kprobes/x86: Allow to handle reentered kprobe on single-stepping

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>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Jonathan Lebon <jlebon@redhat.com>
Link: http://lkml.kernel.org/r/20140417081651.26341.10593.stgit@ltc230.yrl.intra.hitachi.co.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 61b17dc2c277..da7bdaa3ce15 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.