linux-kernel - Re: [PATCH 8/7] uprobes: Fix arch_uprobe_disable_step() && UTASK_SSTEP

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Message-ID: <20120912123600.GD9582@linux.vnet.ibm.com>
Date:	Wed, 12 Sep 2012 18:06:00 +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>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Roland McGrath <roland@...k.frob.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/7] uprobes: Fix arch_uprobe_disable_step() &&
 UTASK_SSTEP_TRAPPED interaction

* Oleg Nesterov <oleg@...hat.com> [2012-09-08 19:06:23]:

> arch_uprobe_disable_step() should also take UTASK_SSTEP_TRAPPED into
> account. In this case the probed insn was not executed, we need to
> clear X86_EFLAGS_TF if it was set by us and that is all.
> 
> Again, this code will look more clean when we move it into
> arch_uprobe_post_xol() and arch_uprobe_abort_xol().
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>



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

note:
I also think this should be merged into 6/7 patch if possible

-- 
thanks and regards
Srikar

> ---
>  arch/x86/kernel/uprobes.c |   14 ++++++++++----
>  1 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index 7e993d1..9538f00 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -706,14 +706,20 @@ void arch_uprobe_disable_step(struct arch_uprobe *auprobe)
>  {
>  	struct task_struct *task = current;
>  	struct arch_uprobe_task	*autask	= &task->utask->autask;
> +	bool trapped = (task->utask->state == UTASK_SSTEP_TRAPPED);
>  	struct pt_regs *regs = task_pt_regs(task);
>  	/*
>  	 * The state of TIF_BLOCKSTEP was not saved so we can get an extra
>  	 * SIGTRAP if we do not clear TF. We need to examine the opcode to
>  	 * make it right.
>  	 */
> -	if (autask->saved_tf)
> -		send_sig(SIGTRAP, task, 0);
> -	else if (!(auprobe->fixups & UPROBE_FIX_SETF))
> -		regs->flags &= ~X86_EFLAGS_TF;
> +	if (unlikely(trapped)) {
> +		if (!autask->saved_tf)
> +			regs->flags &= ~X86_EFLAGS_TF;
> +	} else {
> +		if (autask->saved_tf)
> +			send_sig(SIGTRAP, task, 0);
> +		else if (!(auprobe->fixups & UPROBE_FIX_SETF))
> +			regs->flags &= ~X86_EFLAGS_TF;
> +	}
>  }
> -- 
> 1.5.5.1
> 
> 

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