On Tue, 2017-02-14 at 00:03 +0900, Masami Hiramatsu wrote:
> This is arm port of commit 6a5022a56ac3 ("kprobes/x86: Allow to
> handle reentered kprobe on single-stepping")
>
> Since the FIQ handlers can interrupt in the single stepping
> (or preparing the single stepping, do_debug etc.), we should
> consider a kprobe is hit in the NMI handler. Even in that
> case, the kprobe is allowed to be reentered as same as the
> kprobes hit in kprobe handlers
> (KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE).
>
> The real issue will happen when a kprobe hit while another
Could to with 'is' being inserted above ^^^
(I know this is a copy of the x86 commit message)
> reentered kprobe is processing (KPROBE_REENTER), because
> we already consumed a saved-area for the previous kprobe.
>
> Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
> ---
Acked-by: Jon Medhurst <t...@linaro.org>
> arch/arm/probes/kprobes/core.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
> index a4ec240..264fedb 100644
> --- a/arch/arm/probes/kprobes/core.c
> +++ b/arch/arm/probes/kprobes/core.c
> @@ -270,6 +270,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
> switch (kcb->kprobe_status) {
> case KPROBE_HIT_ACTIVE:
> case KPROBE_HIT_SSDONE:
> + case KPROBE_HIT_SS:
> /* A pre- or post-handler probe got us here. */
> kprobes_inc_nmissed_count(p);
> save_previous_kprobe(kcb);
> @@ -278,6 +279,11 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
> singlestep(p, regs, kcb);
> restore_previous_kprobe(kcb);
> break;
> + case KPROBE_REENTER:
> + /* A nested probe was hit in FIQ, it is a BUG */
> + pr_warn("Unrecoverable kprobe detected at
> %p.\n",
> + p->addr);
> + /* fall through */
> default:
> /* impossible cases */
> BUG();
>
