linux-kernel - Re: [PATCH] ptrace: copy_thread() should clear TIF_SINGLESTEP and X86_EFLAGS

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Message-Id: <20091106221002.8057DCF@magilla.sf.frob.com>
Date:	Fri,  6 Nov 2009 14:10:02 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH] ptrace: copy_thread() should clear TIF_SINGLESTEP and
	X86_EFLAGS_TF

> I thought this flag has no effect without TIF_SINGLESTEP, and it is
> always updated by enable_single_step().

Right, but to be anal about the semantics you shouldn't clear TF if it's
not set, etc.

> user_disable_single_step() is very much arch-dependent, I am worried
> if it is safe to call it from copy_process(), when the new task_struct,
> thread_info, etc are not properly initialized yet...

Well, arch people can weigh in about if it is problematical.
Skimming over the existing arch definitions, it looks OK to me.


Thanks,
Roland
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