samples/bpf: Fix sockex3 error: Missing BPF prog type

since commit 450b167fb9be("libbpf: clean up SEC() handling"),
sec_def_matches() does not recognize "socket/xxx" as "socket", therefore,
the BPF program type is not recognized.

Instead of sockex3_user.c parsing section names to get the BPF program fd.
We use the program array map to assign a static index to each BPF program
(get inspired by selftests/bpf progs/test_prog_array_init.c).
Therefore, use SEC("socket") as section name instead of SEC("socket/xxx"),
so that the BPF program is parsed to SOCKET_FILTER type. The "missing BPF
prog type" problem is solved.

How to reproduce this error:
$ cd samples/bpf
$ sudo ./sockex3
libbpf: prog 'bpf_func_PARSE_IP': missing BPF prog type, check ELF section name 'socket/3'
libbpf: prog 'bpf_func_PARSE_IP': failed to load: -22
libbpf: failed to load object './sockex3_kern.o'
ERROR: loading BPF object file failed

Signed-off-by: Rong Tao <rongtao@cestc.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/tencent_EBA3C18864069E42175946973C2ACBAF5408@qq.com

1 files changed, 10 insertions, 13 deletions

diff --git a/samples/bpf/sockex3_user.c b/samples/bpf/sockex3_user.c
index cd6fa79df900..56044acbd25d 100644
--- a/samples/bpf/sockex3_user.c
+++ b/samples/bpf/sockex3_user.c
@@ -24,10 +24,9 @@ struct pair {
 
 int main(int argc, char **argv)
 {
-	int i, sock, key, fd, main_prog_fd, jmp_table_fd, hash_map_fd;
+	int i, sock, fd, main_prog_fd, hash_map_fd;
 	struct bpf_program *prog;
 	struct bpf_object *obj;
-	const char *section;
 	char filename[256];
 	FILE *f;
 
@@ -45,26 +44,24 @@ int main(int argc, char **argv)
 		goto cleanup;
 	}
 
-	jmp_table_fd = bpf_object__find_map_fd_by_name(obj, "jmp_table");
 	hash_map_fd = bpf_object__find_map_fd_by_name(obj, "hash_map");
-	if (jmp_table_fd < 0 || hash_map_fd < 0) {
+	if (hash_map_fd < 0) {
 		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
 		goto cleanup;
 	}
 
+	/* find BPF main program */
+	main_prog_fd = 0;
 	bpf_object__for_each_program(prog, obj) {
 		fd = bpf_program__fd(prog);
 
-		section = bpf_program__section_name(prog);
-		if (sscanf(section, "socket/%d", &key) != 1) {
-			fprintf(stderr, "ERROR: finding prog failed\n");
-			goto cleanup;
-		}
-
-		if (key == 0)
+		if (!strcmp(bpf_program__name(prog), "main_prog"))
 			main_prog_fd = fd;
-		else
-			bpf_map_update_elem(jmp_table_fd, &key, &fd, BPF_ANY);
+	}
+
+	if (main_prog_fd == 0) {
+		fprintf(stderr, "ERROR: can't find main_prog\n");
+		goto cleanup;
 	}
 
 	sock = open_raw_sock("lo");