[PATCH v4] perf data convert: Fix segfault when converting to json when cpu_desc isn't set

From: Ilkka Koskinen
Date: Fri Feb 23 2024 - 17:05:45 EST


Arm64 doesn't have Model in /proc/cpuinfo and, thus, cpu_desc doesn't get
assigned.

Running
$ perf data convert --to-json perf.data.json

ends up calling output_json_string() with NULL pointer, which causes a
segmentation fault.

Signed-off-by: Ilkka Koskinen <ilkka@xxxxxxxxxxxxxxxxxxxxxx>
---

v1:
- https://lore.kernel.org/all/20240111232923.8138-1-ilkka@xxxxxxxxxxxxxxxxxxxxxx/
v2:
- Changed the patch based on James's comments.
v3:
- The architecture is checked from the actual data file to allow one to do
conversion on another system. (thanks to James for the feedback)
- https://lore.kernel.org/all/20240117215101.77713-1-ilkka@xxxxxxxxxxxxxxxxxxxxxx/
v4:
- Made the fix more generic in case there are other architectures where cpu_desc
isn't assigned as asked by Namhyung
- Rephrased the subject line
---

tools/perf/util/data-convert-json.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data-convert-json.c
index 5bb3c2ba95ca..09d57efd2d9d 100644
--- a/tools/perf/util/data-convert-json.c
+++ b/tools/perf/util/data-convert-json.c
@@ -284,7 +284,9 @@ static void output_headers(struct perf_session *session, struct convert_json *c)
output_json_key_string(out, true, 2, "os-release", header->env.os_release);
output_json_key_string(out, true, 2, "arch", header->env.arch);

- output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_desc);
+ if (header->env.cpu_desc)
+ output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_desc);
+
output_json_key_string(out, true, 2, "cpuid", header->env.cpuid);
output_json_key_format(out, true, 2, "nrcpus-online", "%u", header->env.nr_cpus_online);
output_json_key_format(out, true, 2, "nrcpus-avail", "%u", header->env.nr_cpus_avail);
--
2.43.0