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SubjectRe: i386 PDA patches use of %gs
Ingo Molnar wrote:
> for example, your test_fs() code does:
> for(i = 0; i < COUNT; i++) {
> asm volatile("push %%fs; mov %1, %%fs; addl $1, %%fs:%0; popl %%fs"
> : "+m" (*offset): "r" (seg) : "memory");
> sync();
> }
> that loads (and uses) a single selector value for %fs, and doesnt do any
> mixed use as far as i can see.

I'm not sure what you're getting at. Each loop iteration is analogous
to a user->kernel->user transition with respect to the
save/reload/use/restore pattern on the segment register. In this case,
%fs starts as a null selector, gets reloaded with a non NULL selector,
and then is restored to null. Do you mean some other mixing?

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