void *)(ptr) + (off))); \ - __ptr; }) + ({ unsigned long __ptr; \ + __asm__ ("" : "=g"(__ptr) : "0"(ptr)); \ + (typeof(ptr)) (__ptr + (off)); }) #endif /* __LINUX_COMPILER_H */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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