libbpf: Add error returns to two API functions

This adds an error return to the following API functions:

- bpf_program__set_expected_attach_type()
- bpf_program__set_type()

In both cases, the error occurs when the BPF object has
already been loaded when the function is called. In this
case -EBUSY is returned.

Signed-off-by: Grant Seltzer <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

2 files changed, 13 insertions, 5 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8375021800f3..342340aee948 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8562,9 +8562,13 @@ enum bpf_prog_type bpf_program__type(const struct bpf_program *prog)
 	return prog->type;
 }
 
-void bpf_program__set_type(struct bpf_program *prog, enum bpf_prog_type type)
+int bpf_program__set_type(struct bpf_program *prog, enum bpf_prog_type type)
 {
+	if (prog->obj->loaded)
+		return libbpf_err(-EBUSY);
+
 	prog->type = type;
+	return 0;
 }
 
 static bool bpf_program__is_type(const struct bpf_program *prog,
@@ -8609,10 +8613,14 @@ enum bpf_attach_type bpf_program__expected_attach_type(const struct bpf_program
 	return prog->expected_attach_type;
 }
 
-void bpf_program__set_expected_attach_type(struct bpf_program *prog,
+int bpf_program__set_expected_attach_type(struct bpf_program *prog,
 					   enum bpf_attach_type type)
 {
+	if (prog->obj->loaded)
+		return libbpf_err(-EBUSY);
+
 	prog->expected_attach_type = type;
+	return 0;
 }
 
 __u32 bpf_program__flags(const struct bpf_program *prog)
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 63d66f1adf1a..66735623ca63 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -686,12 +686,12 @@ LIBBPF_DEPRECATED_SINCE(0, 8, "use bpf_program__set_type() instead")
 LIBBPF_API int bpf_program__set_sk_lookup(struct bpf_program *prog);
 
 LIBBPF_API enum bpf_prog_type bpf_program__type(const struct bpf_program *prog);
-LIBBPF_API void bpf_program__set_type(struct bpf_program *prog,
-				      enum bpf_prog_type type);
+LIBBPF_API int bpf_program__set_type(struct bpf_program *prog,
+				     enum bpf_prog_type type);
 
 LIBBPF_API enum bpf_attach_type
 bpf_program__expected_attach_type(const struct bpf_program *prog);
-LIBBPF_API void
+LIBBPF_API int
 bpf_program__set_expected_attach_type(struct bpf_program *prog,
 				      enum bpf_attach_type type);