[PATCH] perf kvm: fix segfault with report and mixed guestmount use

David Ahern
2012-07-02T15:13:08Z

Using the guestmount option on record:
$ perf kvm --guest --host --guestmount=/tmp/guest-mount record -ag

But not the subsequent report:
$ perf kvm report

causes a SEGFAULT in the usual place:
(gdb) bt
0 0x0000000000470356 in machine__mmap_name (self=0x0, bf=0x7fffffffbdb0 " z\370\367\377\177", size=
4096) at util/map.c:712
1 0x00000000004453e8 in perf_event__process_kernel_mmap (tool=0x7fffffffde10, event=0x7ffff7f87e38,
machine=0x0) at util/event.c:550
2 0x00000000004458c9 in perf_event__process_mmap (tool=0x7fffffffde10, event=0x7ffff7f87e38, sample=
0x7fffffffd2a0, machine=0x0) at util/event.c:656
3 0x00000000004733e0 in perf_session_deliver_event (session=0x91aca0, event=0x7ffff7f87e38, sample=
0x7fffffffd2a0, tool=0x7fffffffde10, file_offset=7736) at util/session.c:979
...

The MMAP events in this case already contain the full path to the module. No
need to require it for the report path to.

Signed-off-by: David Ahern <dsahern@gmail.com>
CC: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
tools/perf/util/map.c | 29 +++++++++++++++--------------
1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 35ae568..a1f4e36 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -669,25 +669,26 @@ struct machine *machines__find(struct rb_root *self, pid_t pid)
struct machine *machines__findnew(struct rb_root *self, pid_t pid)
{
char path[PATH_MAX];
- const char *root_dir;
+ const char *root_dir = "";
struct machine *machine = machines__find(self, pid);

- if (!machine || machine->pid != pid) {
- if (pid == HOST_KERNEL_ID || pid == DEFAULT_GUEST_KERNEL_ID)
- root_dir = "";
- else {
- if (!symbol_conf.guestmount)
- goto out;
- sprintf(path, "%s/%d", symbol_conf.guestmount, pid);
- if (access(path, R_OK)) {
- pr_err("Can't access file %s\n", path);
- goto out;
- }
- root_dir = path;
+ if (machine && (machine->pid == pid))
+ goto out;
+
+ if ((pid != HOST_KERNEL_ID) &&
+ (pid != DEFAULT_GUEST_KERNEL_ID) &&
+ (symbol_conf.guestmount)) {
+ sprintf(path, "%s/%d", symbol_conf.guestmount, pid);
+ if (access(path, R_OK)) {
+ pr_err("Can't access file %s\n", path);
+ machine = NULL;
+ goto out;
}
- machine = machines__add(self, pid, root_dir);
+ root_dir = path;
}

+ machine = machines__add(self, pid, root_dir);
+
out:
return machine;
}
--
1.7.10.1