linux-kernel - Re: [PATCH 1/7] uprobes/x86: Only rep+nop can be emulated correctly

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Date:	Sat, 6 Oct 2012 12:50:33 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] uprobes/x86: Only rep+nop can be emulated correctly

* Oleg Nesterov <oleg@...hat.com> [2012-09-30 21:41:58]:

> __skip_sstep() correctly detects the "nontrivial" nop insns,
> but since it doesn't update regs->ip we can not really skip
> "0x0f 0x1f | 0x0f 0x19 | 0x87 0xc0", the probed application
> is killed by SIGILL'ed handle_swbp().
> 
> Remove these additional checks. If we want to implement this
> correctly we need to know the full insn length to update ->ip.
> 
> rep* + nop is fine even without updating ->ip.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

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