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authorAndi Kleen <ak@suse.de>2005-09-12 18:49:24 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-12 10:50:55 -0700
commit6e44f12ba64a58f25f8e6f35aa4c175f613001be (patch)
treed5fc4176f19d75389e652812a9becec4e551d171
parente92343cc8e9ca4bc0db4b007dd37d33a207ef637 (diff)
downloadlinux-linaro-6e44f12ba64a58f25f8e6f35aa4c175f613001be.tar.gz
[PATCH] i386: add memory clobbers to syscall macros
As noted by matz@suse.de The problem is, that on i386 the syscallN macro is defined like so: long __res; \ __asm__ volatile ("int $0x80" \ : "=a" (__res) \ : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \ "d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5))); \ If one of the arguments (in the _llseek syscall it's the arg4) is a pointer which the syscall is expected to write to (to the memory pointed to by this ptr), then this side-effect is not captured in the asm. If anyone uses this macro to define it's own version of the syscall (sometimes necessary when not using glibc) and it's inlined, then GCC doesn't know that this asm write to "*dest", when called like so for instance: out = 1; llseek (fd, bla, blubb, &out, trara) use (out); Here nobody tells GCC that "out" actually is written to (just a pointer to it is passed to the asm). Hence GCC might (and in the above bug did) copy-propagate "1" into the second use of "out". The easiest solution would be to add a "memory" clobber to the definition of this syscall macro. As this is a syscall, it shouldn't inhibit too many optimizations. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--include/asm-i386/unistd.h12
1 files changed, 6 insertions, 6 deletions
diff --git a/include/asm-i386/unistd.h b/include/asm-i386/unistd.h
index a7cb377745b..fbaf90a3968 100644
--- a/include/asm-i386/unistd.h
+++ b/include/asm-i386/unistd.h
@@ -332,7 +332,7 @@ type name(type1 arg1) \
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name),"b" ((long)(arg1))); \
+ : "0" (__NR_##name),"b" ((long)(arg1)) : "memory"); \
__syscall_return(type,__res); \
}
@@ -342,7 +342,7 @@ type name(type1 arg1,type2 arg2) \
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2))); \
+ : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)) : "memory"); \
__syscall_return(type,__res); \
}
@@ -353,7 +353,7 @@ long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
: "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
- "d" ((long)(arg3))); \
+ "d" ((long)(arg3)) : "memory"); \
__syscall_return(type,__res); \
}
@@ -364,7 +364,7 @@ long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
: "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
- "d" ((long)(arg3)),"S" ((long)(arg4))); \
+ "d" ((long)(arg3)),"S" ((long)(arg4)) : "memory"); \
__syscall_return(type,__res); \
}
@@ -376,7 +376,7 @@ long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
: "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
- "d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5))); \
+ "d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5)) : "memory"); \
__syscall_return(type,__res); \
}
@@ -389,7 +389,7 @@ __asm__ volatile ("push %%ebp ; movl %%eax,%%ebp ; movl %1,%%eax ; int $0x80 ; p
: "=a" (__res) \
: "i" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
"d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5)), \
- "0" ((long)(arg6))); \
+ "0" ((long)(arg6)) : "memory"); \
__syscall_return(type,__res); \
}