perf probe: Fix return probe support

Fix a bug to support %return probe syntax again. Previous commit 4235b04 has a
bug which disables the %return syntax on perf probe.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100827113852.22882.87447.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 11 insertions, 0 deletions

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index e72f05c3bef0..fcc16e4349df 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1539,6 +1539,7 @@ static int convert_to_probe_trace_events(struct perf_probe_event *pev,
                 goto error;
         }
         tev->point.offset = pev->point.offset;
+        tev->point.retprobe = pev->point.retprobe;
         tev->nargs = pev->nargs;
         if (tev->nargs) {
                 tev->args = zalloc(sizeof(struct probe_trace_arg)
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 525136684d4e..9b0e1b1f9755 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -783,6 +783,16 @@ static int convert_probe_point(Dwarf_Die *sp_die, struct probe_finder *pf)
                 /* This function has no name. */
                 tev->point.offset = (unsigned long)pf->addr;
 
+        /* Return probe must be on the head of a subprogram */
+        if (pf->pev->point.retprobe) {
+                if (tev->point.offset != 0) {
+                        pr_warning("Return probe must be on the head of"
+                                   " a real function\n");
+                        return -EINVAL;
+                }
+                tev->point.retprobe = true;
+        }
+
         pr_debug("Probe point found: %s+%lu\n", tev->point.symbol,
                  tev->point.offset);