Re: [patch] use __asm__ and __volatile__ in asm-x86_64/msr.h

From: H. Peter Anvin
Date: Wed Jun 20 2007 - 11:54:41 EST


Andi Kleen wrote:
>> asm-i386/msr.h should not be exported to userspace at all, it contains
>> nothing but kernel-internal helpers.
>
> Actually rdtsc and rdtscll and potentially rdpmc which is in there can be very
> useful in user space if you know what you're doing. Unfortunately a lot of its users don't,
> but not having the include probably won't stop them either.

More likely, people will just re-implement them incorrectly.

However, the rdtsc() definition in the kernel is weird (and removable, I
think there are no more users -- I have it removed in my MSR driver
rewrite tree which I need to get off my arse and push.) Most users
would expect the rdtscll() functionality with the rdtsc() name.

-hpa
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