[tip:perf/urgent] perf probe: Set retprobe flag when probe in address-based alternative mode

[tip-bot for He Kuang <tipbot@zytor.com>]

Commit-ID:  9d7b45c5721dfd524666bc1f07cf7d0855edb4d5
Gitweb:     http://git.kernel.org/tip/9d7b45c5721dfd524666bc1f07cf7d0855edb4d5
Author:     He Kuang <hekuang@huawei.com>
AuthorDate: Mon, 13 Apr 2015 19:41:28 +0800
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 13 Apr 2015 17:25:22 -0300

perf probe: Set retprobe flag when probe in address-based alternative mode

When perf probe searched in a debuginfo file and failed, it tried with
an alternative, in function get_alternative_probe_event():

        memcpy(tmp, &pev->point, sizeof(*tmp));
        memset(&pev->point, 0, sizeof(pev->point));

In this case, it drops the retprobe flag and forgets to set it back in
find_alternative_probe_point(), so the problem occurs.

Can be reproduced as following:

  $ perf probe -v -k vmlinux --add='sys_write%return'
  ...
  Added new event:
  Writing event: p:probe/sys_write _stext+1584952
    probe:sys_write      (on sys_write%return)

  $ cat /sys/kernel/debug/tracing/kprobe_events
  p:probe/sys_write _stext+1584952

After this patch:

  $ perf probe -v -k vmlinux --add='sys_write%return'
  Added new event:
  Writing event: r:probe/sys_write SyS_write+0
    probe:sys_write      (on sys_write%return)

  $ cat /sys/kernel/debug/tracing/kprobe_events
  r:probe/sys_write SyS_write

Signed-off-by: He Kuang <hekuang@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1428925290-5623-1-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/probe-event.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 30545ce..5483d98 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -332,6 +332,7 @@ static int find_alternative_probe_point(struct debuginfo *dinfo,
 	else {
 		result->offset += pp->offset;
 		result->line += pp->line;
+		result->retprobe = pp->retprobe;
 		ret = 0;
 	}