From: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Fri, 24 Jun 2005 23:01:24 +0000 (-0700)
Subject: [PATCH] Add "memory" clobbers to the x86 inline asm of strncmp and friends
X-Git-Tag: v2.6.12.2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2e8e121926ee6d15151c8e57ddce97275213c5b2;p=thirdparty%2Fkernel%2Fstable.git

[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 <chrisw@osdl.org>
---

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;
 }