[RFC bpf-next v3 03/11] bpf: add register and unregister functions for struct_ops.

[thinker.li@xxxxxxxxx]

From: Kui-Feng Lee <thinker.li@xxxxxxxxx>

Provide registration functions to add/remove struct_ops types.

Currently, it does linear search to find a struct_ops type. It should be
fine for now since we don't have many struct_ops types.

Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
 include/linux/bpf.h         |  9 +++++++++
 include/linux/btf.h         | 27 +++++++++++++++++++++++++++
 kernel/bpf/bpf_struct_ops.c | 11 -----------
 kernel/bpf/btf.c            |  2 +-
 4 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 30063a760b5a..67554f2f81b7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1634,6 +1634,11 @@ struct bpf_struct_ops {
 	u32 value_id;
 };
 
+struct bpf_struct_ops_mod {
+	struct module *owner;
+	struct bpf_struct_ops *st_ops;
+};
+
 #if defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)
 #define BPF_MODULE_OWNER ((void *)((0xeB9FUL << 2) + POISON_POINTER_DELTA))
 const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id);
@@ -3205,4 +3210,8 @@ static inline bool bpf_is_subprog(const struct bpf_prog *prog)
 	return prog->aux->func_idx != 0;
 }
 
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+int register_bpf_struct_ops(struct bpf_struct_ops_mod *mod);
+#endif
+
 #endif /* _LINUX_BPF_H */
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 5fabe23aedd2..8d50e46b21bc 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -12,6 +12,8 @@
 #include <uapi/linux/bpf.h>
 
 #define BTF_TYPE_EMIT(type) ((void)(type *)0)
+#define BTF_STRUCT_OPS_TYPE_EMIT(type) {((void)(struct type *)0);	\
+		((void)(struct bpf_struct_ops_##type *)0); }
 #define BTF_TYPE_EMIT_ENUM(enum_val) ((void)enum_val)
 
 /* These need to be macros, as the expressions are used in assembler input */
@@ -200,6 +202,7 @@ u32 btf_obj_id(const struct btf *btf);
 bool btf_is_kernel(const struct btf *btf);
 bool btf_is_module(const struct btf *btf);
 struct module *btf_try_get_module(const struct btf *btf);
+struct btf *btf_get_module_btf(const struct module *module);
 u32 btf_nr_types(const struct btf *btf);
 bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
 			   const struct btf_member *m,
@@ -580,4 +583,28 @@ int btf_add_struct_ops(struct bpf_struct_ops *st_ops,
 const struct bpf_struct_ops **
 btf_get_struct_ops(struct btf *btf, u32 *ret_cnt);
 
+enum bpf_struct_ops_state {
+	BPF_STRUCT_OPS_STATE_INIT,
+	BPF_STRUCT_OPS_STATE_INUSE,
+	BPF_STRUCT_OPS_STATE_TOBEFREE,
+	BPF_STRUCT_OPS_STATE_READY,
+};
+
+#define BPF_STRUCT_OPS_COMMON_VALUE			\
+	refcount_t refcnt;				\
+	enum bpf_struct_ops_state state
+
+/* bpf_struct_ops_##_name (e.g. bpf_struct_ops_tcp_congestion_ops) is
+ * the map's value exposed to the userspace and its btf-type-id is
+ * stored at the map->btf_vmlinux_value_type_id.
+ *
+ */
+#define DEFINE_STRUCT_OPS_VALUE_TYPE(_name)			\
+extern struct bpf_struct_ops bpf_##_name;			\
+								\
+struct bpf_struct_ops_##_name {					\
+	BPF_STRUCT_OPS_COMMON_VALUE;				\
+	struct _name data ____cacheline_aligned_in_smp;		\
+};
+
 #endif
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 627cf1ea840a..cd688e9033b5 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -13,17 +13,6 @@
 #include <linux/btf_ids.h>
 #include <linux/rcupdate_wait.h>
 
-enum bpf_struct_ops_state {
-	BPF_STRUCT_OPS_STATE_INIT,
-	BPF_STRUCT_OPS_STATE_INUSE,
-	BPF_STRUCT_OPS_STATE_TOBEFREE,
-	BPF_STRUCT_OPS_STATE_READY,
-};
-
-#define BPF_STRUCT_OPS_COMMON_VALUE			\
-	refcount_t refcnt;				\
-	enum bpf_struct_ops_state state
-
 struct bpf_struct_ops_value {
 	BPF_STRUCT_OPS_COMMON_VALUE;
 	char data[] ____cacheline_aligned_in_smp;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 3fb9964f8672..73d19ef99306 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7532,7 +7532,7 @@ struct module *btf_try_get_module(const struct btf *btf)
 /* Returns struct btf corresponding to the struct module.
  * This function can return NULL or ERR_PTR.
  */
-static struct btf *btf_get_module_btf(const struct module *module)
+struct btf *btf_get_module_btf(const struct module *module)
 {
 #ifdef CONFIG_DEBUG_INFO_BTF_MODULES
 	struct btf_module *btf_mod, *tmp;
-- 
2.34.1