[05/07] Add "memory" clobbers to the x86 inline asm of strncmp and friends

Chris Wright
2005-06-27T23:10:41Z

-stable review patch. If anyone has any objections, please let us know.

------------------

From: Linus Torvalds <torvalds@ppc970.osdl.org>

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>
---

include/asm-i386/string.h | 32 ++++++++++++++++++++++----------
1 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/include/asm-i386/string.h b/include/asm-i386/string.h
--- 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
"dec %%edi\n"
"1:"
: "=D" (addr), "=c" (size)
- : "0" (addr), "1" (size), "a" (c));
+ : "0" (addr), "1" (size), "a" (c)
+ : "memory");
return addr;
}