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    SubjectRe: [PATCH 2/5] x86/uprobes: implement x86 specific arch_uprobe_*_step
    On 08/08/2012 04:53 PM, Oleg Nesterov wrote:
    >> Why? I tried 'lock popf' and I got invalid instruction. The same for
    >> 'rep popf'.
    >
    > int main(void)
    > {
    > asm volatile ("pushf; rep; popf");
    >
    > return 0;
    > }
    >

    Just tested and it works. Hmm.

    > OK, probably nobody should do this (although the kernel should not
    > assume this imho), but
    >
    > asm volatile ("pushfw; popfw");
    >
    > doesn't look bad and the code is
    >
    > 000000000040047c<main>:
    > 40047c: 55 push %rbp
    > 40047d: 48 89 e5 mov %rsp,%rbp
    > 400480: 66 9c pushfw
    > 400482: 66 9d popfw
    > 400484: b8 00 00 00 00 mov $0x0,%eax
    > 400489: c9 leaveq
    > 40048a: c3 retq

    Yes, that one works as well.

    > And in any case it would be better to re-use auprobe->fixups.

    Okay.

    > Oleg.
    >

    Sebastian


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