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    SubjectRe: [RFC] gcc feature request: Moving blocks into sections
    On 08/12/2013 09:09 AM, Peter Zijlstra wrote:
    >>
    >> On the majority of architectures, including x86, you cannot simply copy
    >> a piece of code elsewhere and have it still work.
    >
    > I thought we used -fPIC which would allow just that.
    >

    Doubly wrong. The kernel is not compiled with -fPIC, nor does -fPIC
    allow this kind of movement for code that contains intramodule
    references (that is *all* references in the kernel). Since we really
    doesn't want to burden the kernel with a GOT and a PLT, that is life.

    >> You end up doing a
    >> bunch of the work that a JIT would do anyway, and would end up with
    >> considerably higher complexity and worse results than a true JIT.
    >
    > Well, less complexity but worse result, yes. We'd only poke the specific
    > static_branch sites with either NOPs or the (relative) jump target for
    > each of these branches. Then copy the result.

    Once again, you can't "copy the result". You end up with a full
    disassembler.

    -hpa



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