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    SubjectRe: Compat 32-bit syscall entry from 64-bit task!?
    Denys Vlasenko wrote:
    > On Thu, Jan 26, 2012 at 11:31 AM, Jamie Lokier <jamie@shareable.org> wrote:
    > > Indan Zupancic wrote:
    > >> On Thu, January 26, 2012 02:08, Jamie Lokier wrote:
    > >> > Is it disambiguated by PTRACE_EVENT_EXEC happening before the execve
    > >> > returns, and you knowing the TID always changes to the PID?  I haven't
    > >> > yet checked which TID gets the PTRACE_EVENT_EXEC event, but if it's
    > >> > not the old one, perhaps that could be changed.
    > >>
    > >> Please don't ever change the behaviour of PTRACE_EVENT_EXEC, it's
    > >> barely documented already, but if if ever changes it will be also
    > >> unreliable.
    > >>
    > >> It's still unclear if the PTRACE_EVENT_EXEC comes before or after
    > >> or instead of the post-execve ptrace event.
    >
    > Denis <- confused.
    > Was ist das "post-execve ptrace event"? I know no such thing.
    > I know about PTRACE_EVENT_EXEC, and "post-execve SIGTRAP".

    Sorry, I meant to write execve-syscall-exit event.

    > >> I guess before, but
    > >> can I count on that? If it is after then I get a stray weird
    > >> execve event that messes up the system call cadence.
    > >
    > > It should be *sent* before because the exec steps must finish before
    > > the execve() syscall "returns".
    > >
    > > I'm not sure if the events are guaranteed to be received in the same
    > > order as they are sent.
    >
    > All ptrace stops (events and other stops) are synchronous.
    > Tracee stops, tracer notices it, tracer restarts tracee,
    > and only after this tracee can generate next event.
    > Therefore ptrace stops can't get reordered.

    That's good to know, thanks.

    -- Jamie
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