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Message-Id: <20231211045543.31741-4-khuey@kylehuey.com>
Date: Sun, 10 Dec 2023 20:55:42 -0800
From: Kyle Huey <me@...ehuey.com>
To: Kyle Huey <khuey@...ehuey.com>, linux-kernel@...r.kernel.org,
Andrii Nakryiko <andrii.nakryiko@...il.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Marco Elver <elver@...gle.com>,
Yonghong Song <yonghong.song@...ux.dev>
Cc: Robert O'Callahan <robert@...llahan.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
linux-perf-users@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH v3 3/4] perf/bpf: Allow a bpf program to suppress all sample side effects
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@...ehuey.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
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