Re: Compat 32-bit syscall entry from 64-bit task!?

[Indan Zupancic]

On Thu, January 26, 2012 11:40, Denys Vlasenko wrote:
> On Thu, Jan 26, 2012 at 11:31 AM, Jamie Lokier <jamie@xxxxxxxxxxxxx> 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? ïI 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".

I mean the second SIGTRAP | 0x80 event, the syscall return of execve.

> 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 and what I expected.

Since which kernel version does the PTRACE_GETEVENTMSG work and
is there a way to find out before it returns zero?

Greetings,

Indan


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