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Date: Thu, 16 Jun 2011 10:38:28 +0200
From: Tejun Heo <tj@kernel.org>
To: Pedro Alves <pedro@codesourcery.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>, Oleg Nesterov <oleg@redhat.com>,
        jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org,
        torvalds@linux-foundation.org, akpm@linux-foundation.org, indan@nul.nu,
        bdonlan@gmail.com
Subject: Re: [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and
 group stop notification, take#4
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Hello, Pedro.  Sorry about late reply.

On Fri, Jun 03, 2011 at 11:25:15AM +0100, Pedro Alves wrote:
> Some archs started encoding some of that stuff on SIGTRAPs si_code.
> E.g., on a ppc box I got here, I see:
> 
> /* `si_code' values for SIGTRAP signal.  */
> enum
> {
>   TRAP_BRKPT = 1,               /* Process breakpoint.  */
> # define TRAP_BRKPT     TRAP_BRKPT
>   TRAP_TRACE                    /* Process trace trap.  */
> # define TRAP_TRACE     TRAP_TRACE
> };

Yeap, several archs seem to have grown their own tricks.

> It'd be _very_ useful for x86 (and others) to have
> something like TRAP_BRKPT for int3.  Both for ptracers
> and in-process self debuggers.
> 
> I'd be super happy to be told we have that already
> in recent kernels and I missed it.  :-)

Unfortunately, AFAICS, x86 doesn't have it nor is there a generic
mechanism, but this should be solvable without disrupting existing
users.

Thanks.

-- 
tejun