linux-kernel - [PATCH 05/19] perf probe: Fix failure to add multiple probes without debuginfo

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Date:	Sat, 21 Mar 2015 15:54:24 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, He Kuang <hekuang@...wei.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Wang Nan <wangnan0@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 05/19] perf probe: Fix failure to add multiple probes without debuginfo

From: He Kuang <hekuang@...wei.com>

Perf tries to find probe function addresses from map when debuginfo
could not be found.

To the first added function, the value of ref_reloc_sym was set in
maps__set_kallsyms_ref_reloc_sym() and can be obtained from
host_machine->kmaps->maps. After that, new maps are added to
host_machine->kmaps->maps in dso__load_kcore(), all these new added maps
do not have a valid ref_reloc_sym.

When adding a second function, get_target_map() may get a map without
valid ref_reloc_sym, and raise the error "Relocated base symbol is not
found".

Fix this by using kernel_get_ref_reloc_sym() to get ref_reloc_sym.

This problem can be reproduced as following:

  $ perf probe --add='sys_write' --add='sys_open'
  Relocated base symbol is not found!
    Error: Failed to add events.

After this patch:

  $ perf probe --add='sys_write' --add='sys_open'
  Added new event:
    probe:sys_write      (on sys_write)

  You can now use it in all perf tools, such as:

      perf record -e probe:sys_write -aR sleep 1

  Added new event:
    probe:sys_open       (on sys_open)

  You can now use it in all perf tools, such as:

      perf record -e probe:sys_open -aR sleep 1

Signed-off-by: He Kuang <hekuang@...wei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lkml.kernel.org/r/1426816616-2394-1-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/probe-event.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index f272a711ad15..6b95985db5b0 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -2507,7 +2507,6 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
 					    int max_tevs, const char *target)
 {
 	struct map *map = NULL;
-	struct kmap *kmap = NULL;
 	struct ref_reloc_sym *reloc_sym = NULL;
 	struct symbol *sym;
 	struct probe_trace_event *tev;
@@ -2540,8 +2539,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
 	}
 
 	if (!pev->uprobes && !pp->retprobe) {
-		kmap = map__kmap(map);
-		reloc_sym = kmap->ref_reloc_sym;
+		reloc_sym = kernel_get_ref_reloc_sym();
 		if (!reloc_sym) {
 			pr_warning("Relocated base symbol is not found!\n");
 			ret = -EINVAL;
-- 
1.9.3

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