[tip:perf/core] perf tools: Fix segfault due to invalid kernel dso access

[tip-bot for Namhyung Kim <tipbot@zytor.com>]

Commit-ID:  330dfa224fcc8594977785a6493ca06d124f0cfe
Gitweb:     http://git.kernel.org/tip/330dfa224fcc8594977785a6493ca06d124f0cfe
Author:     Namhyung Kim <namhyung@kernel.org>
AuthorDate: Tue, 18 Nov 2014 13:30:28 +0900
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Mon, 24 Nov 2014 18:03:48 -0300

perf tools: Fix segfault due to invalid kernel dso access

Jiri reported that the commit 96d78059d6d9 ("perf tools: Make vmlinux
short name more like kallsyms short name") segfaults on perf script.

When processing kernel mmap event, it should access the 'kernel'
variable as sometimes it cannot find a matching dso from build-id table
so 'dso' might be invalid.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1416285028-30572-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/machine.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index d97309c..b75b487 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1106,8 +1106,8 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
 		if (__machine__create_kernel_maps(machine, kernel) < 0)
 			goto out_problem;
 
-		if (strstr(dso->long_name, "vmlinux"))
-			dso__set_short_name(dso, "[kernel.vmlinux]", false);
+		if (strstr(kernel->long_name, "vmlinux"))
+			dso__set_short_name(kernel, "[kernel.vmlinux]", false);
 
 		machine__set_kernel_mmap_len(machine, event);