Merge branch 'libbpf: rename btf__get_from_id() and btf__load() APIs, support split BTF'

Quentin Monnet says:

====================

As part of the effort to move towards a v1.0 for libbpf [0], this set
improves some confusing function names related to BTF loading from and to
the kernel:

- btf__load() becomes btf__load_into_kernel().
- btf__get_from_id becomes btf__load_from_kernel_by_id().
- A new version btf__load_from_kernel_by_id_split() extends the former to
  add support for split BTF.

The last patch is a trivial change to bpftool to add support for dumping
split BTF objects by referencing them by their id (and not only by their
BTF path).

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

v3:
- Use libbpf_err_ptr() in btf__load_from_kernel_by_id(), ERR_PTR() in
  bpftool's get_map_kv_btf().
- Move the definition of btf__load_from_kernel_by_id() closer to the
  btf__parse() group in btf.h (move the legacy function with it).
- Fix a bug on the return value in libbpf_find_prog_btf_id(), as a new
  patch.
- Move the btf__free() fixes to their own patch.
- Add "Fixes:" tags to relevant patches.

v2:
- Remove deprecation marking of legacy functions (patch 4/6 from v1).
- Make btf__load_from_kernel_by_id{,_split}() return the btf struct, adjust
  surrounding code and call btf__free() when missing.
- Add new functions to v0.5.0 API (and not v0.6.0).
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 24 insertions, 9 deletions

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index b46760b93bb4..cafa4f6bd9b1 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1180,7 +1180,7 @@ int btf__finalize_data(struct bpf_object *obj, struct btf *btf)
 
 static void *btf_get_raw_data(const struct btf *btf, __u32 *size, bool swap_endian);
 
-int btf__load(struct btf *btf)
+int btf__load_into_kernel(struct btf *btf)
 {
 	__u32 log_buf_size = 0, raw_size;
 	char *log_buf = NULL;
@@ -1228,6 +1228,7 @@ done:
 	free(log_buf);
 	return libbpf_err(err);
 }
+int btf__load(struct btf *) __attribute__((alias("btf__load_into_kernel")));
 
 int btf__fd(const struct btf *btf)
 {
@@ -1382,21 +1383,35 @@ exit_free:
 	return btf;
 }
 
-int btf__get_from_id(__u32 id, struct btf **btf)
+struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf)
 {
-	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, base_btf);
 	close(btf_fd);
 
+	return libbpf_ptr(btf);
+}
+
+struct btf *btf__load_from_kernel_by_id(__u32 id)
+{
+	return btf__load_from_kernel_by_id_split(id, NULL);
+}
+
+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);