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Date:      Sat, 9 Feb 2002 18:08:04 -0500 (EST)
From:      Zhihui Zhang <zzhang@cs.binghamton.edu>
To:        Dag-Erling Smorgrav <des@ofug.org>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: Ptrace and SIGTRAP problem
Message-ID:  <Pine.SOL.4.21.0202091803260.3949-100000@opal>
In-Reply-To: <xzppu3ez2iw.fsf@flood.ping.uio.no>

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On 9 Feb 2002, Dag-Erling Smorgrav wrote:

> Zhihui Zhang <zzhang@cs.binghamton.edu> writes:
> > - PT_CONTINUE + waitpid() works fine, the trace program prints out values.
> 
> This is expected behaviour.
> 
> > - PT_CONTINUE alone does not work but no core-dump caused by SIGTRAP
> > - PT_DETACH + waitpid() does not work and core-dump
> > - PT_DETACH alone does not work and core-dump.
> 
> These three cases are unexpected.  I'll have to dig some more into
> this, but I'm afraid I won't have time until some time next week.
> 
> > Who is sending the SIGRAP (5) signal?
> 
> execve(2) in kern_exec.c posts SIGTRAP if the process has debugging
> turned on (which it does as a result of PT_TRACE_ME). 

This is one time thing. It will be catched by the first wait()  
call in the parent process.

Thanks for your reply.

-Zhihui


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