netdev - [PATCH bpf-next 2/4] libbpf: Add helpers for pinning bpf prog through bpf object skeleton

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Message-Id: <20220423140058.54414-3-laoar.shao@gmail.com>
Date:   Sat, 23 Apr 2022 14:00:56 +0000
From:   Yafang Shao <laoar.shao@...il.com>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH bpf-next 2/4] libbpf: Add helpers for pinning bpf prog through bpf object skeleton

Currently there're helpers for allowing to open/load/attach BPF object
through BPF object skeleton. Let's also add helpers for pinning through
BPF object skeleton. It could simplify BPF userspace code which wants to
pin the progs into bpffs.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 tools/lib/bpf/libbpf.c   | 59 ++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |  4 +++
 tools/lib/bpf/libbpf.map |  2 ++
 3 files changed, 65 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 13fcf91e9e0e..e7ed6c53c525 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -12726,6 +12726,65 @@ void bpf_object__detach_skeleton(struct bpf_object_skeleton *s)
 	}
 }
 
+int bpf_object__pin_skeleton_prog(struct bpf_object_skeleton *s,
+				  const char *path)
+{
+	struct bpf_link *link;
+	int err;
+	int i;
+
+	if (!s->prog_cnt)
+		return libbpf_err(-EINVAL);
+
+	if (!path)
+		path = DEFAULT_BPFFS;
+
+	for (i = 0; i < s->prog_cnt; i++) {
+		char buf[PATH_MAX];
+		int len;
+
+		len = snprintf(buf, PATH_MAX, "%s/%s", path, s->progs[i].name);
+		if (len < 0) {
+			err = -EINVAL;
+			goto err_unpin_prog;
+		} else if (len >= PATH_MAX) {
+			err = -ENAMETOOLONG;
+			goto err_unpin_prog;
+		}
+
+		link = *s->progs[i].link;
+		if (!link) {
+			err = -EINVAL;
+			goto err_unpin_prog;
+		}
+
+		err = bpf_link__pin(link, buf);
+		if (err)
+			goto err_unpin_prog;
+	}
+
+	return 0;
+
+err_unpin_prog:
+	bpf_object__unpin_skeleton_prog(s);
+
+	return libbpf_err(err);
+}
+
+void bpf_object__unpin_skeleton_prog(struct bpf_object_skeleton *s)
+{
+	struct bpf_link *link;
+	int i;
+
+	for (i = 0; i < s->prog_cnt; i++) {
+		link = *s->progs[i].link;
+		if (!link || !link->pin_path)
+			continue;
+
+		bpf_link__unpin(link);
+	}
+}
+
 void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s)
 {
 	if (!s)
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 3784867811a4..af44b0968cca 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1427,6 +1427,10 @@ bpf_object__open_skeleton(struct bpf_object_skeleton *s,
 LIBBPF_API int bpf_object__load_skeleton(struct bpf_object_skeleton *s);
 LIBBPF_API int bpf_object__attach_skeleton(struct bpf_object_skeleton *s);
 LIBBPF_API void bpf_object__detach_skeleton(struct bpf_object_skeleton *s);
+LIBBPF_API int
+bpf_object__pin_skeleton_prog(struct bpf_object_skeleton *s, const char *path);
+LIBBPF_API void
+bpf_object__unpin_skeleton_prog(struct bpf_object_skeleton *s);
 LIBBPF_API void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s);
 
 struct bpf_var_skeleton {
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 82f6d62176dd..4e3e37b84b3a 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -55,6 +55,8 @@ LIBBPF_0.0.1 {
 		bpf_object__unload;
 		bpf_object__unpin_maps;
 		bpf_object__unpin_programs;
+		bpf_object__pin_skeleton_prog;
+		bpf_object__unpin_skeleton_prog;
 		bpf_perf_event_read_simple;
 		bpf_prog_attach;
 		bpf_prog_detach;
-- 
2.17.1