Commit f3fbd7ec authored Feb 14, 2017 by Masami Hiramatsu Committed by Jon Medhurst Mar 21, 2017

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



This is arm port of commit 6a5022a5 ("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>

parent 4495c08e

arch/arm/probes/kprobes/core.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -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();