linux-kernel - Re: [PATCH 3/7] ptrace: Introduce set_task

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Message-ID: <20120907150037.GP30238@linux.vnet.ibm.com>
Date:	Fri, 7 Sep 2012 20:30:37 +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 3/7] ptrace: Introduce set_task_blockstep() helper

* Oleg Nesterov <oleg@...hat.com> [2012-09-03 17:26:06]:

> No functional changes, preparation for the next fix and for uprobes
> single-step fixes.
> 
> Move the code playing with TIF_BLOCKSTEP/DEBUGCTLMSR_BTF into the
> new helper, set_task_blockstep().
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

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

> ---
>  arch/x86/kernel/step.c |   41 +++++++++++++++++++++--------------------
>  1 files changed, 21 insertions(+), 20 deletions(-)
> 
> diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
> index c346d11..7a51498 100644
> --- a/arch/x86/kernel/step.c
> +++ b/arch/x86/kernel/step.c
> @@ -157,6 +157,21 @@ static int enable_single_step(struct task_struct *child)
>  	return 1;
>  }
> 
> +static void set_task_blockstep(struct task_struct *task, bool on)
> +{
> +	unsigned long debugctl;
> +
> +	debugctl = get_debugctlmsr();
> +	if (on) {
> +		debugctl |= DEBUGCTLMSR_BTF;
> +		set_tsk_thread_flag(task, TIF_BLOCKSTEP);
> +	} else {
> +		debugctl &= ~DEBUGCTLMSR_BTF;
> +		clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
> +	}
> +	update_debugctlmsr(debugctl);
> +}
> +
>  /*
>   * Enable single or block step.
>   */
> @@ -169,19 +184,10 @@ static void enable_step(struct task_struct *child, bool block)
>  	 * So no one should try to use debugger block stepping in a program
>  	 * that uses user-mode single stepping itself.
>  	 */
> -	if (enable_single_step(child) && block) {
> -		unsigned long debugctl = get_debugctlmsr();
> -
> -		debugctl |= DEBUGCTLMSR_BTF;
> -		update_debugctlmsr(debugctl);
> -		set_tsk_thread_flag(child, TIF_BLOCKSTEP);
> -	} else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {
> -		unsigned long debugctl = get_debugctlmsr();
> -
> -		debugctl &= ~DEBUGCTLMSR_BTF;
> -		update_debugctlmsr(debugctl);
> -		clear_tsk_thread_flag(child, TIF_BLOCKSTEP);
> -	}
> +	if (enable_single_step(child) && block)
> +		set_task_blockstep(child, true);
> +	else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
> +		set_task_blockstep(child, false);
>  }
> 
>  void user_enable_single_step(struct task_struct *child)
> @@ -199,13 +205,8 @@ void user_disable_single_step(struct task_struct *child)
>  	/*
>  	 * Make sure block stepping (BTF) is disabled.
>  	 */
> -	if (test_tsk_thread_flag(child, TIF_BLOCKSTEP)) {
> -		unsigned long debugctl = get_debugctlmsr();
> -
> -		debugctl &= ~DEBUGCTLMSR_BTF;
> -		update_debugctlmsr(debugctl);
> -		clear_tsk_thread_flag(child, TIF_BLOCKSTEP);
> -	}
> +	if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))
> +		set_task_blockstep(child, false);
> 
>  	/* Always clear TIF_SINGLESTEP... */
>  	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
> -- 
> 1.5.5.1
> 

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