Fix bad asm constrants for x86-64 cpuid()
Bruce reports:
It seems there's a bug in the x86_64 version of do_cpuid() that causes
fio to segfault when built with clang at lower optimization levels:
static inline void do_cpuid(unsigned int *eax, unsigned int *ebx,
unsigned int *ecx, unsigned int *edx)
{
asm volatile("cpuid"
: "=a" (*eax), "=b" (*ebx), "=r" (*ecx), "=d" (*edx)
: "0" (*eax), "2" (*ecx)
: "memory");
}
via Tijl Coosemans:
Should be: "=c" (*ecx)
But you can also use the '+' modifier and remove the input operands:
: "+a" (*eax), "=b" (*ebx), "+c" (*ecx), "=d" (*edx)
:
: "memory"
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/arch/arch-x86_64.h b/arch/arch-x86_64.h
index d7ea12e..61ac75e 100644
--- a/arch/arch-x86_64.h
+++ b/arch/arch-x86_64.h
@@ -5,7 +5,7 @@
unsigned int *ecx, unsigned int *edx)
{
asm volatile("cpuid"
- : "=a" (*eax), "=b" (*ebx), "=r" (*ecx), "=d" (*edx)
+ : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
: "0" (*eax), "2" (*ecx)
: "memory");
}