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    SubjectRe: [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls

    * <> wrote:

    > On 8 Jun 2011 at 12:06, Andi Kleen wrote:
    > > > eventually may even go away as time progresses and linux
    > > > systems begin to fully rely on the vdso instead.
    > >
    > > That assumes that everyone uses glibc and also updates their
    > > userland. As pointed out many times that's a deeply flawed
    > > assumption.
    > i think the assumption is not that everyone uses glibc but that
    > everyone else (as in, every other libc) can simply take the
    > necessary changes from glibc, provided they need such changes at
    > all (i.e., they're using the vsyscall entry points over the vdso
    > ones).
    > i frankly didn't check any of the alternatives myself
    > (uclibc/klibc/bionic/etc) but i can't imagine that it'd be that
    > much harder to patch them than glibc.

    Correct. Also, as i pointed it out in the previous mail, ABI does not
    mean 'will execute the same instructions', that would be silly. We
    *do* fix serious wide-scale performance regressions (obviously), but
    if it's about some weird crazy legacy path that we had good security
    reasons to change, and which is trivial to performance-improve in the
    library then we are well within our boundaries to keep the change.

    > as i said, this was a compromise solution but then i think you
    > already made it clear that you didn't even think there was a
    > problem here to solve, so i guess we should work that out first, if
    > you want to ;).

    Heh, indeed ;-)



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