[PATCH] perf: report/annotate: fix segfault problem.

[Wang Nan]

perf report and perf annotate are easy to trigger segfault if trace data
contain kernel module information like this:

 # perf report -D -i ./perf.data
 ...
 0 0 0x188 [0x50]: PERF_RECORD_MMAP -1/0: [0xffffffbff1018000(0xf068000) @ 0]: x [test_module]
 ...

 # perf report -i ./perf.data --objdump=/path/to/objdump --kallsyms=/path/to/kallsyms

 perf: Segmentation fault
 -------- backtrace --------
 /path/to/perf[0x503478]
 /lib64/libc.so.6(+0x3545f)[0x7fb201f3745f]
 /path/to/perf[0x499b56]
 /path/to/perf(dso__load_kallsyms+0x13c)[0x49b56c]
 /path/to/perf(dso__load+0x72e)[0x49c21e]
 /path/to/perf(map__load+0x6e)[0x4ae9ee]
 /path/to/perf(thread__find_addr_map+0x24c)[0x47deec]
 /path/to/perf(perf_event__preprocess_sample+0x88)[0x47e238]
 /path/to/perf[0x43ad02]
 /path/to/perf[0x4b55bc]
 /path/to/perf(ordered_events__flush+0xca)[0x4b57ea]
 /path/to/perf[0x4b1a01]
 /path/to/perf(perf_session__process_events+0x3be)[0x4b428e]
 /path/to/perf(cmd_report+0xf11)[0x43bfc1]
 /path/to/perf[0x474702]
 /path/to/perf(main+0x5f5)[0x42de95]
 /lib64/libc.so.6(__libc_start_main+0xf4)[0x7fb201f23bd4]
 /path/to/perf[0x42dfc4]

This is because __kmod_path__parse regard '[' leading name as kernel
instead of kernel module. The DSO will then be passed to
dso__load_kernel_sym() then dso__load_kcore() because of --kallsyms
argument. The segfault is triggered because the kmap structure is not
initialized.

Although in --vmlinux case such segfault can be avoided, the symbols in
the kernel module are unable to be retrived since the attribute of DSO
is incorrect.

This patch fixes __kmod_path__parse, make it regard names like
'[test_module]' as kernel module.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
---
 tools/perf/util/dso.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index fc0ddd5..4afeeaf 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -220,6 +220,8 @@ int __kmod_path__parse(struct kmod_path *m, const char *path,
 
 	/* No extension, just return name. */
 	if (ext == NULL) {
+		if ((name[0] == '[') &&	(strncmp(name, "[vdso]", 6) != 0))
+			m->kmod = true;
 		if (alloc_name) {
 			m->name = strdup(name);
 			return m->name ? 0 : -ENOMEM;
-- 
1.8.3.4

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