[PATCH bpf-next v2 13/15] libbpf: Support attaching struct_ops to a cgroup

[Amery Hung <ameryhung@gmail.com>]

From: Martin KaFai Lau <martin.lau@kernel.org>

Add bpf_map__attach_cgroup_opts() to attach a struct_ops map to a cgroup
through a BPF link.

Also extend struct bpf_prog_query_opts with a type_id field so a
BPF_STRUCT_OPS query on a cgroup can select the struct_ops type to
enumerate.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
 tools/lib/bpf/bpf.c            |  2 ++
 tools/lib/bpf/bpf.h            |  3 +-
 tools/lib/bpf/libbpf.c         | 59 ++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h         |  3 ++
 tools/lib/bpf/libbpf.map       |  5 +++
 tools/lib/bpf/libbpf_version.h |  2 +-
 6 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 96819c082c77..a9de7f107cf7 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -934,6 +934,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 	case BPF_CGROUP_GETSOCKOPT:
 	case BPF_CGROUP_SETSOCKOPT:
 	case BPF_LSM_CGROUP:
+	case BPF_STRUCT_OPS:
 		relative_fd = OPTS_GET(opts, cgroup.relative_fd, 0);
 		relative_id = OPTS_GET(opts, cgroup.relative_id, 0);
 		if (relative_fd && relative_id)
@@ -1056,6 +1057,7 @@ int bpf_prog_query_opts(int target, enum bpf_attach_type type,
 	attr.query.attach_type		= type;
 	attr.query.query_flags		= OPTS_GET(opts, query_flags, 0);
 	attr.query.count		= OPTS_GET(opts, count, 0);
+	attr.query.type_id		= OPTS_GET(opts, type_id, 0);
 	attr.query.prog_ids		= ptr_to_u64(OPTS_GET(opts, prog_ids, NULL));
 	attr.query.link_ids		= ptr_to_u64(OPTS_GET(opts, link_ids, NULL));
 	attr.query.prog_attach_flags	= ptr_to_u64(OPTS_GET(opts, prog_attach_flags, NULL));
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 7534a593edae..490e8cb4ba53 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -637,9 +637,10 @@ struct bpf_prog_query_opts {
 	__u32 *link_ids;
 	__u32 *link_attach_flags;
 	__u64 revision;
+	__u32 type_id;
 	size_t :0;
 };
-#define bpf_prog_query_opts__last_field revision
+#define bpf_prog_query_opts__last_field type_id
 
 /**
  * @brief **bpf_prog_query_opts()** queries the BPF programs and BPF links
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1368752aa13c..17f8466e33fa 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -14104,6 +14104,65 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map)
 	return &link->link;
 }
 
+struct bpf_link *bpf_map__attach_cgroup_opts(const struct bpf_map *map, int cgroup_fd,
+					     const struct bpf_cgroup_opts *opts)
+{
+	LIBBPF_OPTS(bpf_link_create_opts, link_create_opts);
+	struct bpf_link_struct_ops *link;
+	__u32 relative_id, zero = 0;
+	int err, fd, relative_fd;
+
+	if (!OPTS_VALID(opts, bpf_cgroup_opts))
+		return libbpf_err_ptr(-EINVAL);
+
+	if (!bpf_map__is_struct_ops(map)) {
+		pr_warn("map '%s': can't attach non-struct_ops map\n", map->name);
+		return libbpf_err_ptr(-EINVAL);
+	}
+
+	if (map->fd < 0) {
+		pr_warn("map '%s': can't attach BPF map without FD (was it created?)\n", map->name);
+		return libbpf_err_ptr(-EINVAL);
+	}
+
+	relative_id = OPTS_GET(opts, relative_id, 0);
+	relative_fd = OPTS_GET(opts, relative_fd, 0);
+
+	if (relative_fd && relative_id) {
+		pr_warn("map '%s': relative_fd and relative_id cannot be set at the same time\n",
+			map->name);
+		return libbpf_err_ptr(-EINVAL);
+	}
+
+	link_create_opts.cgroup.expected_revision = OPTS_GET(opts, expected_revision, 0);
+	link_create_opts.cgroup.relative_fd = relative_fd;
+	link_create_opts.cgroup.relative_id = relative_id;
+	link_create_opts.flags = OPTS_GET(opts, flags, 0);
+
+	link = calloc(1, sizeof(*link));
+	if (!link)
+		return libbpf_err_ptr(-ENOMEM);
+
+	err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0);
+	if (err && err != -EBUSY) {
+		free(link);
+		return libbpf_err_ptr(err);
+	}
+
+	link->link.detach = bpf_link__detach_struct_ops;
+
+	fd = bpf_link_create(map->fd, cgroup_fd, BPF_STRUCT_OPS, &link_create_opts);
+	if (fd < 0) {
+		free(link);
+		return libbpf_err_ptr(fd);
+	}
+
+	link->link.fd = fd;
+	link->map_fd = map->fd;
+
+	return &link->link;
+}
+
 /*
  * Swap the back struct_ops of a link with a new struct_ops map.
  */
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index b965ad571540..0e5f4e9bba41 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -960,6 +960,9 @@ bpf_program__attach_cgroup_opts(const struct bpf_program *prog, int cgroup_fd,
 struct bpf_map;
 
 LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map);
+LIBBPF_API struct bpf_link *bpf_map__attach_cgroup_opts(const struct bpf_map *map,
+							int cgroup_fd,
+							const struct bpf_cgroup_opts *opts);
 LIBBPF_API int bpf_link__update_map(struct bpf_link *link, const struct bpf_map *map);
 
 struct bpf_iter_attach_opts {
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b731df19ae69..1b01d49e58eb 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -462,3 +462,8 @@ LIBBPF_1.8.0 {
 		bpf_program__clone;
 		btf__new_empty_opts;
 } LIBBPF_1.7.0;
+
+LIBBPF_1.9.0 {
+	global:
+		bpf_map__attach_cgroup_opts;
+} LIBBPF_1.8.0;
diff --git a/tools/lib/bpf/libbpf_version.h b/tools/lib/bpf/libbpf_version.h
index c446c0cd8cf9..57b74ef3618c 100644
--- a/tools/lib/bpf/libbpf_version.h
+++ b/tools/lib/bpf/libbpf_version.h
@@ -4,6 +4,6 @@
 #define __LIBBPF_VERSION_H
 
 #define LIBBPF_MAJOR_VERSION 1
-#define LIBBPF_MINOR_VERSION 8
+#define LIBBPF_MINOR_VERSION 9
 
 #endif /* __LIBBPF_VERSION_H */
-- 
2.53.0-Meta