BPF struct_ops maps are employed directly to register TCP Congestion
Control algorithms. Unlike other BPF programs that terminate when
their links gone, the struct_ops program reduces its refcount solely
upon death of its FD. The link of a BPF struct_ops map provides a
uniform experience akin to other types of BPF programs. A TCP
Congestion Control algorithm will be unregistered upon destroying the
FD in the following patches.
Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx>
---
include/linux/bpf.h | 6 +++-
include/uapi/linux/bpf.h | 4 +++
kernel/bpf/bpf_struct_ops.c | 66 ++++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 29 ++++++++++-----
tools/include/uapi/linux/bpf.h | 4 +++
tools/lib/bpf/bpf.c | 2 ++
tools/lib/bpf/libbpf.c | 1 +
7 files changed, 102 insertions(+), 10 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8b5d0b4c4ada..13683584b071 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1391,7 +1391,11 @@ struct bpf_link {
u32 id;
enum bpf_link_type type;
const struct bpf_link_ops *ops;
- struct bpf_prog *prog;
+ union {
+ struct bpf_prog *prog;
+ /* Backed by a struct_ops (type == BPF_LINK_UPDATE_STRUCT_OPS) */
+ struct bpf_map *map;
+ };
struct work_struct work;
};
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 17afd2b35ee5..1e6cdd0f355d 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1033,6 +1033,7 @@ enum bpf_attach_type {
BPF_PERF_EVENT,
BPF_TRACE_KPROBE_MULTI,
BPF_LSM_CGROUP,
+ BPF_STRUCT_OPS_MAP,
__MAX_BPF_ATTACH_TYPE
};
@@ -6354,6 +6355,9 @@ struct bpf_link_info {
struct {
__u32 ifindex;
} xdp;
+ struct {
+ __u32 map_id;
+ } struct_ops_map;
};
} __attribute__((aligned(8)));
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index ece9870cab68..621c8e24481a 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -698,3 +698,69 @@ void bpf_struct_ops_put(const void *kdata)
call_rcu(&st_map->rcu, bpf_struct_ops_put_rcu);
}
}
+
+static void bpf_struct_ops_map_link_release(struct bpf_link *link)
+{
+ if (link->map) {
+ bpf_map_put(link->map);
+ link->map = NULL;
+ }
+}
+
+static void bpf_struct_ops_map_link_dealloc(struct bpf_link *link)
+{
+ kfree(link);
+}
+
+static void bpf_struct_ops_map_link_show_fdinfo(const struct bpf_link *link,
+ struct seq_file *seq)
+{
+ seq_printf(seq, "map_id:\t%d\n",
+ link->map->id);
+}
+
+static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
+ struct bpf_link_info *info)
+{
+ info->struct_ops_map.map_id = link->map->id;
+ return 0;
+}
+
+static const struct bpf_link_ops bpf_struct_ops_map_lops = {
+ .release = bpf_struct_ops_map_link_release,
+ .dealloc = bpf_struct_ops_map_link_dealloc,
+ .show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
+ .fill_link_info = bpf_struct_ops_map_link_fill_link_info,
+};
+
+int link_create_struct_ops_map(union bpf_attr *attr, bpfptr_t uattr)
+{
+ struct bpf_link_primer link_primer;
+ struct bpf_map *map;
+ struct bpf_link *link = NULL;
+ int err;
+
+ map = bpf_map_get(attr->link_create.prog_fd);
+ if (map->map_type != BPF_MAP_TYPE_STRUCT_OPS)
+ return -EINVAL;
+
+ link = kzalloc(sizeof(*link), GFP_USER);
+ if (!link) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ bpf_link_init(link, BPF_LINK_TYPE_STRUCT_OPS, &bpf_struct_ops_map_lops, NULL);
+ link->map = map;
+
+ err = bpf_link_prime(link, &link_primer);
+ if (err)
+ goto err_out;
+
+ return bpf_link_settle(&link_primer);
+
+err_out:
+ bpf_map_put(map);
+ kfree(link);
+ return err;
+}
+
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index cda8d00f3762..54e172d8f5d1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2738,7 +2738,9 @@ static void bpf_link_free(struct bpf_link *link)
if (link->prog) {
/* detach BPF program, clean up used resources */
link->ops->release(link);
- bpf_prog_put(link->prog);
+ if (link->type != BPF_LINK_TYPE_STRUCT_OPS)
+ bpf_prog_put(link->prog);
+ /* The struct_ops links clean up map by them-selves. */
}
/* free bpf_link and its containing memory */
link->ops->dealloc(link);
@@ -2794,16 +2796,19 @@ static void bpf_link_show_fdinfo(struct seq_file *m, struct file *filp)
const struct bpf_prog *prog = link->prog;
char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
- bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
seq_printf(m,
"link_type:\t%s\n"
- "link_id:\t%u\n"
- "prog_tag:\t%s\n"
- "prog_id:\t%u\n",
+ "link_id:\t%u\n",
bpf_link_type_strs[link->type],
- link->id,
- prog_tag,
- prog->aux->id);
+ link->id);
+ if (link->type != BPF_LINK_TYPE_STRUCT_OPS) {
+ bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
+ seq_printf(m,
+ "prog_tag:\t%s\n"
+ "prog_id:\t%u\n",
+ prog_tag,
+ prog->aux->id);
+ }
if (link->ops->show_fdinfo)
link->ops->show_fdinfo(link, m);
}
@@ -4278,7 +4283,8 @@ static int bpf_link_get_info_by_fd(struct file *file,
info.type = link->type;
info.id = link->id;
- info.prog_id = link->prog->aux->id;
+ if (link->type != BPF_LINK_TYPE_STRUCT_OPS)
+ info.prog_id = link->prog->aux->id;
if (link->ops->fill_link_info) {
err = link->ops->fill_link_info(link, &info);
@@ -4531,6 +4537,8 @@ static int bpf_map_do_batch(const union bpf_attr *attr,
return err;
}
+extern int link_create_struct_ops_map(union bpf_attr *attr, bpfptr_t uattr);
+
#define BPF_LINK_CREATE_LAST_FIELD link_create.kprobe_multi.cookies
static int link_create(union bpf_attr *attr, bpfptr_t uattr)
{
@@ -4541,6 +4549,9 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
if (CHECK_ATTR(BPF_LINK_CREATE))
return -EINVAL;
+ if (attr->link_create.attach_type == BPF_STRUCT_OPS_MAP)
+ return link_create_struct_ops_map(attr, uattr);
+
prog = bpf_prog_get(attr->link_create.prog_fd);
if (IS_ERR(prog))
return PTR_ERR(prog);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 17afd2b35ee5..1e6cdd0f355d 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1033,6 +1033,7 @@ enum bpf_attach_type {
BPF_PERF_EVENT,
BPF_TRACE_KPROBE_MULTI,
BPF_LSM_CGROUP,
+ BPF_STRUCT_OPS_MAP,
__MAX_BPF_ATTACH_TYPE
};
@@ -6354,6 +6355,9 @@ struct bpf_link_info {
struct {
__u32 ifindex;
} xdp;
+ struct {
+ __u32 map_id;
+ } struct_ops_map;
};
} __attribute__((aligned(8)));
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 9aff98f42a3d..e44d49f17c86 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -731,6 +731,8 @@ int bpf_link_create(int prog_fd, int target_fd,
if (!OPTS_ZEROED(opts, tracing))
return libbpf_err(-EINVAL);
break;
+ case BPF_STRUCT_OPS_MAP:
+ break;
default:
if (!OPTS_ZEROED(opts, flags))
return libbpf_err(-EINVAL);
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 35a698eb825d..75ed95b7e455 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -115,6 +115,7 @@ static const char * const attach_type_name[] = {
[BPF_SK_REUSEPORT_SELECT_OR_MIGRATE] = "sk_reuseport_select_or_migrate",
[BPF_PERF_EVENT] = "perf_event",
[BPF_TRACE_KPROBE_MULTI] = "trace_kprobe_multi",
+ [BPF_STRUCT_OPS_MAP] = "struct_ops_map",
};
static const char * const link_type_name[] = {
--
2.30.2
