[PATCH bpf-next] libbpf: add libbpf_load_vmlinux_btf/libbpf_load_module_btf APIs

[Hengqi Chen <hengqi.chen@gmail.com>]

Add libbpf_load_vmlinux_btf/libbpf_load_module_btf APIs.
This is part of the libbpf v1.0. [1]

[1] https://github.com/libbpf/libbpf/issues/280

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 tools/lib/bpf/btf.c      | 24 +++++++++++++++++++++++-
 tools/lib/bpf/btf.h      |  2 ++
 tools/lib/bpf/libbpf.c   |  8 ++++----
 tools/lib/bpf/libbpf.map |  2 ++
 4 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index b46760b93bb4..414e1c5635ef 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -4021,7 +4021,7 @@ static void btf_dedup_merge_hypot_map(struct btf_dedup *d)
 		 */
 		if (d->hypot_adjust_canon)
 			continue;
-		
+
 		if (t_kind == BTF_KIND_FWD && c_kind != BTF_KIND_FWD)
 			d->map[t_id] = c_id;
 
@@ -4395,6 +4395,11 @@ static int btf_dedup_remap_types(struct btf_dedup *d)
  * data out of it to use for target BTF.
  */
 struct btf *libbpf_find_kernel_btf(void)
+{
+	return libbpf_load_vmlinux_btf();
+}
+
+struct btf *libbpf_load_vmlinux_btf(void)
 {
 	struct {
 		const char *path_fmt;
@@ -4440,6 +4445,23 @@ struct btf *libbpf_find_kernel_btf(void)
 	return libbpf_err_ptr(-ESRCH);
 }
 
+struct btf *libbpf_load_module_btf(const char *mod)
+{
+	char path[80];
+	struct btf *base;
+	int err;
+
+	base = libbpf_load_vmlinux_btf();
+	err = libbpf_get_error(base);
+	if (err) {
+		pr_warn("Error loading vmlinux BTF: %d\n", err);
+		return base;
+	}
+
+	snprintf(path, sizeof(path), "/sys/kernel/btf/%s", mod);
+	return btf__parse_split(path, base);
+}
+
 int btf_type_visit_type_ids(struct btf_type *t, type_id_visit_fn visit, void *ctx)
 {
 	int i, n, err;
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 374e9f15de2e..d27cc2e2f220 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -90,6 +90,8 @@ LIBBPF_API __u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext);
 LIBBPF_API __u32 btf_ext__line_info_rec_size(const struct btf_ext *btf_ext);
 
 LIBBPF_API struct btf *libbpf_find_kernel_btf(void);
+LIBBPF_API struct btf *libbpf_load_vmlinux_btf(void);
+LIBBPF_API struct btf *libbpf_load_module_btf(const char *mod);
 
 LIBBPF_API int btf__find_str(struct btf *btf, const char *s);
 LIBBPF_API int btf__add_str(struct btf *btf, const char *s);
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a53ca29b44ab..6e4ead454c0e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2685,7 +2685,7 @@ static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
 	if (!force && !obj_needs_vmlinux_btf(obj))
 		return 0;
 
-	obj->btf_vmlinux = libbpf_find_kernel_btf();
+	obj->btf_vmlinux = libbpf_load_vmlinux_btf();
 	err = libbpf_get_error(obj->btf_vmlinux);
 	if (err) {
 		pr_warn("Error loading vmlinux BTF: %d\n", err);
@@ -7236,7 +7236,7 @@ static int bpf_object__collect_relos(struct bpf_object *obj)
 
 	for (i = 0; i < obj->nr_programs; i++) {
 		struct bpf_program *p = &obj->programs[i];
-		
+
 		if (!p->nr_reloc)
 			continue;
 
@@ -9562,7 +9562,7 @@ int libbpf_find_vmlinux_btf_id(const char *name,
 	struct btf *btf;
 	int err;
 
-	btf = libbpf_find_kernel_btf();
+	btf = libbpf_load_vmlinux_btf();
 	err = libbpf_get_error(btf);
 	if (err) {
 		pr_warn("vmlinux BTF is not found\n");
@@ -10080,7 +10080,7 @@ struct bpf_link {
 int bpf_link__update_program(struct bpf_link *link, struct bpf_program *prog)
 {
 	int ret;
-	
+
 	ret = bpf_link_update(bpf_link__fd(link), bpf_program__fd(prog), NULL);
 	return libbpf_err_errno(ret);
 }
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index c240d488eb5e..2088bdbc0f50 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -377,4 +377,6 @@ LIBBPF_0.5.0 {
 		bpf_object__gen_loader;
 		btf_dump__dump_type_data;
 		libbpf_set_strict_mode;
+		libbpf_load_vmlinux_btf;
+		libbpf_load_module_btf;
 } LIBBPF_0.4.0;
-- 
2.25.1