Commit 20f49859 authored Oct 01, 2015 by Masami Hiramatsu Committed by Arnaldo Carvalho de Melo Sep 30, 2015

perf probe: Fix a segfault bug in debuginfo_cache



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>

parent 9b239a12

tools/perf/util/probe-event.c

+12 −9

Original line number	Diff line number	Diff line
		@@ -441,20 +441,23 @@ 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);
		debuginfo_cache_path = strdup(path);
		if (!debuginfo_cache_path) {
		debuginfo__delete(debuginfo_cache);
		debuginfo_cache = NULL;
		goto out;
		}
		}

		debuginfo_cache = open_debuginfo(module, silent);
		if (!debuginfo_cache)