Re: [PATCH v2 5/5] powerpc: kprobes: emulate instructions on kprobe handler re-entry

Masami Hiramatsu
2017-04-13T04:38:11Z

On Wed, 12 Apr 2017 16:28:28 +0530
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:

> On kprobe handler re-entry, try to emulate the instruction rather than
> single stepping always.
>

> As a related change, remove the duplicate saving of msr as that is
> already done in set_current_kprobe()

If so, this part might be separated as a cleanup patch...

Thanks,

>
> Acked-by: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> arch/powerpc/kernel/kprobes.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index 8b48f7d046bd..005bd4a75902 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -273,10 +273,17 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
> */
> save_previous_kprobe(kcb);
> set_current_kprobe(p, regs, kcb);
> - kcb->kprobe_saved_msr = regs->msr;
> 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@kernel.org>