Messages in this thread | | | Date | Mon, 27 Jun 2011 17:18:27 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH] ptrace: make former thread ID available via PTRACE_GETEVENTMSG after PTRACE_EVENT_EXEC stop (v.2) |
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On 06/27, Tejun Heo wrote: > > Hello, Oleg. > > On Mon, Jun 27, 2011 at 03:47:13PM +0200, Oleg Nesterov wrote: > > > Do we want to enable this silently? Wouldn't it be better to make it > > > dependent on PT_SEIZED? > > > > Hmm. Not sure I understand. Why can't PTRACE_SEIZE add PT_TRACE_EXEC > > (and PT_TRACESYSGOOD) along with PT_SEIZED during attach? > > I'm worrying about !PT_SEIZED case. If we make it solely depend on > PT_TRACE_EXEC, newer kernels report the old pid while olders ones > don't
Ah, understood. So you think that the old pid should be only reported if PT_SEIZED.
May be... Denys, what do you think?
OTOH, it looks simpler if PT_TRACE_EXEC always reports the old pid, this can't break the applications which do not know about this new feature.
> and the only way to discover would be either comparing kernel > version or actually trying it - both aren't too nice.
Fortunately, currently tracehook_report_exec() zeroes ->ptrace_message. At least this means that anything != 0 means it works.
Oleg.
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