Re: [PATCH bpf-next v5 6/9] bpf, net: switch to dynamic registration

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On 10/17/23 9:23 AM, thinker.li@xxxxxxxxx wrote:
From: Kui-Feng Lee <thinker.li@xxxxxxxxx>

Replace the static list of struct_ops types with pre-btf struct_ops_tab to
enable dynamic registration.

Both bpf_dummy_ops and bpf_tcp_ca now utilize the registration function
instead of being listed in bpf_struct_ops_types.h.

Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
  include/linux/bpf.h               |   2 +
  include/linux/btf.h               |  29 +++++++
  kernel/bpf/bpf_struct_ops.c       | 124 +++++++++++++++---------------
  kernel/bpf/bpf_struct_ops_types.h |  12 ---
  kernel/bpf/btf.c                  |   2 +-
  net/bpf/bpf_dummy_struct_ops.c    |  14 +++-
  net/ipv4/bpf_tcp_ca.c             |  16 +++-
  7 files changed, 119 insertions(+), 80 deletions(-)
  delete mode 100644 kernel/bpf/bpf_struct_ops_types.h

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1e1647c8b0ce..b0f33147aa93 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -3207,4 +3207,6 @@ static inline bool bpf_is_subprog(const struct bpf_prog *prog)
  	return prog->aux->func_idx != 0;
  }
+int register_bpf_struct_ops(struct bpf_struct_ops *st_ops);
+
  #endif /* _LINUX_BPF_H */
diff --git a/include/linux/btf.h b/include/linux/btf.h
index aa2ba77648be..fdc83aa10462 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,
@@ -577,4 +580,30 @@ 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,
+};
+
+struct bpf_struct_ops_common_value {
+	refcount_t refcnt;
+	enum bpf_struct_ops_state state;
+};
+#define BPF_STRUCT_OPS_COMMON_VALUE struct bpf_struct_ops_common_value common

Since there is 'struct bpf_struct_ops_common_value' now, the BPF_STRUCT_OPS_COMMON_VALUE macro is not as useful as before. Lets remove it.

+
+/* 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;		\
+}

I think the bpp_struct_ops_* should not be in btf.h. Probably move them to bpf.h instead. or there is some other considerations I am missing?

+
  #endif
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 60445ff32275..175068b083cb 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -13,19 +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,
-};
-
-struct bpf_struct_ops_common_value {
-	refcount_t refcnt;
-	enum bpf_struct_ops_state state;
-};
-#define BPF_STRUCT_OPS_COMMON_VALUE struct bpf_struct_ops_common_value common
-
  struct bpf_struct_ops_value {
  	BPF_STRUCT_OPS_COMMON_VALUE;
  	char data[] ____cacheline_aligned_in_smp;
@@ -72,35 +59,6 @@ static DEFINE_MUTEX(update_mutex);
  #define VALUE_PREFIX "bpf_struct_ops_"
  #define VALUE_PREFIX_LEN (sizeof(VALUE_PREFIX) - 1)
-/* 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 BPF_STRUCT_OPS_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;		\
-};
-#include "bpf_struct_ops_types.h"
-#undef BPF_STRUCT_OPS_TYPE
-
-enum {
-#define BPF_STRUCT_OPS_TYPE(_name) BPF_STRUCT_OPS_TYPE_##_name,
-#include "bpf_struct_ops_types.h"
-#undef BPF_STRUCT_OPS_TYPE
-	__NR_BPF_STRUCT_OPS_TYPE,
-};
-
-static struct bpf_struct_ops * const bpf_struct_ops[] = {
-#define BPF_STRUCT_OPS_TYPE(_name)				\
-	[BPF_STRUCT_OPS_TYPE_##_name] = &bpf_##_name,
-#include "bpf_struct_ops_types.h"
-#undef BPF_STRUCT_OPS_TYPE
-};
-
  const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {
  };
@@ -234,16 +192,51 @@ static void bpf_struct_ops_init_one(struct bpf_struct_ops *st_ops, } +static int register_bpf_struct_ops_btf(struct bpf_struct_ops *st_ops,
+				       struct btf *btf)

Please combine this function into register_bpf_struct_ops(). They are both very short.

+{
+	struct bpf_verifier_log *log;
+	int err;
+
+	if (st_ops == NULL)
+		return -EINVAL;
+
+	log = kzalloc(sizeof(*log), GFP_KERNEL | __GFP_NOWARN);
+	if (!log) {
+		err = -ENOMEM;
+		goto errout;
+	}
+
+	log->level = BPF_LOG_KERNEL;
+
+	bpf_struct_ops_init_one(st_ops, btf, st_ops->owner, log);
+
+	err = btf_add_struct_ops(st_ops);
+
+errout:
+	kfree(log);
+
+	return err;
+}
+
+int register_bpf_struct_ops(struct bpf_struct_ops *st_ops)

Similar to the register kfunc counterpart, can this be moved to btf.c instead by extern-ing bpf_struct_ops_init_one()? or there are some other structs/functions need to extern?

+{
+	struct btf *btf;
+	int err;
+
+	btf = btf_get_module_btf(st_ops->owner);
+	if (!btf)
+		return -EINVAL;
+	err = register_bpf_struct_ops_btf(st_ops, btf);
+	btf_put(btf);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(register_bpf_struct_ops);
+
  void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)

The bpf_struct_ops_init() is pretty much only finding the btf "module_id" and "common_value_id". Lets use the BTF_ID_LIST to do it instead. Then the newly added bpf_struct_ops_init_one() could use a proper name bpf_struct_ops_init() instead of having the special "_one" suffix.

  {
-	struct bpf_struct_ops *st_ops;
  	s32 module_id, common_value_id;
-	u32 i;
-
-	/* Ensure BTF type is emitted for "struct bpf_struct_ops_##_name" */
-#define BPF_STRUCT_OPS_TYPE(_name) BTF_TYPE_EMIT(struct bpf_struct_ops_##_name);
-#include "bpf_struct_ops_types.h"
-#undef BPF_STRUCT_OPS_TYPE
module_id = btf_find_by_name_kind(btf, "module", BTF_KIND_STRUCT);
  	if (module_id < 0) {
@@ -259,11 +252,6 @@ void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
  		return;
  	}
  	common_value_type = btf_type_by_id(btf, common_value_id);
-
-	for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
-		st_ops = bpf_struct_ops[i];
-		bpf_struct_ops_init_one(st_ops, btf, NULL, log);
-	}
  }
extern struct btf *btf_vmlinux;
@@ -271,32 +259,44 @@ extern struct btf *btf_vmlinux;
  static const struct bpf_struct_ops *
  bpf_struct_ops_find_value(struct btf *btf, u32 value_id)
  {
+	const struct bpf_struct_ops *st_ops = NULL;
+	const struct bpf_struct_ops **st_ops_list;
  	unsigned int i;
+	u32 cnt = 0;
if (!value_id || !btf_vmlinux)

The "!btf_vmlinux" should have been changed to "!btf" in the earlier patch (patch 2?),

and is this null check still needed now?

  		return NULL;
- for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
-		if (bpf_struct_ops[i]->value_id == value_id)
-			return bpf_struct_ops[i];
+	st_ops_list = btf_get_struct_ops(btf, &cnt);
+	for (i = 0; i < cnt; i++) {
+		if (st_ops_list[i]->value_id == value_id) {
+			st_ops = st_ops_list[i];

nit. Like the change in the earlier patch that is being replaced here,
directly "return st_ops_list[i];".

+			break;
+		}
  	}
- return NULL;
+	return st_ops;
  }
const struct bpf_struct_ops *bpf_struct_ops_find(struct btf *btf, u32 type_id)
  {
+	const struct bpf_struct_ops *st_ops = NULL;
+	const struct bpf_struct_ops **st_ops_list;
  	unsigned int i;
+	u32 cnt;
if (!type_id || !btf_vmlinux)
  		return NULL;
- for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
-		if (bpf_struct_ops[i]->type_id == type_id)
-			return bpf_struct_ops[i];
+	st_ops_list = btf_get_struct_ops(btf, &cnt);
+	for (i = 0; i < cnt; i++) {
+		if (st_ops_list[i]->type_id == type_id) {
+			st_ops = st_ops_list[i];

Same.

+			break;
+		}
  	}
- return NULL;
+	return st_ops;
  }
static int bpf_struct_ops_map_get_next_key(struct bpf_map *map, void *key,
diff --git a/kernel/bpf/bpf_struct_ops_types.h b/kernel/bpf/bpf_struct_ops_types.h
deleted file mode 100644
index 5678a9ddf817..000000000000
--- a/kernel/bpf/bpf_struct_ops_types.h
+++ /dev/null
@@ -1,12 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/* internal file - do not include directly */
-
-#ifdef CONFIG_BPF_JIT
-#ifdef CONFIG_NET
-BPF_STRUCT_OPS_TYPE(bpf_dummy_ops)
-#endif
-#ifdef CONFIG_INET
-#include <net/tcp.h>
-BPF_STRUCT_OPS_TYPE(tcp_congestion_ops)
-#endif
-#endif

Seeing this gone is satisfying.

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index be5144dbb53d..990973d6057d 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;
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
index 5918d1b32e19..724bb7224079 100644
--- a/net/bpf/bpf_dummy_struct_ops.c
+++ b/net/bpf/bpf_dummy_struct_ops.c
@@ -7,7 +7,7 @@
  #include <linux/bpf.h>
  #include <linux/btf.h>
-extern struct bpf_struct_ops bpf_bpf_dummy_ops;
+static struct bpf_struct_ops bpf_bpf_dummy_ops;

Is it still needed ?







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