bpf: avoid excessive stack usage for perf_sample_data (20b9d7ac) · Commits · 戴 / test

perf_sample_data consumes 386 bytes on stack, reduce excessive stack usage and move it to per cpu buffer. It's allowed due to preemption being disabled for tracing, xdp and tc programs, thus at all times only one program can run on a specific CPU and programs cannot run from interrupt. We similarly also handle bpf_pt_regs. Signed-off-by:

Daniel Borkmann <daniel@iogearbox.net> Acked-by:

Alexei Starovoitov <ast@kernel.org> Signed-off-by:

David S. Miller <davem@davemloft.net>

kernel/trace/bpf_trace.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -266,14 +266,16 @@ static const struct bpf_func_proto bpf_perf_event_read_proto = {
		.arg2_type = ARG_ANYTHING,
		};

		static DEFINE_PER_CPU(struct perf_sample_data, bpf_sd);

		static __always_inline u64
		__bpf_perf_event_output(struct pt_regs regs, struct bpf_map map,
		u64 flags, struct perf_raw_record *raw)
		{
		struct bpf_array *array = container_of(map, struct bpf_array, map);
		struct perf_sample_data *sd = this_cpu_ptr(&bpf_sd);
		unsigned int cpu = smp_processor_id();
		u64 index = flags & BPF_F_INDEX_MASK;
		struct perf_sample_data sample_data;
		struct bpf_event_entry *ee;
		struct perf_event *event;

		@@ -294,9 +296,9 @@ __bpf_perf_event_output(struct pt_regs regs, struct bpf_map map,
		if (unlikely(event->oncpu != cpu))
		return -EOPNOTSUPP;

		perf_sample_data_init(&sample_data, 0, 0);
		sample_data.raw = raw;
		perf_event_output(event, &sample_data, regs);
		perf_sample_data_init(sd, 0, 0);
		sd->raw = raw;
		perf_event_output(event, sd, regs);
		return 0;
		}

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