samples: bpf: Refactor tracepoint tracing programs with libbpf

For the problem of increasing fragmentation of the bpf loader programs,
instead of using bpf_loader.o, which is used in samples/bpf, this
commit refactors the existing tracepoint tracing programs with libbbpf
bpf loader.

    - Adding a tracepoint event and attaching a bpf program to it was done
    through bpf_program_attach().
    - Instead of using the existing BPF MAP definition, MAP definition
    has been refactored with the new BTF-defined MAP format.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200823085334.9413-4-danieltimlee@gmail.com

1 files changed, 51 insertions, 15 deletions

diff --git a/samples/bpf/offwaketime_user.c b/samples/bpf/offwaketime_user.c
index 51c7da5341cc..5734cfdaaacb 100644
--- a/samples/bpf/offwaketime_user.c
+++ b/samples/bpf/offwaketime_user.c
@@ -5,19 +5,19 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <signal.h>
-#include <linux/bpf.h>
-#include <string.h>
 #include <linux/perf_event.h>
 #include <errno.h>
-#include <assert.h>
 #include <stdbool.h>
 #include <sys/resource.h>
 #include <bpf/libbpf.h>
-#include "bpf_load.h"
+#include <bpf/bpf.h>
 #include "trace_helpers.h"
 
 #define PRINT_RAW_ADDR 0
 
+/* counts, stackmap */
+static int map_fd[2];
+
 static void print_ksym(__u64 addr)
 {
 	struct ksym *sym;
@@ -52,14 +52,14 @@ static void print_stack(struct key_t *key, __u64 count)
 	int i;
 
 	printf("%s;", key->target);
-	if (bpf_map_lookup_elem(map_fd[3], &key->tret, ip) != 0) {
+	if (bpf_map_lookup_elem(map_fd[1], &key->tret, ip) != 0) {
 		printf("---;");
 	} else {
 		for (i = PERF_MAX_STACK_DEPTH - 1; i >= 0; i--)
 			print_ksym(ip[i]);
 	}
 	printf("-;");
-	if (bpf_map_lookup_elem(map_fd[3], &key->wret, ip) != 0) {
+	if (bpf_map_lookup_elem(map_fd[1], &key->wret, ip) != 0) {
 		printf("---;");
 	} else {
 		for (i = 0; i < PERF_MAX_STACK_DEPTH; i++)
@@ -96,23 +96,54 @@ static void int_exit(int sig)
 int main(int argc, char **argv)
 {
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+	struct bpf_object *obj = NULL;
+	struct bpf_link *links[2];
+	struct bpf_program *prog;
+	int delay = 1, i = 0;
 	char filename[256];
-	int delay = 1;
-
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
-	setrlimit(RLIMIT_MEMLOCK, &r);
 
-	signal(SIGINT, int_exit);
-	signal(SIGTERM, int_exit);
+	if (setrlimit(RLIMIT_MEMLOCK, &r)) {
+		perror("setrlimit(RLIMIT_MEMLOCK)");
+		return 1;
+	}
 
 	if (load_kallsyms()) {
 		printf("failed to process /proc/kallsyms\n");
 		return 2;
 	}
 
-	if (load_bpf_file(filename)) {
-		printf("%s", bpf_log_buf);
-		return 1;
+	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+	obj = bpf_object__open_file(filename, NULL);
+	if (libbpf_get_error(obj)) {
+		fprintf(stderr, "ERROR: opening BPF object file failed\n");
+		obj = NULL;
+		goto cleanup;
+	}
+
+	/* load BPF program */
+	if (bpf_object__load(obj)) {
+		fprintf(stderr, "ERROR: loading BPF object file failed\n");
+		goto cleanup;
+	}
+
+	map_fd[0] = bpf_object__find_map_fd_by_name(obj, "counts");
+	map_fd[1] = bpf_object__find_map_fd_by_name(obj, "stackmap");
+	if (map_fd[0] < 0 || map_fd[1] < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
+		goto cleanup;
+	}
+
+	signal(SIGINT, int_exit);
+	signal(SIGTERM, int_exit);
+
+	bpf_object__for_each_program(prog, obj) {
+		links[i] = bpf_program__attach(prog);
+		if (libbpf_get_error(links[i])) {
+			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+			links[i] = NULL;
+			goto cleanup;
+		}
+		i++;
 	}
 
 	if (argc > 1)
@@ -120,5 +151,10 @@ int main(int argc, char **argv)
 	sleep(delay);
 	print_stacks(map_fd[0]);
 
+cleanup:
+	for (i--; i >= 0; i--)
+		bpf_link__destroy(links[i]);
+
+	bpf_object__close(obj);
 	return 0;
 }