Add "memory" clobbers to the x86 inline asm of strncmp and friends,

forwarded by jgarzik.

diff --git a/queue/memory-clobber-on-x86.patch b/queue/memory-clobber-on-x86.patch
new file mode 100644 (file)
index 0000000..855d0f4
--- /dev/null
+++ b/queue/memory-clobber-on-x86.patch
@@ -0,0 +1,122 @@
+From SRS0=Ut8f=U6=vger.kernel.org=bk-commits-head-owner@bounce2.pobox.com Fri Jun 24 16:02:22 2005
+Date: Fri, 24 Jun 2005 16:01:24 -0700
+From: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
+To: bk-commits-head@vger.kernel.org
+Subject: Add "memory" clobbers to the x86 inline asm of strncmp and friends
+
+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;
+ }
+