[PATCH bpf-next v2 4/9] bpf: trampoline: introduce bpf_tramp_multi_link

[Menglong Dong]

Introduce the struct bpf_tramp_multi_link, which is used to attach
a bpf_link to multi trampoline. Meanwhile, introduce corresponding
function bpf_trampoline_multi_{link,unlink}_prog.

Signed-off-by: Menglong Dong <dongmenglong.8 at bytedance.com>
---
 include/linux/bpf.h     | 14 ++++++++++++
 kernel/bpf/trampoline.c | 47 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2b5cd6100fc4..4e8f17d9f022 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -57,6 +57,7 @@ struct user_namespace;
 struct super_block;
 struct inode;
 struct bpf_tramp_link;
+struct bpf_tramp_multi_link;
 
 extern struct idr btf_idr;
 extern spinlock_t btf_idr_lock;
@@ -1282,6 +1283,8 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key,
 					  struct bpf_attach_target_info *tgt_info);
 void bpf_trampoline_put(struct bpf_trampoline *tr);
 int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs);
+int bpf_trampoline_multi_link_prog(struct bpf_tramp_multi_link *link);
+int bpf_trampoline_multi_unlink_prog(struct bpf_tramp_multi_link *link);
 
 /*
  * When the architecture supports STATIC_CALL replace the bpf_dispatcher_fn
@@ -1614,6 +1617,17 @@ struct bpf_shim_tramp_link {
 	struct bpf_trampoline *trampoline;
 };
 
+struct bpf_tramp_multi_link_entry {
+	struct bpf_trampoline *trampoline;
+	struct bpf_tramp_link_conn conn;
+};
+
+struct bpf_tramp_multi_link {
+	struct bpf_link link;
+	u32 cnt;
+	struct bpf_tramp_multi_link_entry *entries;
+};
+
 struct bpf_tracing_link {
 	struct bpf_tramp_link link;
 	enum bpf_attach_type attach_type;
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index cf9b84f785f3..2167aa3fe583 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -607,6 +607,53 @@ int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampolin
 	return err;
 }
 
+static int __bpf_trampoline_multi_unlink_prog(struct bpf_tramp_multi_link *link,
+					      u32 cnt)
+{
+	struct bpf_tramp_multi_link_entry *entry;
+	struct bpf_trampoline *tr;
+	int err = 0, i;
+
+	for (i = 0; i < cnt; i++) {
+		entry = &link->entries[i];
+		tr = entry->trampoline;
+		mutex_lock(&tr->mutex);
+		err = __bpf_trampoline_unlink_prog(&entry->conn,
+						   entry->trampoline);
+		mutex_unlock(&tr->mutex);
+		if (err)
+			break;
+	}
+	return err;
+}
+
+int bpf_trampoline_multi_unlink_prog(struct bpf_tramp_multi_link *link)
+{
+	return __bpf_trampoline_multi_unlink_prog(link, link->cnt);
+}
+
+int bpf_trampoline_multi_link_prog(struct bpf_tramp_multi_link *link)
+{
+	struct bpf_tramp_multi_link_entry *entry;
+	struct bpf_trampoline *tr;
+	int err = 0, i;
+
+	for (i = 0; i < link->cnt; i++) {
+		entry = &link->entries[i];
+		tr = entry->trampoline;
+		mutex_lock(&tr->mutex);
+		err = __bpf_trampoline_link_prog(&entry->conn, tr);
+		mutex_unlock(&tr->mutex);
+		if (err)
+			goto unlink;
+	}
+
+	return 0;
+unlink:
+	__bpf_trampoline_multi_unlink_prog(link, i);
+	return err;
+}
+
 #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_LSM)
 static void bpf_shim_tramp_link_release(struct bpf_link *link)
 {
-- 
2.39.2