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@redhat.com>
Tested-by: Joe Mario <jmario@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1408591511-57884-1-git-send-email-dzickus@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index e00daf0..b2ec38b 100644 (file)
--- 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,
                                   &al);
+       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;