[PATCH bpf-next v5 2/9] bpf: add struct_ops_tab to btf.

[thinker.li@gmail.com]

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

Maintain a registry of registered struct_ops types in the per-btf (module)
struct_ops_tab. This registry allows for easy lookup of struct_ops types
that are registered by a specific module.

Every struct_ops type should have an associated module BTF to provide type
information since we are going to allow modules to define and register new
struct_ops types. Once this change is made, the bpf_struct_ops subsystem
knows where to look up type info with just a bpf_struct_ops.

The subsystem looks up struct_ops types from a given module BTF although it
is always btf_vmlinux now. Once start using struct_ops_tab, btfs other than
btf_vmlinux can be used as well.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
---
 include/linux/bpf.h         |  5 +--
 include/linux/btf.h         |  6 ++++
 kernel/bpf/bpf_struct_ops.c | 17 ++++-----
 kernel/bpf/btf.c            | 70 +++++++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c       |  2 +-
 5 files changed, 89 insertions(+), 11 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 30063a760b5a..e6a648af2daa 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1626,6 +1626,7 @@ struct bpf_struct_ops {
 	void (*unreg)(void *kdata);
 	int (*update)(void *kdata, void *old_kdata);
 	int (*validate)(void *kdata);
+	struct btf *btf;
 	const struct btf_type *type;
 	const struct btf_type *value_type;
 	const char *name;
@@ -1636,7 +1637,7 @@ struct bpf_struct_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);
+const struct bpf_struct_ops *bpf_struct_ops_find(struct btf *btf, u32 type_id);
 void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log);
 bool bpf_struct_ops_get(const void *kdata);
 void bpf_struct_ops_put(const void *kdata);
@@ -1679,7 +1680,7 @@ int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
 			    union bpf_attr __user *uattr);
 #endif
 #else
-static inline const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
+static inline const struct bpf_struct_ops *bpf_struct_ops_find(struct btf *btf, u32 type_id)
 {
 	return NULL;
 }
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 928113a80a95..aa2ba77648be 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -571,4 +571,10 @@ static inline bool btf_type_is_struct_ptr(struct btf *btf, const struct btf_type
 	return btf_type_is_struct(t);
 }
 
+struct bpf_struct_ops;
+
+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);
+
 #endif
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 627cf1ea840a..7758f66ad734 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -185,6 +185,7 @@ static void bpf_struct_ops_init_one(struct bpf_struct_ops *st_ops,
 			pr_warn("Error in init bpf_struct_ops %s\n",
 				st_ops->name);
 		} else {
+			st_ops->btf = btf;
 			st_ops->type_id = type_id;
 			st_ops->type = t;
 			st_ops->value_id = value_id;
@@ -221,7 +222,7 @@ void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
 extern struct btf *btf_vmlinux;
 
 static const struct bpf_struct_ops *
-bpf_struct_ops_find_value(u32 value_id)
+bpf_struct_ops_find_value(struct btf *btf, u32 value_id)
 {
 	unsigned int i;
 
@@ -236,7 +237,7 @@ bpf_struct_ops_find_value(u32 value_id)
 	return NULL;
 }
 
-const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
+const struct bpf_struct_ops *bpf_struct_ops_find(struct btf *btf, u32 type_id)
 {
 	unsigned int i;
 
@@ -316,7 +317,7 @@ static void bpf_struct_ops_map_put_progs(struct bpf_struct_ops_map *st_map)
 	}
 }
 
-static int check_zero_holes(const struct btf_type *t, void *data)
+static int check_zero_holes(const struct btf *btf, const struct btf_type *t, void *data)
 {
 	const struct btf_member *member;
 	u32 i, moff, msize, prev_mend = 0;
@@ -328,8 +329,8 @@ static int check_zero_holes(const struct btf_type *t, void *data)
 		    memchr_inv(data + prev_mend, 0, moff - prev_mend))
 			return -EINVAL;
 
-		mtype = btf_type_by_id(btf_vmlinux, member->type);
-		mtype = btf_resolve_size(btf_vmlinux, mtype, &msize);
+		mtype = btf_type_by_id(btf, member->type);
+		mtype = btf_resolve_size(btf, mtype, &msize);
 		if (IS_ERR(mtype))
 			return PTR_ERR(mtype);
 		prev_mend = moff + msize;
@@ -395,12 +396,12 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
 	if (*(u32 *)key != 0)
 		return -E2BIG;
 
-	err = check_zero_holes(st_ops->value_type, value);
+	err = check_zero_holes(st_ops->btf, st_ops->value_type, value);
 	if (err)
 		return err;
 
 	uvalue = value;
-	err = check_zero_holes(t, uvalue->data);
+	err = check_zero_holes(st_ops->btf, t, uvalue->data);
 	if (err)
 		return err;
 
@@ -671,7 +672,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 	struct bpf_map *map;
 	int ret;
 
-	st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id);
+	st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id, btf_vmlinux);
 	if (!st_ops)
 		return ERR_PTR(-ENOTSUPP);
 
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index f93e835d90af..be5144dbb53d 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -241,6 +241,12 @@ struct btf_id_dtor_kfunc_tab {
 	struct btf_id_dtor_kfunc dtors[];
 };
 
+struct btf_struct_ops_tab {
+	u32 cnt;
+	u32 capacity;
+	struct bpf_struct_ops *ops[];
+};
+
 struct btf {
 	void *data;
 	struct btf_type **types;
@@ -258,6 +264,7 @@ struct btf {
 	struct btf_kfunc_set_tab *kfunc_set_tab;
 	struct btf_id_dtor_kfunc_tab *dtor_kfunc_tab;
 	struct btf_struct_metas *struct_meta_tab;
+	struct btf_struct_ops_tab *struct_ops_tab;
 
 	/* split BTF support */
 	struct btf *base_btf;
@@ -1688,11 +1695,20 @@ static void btf_free_struct_meta_tab(struct btf *btf)
 	btf->struct_meta_tab = NULL;
 }
 
+static void btf_free_struct_ops_tab(struct btf *btf)
+{
+	struct btf_struct_ops_tab *tab = btf->struct_ops_tab;
+
+	kfree(tab);
+	btf->struct_ops_tab = NULL;
+}
+
 static void btf_free(struct btf *btf)
 {
 	btf_free_struct_meta_tab(btf);
 	btf_free_dtor_kfunc_tab(btf);
 	btf_free_kfunc_set_tab(btf);
+	btf_free_struct_ops_tab(btf);
 	kvfree(btf->types);
 	kvfree(btf->resolved_sizes);
 	kvfree(btf->resolved_ids);
@@ -8601,3 +8617,57 @@ bool btf_type_ids_nocast_alias(struct bpf_verifier_log *log,
 
 	return !strncmp(reg_name, arg_name, cmp_len);
 }
+
+int btf_add_struct_ops(struct bpf_struct_ops *st_ops)
+{
+	struct btf_struct_ops_tab *tab, *new_tab;
+	struct btf *btf = st_ops->btf;
+	int i;
+
+	if (!btf)
+		return -ENOENT;
+
+	/* Assume this function is called for a module when the module is
+	 * loading.
+	 */
+
+	tab = btf->struct_ops_tab;
+	if (!tab) {
+		tab = kzalloc(offsetof(struct btf_struct_ops_tab, ops[4]),
+			      GFP_KERNEL);
+		if (!tab)
+			return -ENOMEM;
+		tab->capacity = 4;
+		btf->struct_ops_tab = tab;
+	}
+
+	for (i = 0; i < tab->cnt; i++)
+		if (tab->ops[i] == st_ops)
+			return -EEXIST;
+
+	if (tab->cnt == tab->capacity) {
+		new_tab = krealloc(tab, sizeof(*tab) +
+				   sizeof(struct bpf_struct_ops *) *
+				   tab->capacity * 2, GFP_KERNEL);
+		if (!new_tab)
+			return -ENOMEM;
+		tab = new_tab;
+		tab->capacity *= 2;
+		btf->struct_ops_tab = tab;
+	}
+
+	btf->struct_ops_tab->ops[btf->struct_ops_tab->cnt++] = st_ops;
+
+	return 0;
+}
+
+const struct bpf_struct_ops **btf_get_struct_ops(struct btf *btf, u32 *ret_cnt)
+{
+	if (!btf)
+		return NULL;
+	if (!btf->struct_ops_tab)
+		return NULL;
+
+	*ret_cnt = btf->struct_ops_tab->cnt;
+	return (const struct bpf_struct_ops **)btf->struct_ops_tab->ops;
+}
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a7178ecf676d..6564a03c425d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19631,7 +19631,7 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
 	}
 
 	btf_id = prog->aux->attach_btf_id;
-	st_ops = bpf_struct_ops_find(btf_id);
+	st_ops = bpf_struct_ops_find(btf_vmlinux, btf_id);
 	if (!st_ops) {
 		verbose(env, "attach_btf_id %u is not a supported struct\n",
 			btf_id);
-- 
2.34.1