samples: bpf: Refactor test_overhead program with libbpf

This commit refactors the existing program with libbpf bpf loader.
Since the kprobe, tracepoint and raw_tracepoint bpf program can be
attached with single bpf_program__attach() interface, so the
corresponding function of libbpf is used here.

Rather than specifying the number of cpus inside the code, this commit
uses the number of available cpus with _SC_NPROCESSORS_ONLN.
Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201124090310.24374-6-danieltimlee@gmail.com

samples/bpf/Makefile

@@ -78,7 +78,7 @@ lathist-objs := lathist_user.o
 offwaketime-objs := offwaketime_user.o $(TRACE_HELPERS)
 spintest-objs := spintest_user.o $(TRACE_HELPERS)
 map_perf_test-objs := map_perf_test_user.o
-test_overhead-objs := bpf_load.o test_overhead_user.o
+test_overhead-objs := test_overhead_user.o
 test_cgrp2_array_pin-objs := test_cgrp2_array_pin.o
 test_cgrp2_attach-objs := test_cgrp2_attach.o
 test_cgrp2_sock-objs := test_cgrp2_sock.o

samples/bpf/test_overhead_user.c

@@ -18,10 +18,14 @@
 #include <time.h>
 #include <sys/resource.h>
 #include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
 
 #define MAX_CNT 1000000
 
+static struct bpf_link *links[2];
+static struct bpf_object *obj;
+static int cnt;
+
 static __u64 time_get_ns(void)
 {
 	struct timespec ts;
@@ -115,20 +119,54 @@ static void run_perf_test(int tasks, int flags)
 	}
 }
 
+static int load_progs(char *filename)
+{
+	struct bpf_program *prog;
+	int err = 0;
+
+	obj = bpf_object__open_file(filename, NULL);
+	err = libbpf_get_error(obj);
+	if (err < 0) {
+		fprintf(stderr, "ERROR: opening BPF object file failed\n");
+		return err;
+	}
+
+	/* load BPF program */
+	err = bpf_object__load(obj);
+	if (err < 0) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		return err;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		links[cnt] = bpf_program__attach(prog);
+		err = libbpf_get_error(links[cnt]);
+		if (err < 0) {
+			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+			links[cnt] = NULL;
+			return err;
+		}
+		cnt++;
+	}
+
+	return err;
+}
+
 static void unload_progs(void)
 {
-	close(prog_fd[0]);
-	close(prog_fd[1]);
-	close(event_fd[0]);
-	close(event_fd[1]);
+	while (cnt)
+		bpf_link__destroy(links[--cnt]);
+
+	bpf_object__close(obj);
 }
 
 int main(int argc, char **argv)
 {
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
-	char filename[256];
-	int num_cpu = 8;
+	int num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
 	int test_flags = ~0;
+	char filename[256];
+	int err = 0;
 
 	setrlimit(RLIMIT_MEMLOCK, &r);
 
@@ -145,38 +183,36 @@ int main(int argc, char **argv)
 	if (test_flags & 0xC) {
 		snprintf(filename, sizeof(filename),
 			 "%s_kprobe_kern.o", argv[0]);
-		if (load_bpf_file(filename)) {
-			printf("%s", bpf_log_buf);
-			return 1;
-		}
+
 		printf("w/KPROBE\n");
-		run_perf_test(num_cpu, test_flags >> 2);
+		err = load_progs(filename);
+		if (!err)
+			run_perf_test(num_cpu, test_flags >> 2);
+
 		unload_progs();
 	}
 
 	if (test_flags & 0x30) {
 		snprintf(filename, sizeof(filename),
 			 "%s_tp_kern.o", argv[0]);
-		if (load_bpf_file(filename)) {
-			printf("%s", bpf_log_buf);
-			return 1;
-		}
 		printf("w/TRACEPOINT\n");
-		run_perf_test(num_cpu, test_flags >> 4);
+		err = load_progs(filename);
+		if (!err)
+			run_perf_test(num_cpu, test_flags >> 4);
+
 		unload_progs();
 	}
 
 	if (test_flags & 0xC0) {
 		snprintf(filename, sizeof(filename),
 			 "%s_raw_tp_kern.o", argv[0]);
-		if (load_bpf_file(filename)) {
-			printf("%s", bpf_log_buf);
-			return 1;
-		}
 		printf("w/RAW_TRACEPOINT\n");
-		run_perf_test(num_cpu, test_flags >> 6);
+		err = load_progs(filename);
+		if (!err)
+			run_perf_test(num_cpu, test_flags >> 6);
+
 		unload_progs();
 	}
 
-	return 0;
+	return err;
 }