linux-kernel - Re: [PATCH 5/7] ptrace: kill clone/exec tracehooks

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Date:	Tue, 21 Jun 2011 09:24:15 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, hch@...radead.org
Subject: Re: [PATCH 5/7] ptrace: kill clone/exec tracehooks

Hello,

On Mon, Jun 20, 2011 at 10:33 PM, Oleg Nesterov <oleg@...hat.com> wrote:
>> +     if (likely(user_mode(regs)) && !(clone_flags & CLONE_UNTRACED)) {
>
> Off-topic, but I never understood this user_mode() check... OK, a
> traced task can call kernel_thread() in kernel, but this used
> CLONE_UNTRACED.

Me neither.  I suppose it's added as a safety net.  Maybe we can turn
it into WARN_ON(!user_mode) && !CLONE_UNTRACED) but just leaving it
alone doesn't sound like a bad idea.

>> +             if (clone_flags & CLONE_VFORK)
>> +                     trace = PTRACE_EVENT_VFORK;
>> +             else if ((clone_flags & CSIGNAL) != SIGCHLD)
>> +                     trace = PTRACE_EVENT_CLONE;
>> +             else
>> +                     trace = PTRACE_EVENT_FORK;
>> +
>> +             if (likely(!ptrace_event_enabled(current, trace)))
>> +                     trace = 0;
>> +     }
>
> As I said am going to apply this all except 6/7, but imho this
> deserves a trivial helper anyway.

Yeah, maybe.  Preference, I guess.

Thanks.

-- 
tejun
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