linux-kernel - Re: [RFC] Proposal for ptrace improvements

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Message-ID: <20110302152550.GM3319@htj.dyndns.org>
Date:	Wed, 2 Mar 2011 16:25:50 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Roland McGrath <roland@...hat.com>, jan.kratochvil@...hat.com,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org
Subject: Re: [RFC] Proposal for ptrace improvements

Hey,

On Wed, Mar 02, 2011 at 04:16:50PM +0100, Denys Vlasenko wrote:
> Assuming the program is run under simple debugger which
> resumes execution using PTRACE_CONT(sig) on signal delivery stops,
> with PTRACE_CONT(0) on ptrace stops,
> and doesn't do any PTRACE_CONT on job control stops,
> with your proposal the debugger will see and perform
> the following actions:
> 
> waitpid...
>   <------ kill -STOP 16382
> waitpid returns WSTOPPED, WSTOPSIG = SIGSTOP
> ptrace(PTRACE_GETSIGINFO) doesn't fail (=> it's signal delivery)
> ptrace(PTRACE_CONT, SIGSTOP)
> waitpid returns WSTOPPED, WSTOPSIG = SIGSTOP
> ptrace(PTRACE_GETSIGINFO) fails (=> it's job control stop)
> waitpid...
>   <------ kill -ABRT 16382
> ...debugger doesn't wake up...
>   <------ kill -WINCH 16382
> ...debugger doesn't wake up...
>   <------ kill -CONT 16382
> waitpid returns WSTOPPED, WSTOPSIG = SIGTRAP (it's a ptrace-stop)
> ptrace(PTRACE_CONT, 0)
> waitpid returns WSTOPPED, WSTOPSIG = SIGWINCH
> ptrace(PTRACE_CONT, SIGWINCH)
> waitpid returns WSTOPPED, WSTOPSIG = SIGCONT
> ptrace(PTRACE_CONT, SIGCONT)
> waitpid returns WSTOPPED, WSTOPSIG = SIGABRT
> ptrace(PTRACE_CONT, SIGABRT)
> 
> Correct?

Yeah, seems correct to me.

Thanks.

-- 
tejun
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