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Re: [PATCH] MIPS Kprobes: Support branch instructions probing

To: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Subject: Re: [PATCH] MIPS Kprobes: Support branch instructions probing
From: Maneesh Soni <manesoni@cisco.com>
Date: Thu, 13 Oct 2011 15:42:18 +0530
Cc: ralf@linux-mips.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, david.daney@cavium.com, kamensky@cisco.com
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In-reply-to: <20111013094137.GA19054@in.ibm.com>
References: <20111013090749.GB16761@cisco.com> <20111013094137.GA19054@in.ibm.com>
Reply-to: manesoni@cisco.com
Sender: linux-mips-bounce@linux-mips.org
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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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