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.
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@ -116,7 +116,8 @@ __asm__ __volatile__(
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"orb $1,%%al\n"
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"3:"
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:"=a" (__res), "=&S" (d0), "=&D" (d1)
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:"1" (cs),"2" (ct));
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:"1" (cs),"2" (ct)
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:"memory");
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return __res;
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}
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@ -138,8 +139,9 @@ __asm__ __volatile__(
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"3:\tsbbl %%eax,%%eax\n\t"
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"orb $1,%%al\n"
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"4:"
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:"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2)
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:"1" (cs),"2" (ct),"3" (count));
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:"=a" (__res), "=&S" (d0), "=&D" (d1), "=&c" (d2)
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:"1" (cs),"2" (ct),"3" (count)
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:"memory");
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return __res;
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}
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@ -158,7 +160,9 @@ __asm__ __volatile__(
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"movl $1,%1\n"
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"2:\tmovl %1,%0\n\t"
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"decl %0"
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:"=a" (__res), "=&S" (d0) : "1" (s),"0" (c));
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:"=a" (__res), "=&S" (d0)
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:"1" (s),"0" (c)
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:"memory");
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return __res;
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}
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@ -175,7 +179,9 @@ __asm__ __volatile__(
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"leal -1(%%esi),%0\n"
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"2:\ttestb %%al,%%al\n\t"
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"jne 1b"
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:"=g" (__res), "=&S" (d0), "=&a" (d1) :"0" (0),"1" (s),"2" (c));
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:"=g" (__res), "=&S" (d0), "=&a" (d1)
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:"0" (0),"1" (s),"2" (c)
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:"memory");
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return __res;
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}
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@ -189,7 +195,9 @@ __asm__ __volatile__(
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"scasb\n\t"
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"notl %0\n\t"
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"decl %0"
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:"=c" (__res), "=&D" (d0) :"1" (s),"a" (0), "0" (0xffffffffu));
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:"=c" (__res), "=&D" (d0)
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:"1" (s),"a" (0), "0" (0xffffffffu)
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:"memory");
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return __res;
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}
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@ -333,7 +341,9 @@ __asm__ __volatile__(
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"je 1f\n\t"
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"movl $1,%0\n"
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"1:\tdecl %0"
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:"=D" (__res), "=&c" (d0) : "a" (c),"0" (cs),"1" (count));
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:"=D" (__res), "=&c" (d0)
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:"a" (c),"0" (cs),"1" (count)
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:"memory");
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return __res;
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}
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@ -369,7 +379,7 @@ __asm__ __volatile__(
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"je 2f\n\t"
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"stosb\n"
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"2:"
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: "=&c" (d0), "=&D" (d1)
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:"=&c" (d0), "=&D" (d1)
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:"a" (c), "q" (count), "0" (count/4), "1" ((long) s)
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:"memory");
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return (s);
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@ -392,7 +402,8 @@ __asm__ __volatile__(
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"jne 1b\n"
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"3:\tsubl %2,%0"
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:"=a" (__res), "=&d" (d0)
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:"c" (s),"1" (count));
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:"c" (s),"1" (count)
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:"memory");
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return __res;
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}
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/* end of additional stuff */
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@ -473,7 +484,8 @@ static inline void * memscan(void * addr, int c, size_t size)
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"dec %%edi\n"
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"1:"
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: "=D" (addr), "=c" (size)
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: "0" (addr), "1" (size), "a" (c));
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: "0" (addr), "1" (size), "a" (c)
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: "memory");
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return addr;
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}
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