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SubjectRe: [PATCH] perf record: Fix perf_can_aux_sample_size()
Em Fri, Nov 22, 2019 at 11:48:56AM +0200, Adrian Hunter escreveu:
> perf_can_aux_sample_size() always returned true because it did not pass
> the attribute size to sys_perf_event_open, nor correctly check the
> return value and errno.
>
> Before:
>
> # perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
> Error:
> The sys_perf_event_open() syscall returned with 7 (Argument list too long) for event (branch-misses:u).
> /bin/dmesg | grep -i perf may provide additional information.
>
> After:
>
> # perf record --aux-sample -e '{intel_pt//u,branch-misses:u}'
> AUX area sampling is not supported by kernel

Since this hasn't been sent to Ingo, I combined it with the patch that
introduced the problem, this one:

c31d79e7a052 perf record: Add a function to test for kernel support for AUX area sampling

Thanks for the quick fix,

- Arnaldo


> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> tools/perf/util/record.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
> index e2321edcdd8f..7def66168503 100644
> --- a/tools/perf/util/record.c
> +++ b/tools/perf/util/record.c
> @@ -143,6 +143,7 @@ bool perf_can_record_cpu_wide(void)
> bool perf_can_aux_sample(void)
> {
> struct perf_event_attr attr = {
> + .size = sizeof(struct perf_event_attr),
> .exclude_kernel = 1,
> /*
> * Non-zero value causes the kernel to calculate the effective
> @@ -158,7 +159,7 @@ bool perf_can_aux_sample(void)
> * then we assume that it is supported. We are relying on the kernel to
> * validate the attribute size before anything else that could be wrong.
> */
> - if (fd == -E2BIG)
> + if (fd < 0 && errno == E2BIG)
> return false;
> if (fd >= 0)
> close(fd);
> --
> 2.17.1

--

- Arnaldo

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