linux-kernel - Re: [PATCH 2/2] ptrace: fix set_task_blockstep()->update

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Date:	Tue, 07 Aug 2012 12:52:56 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Roland McGrath <roland@...k.frob.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ptrace: fix set_task_blockstep()->update_debugctlmsr()
 logic

On 08/07/2012 11:41 AM, Sebastian Andrzej Siewior wrote:
> On 08/03/2012 06:29 PM, Oleg Nesterov wrote:
> For uprobes we never set the bit, we only need it cleared. We get here
> via int 3 and do_debug() already clears TIF_BLOCKSTEP because the
> CPU clears the bit in CPU. So both, TIF_BLOCKSTEP and DEBUGCTLMSR_BTF
> are never set.

Actually I'm, wrong. Syscalls do clear the DEBUGCTLMSR_BTF bit, int3
does not. So yes, we need it after all…

Sebastian
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