From: Joerg Roedel Date: Fri, 11 May 2007 05:22:14 +0000 (-0700) Subject: i386: work around miscompilation of alternatives code X-Git-Tag: v2.6.22-rc1~103 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6041b57c6c99dcb59524f1bb0db0628c2689a464;p=linux-2.6 i386: work around miscompilation of alternatives code A recent change makes my Dell 1501 hang on boot. It's an AMD MK-36. I use an x86_64 kernel. It is 100% reproducible. I debugged this problem a bit and my compiler[1]interprets the =A constraint as %rax instead of %edx:%eax on x86_64 which causes the problem. The appended patch provides a workaround for this and fixed the hang on my machine. [1] gcc version 4.1.3 20070429 (prerelease) (Debian 4.1.2-5) Signed-off-by: Joerg Roedel Cc: Andi Kleen Cc: Benny Halevy Cc: Pete Zaitcev Cc: "Joerg Roedel" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/asm-i386/alternative.h b/include/asm-i386/alternative.h index 0f70b379b0..eb7da5402b 100644 --- a/include/asm-i386/alternative.h +++ b/include/asm-i386/alternative.h @@ -97,6 +97,12 @@ static inline void alternatives_smp_switch(int smp) {} "663:\n\t" newinstr "\n664:\n" /* replacement */ \ ".previous" : output : [feat] "i" (feature), ##input) +/* + * use this macro(s) if you need more than one output parameter + * in alternative_io + */ +#define ASM_OUTPUT2(a, b) a, b + /* * Alternative inline assembly for SMP. * diff --git a/include/asm-i386/tsc.h b/include/asm-i386/tsc.h index 3f3c1fa000..62c091ffcc 100644 --- a/include/asm-i386/tsc.h +++ b/include/asm-i386/tsc.h @@ -35,14 +35,16 @@ static inline cycles_t get_cycles(void) static __always_inline cycles_t get_cycles_sync(void) { unsigned long long ret; - unsigned eax; + unsigned eax, edx; /* * Use RDTSCP if possible; it is guaranteed to be synchronous * and doesn't cause a VMEXIT on Hypervisors */ alternative_io(ASM_NOP3, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP, - "=A" (ret), "0" (0ULL) : "ecx", "memory"); + ASM_OUTPUT2("=a" (eax), "=d" (edx)), + "a" (0U), "d" (0U) : "ecx", "memory"); + ret = (((unsigned long long)edx) << 32) | ((unsigned long long)eax); if (ret) return ret; diff --git a/include/asm-x86_64/alternative.h b/include/asm-x86_64/alternative.h index a09fe85c26..a094276407 100644 --- a/include/asm-x86_64/alternative.h +++ b/include/asm-x86_64/alternative.h @@ -102,6 +102,12 @@ static inline void alternatives_smp_switch(int smp) {} "663:\n\t" newinstr "\n664:\n" /* replacement */ \ ".previous" : output : [feat] "i" (feature), ##input) +/* + * use this macro(s) if you need more than one output parameter + * in alternative_io + */ +#define ASM_OUTPUT2(a, b) a, b + /* * Alternative inline assembly for SMP. *