2024-01-17 07:14:06

by Ilkka Koskinen

Subject: [PATCH v2] perf data convert: Fix segfault when converting to json on arm64

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 <[email protected]>
---
v1:
- https://lore.kernel.org/all/[email protected]/
v2:
- Changed the patch based on James's comments.
---
tools/perf/util/data-convert-json.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data-convert-json.c
index 5bb3c2ba95ca..e8b006c3581f 100644
--- a/tools/perf/util/data-convert-json.c
+++ b/tools/perf/util/data-convert-json.c
@@ -284,7 +284,13 @@ 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);

+#if !defined(__aarch64__)
+ /*
+ * arm64 doesn't have Model section in /proc/cpuinfo and, thus, cpu-desc
+ * is not set.
+ */
output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_desc);
+#endif
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

2024-01-17 15:31:43

by James Clark

Subject: Re: [PATCH v2] perf data convert: Fix segfault when converting to json on arm64

On 17/01/2024 07:13, Ilkka Koskinen wrote:
> 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 <[email protected]>
> ---
> v1:
> - https://lore.kernel.org/all/[email protected]/
> v2:
> - Changed the patch based on James's comments.
> ---
> tools/perf/util/data-convert-json.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data-convert-json.c
> index 5bb3c2ba95ca..e8b006c3581f 100644
> --- a/tools/perf/util/data-convert-json.c
> +++ b/tools/perf/util/data-convert-json.c
> @@ -284,7 +284,13 @@ 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);
>
> +#if !defined(__aarch64__)

I think this needs to read from header->env.arch, otherwise it won't
work if you run data convert on another machine.

I'm assuming that perf data convert is one of the commands that runs on
a pre-recorded file, rather than a command that creates the perf.data
file to begin with?

> + /*
> + * arm64 doesn't have Model section in /proc/cpuinfo and, thus, cpu-desc
> + * is not set.
> + */
> output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_desc);
> +#endif
> 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);

2024-01-17 21:39:13

by Ilkka Koskinen

Subject: Re: [PATCH v2] perf data convert: Fix segfault when converting to json on arm64

On Wed, 17 Jan 2024, James Clark wrote:

>
>
> On 17/01/2024 07:13, Ilkka Koskinen wrote:
>> 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 <[email protected]>
>> ---
>> v1:
>> - https://lore.kernel.org/all/[email protected]/
>> v2:
>> - Changed the patch based on James's comments.
>> ---
>> tools/perf/util/data-convert-json.c | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>> diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data-convert-json.c
>> index 5bb3c2ba95ca..e8b006c3581f 100644
>> --- a/tools/perf/util/data-convert-json.c
>> +++ b/tools/perf/util/data-convert-json.c
>> @@ -284,7 +284,13 @@ 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);
>>
>> +#if !defined(__aarch64__)
>
> I think this needs to read from header->env.arch, otherwise it won't
> work if you run data convert on another machine.
>
> I'm assuming that perf data convert is one of the commands that runs on
> a pre-recorded file, rather than a command that creates the perf.data
> file to begin with?

Oh, right. I'll fix it right away.

Cheers, Ilkka

>
>> + /*
>> + * arm64 doesn't have Model section in /proc/cpuinfo and, thus, cpu-desc
>> + * is not set.
>> + */
>> output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_desc);
>> +#endif
>> 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);
>