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>

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 61b17dc2c277346ae2c869da691ec19ab000e1ad..da7bdaa3ce159e76a649370af2a1e8f38c1bccf0 100644 (file)
--- 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.