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arm: kprobes: Allow to handle reentered kprobe on single-stepping

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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
reentered kprobe is processing (KPROBE_REENTER), because
we already consumed a saved-area for the previous kprobe.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
This commit is contained in:
Masami Hiramatsu
2017-02-14 00:03:38 +09:00
committed by Jon Medhurst
parent 4495c08e84
commit f3fbd7ec62
1 changed files with 6 additions and 0 deletions
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6
arch/arm/probes/kprobes/core.c
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@ -271,6 +271,7 @@ 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);
@ -279,6 +280,11 @@ 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();