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Subject[PATCH -tip v8 02/26] kprobes/x86: Allow to handle reentered kprobe on singlestepping
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Since the NMI handlers(e.g. perf) 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 <masami.hiramatsu.pt@hitachi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
---
arch/x86/kernel/kprobes/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index b482e96..a9a42fa 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -531,10 +531,11 @@ reenter_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb
switch (kcb->kprobe_status) {
case KPROBE_HIT_SSDONE:
case KPROBE_HIT_ACTIVE:
+ case KPROBE_HIT_SS:
kprobes_inc_nmissed_count(p);
setup_singlestep(p, regs, kcb, 1);
break;
- case KPROBE_HIT_SS:
+ case KPROBE_REENTER:
/* A probe has been hit in the codepath leading up to, or just
* after, single-stepping of a probed instruction. This entire
* codepath should strictly reside in .kprobes.text section.



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