netdev - [PATCH bpf-next] libbpf: Export bpf_object__load_vmlinux

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Message-Id: <20200527015704.2294223-1-dxu@dxuuu.xyz>
Date:   Tue, 26 May 2020 18:57:04 -0700
From:   Daniel Xu <dxu@...uu.xyz>
To:     ast@...nel.org, daniel@...earbox.net, kafai@...com,
        songliubraving@...com, yhs@...com, andriin@...com,
        john.fastabend@...il.com, kpsingh@...omium.org,
        davem@...emloft.net, kuba@...nel.org, hawk@...nel.org,
        bpf@...r.kernel.org
Cc:     Daniel Xu <dxu@...uu.xyz>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: [PATCH bpf-next] libbpf: Export bpf_object__load_vmlinux_btf

Right now the libbpf model encourages loading the entire object at once.
In this model, libbpf handles loading BTF from vmlinux for us. However,
it can be useful to selectively load certain maps and programs inside an
object without loading everything else.

In the latter model, there was perviously no way to load BTF on-demand.
This commit exports the bpf_object__load_vmlinux_btf such that we are
able to load BTF on demand.

Signed-off-by: Daniel Xu <dxu@...uu.xyz>
---
 tools/lib/bpf/libbpf.c   | 2 +-
 tools/lib/bpf/libbpf.h   | 1 +
 tools/lib/bpf/libbpf.map | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5d60de6fd818..399094b1f580 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2477,7 +2477,7 @@ static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
 	return false;
 }
 
-static int bpf_object__load_vmlinux_btf(struct bpf_object *obj)
+int bpf_object__load_vmlinux_btf(struct bpf_object *obj)
 {
 	struct bpf_program *prog;
 	int err;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 1e2e399a5f2c..6cbd678eb124 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -147,6 +147,7 @@ LIBBPF_API unsigned int bpf_object__kversion(const struct bpf_object *obj);
 struct btf;
 LIBBPF_API struct btf *bpf_object__btf(const struct bpf_object *obj);
 LIBBPF_API int bpf_object__btf_fd(const struct bpf_object *obj);
+LIBBPF_API int bpf_object__load_vmlinux_btf(struct bpf_object *obj);
 
 LIBBPF_API struct bpf_program *
 bpf_object__find_program_by_title(const struct bpf_object *obj,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 381a7342ecfc..56415e671c70 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -261,6 +261,7 @@ LIBBPF_0.0.9 {
 		bpf_iter_create;
 		bpf_link_get_fd_by_id;
 		bpf_link_get_next_id;
+		bpf_object__load_vmlinux_btf;
 		bpf_program__attach_iter;
 		perf_buffer__consume;
 } LIBBPF_0.0.8;
-- 
2.26.2