linux-kernel - Re: [PATCH v3 6/7] powerpc: kprobes: emulate instructions on kprobe handler re-entry

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Message-Id: <20170419234319.7893df9c158e565fede4a386@kernel.org>
Date:   Wed, 19 Apr 2017 23:43:19 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Ingo Molnar <mingo@...nel.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/7] powerpc: kprobes: emulate instructions on kprobe
 handler re-entry


BTW, as I pointed, 5/7 and 6/7 should be merged since this actually
makes meaningful change.

Thank you,

On Wed, 19 Apr 2017 18:21:05 +0530
"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:

> On kprobe handler re-entry, try to emulate the instruction rather than
> single stepping always.
> 
> Acked-by: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/kprobes.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index 46e8c1e03ce4..067e9863bfdf 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -276,6 +276,14 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
>  			kprobes_inc_nmissed_count(p);
>  			prepare_singlestep(p, regs);
>  			kcb->kprobe_status = KPROBE_REENTER;
> +			if (p->ainsn.boostable >= 0) {
> +				ret = try_to_emulate(p, regs);
> +
> +				if (ret > 0) {
> +					restore_previous_kprobe(kcb);
> +					return 1;
> +				}
> +			}
>  			return 1;
>  		} else {
>  			if (*addr != BREAKPOINT_INSTRUCTION) {
> -- 
> 2.12.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>