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

* pageexec@freemail.hu <pageexec@freemail.hu> 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 ;-)

Thanks,

Ingo


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