linux-kernel - Re: [PATCH] ptrace: copy_process() should disable stepping

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Date:	Mon, 9 Nov 2009 17:24:08 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Roland McGrath <roland@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] ptrace: copy_process() should disable stepping

On 11/08, Roland McGrath wrote:
>
> That is inappropriate use of arch details in generic code.  It might
> happen to be harmless fritter in practice on the arch's we have but it
> is certainly not the correct way to go about things.  You should just
> call user_disable_single_step() unconditionally.  Even on an arch with
> no such machinery at all that should be defined safely as a no-op (see
> linux/ptrace.h).  If there is some reason not to do that, please
> explain it.

Yes, we have arch_has_single_step.

I added test_tsk_thread_flag(TIF_SINGLESTEP) check for 2 reasons: to
optimize out user_disable_single_step() in the likely case, and because
I wasn't sure it is safe to call user_disable_single_step() unconditionally.

OK, will resend, thanks.

Oleg.

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