libbpf: Use func name when pinning programs with LIBBPF_STRICT_SEC_NAME

We can't use section name anymore because they are not unique
and pinning objects with multiple programs with the same
progtype/secname will fail.

  [0] Closes: https://github.com/libbpf/libbpf/issues/273

Fixes: 33a2c75c55e2 ("libbpf: add internal pin_name")
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20211021214814.1236114-2-sdf@google.com
diff --git a/src/libbpf.c b/src/libbpf.c
index 19c133d..49a52b0 100644
--- a/src/libbpf.c
+++ b/src/libbpf.c
@@ -285,7 +285,7 @@
 	size_t sub_insn_off;
 
 	char *name;
-	/* sec_name with / replaced by _; makes recursive pinning
+	/* name with / replaced by _; makes recursive pinning
 	 * in bpf_object__pin_programs easier
 	 */
 	char *pin_name;
@@ -618,7 +618,16 @@
 {
 	char *name, *p;
 
-	name = p = strdup(prog->sec_name);
+	if (libbpf_mode & LIBBPF_STRICT_SEC_NAME)
+		name = strdup(prog->name);
+	else
+		name = strdup(prog->sec_name);
+
+	if (!name)
+		return NULL;
+
+	p = name;
+
 	while ((p = strchr(p, '/')))
 		*p = '_';
 
diff --git a/src/libbpf_legacy.h b/src/libbpf_legacy.h
index 74e6f86..29ccafa 100644
--- a/src/libbpf_legacy.h
+++ b/src/libbpf_legacy.h
@@ -52,6 +52,9 @@
 	 * allowed, with LIBBPF_STRICT_SEC_PREFIX this will become
 	 * unrecognized by libbpf and would have to be just SEC("xdp") and
 	 * SEC("xdp") and SEC("perf_event").
+	 *
+	 * Note, in this mode the program pin path will be based on the
+	 * function name instead of section name.
 	 */
 	LIBBPF_STRICT_SEC_NAME = 0x04,