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Subject[PATCH 13/16] perf probe: Fix a segfault bug in debuginfo_cache
Date
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

perf probe --list will get a segfault if the first kprobe event is on a
module and the second or latter one is on the kernel.

e.g.
----
# ./perf probe -q -m pcspkr pcspkr_event
# ./perf probe -q vfs_read
# ./perf probe -l
Segmentation fault (core dumped)
----

This is because the debuginfo_cache fails to handle NULL module name,
which causes segfault on strcmp. (Note that strcmp("something", NULL)
always causes segfault)

To fix this debuginfo_cache__open always translates the NULL module name
to "kernel" (this is correct, because NULL module name means opening the
debuginfo for the kernel)

----
# ./perf probe -l
probe:pcspkr_event (on pcspkr_event@drivers/input/misc/pcspkr.c
in pcspkr)
probe:vfs_read (on vfs_read@ksrc/linux-3/fs/read_write.c)
----

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/20150930164135.3733.23993.stgit@localhost.localdomain
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/probe-event.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 65be284823d5..3010abc071ff 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -441,19 +441,22 @@ static char *debuginfo_cache_path;

static struct debuginfo *debuginfo_cache__open(const char *module, bool silent)
{
- if ((debuginfo_cache_path && !strcmp(debuginfo_cache_path, module)) ||
- (!debuginfo_cache_path && !module && debuginfo_cache))
+ const char *path = module;
+
+ /* If the module is NULL, it should be the kernel. */
+ if (!module)
+ path = "kernel";
+
+ if (debuginfo_cache_path && !strcmp(debuginfo_cache_path, path))
goto out;

/* Copy module path */
free(debuginfo_cache_path);
- if (module) {
- debuginfo_cache_path = strdup(module);
- if (!debuginfo_cache_path) {
- debuginfo__delete(debuginfo_cache);
- debuginfo_cache = NULL;
- goto out;
- }
+ debuginfo_cache_path = strdup(path);
+ if (!debuginfo_cache_path) {
+ debuginfo__delete(debuginfo_cache);
+ debuginfo_cache = NULL;
+ goto out;
}

debuginfo_cache = open_debuginfo(module, silent);
--
2.1.0


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