Setup development environment with libbpf

external/libbpf-bootstrap/examples/c/fentry.c

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+/* Copyright (c) 2021 Sartura
+ * Based on minimal.c by Facebook */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <signal.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/resource.h>
+#include <bpf/libbpf.h>
+#include "fentry.skel.h"
+
+static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
+{
+	return vfprintf(stderr, format, args);
+}
+
+static void bump_memlock_rlimit(void)
+{
+	struct rlimit rlim_new = {
+		.rlim_cur	= RLIM_INFINITY,
+		.rlim_max	= RLIM_INFINITY,
+	};
+
+	if (setrlimit(RLIMIT_MEMLOCK, &rlim_new)) {
+		fprintf(stderr, "Failed to increase RLIMIT_MEMLOCK limit!\n");
+		exit(1);
+	}
+}
+
+static volatile sig_atomic_t stop;
+
+void sig_int(int signo)
+{
+	stop = 1;
+}
+
+int main(int argc, char **argv)
+{
+	struct fentry_bpf *skel;
+	int err;
+
+	/* Set up libbpf errors and debug info callback */
+	libbpf_set_print(libbpf_print_fn);
+
+	/* Bump RLIMIT_MEMLOCK to allow BPF sub-system to do anything */
+	bump_memlock_rlimit();
+
+	/* Open load and verify BPF application */
+	skel = fentry_bpf__open_and_load();
+	if (!skel) {
+		fprintf(stderr, "Failed to open BPF skeleton\n");
+		return 1;
+	}
+
+	/* Attach tracepoint handler */
+	err = fentry_bpf__attach(skel);
+	if (err) {
+		fprintf(stderr, "Failed to attach BPF skeleton\n");
+		goto cleanup;
+	}
+
+	if (signal(SIGINT, sig_int) == SIG_ERR) {
+		fprintf(stderr, "can't set signal handler: %s\n", strerror(errno));
+		goto cleanup;
+	}
+
+	printf("Successfully started! Please run `sudo cat /sys/kernel/debug/tracing/trace_pipe` "
+	       "to see output of the BPF programs.\n");
+
+	while (!stop) {
+		fprintf(stderr, ".");
+		sleep(1);
+	}
+
+cleanup:
+	fentry_bpf__destroy(skel);
+	return -err;
+}