linux-kernel - Re: [PATCH] MIPS Kprobes: Support branch instructions probing

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Message-ID: <20111013101217.GD16761@cisco.com>
Date:	Thu, 13 Oct 2011 15:42:18 +0530
From:	Maneesh Soni <manesoni@...co.com>
To:	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Cc:	ralf@...ux-mips.org, linux-kernel@...r.kernel.org,
	linux-mips@...ux-mips.org, david.daney@...ium.com,
	kamensky@...co.com
Subject: Re: [PATCH] MIPS Kprobes: Support branch instructions probing

On Thu, Oct 13, 2011 at 03:11:38PM +0530, Ananth N Mavinakayanahalli wrote:
> On Thu, Oct 13, 2011 at 02:37:49PM +0530, Maneesh Soni wrote:
> 
> ...
> 
> I know nothing of MIPS internals, but...
>  
> >  static int __kprobes kprobe_handler(struct pt_regs *regs)
> > @@ -239,8 +531,13 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
> >  			save_previous_kprobe(kcb);
> >  			set_current_kprobe(p, regs, kcb);
> >  			kprobes_inc_nmissed_count(p);
> > -			prepare_singlestep(p, regs);
> > +			prepare_singlestep(p, regs, kcb);
> >  			kcb->kprobe_status = KPROBE_REENTER;
> > +			if (kcb->flags & SKIP_DELAYSLOT) {
> > +				resume_execution(p, regs, kcb);
> > +				restore_previous_kprobe(kcb);
> > +				preempt_enable_no_resched();
> > +			}
> >  			return 1;
> >  		} else {
> >  			if (addr->word != breakpoint_insn.word) {
> > @@ -284,8 +581,15 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
> >  	}
> > 
> >  ss_probe:
> > -	prepare_singlestep(p, regs);
> > -	kcb->kprobe_status = KPROBE_HIT_SS;
> > +	prepare_singlestep(p, regs, kcb);
> > +	if (kcb->flags & SKIP_DELAYSLOT) {
> > +		kcb->kprobe_status = KPROBE_HIT_SSDONE;
> > +		if (p->post_handler)
> > +			p->post_handler(p, regs, 0);
> > +		resume_execution(p, regs, kcb);
> 
> You are missing a preempt_disable_no_resched() here.
> 
ok.. you meant preempt_enable_no_resched(). Will add it in the next
version. Thanks for pointing it out.

Thanks
Maneesh
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