linux-kernel - Re: [PATCH 1/3] powerpc: kprobes: add support for KPROBES_ON

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Message-Id: <20170216194935.GF4515@naverao1-tp.localdomain>
Date:   Fri, 17 Feb 2017 01:19:35 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/3] powerpc: kprobes: add support for KPROBES_ON_FTRACE

On 2017/02/15 04:11PM, Masami Hiramatsu wrote:
> Hi Naveen,
> 
> On Wed, 15 Feb 2017 00:28:34 +0530
> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> 
> > diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> > index e51a045f3d3b..a8f414a0b141 100644
> > --- a/arch/powerpc/kernel/optprobes.c
> > +++ b/arch/powerpc/kernel/optprobes.c
> > @@ -70,6 +70,9 @@ static unsigned long can_optimize(struct kprobe *p)
> >  	struct instruction_op op;
> >  	unsigned long nip = 0;
> >  
> > +	if (unlikely(kprobe_ftrace(p)))
> > +		return 0;
> > +
> 
> Hmm, this should not be checked in arch-depend code, since it may duplicate
> code in each arch. Please try below.

Thanks, Masami!

> 
> Thanks,
> 
> commit 897bb304974c1b0c19a4274fea220b175b07f353
> Author: Masami Hiramatsu <mhiramat@...nel.org>
> Date:   Wed Feb 15 15:48:14 2017 +0900
> 
>     kprobes: Skip preparing optprobe if the probe is ftrace-based
>     
>     Skip preparing optprobe if the probe is ftrace-based, since
>     anyway, it must not be optimized (or already optimized by
>     ftrace).
>     
>     Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>

This works for me.
Tested-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>


Regards,
Naveen


> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index ebb4dad..546a8b1 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -746,13 +746,20 @@ static void kill_optimized_kprobe(struct kprobe *p)
>  	arch_remove_optimized_kprobe(op);
>  }
> 
> +static inline
> +void __prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
> +{
> +	if (!kprobe_ftrace(p))
> +		arch_prepare_optimized_kprobe(op, p);
> +}
> +
>  /* Try to prepare optimized instructions */
>  static void prepare_optimized_kprobe(struct kprobe *p)
>  {
>  	struct optimized_kprobe *op;
> 
>  	op = container_of(p, struct optimized_kprobe, kp);
> -	arch_prepare_optimized_kprobe(op, p);
> +	__prepare_optimized_kprobe(op, p);
>  }
> 
>  /* Allocate new optimized_kprobe and try to prepare optimized instructions */
> @@ -766,7 +773,7 @@ static struct kprobe *alloc_aggr_kprobe(struct kprobe *p)
> 
>  	INIT_LIST_HEAD(&op->list);
>  	op->kp.addr = p->addr;
> -	arch_prepare_optimized_kprobe(op, p);
> +	__prepare_optimized_kprobe(op, p);
> 
>  	return &op->kp;
>  }
> 
> 
> 
> -- 
> Masami Hiramatsu <mhiramat@...nel.org>
>