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[76.126.33.191]) by smtp.gmail.com with ESMTPSA id e11-20020a170902b78b00b001d2ffeac9d3sm3300623pls.186.2023.12.10.20.55.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 10 Dec 2023 20:55:53 -0800 (PST) From: Kyle Huey X-Google-Original-From: Kyle Huey To: Kyle Huey , linux-kernel@vger.kernel.org, Andrii Nakryiko , Jiri Olsa , Namhyung Kim , Marco Elver , Yonghong Song Cc: Robert O'Callahan , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Ian Rogers , Adrian Hunter , linux-perf-users@vger.kernel.org, bpf@vger.kernel.org Subject: [PATCH v3 1/4] perf/bpf: Call bpf handler directly, not through overflow machinery Date: Sun, 10 Dec 2023 20:55:40 -0800 Message-Id: <20231211045543.31741-2-khuey@kylehuey.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231211045543.31741-1-khuey@kylehuey.com> References: <20231211045543.31741-1-khuey@kylehuey.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" To ultimately allow bpf programs attached to perf events to completely suppress all of the effects of a perf event overflow (rather than just the sample output, as they do today), call bpf_overflow_handler() from __perf_event_overflow() directly rather than modifying struct perf_event's overflow_handler. Return the bpf program's return value from bpf_overflow_handler() so that __perf_event_overflow() knows how to proceed. Remove the now unnecessary orig_overflow_handler from struct perf_event. This patch is solely a refactoring and results in no behavior change. Signed-off-by: Kyle Huey Suggested-by: Namhyung Kim Acked-by: Song Liu --- include/linux/perf_event.h | 6 +----- kernel/events/core.c | 28 +++++++++++++++------------- 2 files changed, 16 insertions(+), 18 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 5547ba68e6e4..312b9f31442c 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -810,7 +810,6 @@ struct perf_event { perf_overflow_handler_t overflow_handler; void *overflow_handler_context; #ifdef CONFIG_BPF_SYSCALL - perf_overflow_handler_t orig_overflow_handler; struct bpf_prog *prog; u64 bpf_cookie; #endif @@ -1337,10 +1336,7 @@ __is_default_overflow_handler(perf_overflow_handler_= t overflow_handler) #ifdef CONFIG_BPF_SYSCALL static inline bool uses_default_overflow_handler(struct perf_event *event) { - if (likely(is_default_overflow_handler(event))) - return true; - - return __is_default_overflow_handler(event->orig_overflow_handler); + return is_default_overflow_handler(event); } #else #define uses_default_overflow_handler(event) \ diff --git a/kernel/events/core.c b/kernel/events/core.c index b704d83a28b2..54f6372d2634 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9515,6 +9515,12 @@ static inline bool sample_is_allowed(struct perf_eve= nt *event, struct pt_regs *r return true; } =20 +#ifdef CONFIG_BPF_SYSCALL +static int bpf_overflow_handler(struct perf_event *event, + struct perf_sample_data *data, + struct pt_regs *regs); +#endif + /* * Generic event overflow handling, sampling. */ @@ -9584,7 +9590,10 @@ static int __perf_event_overflow(struct perf_event *= event, irq_work_queue(&event->pending_irq); } =20 - READ_ONCE(event->overflow_handler)(event, data, regs); +#ifdef CONFIG_BPF_SYSCALL + if (!(event->prog && !bpf_overflow_handler(event, data, regs))) +#endif + READ_ONCE(event->overflow_handler)(event, data, regs); =20 if (*perf_event_fasync(event) && event->pending_kill) { event->pending_wakeup =3D 1; @@ -10394,9 +10403,9 @@ static void perf_event_free_filter(struct perf_even= t *event) } =20 #ifdef CONFIG_BPF_SYSCALL -static void bpf_overflow_handler(struct perf_event *event, - struct perf_sample_data *data, - struct pt_regs *regs) +static int bpf_overflow_handler(struct perf_event *event, + struct perf_sample_data *data, + struct pt_regs *regs) { struct bpf_perf_event_data_kern ctx =3D { .data =3D data, @@ -10417,10 +10426,8 @@ static void bpf_overflow_handler(struct perf_event= *event, rcu_read_unlock(); out: __this_cpu_dec(bpf_prog_active); - if (!ret) - return; =20 - event->orig_overflow_handler(event, data, regs); + return ret; } =20 static int perf_event_set_bpf_handler(struct perf_event *event, @@ -10456,8 +10463,6 @@ static int perf_event_set_bpf_handler(struct perf_e= vent *event, =20 event->prog =3D prog; event->bpf_cookie =3D bpf_cookie; - event->orig_overflow_handler =3D READ_ONCE(event->overflow_handler); - WRITE_ONCE(event->overflow_handler, bpf_overflow_handler); return 0; } =20 @@ -10468,7 +10473,6 @@ static void perf_event_free_bpf_handler(struct perf= _event *event) if (!prog) return; =20 - WRITE_ONCE(event->overflow_handler, event->orig_overflow_handler); event->prog =3D NULL; bpf_prog_put(prog); } @@ -11928,13 +11932,11 @@ perf_event_alloc(struct perf_event_attr *attr, in= t cpu, overflow_handler =3D parent_event->overflow_handler; context =3D parent_event->overflow_handler_context; #if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_EVENT_TRACING) - if (overflow_handler =3D=3D bpf_overflow_handler) { + if (parent_event->prog) { struct bpf_prog *prog =3D parent_event->prog; =20 bpf_prog_inc(prog); event->prog =3D prog; - event->orig_overflow_handler =3D - parent_event->orig_overflow_handler; } #endif } --=20 2.34.1