netdev - [PATCH bpf-next v2 2/5] libbpf: rename btf__get_from_id() as btf__load_from_kernel_by

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Date:   Wed, 21 Jul 2021 16:38:05 +0100
From:   Quentin Monnet <quentin@...valent.com>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Quentin Monnet <quentin@...valent.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: [PATCH bpf-next v2 2/5] 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 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

v2:
- Instead of a simple renaming, change the new function to make it
  return the pointer to the btf struct.
- API v0.5.0 instead of v0.6.0.

Signed-off-by: Quentin Monnet <quentin@...valent.com>
Acked-by: John Fastabend <john.fastabend@...il.com>
---
 tools/lib/bpf/btf.c      | 25 +++++++++++++++++--------
 tools/lib/bpf/btf.h      |  1 +
 tools/lib/bpf/libbpf.c   |  5 +++--
 tools/lib/bpf/libbpf.map |  1 +
 4 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 7e0de560490e..6654bdee7ad7 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1383,21 +1383,30 @@ struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf)
 	return btf;
 }
 
+struct btf *btf__load_from_kernel_by_id(__u32 id)
+{
+	struct btf *btf;
+	int btf_fd;
+
+	btf_fd = bpf_btf_get_fd_by_id(id);
+	if (btf_fd < 0)
+		return 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_fd;
+	int err;
 
 	*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);
+	res = btf__load_from_kernel_by_id(id);
 	err = libbpf_get_error(res);
 
-	close(btf_fd);
-
 	if (err)
 		return libbpf_err(err);
 
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index fd8a21d936ef..3db9446bc133 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -68,6 +68,7 @@ LIBBPF_API const void *btf__get_raw_data(const struct btf *btf, __u32 *size);
 LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API const char *btf__str_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
+LIBBPF_API struct btf *btf__load_from_kernel_by_id(__u32 id);
 LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
 				    __u32 expected_key_size,
 				    __u32 expected_value_size,
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 242e97892043..eff005b1eba1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9576,8 +9576,8 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
 {
 	struct bpf_prog_info_linear *info_linear;
 	struct bpf_prog_info *info;
-	struct btf *btf = NULL;
 	int err = -EINVAL;
+	struct btf *btf;
 
 	info_linear = bpf_program__get_prog_info_linear(attach_prog_fd, 0);
 	err = libbpf_get_error(info_linear);
@@ -9591,7 +9591,8 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
 		pr_warn("The target program doesn't have BTF\n");
 		goto out;
 	}
-	if (btf__get_from_id(info->btf_id, &btf)) {
+	btf = btf__load_from_kernel_by_id(info->btf_id);
+	if (libbpf_get_error(btf)) {
 		pr_warn("Failed to get BTF of the program\n");
 		goto out;
 	}
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index f7d52d76ca3a..ca8cc7a7faad 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -373,6 +373,7 @@ LIBBPF_0.5.0 {
 		bpf_map__initial_value;
 		bpf_map_lookup_and_delete_elem_flags;
 		bpf_object__gen_loader;
+		btf__load_from_kernel_by_id;
 		btf__load_into_kernel;
 		btf_dump__dump_type_data;
 		libbpf_set_strict_mode;
-- 
2.30.2