Re: [PATCH bpf] traceevent: ignore __attribute__ in fields format

[John Koepi <john.koepi@gmail.com>]

I am not sure this is the right mailing list (I was not sure about
@netdev). If it is not - I am sorry, I can resend it. The test for
this change is at https://github.com/sitano/traceevent_attribute.

On Wed, Jan 15, 2020 at 8:06 PM Ivan Prisyazhnyy <john.koepi@gmail.com> wrote:
>
> To support kernel (e.g. Arch linux) tracing that
> have events fields with C attributes (__attribute__((xxx))),
> traceevent must ignore __attribute__ parts when
> parsing fields types.
>
> An example from Arch linux kernel 4.2:
>
>   $ cat /sys/kernel/.../sys_enter_io_submit/format
>   ...
>   field:struct iocb __attribute__((user)) * ...
>                     ^^^
>
> This fix adds support for fields types C attributes
> parsing to event_read_fields function. When it sees
> __attribute__ ((attribute-list)) expression it skips
> it.
>
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=205857
> Base: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/
> Signed-off-by: Ivan Prisyazhnyy <john.koepi@gmail.com>
> ---
>  tools/lib/traceevent/event-parse.c | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index beaa8b8c08ff..fbc1ea536742 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -1486,6 +1486,28 @@ static int event_read_fields(struct tep_event *event, struct tep_format_field **
>                             (event->flags & TEP_EVENT_FL_ISFTRACE &&
>                              type == TEP_EVENT_OP && strcmp(token, ".") == 0)) {
>
> +                               /* ignore C attributes: __attribute__((expr)) */
> +                               if (strcmp(token, "__attribute__") == 0) {
> +                                       free(token);
> +                                       for (int i = 0; i < 2; i++) {
> +                                               if (read_expected_item(TEP_EVENT_DELIM, "(") < 0) {
> +                                                       goto fail_expect;
> +                                               }
> +                                       }
> +                                       for (int brackets = 2; brackets > 0;) {
> +                                               if (read_token(&token) == TEP_EVENT_NONE) {
> +                                                       do_warning_event(event, "%s: __attribute__ not full", __func__);
> +                                                       goto fail_expect;
> +                                               }
> +                                               if (strcmp(token, "(") == 0)
> +                                                       brackets++;
> +                                               else if (strcmp(token, ")") == 0)
> +                                                       brackets--;
> +                                               free(token);
> +                                       }
> +                                       continue;
> +                               }
> +
>                                 if (strcmp(token, "*") == 0)
>                                         field->flags |= TEP_FIELD_IS_POINTER;
>
> --
> 2.24.1
>


-- 
-- Ivan