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From: Kyle Huey <me@kylehuey.com>
To: Kyle Huey <khuey@kylehuey.com>,
	linux-kernel@vger.kernel.org,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
	Marco Elver <elver@google.com>,
	Yonghong Song <yonghong.song@linux.dev>
Cc: Robert O'Callahan <robert@ocallahan.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Ian Rogers <irogers@google.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	linux-perf-users@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH v3 3/4] perf/bpf: Allow a bpf program to suppress all sample side effects
Date: Sun, 10 Dec 2023 20:55:42 -0800	[thread overview]
Message-ID: <20231211045543.31741-4-khuey@kylehuey.com> (raw)
In-Reply-To: <20231211045543.31741-1-khuey@kylehuey.com>

Returning zero from a bpf program attached to a perf event already
suppresses any data output. Return early from __perf_event_overflow() in
this case so it will also suppress event_limit accounting, SIGTRAP
generation, and F_ASYNC signalling.

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
 kernel/events/core.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 54f6372d2634..d6093fe893c8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9541,6 +9541,11 @@ static int __perf_event_overflow(struct perf_event *event,
 
 	ret = __perf_event_account_interrupt(event, throttle);
 
+#ifdef CONFIG_BPF_SYSCALL
+	if (event->prog && !bpf_overflow_handler(event, data, regs))
+		return ret;
+#endif
+
 	/*
 	 * XXX event_limit might not quite work as expected on inherited
 	 * events
@@ -9590,10 +9595,7 @@ static int __perf_event_overflow(struct perf_event *event,
 		irq_work_queue(&event->pending_irq);
 	}
 
-#ifdef CONFIG_BPF_SYSCALL
-	if (!(event->prog && !bpf_overflow_handler(event, data, regs)))
-#endif
-		READ_ONCE(event->overflow_handler)(event, data, regs);
+	READ_ONCE(event->overflow_handler)(event, data, regs);
 
 	if (*perf_event_fasync(event) && event->pending_kill) {
 		event->pending_wakeup = 1;
-- 
2.34.1


  parent reply	other threads:[~2023-12-11  4:56 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-11  4:55 [PATCH v3 0/4] Combine perf and bpf for fast eval of hw breakpoint conditions Kyle Huey
2023-12-11  4:55 ` [PATCH v3 1/4] perf/bpf: Call bpf handler directly, not through overflow machinery Kyle Huey
2023-12-11 14:20   ` Marco Elver
2023-12-11 15:20     ` Kyle Huey
2024-01-02 22:56   ` Song Liu
2024-01-02 23:05   ` Song Liu
2024-01-19  0:07     ` Kyle Huey
2023-12-11  4:55 ` [PATCH v3 2/4] perf/bpf: Remove unneeded uses_default_overflow_handler Kyle Huey
2023-12-11  4:55   ` Kyle Huey
2023-12-12  9:22   ` Will Deacon
2023-12-12  9:22     ` Will Deacon
2024-01-02 22:56     ` Song Liu
2024-01-02 22:56       ` Song Liu
2023-12-11  4:55 ` Kyle Huey [this message]
2024-01-02 23:10   ` [PATCH v3 3/4] perf/bpf: Allow a bpf program to suppress all sample side effects Song Liu
2023-12-11  4:55 ` [PATCH v3 4/4] selftest/bpf: Test a perf bpf program that suppresses " Kyle Huey
2024-01-02 22:49   ` Song Liu
2024-01-19  0:08     ` Kyle Huey
2023-12-13  1:38 ` [PATCH v3 0/4] Combine perf and bpf for fast eval of hw breakpoint conditions Namhyung Kim

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