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    SubjectRe: [GIT pull] x86 vdso updates
    On Sun, May 29, 2011 at 5:51 AM, richard -rw- weinberger
    <richard.weinberger@gmail.com> wrote:
    > On Fri, May 27, 2011 at 5:05 PM, Andrew Lutomirski <luto@mit.edu> wrote:
    >> On Fri, May 27, 2011 at 10:59 AM, richard -rw- weinberger
    >> <richard.weinberger@gmail.com> wrote:
    >>> On Fri, May 27, 2011 at 2:10 PM, Andrew Lutomirski <luto@mit.edu> wrote:
    >>>> On Fri, May 27, 2011 at 7:59 AM, richard -rw- weinberger
    >>>> If this is considered enough of a regression, then I guess we can
    >>>> leave vsyscall64 around for awhile, but it will require extra work in
    >>>> the soon-to-be syscall emulation hack to make sure that UML can still
    >>>> trap the syscall.
    >>>
    >>> As long the time within UML is synchronous with the host everything is
    >>> fine, right?
    >>
    >> I think so.  I haven't used UML in a long time.
    >>
    >>> So, as _last_ choice we could disable the ability to change the time within UML.
    >>>
    >>> IMHO it's not a big deal when getcpu() returns a wrong CPU layout on UML.
    >>>
    >>>> The real solution is to fix glibc to use the vDSO which should avoid
    >>>> this problem entirely.
    >>>
    >
    > Yesterday I had a closer look at 64bit UML.
    > Glibc is always using vsyscalls because 64bit UML does not support the vDSO.
    >
    > On 32bit UML simply scans the ELF auxiliary vector provided by the host to
    > get the address of the vDSO.
    > How can I get this address on a 64bit host?

    I believe it's exactly the same. There's an auxv entry that points to the vDSO.

    --Andy
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