linux-kernel - [PATCH PATCH v2 v2 2/6] bpf: Add bpf_perf_event_aux

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Message-Id: <20250718-perf_aux_pause_resume_bpf_rebase-v2-2-992557b8fb16@arm.com>
Date: Fri, 18 Jul 2025 16:25:36 +0100
From: Leo Yan <leo.yan@....com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
 Arnaldo Carvalho de Melo <acme@...nel.org>, 
 Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
 KP Singh <kpsingh@...nel.org>, Matt Bobrowski <mattbobrowski@...gle.com>, 
 Song Liu <song@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Steven Rostedt <rostedt@...dmis.org>, 
 Masami Hiramatsu <mhiramat@...nel.org>, 
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
 James Clark <james.clark@...aro.org>, 
 Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
 bpf@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
 Leo Yan <leo.yan@....com>
Subject: [PATCH PATCH v2 v2 2/6] bpf: Add bpf_perf_event_aux_pause kfunc

The bpf_perf_event_aux_pause kfunc is introduced for pause and resume
the Perf AUX trace used by eBPF programs.

An attached tracepoint (e.g., ftrace tracepoint or a dynamic tracepoint
using uprobe or kprobe) can invoke bpf_perf_event_aux_pause() to pause
or resume AUX trace. This is useful for fine-grained tracing.

Signed-off-by: Leo Yan <leo.yan@....com>
---
 kernel/trace/bpf_trace.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3ae52978cae61a5d60b43c764d3e267bd32e1085..d024e0d0de4a9496e10e2b1a1fbe44434a824a0f 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -704,6 +704,66 @@ static const struct bpf_func_proto bpf_perf_event_output_proto = {
 	.arg5_type	= ARG_CONST_SIZE_OR_ZERO,
 };
 
+__bpf_kfunc_start_defs();
+
+__bpf_kfunc int bpf_perf_event_aux_pause(void *p__map, u64 flags, u32 pause)
+{
+	struct bpf_map *map = p__map;
+	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	unsigned int cpu = smp_processor_id();
+	u64 index = flags & BPF_F_INDEX_MASK;
+	struct bpf_event_entry *ee;
+	int ret = 0;
+
+	/* Disabling IRQ avoids race condition with perf event flows. */
+	guard(irqsave)();
+
+	if (unlikely(flags & ~(BPF_F_INDEX_MASK))) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (index == BPF_F_CURRENT_CPU)
+		index = cpu;
+
+	if (unlikely(index >= array->map.max_entries)) {
+		ret = -E2BIG;
+		goto out;
+	}
+
+	ee = READ_ONCE(array->ptrs[index]);
+	if (!ee) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	if (!has_aux(ee->event))
+		ret = -EINVAL;
+
+	perf_event_aux_pause(ee->event, pause);
+out:
+	return ret;
+}
+
+__bpf_kfunc_end_defs();
+
+BTF_KFUNCS_START(perf_event_kfunc_set_ids)
+BTF_ID_FLAGS(func, bpf_perf_event_aux_pause, KF_TRUSTED_ARGS)
+BTF_KFUNCS_END(perf_event_kfunc_set_ids)
+
+static const struct btf_kfunc_id_set bpf_perf_event_kfunc_set = {
+	.owner = THIS_MODULE,
+	.set = &perf_event_kfunc_set_ids,
+};
+
+static int __init bpf_perf_event_kfuncs_init(void)
+{
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_UNSPEC,
+					 &bpf_perf_event_kfunc_set);
+}
+
+late_initcall(bpf_perf_event_kfuncs_init);
+
 static DEFINE_PER_CPU(int, bpf_event_output_nest_level);
 struct bpf_nested_pt_regs {
 	struct pt_regs regs[3];

-- 
2.34.1