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SubjectRe: [PATCH v3 5/7] powerpc: kprobes: factor out code to emulate instruction into a helper
On Wed, 19 Apr 2017 18:21:04 +0530
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:

Factor out code to emulate instruction into a try_to_emulate()
helper function. This makes ...

> No functional changes.

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 | 52 ++++++++++++++++++++++++++-----------------
> 1 file changed, 31 insertions(+), 21 deletions(-)
>
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index d743bacefa8c..46e8c1e03ce4 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -206,6 +206,35 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
> regs->link = (unsigned long)kretprobe_trampoline;
> }
>
> +int __kprobes try_to_emulate(struct kprobe *p, struct pt_regs *regs)
> +{
> + int ret;
> + unsigned int insn = *p->ainsn.insn;
> +
> + /* regs->nip is also adjusted if emulate_step returns 1 */
> + ret = emulate_step(regs, insn);
> + if (ret > 0) {
> + /*
> + * Once this instruction has been boosted
> + * successfully, set the boostable flag
> + */
> + if (unlikely(p->ainsn.boostable == 0))
> + p->ainsn.boostable = 1;
> + } else if (ret < 0) {
> + /*
> + * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
> + * So, we should never get here... but, its still
> + * good to catch them, just in case...
> + */
> + printk("Can't step on instruction %x\n", insn);
> + BUG();
> + } else if (ret == 0)
> + /* This instruction can't be boosted */
> + p->ainsn.boostable = -1;
> +
> + return ret;
> +}
> +
> int __kprobes kprobe_handler(struct pt_regs *regs)
> {
> struct kprobe *p;
> @@ -301,18 +330,9 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
>
> ss_probe:
> if (p->ainsn.boostable >= 0) {
> - unsigned int insn = *p->ainsn.insn;
> + ret = try_to_emulate(p, regs);
>
> - /* regs->nip is also adjusted if emulate_step returns 1 */
> - ret = emulate_step(regs, insn);
> if (ret > 0) {
> - /*
> - * Once this instruction has been boosted
> - * successfully, set the boostable flag
> - */
> - if (unlikely(p->ainsn.boostable == 0))
> - p->ainsn.boostable = 1;
> -
> if (p->post_handler)
> p->post_handler(p, regs, 0);
>
> @@ -320,17 +340,7 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
> reset_current_kprobe();
> preempt_enable_no_resched();
> return 1;
> - } else if (ret < 0) {
> - /*
> - * We don't allow kprobes on mtmsr(d)/rfi(d), etc.
> - * So, we should never get here... but, its still
> - * good to catch them, just in case...
> - */
> - printk("Can't step on instruction %x\n", insn);
> - BUG();
> - } else if (ret == 0)
> - /* This instruction can't be boosted */
> - p->ainsn.boostable = -1;
> + }
> }
> prepare_singlestep(p, regs);
> kcb->kprobe_status = KPROBE_HIT_SS;
> --
> 2.12.1
>


--
Masami Hiramatsu <mhiramat@kernel.org>

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