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    SubjectRe: [PATCH 1/1] x86: fix text_poke
    * Linus Torvalds (torvalds@linux-foundation.org) wrote:
    >
    >
    > On Fri, 25 Apr 2008, Ingo Molnar wrote:
    > >
    > > something like the patch below? (untested)
    >
    > No. That whole code sequence is total and utter crap. It needs to be
    > rewritten.
    >
    > It first does a BUG_ON() if it's not naturally aligned (because that
    > wouldn't be atomic), and then it has code for page crossing! What a TOTAL
    > PIECE OF SH*T!
    >
    > Hint:
    > - if it's naturally aligned, it couldn't be page crossing ANYWAY
    > - and if it was a page-crosser, it sure as hell couldn't be atomic!
    >
    > The code is just crap, crap, crap. It needs to be rewritten from scratch.
    > I'll have a patch soonish.
    >
    > Linus


    Woooow, just a sec here. I removed the atomicity test _because_ there
    happen to be a case where it's safe to do non-atomic instruction
    modification. If we do :

    1) replace the instruction first byte by a breakpoint, execute an
    instruction bypass (see the immediate values patches for detail)
    2) modify the instruction non-atomically
    3) put back the original instruction first byte.

    That's why I removed the BUG_ONs at the beginning of the function.
    That's also why it's required to deal with page crossing.

    Mathieu


    --
    Mathieu Desnoyers
    Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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