[tip:perf/urgent] perf probe: Use existing routine to look for a kernel module by dso->short_name

From: tip-bot for Arnaldo Carvalho de Melo
Date: Sat Sep 26 2015 - 02:22:18 EST

Commit-ID: 266fa2b22294909ddf6e7d2f8acfe07adf9fd978
Gitweb: http://git.kernel.org/tip/266fa2b22294909ddf6e7d2f8acfe07adf9fd978
Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Thu, 24 Sep 2015 11:24:18 -0300
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Fri, 25 Sep 2015 10:41:31 -0300

perf probe: Use existing routine to look for a kernel module by dso->short_name

We have map_groups__find_by_name() to look at the list of modules that
are in place for a given machine, so use it instead of traversing the
machine dso list, which also includes DSOs for userspace.

When merging the user and kernel DSO lists a bug was introduced where
'perf probe' stopped being able to add probes to modules using its short

# perf probe -m usbnet --add usbnet_start_xmit
usbnet_start_xmit is out of .text, skip it.
Error: Failed to add events.

With this fix it works again:

# perf probe -m usbnet --add usbnet_start_xmit
Added new event:
probe:usbnet_start_xmit (on usbnet_start_xmit in usbnet)

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

perf record -e probe:usbnet_start_xmit -aR sleep 1

Reported-by: Wang Nan <wangnan0@xxxxxxxxxx>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Fixes: 3d39ac538629 ("perf machine: No need to have two DSOs lists")
Link: http://lkml.kernel.org/r/20150924015008.GE1897@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/util/probe-event.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index eb5f18b..c6f9af7 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -270,12 +270,13 @@ static int kernel_get_module_dso(const char *module, struct dso **pdso)
int ret = 0;

if (module) {
- list_for_each_entry(dso, &host_machine->dsos.head, node) {
- if (!dso->kernel)
- continue;
- if (strncmp(dso->short_name + 1, module,
- dso->short_name_len - 2) == 0)
- goto found;
+ char module_name[128];
+ snprintf(module_name, sizeof(module_name), "[%s]", module);
+ map = map_groups__find_by_name(&host_machine->kmaps, MAP__FUNCTION, module_name);
+ if (map) {
+ dso = map->dso;
+ goto found;
pr_debug("Failed to find module %s.\n", module);
return -ENOENT;
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