From: Denys Vlasenko <vda.linux@googlemail.com>
To: "Indan Zupancic" <indan@nul.nu>
Subject: Re: Compat 32-bit syscall entry from 64-bit task!?
Date: Fri, 10 Feb 2012 22:19:29 +0100
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On Friday 10 February 2012 04:37, Indan Zupancic wrote:
> > I read somewhere about a bug report where syscall-exit was seen after
> > attach, but I don't remember where now.
> 
> Well, if you attach at a random moment you can get a syscall-exit first,
> I guess. I suppose you have to wait till you get the SIGSTOP notification
> before you can be sure that the next syscall event will be an entry one.

No. After PTRACE_ATTACH, next reported waitpid result will be either
a ptrace-stop of signal-delivery-stop variety,
or death (WIFEXITED/WIFSIGNALED). Syscall exit notification
is not possible (modulo kernel bugs). For one, syscall entry/exit
notifications must be explicitly requested by PTRACE_SYSCALL, which
wasn't yet done!

-- 
vda
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