libbpf: Fix BTF handling in bpf_program__clone()

Align bpf_program__clone() with bpf_object_load_prog() by gating
BTF func/line info on FEAT_BTF_FUNC kernel support, and resolve
caller-provided prog_btf_fd before checking obj->btf so that callers
with their own BTF can use clone() even when the object has no BTF
loaded.

While at it, treat func_info and line_info fields as atomic groups
to prevent mismatches between pointer and count from different sources.

Move bpf_program__clone() to libbpf 1.8.

Fixes: 970bd2dced35 ("libbpf: Introduce bpf_program__clone()")
Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260401151640.356419-1-mykyta.yatsenko5@gmail.com

src/libbpf.c

@@ -9852,7 +9852,9 @@ int bpf_program__clone(struct bpf_program *prog, const struct bpf_prog_load_opts
 {
 	LIBBPF_OPTS(bpf_prog_load_opts, attr);
 	struct bpf_object *obj;
-	int err, fd;
+	const void *info;
+	__u32 info_cnt, info_rec_size;
+	int err, fd, prog_btf_fd;
 
 	if (!prog)
 		return libbpf_err(-EINVAL);
@@ -9878,19 +9880,41 @@ int bpf_program__clone(struct bpf_program *prog, const struct bpf_prog_load_opts
 	if (attr.token_fd)
 		attr.prog_flags |= BPF_F_TOKEN_FD;
 
-	/* BTF func/line info */
-	if (obj->btf && btf__fd(obj->btf) >= 0) {
-		attr.prog_btf_fd = OPTS_GET(opts, prog_btf_fd, 0) ?: btf__fd(obj->btf);
-		attr.func_info = OPTS_GET(opts, func_info, NULL) ?: prog->func_info;
-		attr.func_info_cnt = OPTS_GET(opts, func_info_cnt, 0) ?: prog->func_info_cnt;
-		attr.func_info_rec_size =
-			OPTS_GET(opts, func_info_rec_size, 0) ?: prog->func_info_rec_size;
-		attr.line_info = OPTS_GET(opts, line_info, NULL) ?: prog->line_info;
-		attr.line_info_cnt = OPTS_GET(opts, line_info_cnt, 0) ?: prog->line_info_cnt;
-		attr.line_info_rec_size =
-			OPTS_GET(opts, line_info_rec_size, 0) ?: prog->line_info_rec_size;
+	prog_btf_fd = OPTS_GET(opts, prog_btf_fd, 0);
+	if (!prog_btf_fd && obj->btf)
+		prog_btf_fd = btf__fd(obj->btf);
+
+	/* BTF func/line info: only pass if kernel supports it */
+	if (kernel_supports(obj, FEAT_BTF_FUNC) && prog_btf_fd > 0) {
+		attr.prog_btf_fd = prog_btf_fd;
+
+		/* func_info/line_info triples: all-or-nothing from caller */
+		info = OPTS_GET(opts, func_info, NULL);
+		info_cnt = OPTS_GET(opts, func_info_cnt, 0);
+		info_rec_size = OPTS_GET(opts, func_info_rec_size, 0);
+		if (!!info != !!info_cnt || !!info != !!info_rec_size) {
+			pr_warn("prog '%s': func_info, func_info_cnt, and func_info_rec_size must all be specified or all omitted\n",
+				prog->name);
+			return libbpf_err(-EINVAL);
+		}
+		attr.func_info = info ?: prog->func_info;
+		attr.func_info_cnt = info ? info_cnt : prog->func_info_cnt;
+		attr.func_info_rec_size = info ? info_rec_size : prog->func_info_rec_size;
+
+		info = OPTS_GET(opts, line_info, NULL);
+		info_cnt = OPTS_GET(opts, line_info_cnt, 0);
+		info_rec_size = OPTS_GET(opts, line_info_rec_size, 0);
+		if (!!info != !!info_cnt || !!info != !!info_rec_size) {
+			pr_warn("prog '%s': line_info, line_info_cnt, and line_info_rec_size must all be specified or all omitted\n",
+				prog->name);
+			return libbpf_err(-EINVAL);
+		}
+		attr.line_info = info ?: prog->line_info;
+		attr.line_info_cnt = info ? info_cnt : prog->line_info_cnt;
+		attr.line_info_rec_size = info ? info_rec_size : prog->line_info_rec_size;
 	}
 
+	/* Logging is caller-controlled; no fallback to prog/obj log settings */
 	attr.log_buf = OPTS_GET(opts, log_buf, NULL);
 	attr.log_size = OPTS_GET(opts, log_size, 0);
 	attr.log_level = OPTS_GET(opts, log_level, 0);
@@ -9912,14 +9936,17 @@ int bpf_program__clone(struct bpf_program *prog, const struct bpf_prog_load_opts
 
 	/* Re-apply caller overrides for output fields */
 	if (OPTS_GET(opts, expected_attach_type, 0))
-		attr.expected_attach_type =
-			OPTS_GET(opts, expected_attach_type, 0);
+		attr.expected_attach_type = OPTS_GET(opts, expected_attach_type, 0);
 	if (OPTS_GET(opts, attach_btf_id, 0))
 		attr.attach_btf_id = OPTS_GET(opts, attach_btf_id, 0);
 	if (OPTS_GET(opts, attach_btf_obj_fd, 0))
-		attr.attach_btf_obj_fd =
-			OPTS_GET(opts, attach_btf_obj_fd, 0);
+		attr.attach_btf_obj_fd = OPTS_GET(opts, attach_btf_obj_fd, 0);
 
+	/*
+	 * Unlike bpf_object_load_prog(), we intentionally do not call bpf_prog_bind_map()
+	 * for RODATA maps here to avoid mutating the object's state. Callers can bind the
+	 * required maps themselves using bpf_prog_bind_map().
+	 */
 	fd = bpf_prog_load(prog->type, prog->name, obj->license, prog->insns, prog->insns_cnt,
 			   &attr);
 

src/libbpf.map

@@ -452,12 +452,12 @@ LIBBPF_1.7.0 {
 		bpf_map__set_exclusive_program;
 		bpf_map__exclusive_program;
 		bpf_prog_assoc_struct_ops;
-		bpf_program__clone;
 		bpf_program__assoc_struct_ops;
 		btf__permute;
 } LIBBPF_1.6.0;
 
 LIBBPF_1.8.0 {
 	global:
+		bpf_program__clone;
 		btf__new_empty_opts;
 } LIBBPF_1.7.0;