Re: [PATCH 02/26] perf: Introduce mmap3 version of mmap event

Namhyung Kim
2020-09-15T02:55:00Z

Hi Jiri,

On Tue, Sep 15, 2020 at 4:38 AM Jiri Olsa <jolsa@redhat.com> wrote:
>
> On Mon, Sep 14, 2020 at 02:38:27PM +0900, Namhyung Kim wrote:
>
> SNIP
>
> > > diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> > > index 077e7ee69e3d..facfc3c673ed 100644
> > > --- a/include/uapi/linux/perf_event.h
> > > +++ b/include/uapi/linux/perf_event.h
> > > @@ -384,7 +384,8 @@ struct perf_event_attr {
> > > aux_output : 1, /* generate AUX records instead of events */
> > > cgroup : 1, /* include cgroup events */
> > > text_poke : 1, /* include text poke events */
> > > - __reserved_1 : 30;
> > > + mmap3 : 1, /* include bpf events */
> >
> > ???
> >
> > > + __reserved_1 : 29;
> > >
> > > union {
> > > __u32 wakeup_events; /* wakeup every n events */
> > > @@ -1060,6 +1061,30 @@ enum perf_event_type {
> > > */
> > > PERF_RECORD_TEXT_POKE = 20,
> > >
> > > + /*
> > > + * The MMAP3 records are an augmented version of MMAP2, they add
> > > + * build id value to identify the exact binary behind map
> > > + *
> > > + * struct {
> > > + * struct perf_event_header header;
> > > + *
> > > + * u32 pid, tid;
> > > + * u64 addr;
> > > + * u64 len;
> > > + * u64 pgoff;
> > > + * u32 maj;
> > > + * u32 min;
> > > + * u64 ino;
> > > + * u64 ino_generation;
> > > + * u32 prot, flags;
> > > + * u32 reserved;
> > > + * u8 buildid[20];
> > > + * char filename[];
> > > + * struct sample_id sample_id;
> > > + * };
> > > + */
> > > + PERF_RECORD_MMAP3 = 21,
> > > +
> > > PERF_RECORD_MAX, /* non-ABI */
> > > };
> > >
> > [SNIP]
> > > @@ -8098,6 +8116,9 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event)
> > > mmap_event->prot = prot;
> > > mmap_event->flags = flags;
> > >
> > > + if (atomic_read(&nr_mmap3_events))
> > > + build_id_parse(vma, mmap_event->buildid);
> >
> > What about if it failed? We should zero out the build-id..
>
> it is initialized to zero in perf_event_mmap
>
> mmap_event = (struct perf_mmap_event){
> .vma = vma,
> ...
>
> I'll double check build_id_parse won't leave anything half
> baked there, but I dont think so

Oh, you're right. I missed that..

Thanks
Namhyung