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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id qo14-20020a170907874e00b0078d3f96d293sm4027026ejc.30.2022.11.01.03.03.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Nov 2022 03:03:22 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 1 Nov 2022 11:03:19 +0100 To: Namhyung Kim Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Song Liu , Peter Zijlstra , Martin KaFai Lau , Yonghong Song , John Fastabend , KP Singh , Hao Luo , Stanislav Fomichev , LKML , bpf@vger.kernel.org, Steven Rostedt , Ingo Molnar , Arnaldo Carvalho de Melo Subject: Re: [PATCH bpf-next 1/3] perf/core: Prepare sample data before calling BPF Message-ID: References: <20221101052340.1210239-1-namhyung@kernel.org> <20221101052340.1210239-2-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221101052340.1210239-2-namhyung@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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 ;-) thanks, jirka > + > + 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 >