From: Namhyung Kim <namhyung@kernel.org>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Song Liu <songliubraving@fb.com>,
Peter Zijlstra <peterz@infradead.org>,
Martin KaFai Lau <kafai@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
Stanislav Fomichev <sdf@google.com>,
LKML <linux-kernel@vger.kernel.org>,
bpf@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH bpf-next 1/3] perf/core: Prepare sample data before calling BPF
Date: Thu, 3 Nov 2022 23:03:01 -0700 [thread overview]
Message-ID: <CAM9d7cheyGK9oK+SdoDxqwLuPLkAO5TrNrwJ4x1F4BrfMVzh+Q@mail.gmail.com> (raw)
In-Reply-To: <Y2Du5/Iolphxcbv2@krava>
Hi Jiri,
On Tue, Nov 1, 2022 at 3:03 AM Jiri Olsa <olsajiri@gmail.com> wrote:
>
> On Mon, Oct 31, 2022 at 10:23:38PM -0700, Namhyung Kim wrote:
> > To allow bpf overflow handler to access the perf sample data, it needs to
> > prepare missing but requested data before calling the handler.
> >
> > I'm taking a conservative approach to allow a list of sample formats only
> > instead of allowing them all. For now, IP and ADDR data are allowed and
> > I think it's good enough to build and verify general BPF-based sample
> > filters for perf events.
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> > kernel/events/core.c | 40 +++++++++++++++++++++++++++++++---------
> > 1 file changed, 31 insertions(+), 9 deletions(-)
> >
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index aefc1e08e015..519f30c33a24 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -7329,8 +7329,10 @@ void perf_prepare_sample(struct perf_event_header *header,
> > filtered_sample_type = sample_type & ~data->sample_flags;
> > __perf_event_header__init_id(header, data, event, filtered_sample_type);
> >
> > - if (sample_type & (PERF_SAMPLE_IP | PERF_SAMPLE_CODE_PAGE_SIZE))
> > - data->ip = perf_instruction_pointer(regs);
> > + if (sample_type & (PERF_SAMPLE_IP | PERF_SAMPLE_CODE_PAGE_SIZE)) {
> > + if (filtered_sample_type & PERF_SAMPLE_IP)
> > + data->ip = perf_instruction_pointer(regs);
> > + }
> >
> > if (sample_type & PERF_SAMPLE_CALLCHAIN) {
> > int size = 1;
> > @@ -10006,6 +10008,32 @@ static void perf_event_free_filter(struct perf_event *event)
> > }
> >
> > #ifdef CONFIG_BPF_SYSCALL
> > +static void bpf_prepare_sample(struct bpf_prog *prog,
> > + struct perf_event *event,
> > + struct perf_sample_data *data,
> > + struct pt_regs *regs)
> > +{
> > + u64 filtered_sample_type;
> > +
> > + filtered_sample_type = event->attr.sample_type & ~data->sample_flags;
>
> could we add the same comment in here as is in perf_prepare_sample
>
> /*
> * Clear the sample flags that have already been done by the
> * PMU driver.
> */
>
> it took me while to recall while we set addr to 0 in here ;-)
Sorry about that! :) I'll add the comment.
Thanks,
Namhyung
>
> > +
> > + if (prog->call_get_stack &&
> > + (filtered_sample_type & PERF_SAMPLE_CALLCHAIN)) {
> > + data->callchain = perf_callchain(event, regs);
> > + data->sample_flags |= PERF_SAMPLE_CALLCHAIN;
> > + }
> > +
> > + if (filtered_sample_type & PERF_SAMPLE_IP) {
> > + data->ip = perf_instruction_pointer(regs);
> > + data->sample_flags |= PERF_SAMPLE_IP;
> > + }
> > +
> > + if (filtered_sample_type & PERF_SAMPLE_ADDR) {
> > + data->addr = 0;
> > + data->sample_flags |= PERF_SAMPLE_ADDR;
> > + }
> > +}
> > +
> > static void bpf_overflow_handler(struct perf_event *event,
> > struct perf_sample_data *data,
> > struct pt_regs *regs)
> > @@ -10023,13 +10051,7 @@ static void bpf_overflow_handler(struct perf_event *event,
> > rcu_read_lock();
> > prog = READ_ONCE(event->prog);
> > if (prog) {
> > - if (prog->call_get_stack &&
> > - (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) &&
> > - !(data->sample_flags & PERF_SAMPLE_CALLCHAIN)) {
> > - data->callchain = perf_callchain(event, regs);
> > - data->sample_flags |= PERF_SAMPLE_CALLCHAIN;
> > - }
> > -
> > + bpf_prepare_sample(prog, event, data, regs);
> > ret = bpf_prog_run(prog, &ctx);
> > }
> > rcu_read_unlock();
> > --
> > 2.38.1.273.g43a17bfeac-goog
> >
next prev parent reply other threads:[~2022-11-04 6:03 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-01 5:23 [PATCH bpf-next 0/3] bpf: Add bpf_perf_event_read_sample() helper (v1) Namhyung Kim
2022-11-01 5:23 ` [PATCH bpf-next 1/3] perf/core: Prepare sample data before calling BPF Namhyung Kim
2022-11-01 10:03 ` Jiri Olsa
2022-11-04 6:03 ` Namhyung Kim [this message]
2022-11-01 5:23 ` [PATCH bpf-next 2/3] bpf: Add bpf_perf_event_read_sample() helper Namhyung Kim
2022-11-01 10:02 ` Jiri Olsa
2022-11-01 18:26 ` Alexei Starovoitov
2022-11-01 18:46 ` Song Liu
2022-11-01 18:52 ` Alexei Starovoitov
2022-11-01 20:04 ` Song Liu
2022-11-01 22:16 ` Namhyung Kim
2022-11-02 0:13 ` Song Liu
2022-11-02 22:18 ` Namhyung Kim
2022-11-03 18:41 ` Song Liu
2022-11-03 19:45 ` Yonghong Song
2022-11-03 20:55 ` Song Liu
2022-11-03 21:21 ` Yonghong Song
2022-11-04 6:18 ` Namhyung Kim
2022-11-01 5:23 ` [PATCH bpf-next 3/3] bpf: Add perf_event_read_sample test cases Namhyung Kim
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