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    SubjectRe: Re: [RFC] [PATCH 1/2 v2] x86: introduce int3-based instruction patching
    (2013/07/11 6:36), H. Peter Anvin wrote:
    > On 07/10/2013 02:31 PM, Jiri Kosina wrote:
    >>
    >> If any CPU instruction execution would collide with the patching,
    >> it'd be trapped by the int3 breakpoint and redirected to the provided
    >> "handler" (which would typically mean just skipping over the patched
    >> region, acting as "nop" has been there, in case we are doing nop -> jump
    >> and jump -> nop transitions).
    >>
    >
    > I'm wondering if it would be easier/more general to just return to the
    > instruction. The "more general" bit would allow this to be used for
    > other things, like alternatives, and perhaps eventually dynamic call
    > patching.
    >
    > Returning to the instruction will, in effect, be a busy-wait for the
    > faulted CPU until the patch is complete; more or less what stop_machine
    > would do, but only for a CPU which actually strays into the affected region.

    Sounds a good idea :)
    It may minimize the interface and the implementation will be
    self-contained.

    Thank you,

    --
    Masami HIRAMATSU
    IT Management Research Dept. Linux Technology Center
    Hitachi, Ltd., Yokohama Research Laboratory
    E-mail: masami.hiramatsu.pt@hitachi.com




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