libbpf: Rename btf__get_from_id() as btf__load_from_kernel_by_id()

Rename function btf__get_from_id() as btf__load_from_kernel_by_id() to
better indicate what the function does. Change the new function so that,
instead of requiring a pointer to the pointer to update and returning
with an error code, it takes a single argument (the id of the BTF
object) and returns the corresponding pointer. This is more in line with
the existing constructors.

The other tools calling the (soon-to-be) deprecated btf__get_from_id()
function will be updated in a future commit.

References:

- https://github.com/libbpf/libbpf/issues/278
- https://github.com/libbpf/libbpf/wiki/Libbpf:-the-road-to-v1.0#btfh-apis

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210729162028.29512-4-quentin@isovalent.com

1 files changed, 17 insertions, 8 deletions

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 7e0de560490e..948c29fee447 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1383,21 +1383,30 @@ exit_free:
 	return btf;
 }
 
-int btf__get_from_id(__u32 id, struct btf **btf)
+struct btf *btf__load_from_kernel_by_id(__u32 id)
 {
-	struct btf *res;
-	int err, btf_fd;
+	struct btf *btf;
+	int btf_fd;
 
-	*btf = NULL;
 	btf_fd = bpf_btf_get_fd_by_id(id);
 	if (btf_fd < 0)
-		return libbpf_err(-errno);
-
-	res = btf_get_from_fd(btf_fd, NULL);
-	err = libbpf_get_error(res);
+		return libbpf_err_ptr(-errno);
 
+	btf = btf_get_from_fd(btf_fd, NULL);
 	close(btf_fd);
 
+	return libbpf_ptr(btf);
+}
+
+int btf__get_from_id(__u32 id, struct btf **btf)
+{
+	struct btf *res;
+	int err;
+
+	*btf = NULL;
+	res = btf__load_from_kernel_by_id(id);
+	err = libbpf_get_error(res);
+
 	if (err)
 		return libbpf_err(err);