[PATCH bpf-next v3 03/15] bpf: Add bpf_struct_ops accessor helpers

[Amery Hung <ameryhung@gmail.com>]

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

Add the helper functions bpf_struct_ops_map_kdata() and
bpf_struct_ops_map_cfi_stubs() in bpf_struct_ops.c. They will be called
from cgroup.c in the upcoming patch to create a struct_ops to cgroup
attachment link.

bpf_struct_ops_valid_to_reg() is also exposed for the upcoming caller
in cgroup.c.

The link update validation is also refactored into a new function
bpf_struct_ops_link_update_check() such that it can be reused by the
caller in cgroup.c in the upcoming patch.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
 include/linux/bpf.h         | 28 ++++++++++++++++++++
 kernel/bpf/bpf_struct_ops.c | 53 +++++++++++++++++++++++++++----------
 2 files changed, 67 insertions(+), 14 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7ac8873839f4..047ffc029666 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2252,6 +2252,12 @@ u32 bpf_struct_ops_id(const void *kdata);
 int bpf_struct_ops_for_each_prog(const void *kdata,
 				 int (*cb)(struct bpf_prog *prog, void *data),
 				 void *data);
+void *bpf_struct_ops_map_kdata(struct bpf_map *map);
+u32 bpf_struct_ops_kdata_map_id(void *kdata);
+void *bpf_struct_ops_map_cfi_stubs(struct bpf_map *map);
+bool bpf_struct_ops_valid_to_reg(struct bpf_map *map);
+int bpf_struct_ops_link_update_check(struct bpf_map *new_map, struct bpf_map *old_map,
+				     struct bpf_map *expected_old_map);
 
 #ifdef CONFIG_NET
 /* Define it here to avoid the use of forward declaration */
@@ -2316,6 +2322,28 @@ static inline void bpf_map_struct_ops_info_fill(struct bpf_map_info *info, struc
 static inline void bpf_struct_ops_desc_release(struct bpf_struct_ops_desc *st_ops_desc)
 {
 }
+static inline void *bpf_struct_ops_map_kdata(struct bpf_map *map)
+{
+	return NULL;
+}
+static inline u32 bpf_struct_ops_kdata_map_id(void *kdata)
+{
+	return 0;
+}
+static inline void *bpf_struct_ops_map_cfi_stubs(struct bpf_map *map)
+{
+	return NULL;
+}
+static inline bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
+{
+	return false;
+}
+static inline int bpf_struct_ops_link_update_check(struct bpf_map *new_map,
+						   struct bpf_map *old_map,
+						   struct bpf_map *expected_old_map)
+{
+	return -EOPNOTSUPP;
+}
 
 #endif
 
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index c422ce41873e..3d650a7e9f68 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -1236,7 +1236,23 @@ int bpf_struct_ops_for_each_prog(const void *kdata,
 }
 EXPORT_SYMBOL_GPL(bpf_struct_ops_for_each_prog);
 
-static bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
+void *bpf_struct_ops_map_kdata(struct bpf_map *map)
+{
+	struct bpf_struct_ops_map *st_map;
+
+	st_map = container_of(map, struct bpf_struct_ops_map, map);
+	return st_map->kvalue.data;
+}
+
+void *bpf_struct_ops_map_cfi_stubs(struct bpf_map *map)
+{
+	struct bpf_struct_ops_map *st_map;
+
+	st_map = container_of(map, struct bpf_struct_ops_map, map);
+	return st_map->st_ops_desc->st_ops->cfi_stubs;
+}
+
+bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)
 {
 	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;
 
@@ -1289,6 +1305,26 @@ static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
 	return 0;
 }
 
+int bpf_struct_ops_link_update_check(struct bpf_map *new_map,
+				     struct bpf_map *old_map,
+				     struct bpf_map *expected_old_map)
+{
+	struct bpf_struct_ops_map *st_map, *old_st_map;
+
+	if (!old_map)
+		return -ENOLINK;
+	if (expected_old_map && old_map != expected_old_map)
+		return -EPERM;
+
+	st_map = container_of(new_map, struct bpf_struct_ops_map, map);
+	old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
+	/* The new and old struct_ops must be the same type. */
+	if (st_map->st_ops_desc != old_st_map->st_ops_desc)
+		return -EINVAL;
+
+	return 0;
+}
+
 static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map,
 					  struct bpf_map *expected_old_map)
 {
@@ -1307,23 +1343,12 @@ static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map
 		return -EOPNOTSUPP;
 
 	mutex_lock(&update_mutex);
-
 	old_map = st_link->map;
-	if (!old_map) {
-		err = -ENOLINK;
-		goto err_out;
-	}
-	if (expected_old_map && old_map != expected_old_map) {
-		err = -EPERM;
+	err = bpf_struct_ops_link_update_check(new_map, old_map, expected_old_map);
+	if (err)
 		goto err_out;
-	}
 
 	old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
-	/* The new and old struct_ops must be the same type. */
-	if (st_map->st_ops_desc != old_st_map->st_ops_desc) {
-		err = -EINVAL;
-		goto err_out;
-	}
 
 	err = st_map->st_ops_desc->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data, link);
 	if (err)
-- 
2.52.0