How to attach a perf_event_programm, when cpu-profiling?

[Robin3Chan]

I'm trying to do "continuous on-cpu profile". With libbpf, I can attach the programm like below, using "bpf_program__attach_perf_event". How can I achieve this with cilium?

static int open_and_attach_perf_event(struct bpf_program *prog,
				      struct bpf_link *links[])
{
	struct perf_event_attr attr = {
		.type = PERF_TYPE_SOFTWARE,
		.freq = env.freq,
		.sample_freq = env.sample_freq,
		.config = PERF_COUNT_SW_CPU_CLOCK,
	};
	int i, fd;

	for (i = 0; i < nr_cpus; i++) {
		if (env.cpu != -1 && env.cpu != i)
			continue;

		fd = syscall(__NR_perf_event_open, &attr, -1, i, -1, 0);
		if (fd < 0) {
			/* Ignore CPU that is offline */
			if (errno == ENODEV)
				continue;

			fprintf(stderr, "failed to init perf sampling: %s\n",
				strerror(errno));
			return -1;
		}

		links[i] = bpf_program__attach_perf_event(prog, fd);
		if (!links[i]) {
			fprintf(stderr, "failed to attach perf event on cpu: "
				"%d\n", i);
			links[i] = NULL;
			close(fd);
			return -1;
		}
	}

	return 0;
}

[florianl]

cilium/ebpf focuses on the eBPF subsystem of the Linux kernel. libbpf on the other hand is less strict and also implements some parts of the perf subsystem of the Linux kernel.

With https://github.com/florianl/perf-ebpf there are showcases on various Go packages, that implement parts of the perf subsystem and can be used in combination with cilium/ebpf to attach eBPF programs to perf events. But similar to libbpf, attaching to all kinds of perf events is still not possible.

If you are looking for a widely used approach, feel free to checkout this OTel project that attaches eBPF programs to the perf subsystem for sampling based CPU profiling:
https://github.com/open-telemetry/opentelemetry-ebpf-profiler/blob/20c5f9888928328242be774afe7b430d4b9de8ea/tracer/tracer.go#L965-L1013