[PATCH bpf-next v2 4/5] libbpf: add bpf_btf_get_next_id() to cycle through BTF objects

[Quentin Monnet <quentin.monnet@netronome.com>]

Add an API function taking a BTF object id and providing the id of the
next BTF object in the kernel. This can be used to list all BTF objects
loaded on the system.

v2:
- Rebase on top of Andrii's changes regarding libbpf versioning.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
---
 tools/lib/bpf/bpf.c      | 5 +++++
 tools/lib/bpf/bpf.h      | 1 +
 tools/lib/bpf/libbpf.map | 2 ++
 3 files changed, 8 insertions(+)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 1439e99c9be5..cbb933532981 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -593,6 +593,11 @@ int bpf_map_get_next_id(__u32 start_id, __u32 *next_id)
 	return bpf_obj_get_next_id(start_id, next_id, BPF_MAP_GET_NEXT_ID);
 }
 
+int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id)
+{
+	return bpf_obj_get_next_id(start_id, next_id, BPF_BTF_GET_NEXT_ID);
+}
+
 int bpf_prog_get_fd_by_id(__u32 id)
 {
 	union bpf_attr attr;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index ff42ca043dc8..0db01334740f 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -156,6 +156,7 @@ LIBBPF_API int bpf_prog_test_run(int prog_fd, int repeat, void *data,
 				 __u32 *retval, __u32 *duration);
 LIBBPF_API int bpf_prog_get_next_id(__u32 start_id, __u32 *next_id);
 LIBBPF_API int bpf_map_get_next_id(__u32 start_id, __u32 *next_id);
+LIBBPF_API int bpf_btf_get_next_id(__u32 start_id, __u32 *next_id);
 LIBBPF_API int bpf_prog_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_map_get_fd_by_id(__u32 id);
 LIBBPF_API int bpf_btf_get_fd_by_id(__u32 id);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 4e72df8e98ba..664ce8e7a60e 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -186,4 +186,6 @@ LIBBPF_0.0.4 {
 } LIBBPF_0.0.3;
 
 LIBBPF_0.0.5 {
+	global:
+		bpf_btf_get_next_id;
 } LIBBPF_0.0.4;
-- 
2.17.1