selftests/bpf: Switch perf_buffer test to tracepoint and skeleton

Switch perf_buffer test to use skeleton to avoid use of bpf_prog_load() and
make test a bit more succinct. Also switch BPF program to use tracepoint
instead of kprobe, as that allows to support older kernels, which had
tracepoint support before kprobe support in the form that libbpf expects
(i.e., libbpf expects /sys/bus/event_source/devices/kprobe/type, which doesn't
always exist on old kernels).

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200708015318.3827358-7-andriin@fb.com

tools/testing/selftests/bpf/prog_tests/perf_buffer.c

@@ -4,6 +4,7 @@
 #include <sched.h>
 #include <sys/socket.h>
 #include <test_progs.h>
+#include "test_perf_buffer.skel.h"
 #include "bpf/libbpf_internal.h"
 
 /* AddressSanitizer sometimes crashes due to data dereference below, due to
@@ -25,16 +26,11 @@ static void on_sample(void *ctx, int cpu, void *data, __u32 size)
 
 void test_perf_buffer(void)
 {
-	int err, prog_fd, on_len, nr_on_cpus = 0,  nr_cpus, i, duration = 0;
-	const char *prog_name = "kprobe/sys_nanosleep";
-	const char *file = "./test_perf_buffer.o";
+	int err, on_len, nr_on_cpus = 0,  nr_cpus, i, duration = 0;
 	struct perf_buffer_opts pb_opts = {};
-	struct bpf_map *perf_buf_map;
+	struct test_perf_buffer *skel;
 	cpu_set_t cpu_set, cpu_seen;
-	struct bpf_program *prog;
-	struct bpf_object *obj;
 	struct perf_buffer *pb;
-	struct bpf_link *link;
 	bool *online;
 
 	nr_cpus = libbpf_num_possible_cpus();
@@ -51,33 +47,21 @@ void test_perf_buffer(void)
 			nr_on_cpus++;
 
 	/* load program */
-	err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
-	if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno)) {
-		obj = NULL;
-		goto out_close;
-	}
-
-	prog = bpf_object__find_program_by_title(obj, prog_name);
-	if (CHECK(!prog, "find_probe", "prog '%s' not found\n", prog_name))
+	skel = test_perf_buffer__open_and_load();
+	if (CHECK(!skel, "skel_load", "skeleton open/load failed\n"))
 		goto out_close;
 
-	/* load map */
-	perf_buf_map = bpf_object__find_map_by_name(obj, "perf_buf_map");
-	if (CHECK(!perf_buf_map, "find_perf_buf_map", "not found\n"))
-		goto out_close;
-
-	/* attach kprobe */
-	link = bpf_program__attach_kprobe(prog, false /* retprobe */,
-					  SYS_NANOSLEEP_KPROBE_NAME);
-	if (CHECK(IS_ERR(link), "attach_kprobe", "err %ld\n", PTR_ERR(link)))
+	/* attach probe */
+	err = test_perf_buffer__attach(skel);
+	if (CHECK(err, "attach_kprobe", "err %d\n", err))
 		goto out_close;
 
 	/* set up perf buffer */
 	pb_opts.sample_cb = on_sample;
 	pb_opts.ctx = &cpu_seen;
-	pb = perf_buffer__new(bpf_map__fd(perf_buf_map), 1, &pb_opts);
+	pb = perf_buffer__new(bpf_map__fd(skel->maps.perf_buf_map), 1, &pb_opts);
 	if (CHECK(IS_ERR(pb), "perf_buf__new", "err %ld\n", PTR_ERR(pb)))
-		goto out_detach;
+		goto out_close;
 
 	/* trigger kprobe on every CPU */
 	CPU_ZERO(&cpu_seen);
@@ -94,7 +78,7 @@ void test_perf_buffer(void)
 					     &cpu_set);
 		if (err && CHECK(err, "set_affinity", "cpu #%d, err %d\n",
 				 i, err))
-			goto out_detach;
+			goto out_close;
 
 		usleep(1);
 	}
@@ -110,9 +94,7 @@ void test_perf_buffer(void)
 
 out_free_pb:
 	perf_buffer__free(pb);
-out_detach:
-	bpf_link__destroy(link);
 out_close:
-	bpf_object__close(obj);
+	test_perf_buffer__destroy(skel);
 	free(online);
 }

tools/testing/selftests/bpf/progs/test_perf_buffer.c

@@ -12,8 +12,8 @@ struct {
 	__uint(value_size, sizeof(int));
 } perf_buf_map SEC(".maps");
 
-SEC("kprobe/sys_nanosleep")
-int BPF_KPROBE(handle_sys_nanosleep_entry)
+SEC("tp/raw_syscalls/sys_enter")
+int handle_sys_enter(void *ctx)
 {
 	int cpu = bpf_get_smp_processor_id();