From 2e8e121926ee6d15151c8e57ddce97275213c5b2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Fri, 24 Jun 2005 16:01:24 -0700 Subject: [PATCH] [PATCH] Add "memory" clobbers to the x86 inline asm of strncmp and friends Add "memory" clobbers to the x86 inline asm of strncmp and friends They don't actually clobber memory, but gcc doesn't even know they _read_ memory, so can apparently re-order memory accesses around them. Which obviously does the wrong thing if the memory access happens to change the memory that the compare function is accessing.. Verified to fix a strange boot problem by Jens Axboe. Signed-off-by: Chris Wright --- include/asm-i386/string.h | 32 ++++++++++++++++++++++---------- 1 file changed, 22 insertions(+), 10 deletions(-) diff --git a/include/asm-i386/string.h b/include/asm-i386/string.h index 6a78ac58c1946..02c8f5d22065d 100644 --- a/include/asm-i386/string.h +++ b/include/asm-i386/string.h @@ -116,7 +116,8 @@ __asm__ __volatile__( "orb $1,%%al\n" "3:" :"=a" (__res), "=&S" (d0), "=&D" (d1) - :"1" (cs),"2" (ct)); + :"1" (cs),"2" (ct) + :"memory"); return __res; } @@ -138,8 +139,9 @@ __asm__ __volatile__( "3:\tsbbl %%eax,%%eax\n\t" "orb $1,%%al\n" "4:" - :"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2) - :"1" (cs),"2" (ct),"3" (count)); + :"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2) + :"1" (cs),"2" (ct),"3" (count) + :"memory"); return __res; } @@ -158,7 +160,9 @@ __asm__ __volatile__( "movl $1,%1\n" "2:\tmovl %1,%0\n\t" "decl %0" - :"=a" (__res), "=&S" (d0) : "1" (s),"0" (c)); + :"=a" (__res), "=&S" (d0) + :"1" (s),"0" (c) + :"memory"); return __res; } @@ -175,7 +179,9 @@ __asm__ __volatile__( "leal -1(%%esi),%0\n" "2:\ttestb %%al,%%al\n\t" "jne 1b" - :"=g" (__res), "=&S" (d0), "=&a" (d1) :"0" (0),"1" (s),"2" (c)); + :"=g" (__res), "=&S" (d0), "=&a" (d1) + :"0" (0),"1" (s),"2" (c) + :"memory"); return __res; } @@ -189,7 +195,9 @@ __asm__ __volatile__( "scasb\n\t" "notl %0\n\t" "decl %0" - :"=c" (__res), "=&D" (d0) :"1" (s),"a" (0), "0" (0xffffffffu)); + :"=c" (__res), "=&D" (d0) + :"1" (s),"a" (0), "0" (0xffffffffu) + :"memory"); return __res; } @@ -333,7 +341,9 @@ __asm__ __volatile__( "je 1f\n\t" "movl $1,%0\n" "1:\tdecl %0" - :"=D" (__res), "=&c" (d0) : "a" (c),"0" (cs),"1" (count)); + :"=D" (__res), "=&c" (d0) + :"a" (c),"0" (cs),"1" (count) + :"memory"); return __res; } @@ -369,7 +379,7 @@ __asm__ __volatile__( "je 2f\n\t" "stosb\n" "2:" - : "=&c" (d0), "=&D" (d1) + :"=&c" (d0), "=&D" (d1) :"a" (c), "q" (count), "0" (count/4), "1" ((long) s) :"memory"); return (s); @@ -392,7 +402,8 @@ __asm__ __volatile__( "jne 1b\n" "3:\tsubl %2,%0" :"=a" (__res), "=&d" (d0) - :"c" (s),"1" (count)); + :"c" (s),"1" (count) + :"memory"); return __res; } /* end of additional stuff */ @@ -473,7 +484,8 @@ static inline void * memscan(void * addr, int c, size_t size) "dec %%edi\n" "1:" : "=D" (addr), "=c" (size) - : "0" (addr), "1" (size), "a" (c)); + : "0" (addr), "1" (size), "a" (c) + : "memory"); return addr; } -- 2.47.2