From b015124e562a040f7faf361c72e8f5f457ac6cf5 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Wed, 22 Aug 2007 16:28:01 -0700 Subject: [x86 setup] Volatilize asm() statements asm() statements need to be volatile when: a. They have side effects (other than value returned). b. When the value returned can vary over time. c. When they have ordering constraints that cannot be expressed to gcc. In particular, the keyboard and timer reads were violating constraint (b), which resulted in the keyboard/timeout poll getting loop-invariant-removed when compiling with gcc 4.2.0. Thanks to an anonymous bug reporter for pointing this out. Signed-off-by: H. Peter Anvin --- arch/i386/boot/cpucheck.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/i386/boot/cpucheck.c') diff --git a/arch/i386/boot/cpucheck.c b/arch/i386/boot/cpucheck.c index 991e8ceae1d..e655a89c551 100644 --- a/arch/i386/boot/cpucheck.c +++ b/arch/i386/boot/cpucheck.c @@ -96,7 +96,8 @@ static int has_fpu(void) asm volatile("movl %0,%%cr0" : : "r" (cr0)); } - asm("fninit ; fnstsw %0 ; fnstcw %1" : "+m" (fsw), "+m" (fcw)); + asm volatile("fninit ; fnstsw %0 ; fnstcw %1" + : "+m" (fsw), "+m" (fcw)); return fsw == 0 && (fcw & 0x103f) == 0x003f; } -- cgit v1.2.3