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.

1 files changed, 22 insertions, 10 deletions

diff --git a/include/asm-i386/string.h b/include/asm-i386/string.h
index 6a78ac58c19..02c8f5d2206 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;
 }