samples: bpf: Refactor kprobe 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 kprobe tracing programs with libbbpf
bpf loader.

    - For kprobe events pointing to system calls, the SYSCALL() macro in
    trace_common.h was used.
    - Adding a kprobe 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/20200823085334.9413-3-danieltimlee@gmail.com

1 files changed, 55 insertions, 13 deletions

diff --git a/samples/bpf/spintest_user.c b/samples/bpf/spintest_user.c
index fb430ea2ef51..847da9284fa8 100644
--- a/samples/bpf/spintest_user.c
+++ b/samples/bpf/spintest_user.c
@@ -1,40 +1,77 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <stdio.h>
 #include <unistd.h>
-#include <linux/bpf.h>
 #include <string.h>
 #include <assert.h>
 #include <sys/resource.h>
 #include <bpf/libbpf.h>
-#include "bpf_load.h"
+#include <bpf/bpf.h>
 #include "trace_helpers.h"
 
 int main(int ac, char **argv)
 {
 	struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
+	char filename[256], symbol[256];
+	struct bpf_object *obj = NULL;
+	struct bpf_link *links[20];
 	long key, next_key, value;
-	char filename[256];
+	struct bpf_program *prog;
+	int map_fd, i, j = 0;
+	const char *title;
 	struct ksym *sym;
-	int i;
 
-	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
-	setrlimit(RLIMIT_MEMLOCK, &r);
+	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 = bpf_object__find_map_fd_by_name(obj, "my_map");
+	if (map_fd < 0) {
+		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
+		goto cleanup;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		title = bpf_program__title(prog, false);
+		if (sscanf(title, "kprobe/%s", symbol) != 1)
+			continue;
+
+		/* Attach prog only when symbol exists */
+		if (ksym_get_addr(symbol)) {
+			links[j] = bpf_program__attach(prog);
+			if (libbpf_get_error(links[j])) {
+				fprintf(stderr, "bpf_program__attach failed\n");
+				links[j] = NULL;
+				goto cleanup;
+			}
+			j++;
+		}
 	}
 
 	for (i = 0; i < 5; i++) {
 		key = 0;
 		printf("kprobing funcs:");
-		while (bpf_map_get_next_key(map_fd[0], &key, &next_key) == 0) {
-			bpf_map_lookup_elem(map_fd[0], &next_key, &value);
+		while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0) {
+			bpf_map_lookup_elem(map_fd, &next_key, &value);
 			assert(next_key == value);
 			sym = ksym_search(value);
 			key = next_key;
@@ -48,10 +85,15 @@ int main(int ac, char **argv)
 		if (key)
 			printf("\n");
 		key = 0;
-		while (bpf_map_get_next_key(map_fd[0], &key, &next_key) == 0)
-			bpf_map_delete_elem(map_fd[0], &next_key);
+		while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0)
+			bpf_map_delete_elem(map_fd, &next_key);
 		sleep(1);
 	}
 
+cleanup:
+	for (j--; j >= 0; j--)
+		bpf_link__destroy(links[j]);
+
+	bpf_object__close(obj);
 	return 0;
 }