On Tue, 2017-02-14 at 00:04 +0900, Masami Hiramatsu wrote:
> Kprobes/arm skips single-stepping (moreover handling the event)
> if the conditional instruction must not be executed. This
> also apply the rule when we hit the recursing kprobe, so
> that kprobe does not count nmissed up in that case.
Perhaps that last sentence would read better if written something like:
"This also applies that rule when we hit a recursing kprobe, so that the
nmissed count isn't incremented in that case."
> Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
Acked-by: Jon Medhurst <t...@linaro.org>
> ---
> arch/arm/probes/kprobes/core.c | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
> index 264fedb..84989ae 100644
> --- a/arch/arm/probes/kprobes/core.c
> +++ b/arch/arm/probes/kprobes/core.c
> @@ -265,7 +265,15 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
> #endif
>
> if (p) {
> - if (cur) {
> + if (!p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
> + /*
> + * Probe hit but conditional execution check failed,
> + * so just skip the instruction and continue as if
> + * nothing had happened.
> + * In this case, we can skip recursing check too.
> + */
> + singlestep_skip(p, regs);
> + } else if (cur) {
> /* Kprobe is pending, so we're recursing. */
> switch (kcb->kprobe_status) {
> case KPROBE_HIT_ACTIVE:
> @@ -288,7 +296,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
> /* impossible cases */
> BUG();
> }
> - } else if (p->ainsn.insn_check_cc(regs->ARM_cpsr)) {
> + } else {
> /* Probe hit and conditional execution check ok. */
> set_current_kprobe(p);
> kcb->kprobe_status = KPROBE_HIT_ACTIVE;
> @@ -309,13 +317,6 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
> }
> reset_current_kprobe();
> }
> - } else {
> - /*
> - * Probe hit but conditional execution check failed,
> - * so just skip the instruction and continue as if
> - * nothing had happened.
> - */
> - singlestep_skip(p, regs);
> }
> } else if (cur) {
> /* We probably hit a jprobe. Call its break handler. */
>
