Messages in this thread | | | Date | Mon, 18 Jun 2007 00:35:52 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [patch] use __asm__ and __volatile__ in asm-x86_64/msr.h |
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Mike Frysinger wrote: > Most of the macros in msr.h already use __asm__ and __volatile__, this patch > brings the rest into line. This is needed since these get exported into > userspace (need to use strict __asm__ vs asm when gcc compiles with GNU > extensions turned off). > --- > diff --git a/include/asm-x86_64/msr.h b/include/asm-x86_64/msr.h > index d5c55b8..ed15d2b 100644 > --- a/include/asm-x86_64/msr.h > +++ b/include/asm-x86_64/msr.h > @@ -33,7 +33,7 @@ > > /* wrmsr with exception handling */ > #define wrmsr_safe(msr,a,b) ({ int ret__; \ > - asm volatile("2: wrmsr ; xorl %0,%0\n" \ > + __asm__ __volatile__("2: wrmsr ; xorl %0,%0\n" \ > "1:\n\t" \ > ".section .fixup,\"ax\"\n\t" \ > "3: movl %4,%0 ; jmp 1b\n\t" \ > @@ -50,7 +50,7 @@ > > #define rdmsr_safe(msr,a,b) \ > ({ int ret__; \ > - asm volatile ("1: rdmsr\n" \ > + __asm__ __volatile__ ("1: rdmsr\n" \ > "2:\n" \ > ".section .fixup,\"ax\"\n" \ > "3: movl %4,%0\n" \
NAK.
This is wrong for two reasons:
- MSRs are not accessible in user space. - .section .fixup is not applicable to user space.
Anything MSR-related should be protected by __KERNEL__ instead.
This NAK doesn't apply to rdtsc* and rdpmc* changes, however, as those instructions are legitimate in userspace.
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