subtle bug in <include/asm-i386/unistd.h>

Markus F.X.J. Oberhumer (markus.oberhumer@jk.uni-linz.ac.at)
Wed, 31 Mar 1999 13:45:43 +0200 (CEST)

While extending our UPX executable packer to support Linux/i386
executables I've stumbled over what I think is a subtle bug in
the `asm volatile' statements.

The diff below is against 2.2.5.

I really wonder why noone has been hit by this before - might be
due to a certain gcc/egcs register allocation scheme.
Also I think that gcc should spit out some warning in this case.

If this turns out to be a true bug the glibc people might be interested
as well - please forward this mail.

Markus

http://wildsau.idv.uni-linz.ac.at/mfx/upx.html

--- include/asm/unistd.h.orig Tue Jan 26 16:00:03 1999
+++ include/asm/unistd.h Wed Mar 31 13:35:30 1999
@@ -214,7 +214,7 @@
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name)); \
+ : "a" (__NR_##name)); \
__syscall_return(type,__res); \
}

@@ -224,7 +224,7 @@
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name),"b" ((long)(arg1))); \
+ : "a" (__NR_##name),"b" ((long)(arg1))); \
__syscall_return(type,__res); \
}

@@ -234,7 +234,7 @@
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2))); \
+ : "a" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2))); \
__syscall_return(type,__res); \
}

@@ -244,7 +244,7 @@
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
+ : "a" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
"d" ((long)(arg3))); \
__syscall_return(type,__res); \
}
@@ -255,7 +255,7 @@
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
+ : "a" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
"d" ((long)(arg3)),"S" ((long)(arg4))); \
__syscall_return(type,__res); \
}
@@ -267,7 +267,7 @@
long __res; \
__asm__ volatile ("int $0x80" \
: "=a" (__res) \
- : "0" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
+ : "a" (__NR_##name),"b" ((long)(arg1)),"c" ((long)(arg2)), \
"d" ((long)(arg3)),"S" ((long)(arg4)),"D" ((long)(arg5))); \
__syscall_return(type,__res); \
}

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