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Commit 793ae774 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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.
parent 59a49e38

include/asm-i386/string.h

+22 −10
Original line number Diff line number Diff line
@@ -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;

}
@@ -139,7 +140,8 @@ __asm__ __volatile__( 
	"orb $1,%%al\n"

	"4:"

	:"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2)

		     :"1" (cs),"2" (ct),"3" (count));

	:"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;

}
@@ -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;

}