sh: kprobes: Fix up race against probe point removal.

Handle a corner case where another CPU or debugger removes the probe
point from underneath us.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/sh/kernel/kprobes.c b/arch/sh/kernel/kprobes.c
index f0e1c78d0bff..a478ba78e752 100644
--- a/arch/sh/kernel/kprobes.c
+++ b/arch/sh/kernel/kprobes.c
@@ -252,6 +252,17 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
         p = get_kprobe(addr);
         if (!p) {
                 /* Not one of ours: let kernel handle it */
+                if (*(kprobe_opcode_t *)addr != BREAKPOINT_INSTRUCTION) {
+                        /*
+                         * The breakpoint instruction was removed right
+                         * after we hit it. Another cpu has removed
+                         * either a probepoint or a debugger breakpoint
+                         * at this address. In either case, no further
+                         * handling of this interrupt is appropriate.
+                         */
+                        ret = 1;
+                }
+
                 goto no_kprobe;
         }