[tip:perf/core] perf machine: Fallback to MAP__FUNCTION if daddr maps are NULL

From: tip-bot for Don Zickus
Date: Sun Aug 24 2014 - 10:59:32 EST

Commit-ID: 06b2afc0b9a26e7673856a24ab57bfb307dad394
Gitweb: http://git.kernel.org/tip/06b2afc0b9a26e7673856a24ab57bfb307dad394
Author: Don Zickus <dzickus@xxxxxxxxxx>
AuthorDate: Wed, 20 Aug 2014 23:25:11 -0400
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Fri, 22 Aug 2014 13:12:13 -0300

perf machine: Fallback to MAP__FUNCTION if daddr maps are NULL

As we run "perf c2c" on more applications, we noticed we're missing
significant samples from a common customer's application. Looking at
the /proc/<pid>/maps file for the app, we see "rwxs" and "rwxp"
permissions on many of the shared memory & heap regions, and on all the
thread stacks.

Because those regions have the "x" bit set, perf marks them with a
MAP_FUNCTION type. Hence ip_resolve_data() never finds load or store
events coming from them.

We fixed this by re-calling thread__find_addr_location with
MAP__FUNCTION in the case where map is NULL as a last ditch effort to
map the sample before giving up and dropping it.

Reported-by: Joe Mario <jmario@xxxxxxxxxx>
Tested-by: Joe Mario <jmario@xxxxxxxxxx>
Signed-off-by: Don Zickus <dzickus@xxxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Joe Mario <jmario@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1408591511-57884-1-git-send-email-dzickus@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/util/machine.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index e00daf0..b2ec38b 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1314,6 +1314,16 @@ static void ip__resolve_data(struct machine *machine, struct thread *thread,

thread__find_addr_location(thread, machine, m, MAP__VARIABLE, addr,
+ if (al.map == NULL) {
+ /*
+ * some shared data regions have execute bit set which puts
+ * their mapping in the MAP__FUNCTION type array.
+ * Check there as a fallback option before dropping the sample.
+ */
+ thread__find_addr_location(thread, machine, m, MAP__FUNCTION, addr,
+ &al);
+ }
ams->addr = addr;
ams->al_addr = al.addr;
ams->sym = al.sym;
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