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| Started by | "Jon Medhurst (Tixy)" <tixy@linaro.org> |
|---|---|
| First post | 2017-02-14 11:10 +0100 |
| Last post | 2017-02-14 16:40 +0100 |
| Articles | 2 — 2 participants |
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Re: [BUGFIX PATCH 2/3] kprobes/arm: Skip single-stepping in recursing path if possible "Jon Medhurst (Tixy)" <tixy@linaro.org> - 2017-02-14 11:10 +0100
Re: [BUGFIX PATCH 2/3] kprobes/arm: Skip single-stepping in recursing path if possible Masami Hiramatsu <mhiramat@kernel.org> - 2017-02-14 16:40 +0100
| From | "Jon Medhurst (Tixy)" <tixy@linaro.org> |
|---|---|
| Date | 2017-02-14 11:10 +0100 |
| Subject | Re: [BUGFIX PATCH 2/3] kprobes/arm: Skip single-stepping in recursing path if possible |
| Message-ID | <taIdz-sN-13@gated-at.bofh.it> |
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 <mhiramat@kernel.org>
Acked-by: Jon Medhurst <tixy@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. */
>
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| From | Masami Hiramatsu <mhiramat@kernel.org> |
|---|---|
| Date | 2017-02-14 16:40 +0100 |
| Message-ID | <taNmW-3BD-15@gated-at.bofh.it> |
| In reply to | #1580448 |
On Tue, 14 Feb 2017 10:07:17 +0000
"Jon Medhurst (Tixy)" <tixy@linaro.org> wrote:
> 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."
OK, Thanks!
>
>
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> Acked-by: Jon Medhurst <tixy@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. */
> >
--
Masami Hiramatsu <mhiramat@kernel.org>
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