linux-kernel - Re: [PATCH 3/5] uprobes: Fix UPROBE_SKIP_SSTEP checks in handle

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Date:	Sat, 15 Sep 2012 13:09:58 +0530
From:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] uprobes: Fix UPROBE_SKIP_SSTEP checks in
	handle_swbp()

On Fri, Sep 14, 2012 at 07:15:57PM +0200, Oleg Nesterov wrote:
> If handle_swbp()->add_utask() fails but UPROBE_SKIP_SSTEP is set,
> cleanup_ret: path do not restart the insn, this is wrong. Remove
> this check and add the additional label for can_skip_sstep() = T
> case.
> 
> Note also that UPROBE_SKIP_SSTEP can be false positive, we simply
> can not trust it unless arch_uprobe_skip_sstep() was already called.
> 
> Also, move another UPROBE_SKIP_SSTEP check before can_skip_sstep()
> into this helper, this looks more clean and understandable.
> 
> Note: probably we should rename "skip" to "emulate" and I think
> that "clear UPROBE_SKIP_SSTEP" should be moved to arch_can_skip.

Agree. emulate is more accurate in this situation since, especially on
powerpc, we do emulate most instructions.

Ananth

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