[PATCH bpf-next v11 10/13] bpf, net: switch to dynamic registration

thinker.li
2023-11-06T20:13:19Z

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

Replace the static list of struct_ops types with per-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@vger.kernel.org
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
---
include/linux/bpf.h | 24 +++++++--
include/linux/btf.h | 2 +
kernel/bpf/bpf_struct_ops.c | 90 ++++++++++---------------------
kernel/bpf/bpf_struct_ops_types.h | 12 -----
kernel/bpf/btf.c | 40 ++++++++++++--
net/bpf/bpf_dummy_struct_ops.c | 14 ++++-
net/ipv4/bpf_tcp_ca.c | 16 ++++--
7 files changed, 109 insertions(+), 89 deletions(-)
delete mode 100644 kernel/bpf/bpf_struct_ops_types.h

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 48e97a255945..432c088d4001 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1643,7 +1643,6 @@ struct bpf_struct_ops_desc {
#if defined(CONFIG_BPF_JIT) && defined(CONFIG_BPF_SYSCALL)
#define BPF_MODULE_OWNER ((void *)((0xeB9FUL << 2) + POISON_POINTER_DELTA))
const struct bpf_struct_ops_desc *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);
int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
@@ -1689,10 +1688,6 @@ static inline const struct bpf_struct_ops_desc *bpf_struct_ops_find(struct btf *
{
return NULL;
}
-static inline void bpf_struct_ops_init(struct btf *btf,
- struct bpf_verifier_log *log)
-{
-}
static inline bool bpf_try_module_get(const void *data, struct module *owner)
{
return try_module_get(owner);
@@ -3232,6 +3227,8 @@ static inline bool bpf_is_subprog(const struct bpf_prog *prog)
}

#ifdef CONFIG_BPF_JIT
+int register_bpf_struct_ops(struct bpf_struct_ops *st_ops);
+
enum bpf_struct_ops_state {
BPF_STRUCT_OPS_STATE_INIT,
BPF_STRUCT_OPS_STATE_INUSE,
@@ -3243,6 +3240,23 @@ struct 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 { \
+ struct bpf_struct_ops_common_value common; \
+ struct _name data ____cacheline_aligned_in_smp; \
+}
+
+extern int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
+ struct btf *btf,
+ struct bpf_verifier_log *log);
#endif /* CONFIG_BPF_JIT */

#endif /* _LINUX_BPF_H */
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 07ee6740e06a..d6fd6c20b3e2 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 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 */
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 2d853431bf09..caacc251655a 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -61,35 +61,6 @@ 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 { \
- struct bpf_struct_ops_common_value common; \
- 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_desc bpf_struct_ops[] = {
-#define BPF_STRUCT_OPS_TYPE(_name) \
- [BPF_STRUCT_OPS_TYPE_##_name] = { .st_ops = &bpf_##_name },
-#include "bpf_struct_ops_types.h"
-#undef BPF_STRUCT_OPS_TYPE
-};
-
const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {
};

@@ -144,9 +115,9 @@ static bool is_valid_value_type(struct btf *btf, s32 value_id,
return true;
}

-static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
- struct btf *btf,
- struct bpf_verifier_log *log)
+int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
+ struct btf *btf,
+ struct bpf_verifier_log *log)
{
struct bpf_struct_ops *st_ops = st_ops_desc->st_ops;
const struct btf_member *member;
@@ -160,7 +131,7 @@ static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
sizeof(value_name)) {
pr_warn("struct_ops name %s is too long\n",
st_ops->name);
- return;
+ return -EINVAL;
}
sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);

@@ -169,13 +140,13 @@ static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
if (type_id < 0) {
pr_warn("Cannot find struct %s in btf_vmlinux\n",
st_ops->name);
- return;
+ return -EINVAL;
}
t = btf_type_by_id(btf, type_id);
if (btf_type_vlen(t) > BPF_STRUCT_OPS_MAX_NR_MEMBERS) {
pr_warn("Cannot support #%u members in struct %s\n",
btf_type_vlen(t), st_ops->name);
- return;
+ return -EINVAL;
}

value_id = btf_find_by_name_kind(btf, value_name,
@@ -183,10 +154,10 @@ static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
if (value_id < 0) {
pr_warn("Cannot find struct %s in btf_vmlinux\n",
value_name);
- return;
+ return -EINVAL;
}
if (!is_valid_value_type(btf, value_id, t, value_name))
- return;
+ return -EINVAL;

for_each_member(i, t, member) {
const struct btf_type *func_proto;
@@ -195,13 +166,13 @@ static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
if (!*mname) {
pr_warn("anon member in struct %s is not supported\n",
st_ops->name);
- break;
+ return -EOPNOTSUPP;
}

if (__btf_member_bitfield_size(t, member)) {
pr_warn("bit field member %s in struct %s is not supported\n",
mname, st_ops->name);
- break;
+ return -EOPNOTSUPP;
}

func_proto = btf_type_resolve_func_ptr(btf,
@@ -213,7 +184,7 @@ static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
&st_ops->func_models[i])) {
pr_warn("Error in parsing func ptr %s in struct %s\n",
mname, st_ops->name);
- break;
+ return -EINVAL;
}
}

@@ -221,6 +192,7 @@ static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
if (st_ops->init(btf)) {
pr_warn("Error in init bpf_struct_ops %s\n",
st_ops->name);
+ return -EINVAL;
} else {
st_ops_desc->type_id = type_id;
st_ops_desc->type = t;
@@ -229,35 +201,24 @@ static void bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
value_id);
}
}
-}

-void bpf_struct_ops_init(struct btf *btf, struct bpf_verifier_log *log)
-{
- struct bpf_struct_ops_desc *st_ops_desc;
- 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
-
- for (i = 0; i < ARRAY_SIZE(bpf_struct_ops); i++) {
- st_ops_desc = &bpf_struct_ops[i];
- bpf_struct_ops_desc_init(st_ops_desc, btf, log);
- }
+ return 0;
}

static const struct bpf_struct_ops_desc *
bpf_struct_ops_find_value(struct btf *btf, u32 value_id)
{
+ const struct bpf_struct_ops_desc *st_ops_list;
unsigned int i;
+ u32 cnt = 0;

- if (!value_id || !btf)
+ if (!value_id)
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)
+ return &st_ops_list[i];
}

return NULL;
@@ -266,14 +227,17 @@ bpf_struct_ops_find_value(struct btf *btf, u32 value_id)
const struct bpf_struct_ops_desc *
bpf_struct_ops_find(struct btf *btf, u32 type_id)
{
+ const struct bpf_struct_ops_desc *st_ops_list;
unsigned int i;
+ u32 cnt;

- if (!type_id || !btf)
+ if (!type_id)
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)
+ return &st_ops_list[i];
}

return NULL;
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
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 263715af10cb..7165a1beeed5 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -19,6 +19,7 @@
#include <linux/bpf_verifier.h>
#include <linux/btf.h>
#include <linux/btf_ids.h>
+#include <linux/bpf.h>
#include <linux/bpf_lsm.h>
#include <linux/skmsg.h>
#include <linux/perf_event.h>
@@ -5796,8 +5797,6 @@ struct btf *btf_parse_vmlinux(void)
/* btf_parse_vmlinux() runs under bpf_verifier_lock */
bpf_ctx_convert.t = btf_type_by_id(btf, bpf_ctx_convert_btf_id[0]);

- bpf_struct_ops_init(btf, log);
-
refcount_set(&btf->refcnt, 1);

err = btf_alloc_id(btf);
@@ -8628,10 +8627,11 @@ bool btf_type_ids_nocast_alias(struct bpf_verifier_log *log,
#ifdef CONFIG_BPF_JIT

static int
-btf_add_struct_ops(struct btf *btf, struct bpf_struct_ops *st_ops)
+btf_add_struct_ops(struct btf *btf, struct bpf_struct_ops *st_ops,
+ struct bpf_verifier_log *log)
{
struct btf_struct_ops_tab *tab, *new_tab;
- int i;
+ int i, err;

if (!btf)
return -ENOENT;
@@ -8668,6 +8668,10 @@ btf_add_struct_ops(struct btf *btf, struct bpf_struct_ops *st_ops)

tab->ops[btf->struct_ops_tab->cnt].st_ops = st_ops;

+ err = bpf_struct_ops_desc_init(&tab->ops[btf->struct_ops_tab->cnt], btf, log);
+ if (err)
+ return err;
+
btf->struct_ops_tab->cnt++;

return 0;
@@ -8684,4 +8688,32 @@ const struct bpf_struct_ops_desc *btf_get_struct_ops(struct btf *btf, u32 *ret_c
return (const struct bpf_struct_ops_desc *)btf->struct_ops_tab->ops;
}

+int register_bpf_struct_ops(struct bpf_struct_ops *st_ops)
+{
+ struct bpf_verifier_log *log;
+ struct btf *btf;
+ int err = 0;
+
+ btf = btf_get_module_btf(st_ops->owner);
+ if (!btf)
+ return -EINVAL;
+
+ log = kzalloc(sizeof(*log), GFP_KERNEL | __GFP_NOWARN);
+ if (!log) {
+ err = -ENOMEM;
+ goto errout;
+ }
+
+ log->level = BPF_LOG_KERNEL;
+
+ err = btf_add_struct_ops(btf, st_ops, log);
+
+errout:
+ kfree(log);
+ btf_put(btf);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(register_bpf_struct_ops);
+
#endif /* CONFIG_BPF_JIT */
diff --git a/net/bpf/bpf_dummy_struct_ops.c b/net/bpf/bpf_dummy_struct_ops.c
index ffa224053a6c..148a5851c4fa 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;

/* A common type for test_N with return value in bpf_dummy_ops */
typedef int (*dummy_ops_test_ret_fn)(struct bpf_dummy_ops_state *state, ...);
@@ -223,11 +223,13 @@ static int bpf_dummy_reg(void *kdata)
return -EOPNOTSUPP;
}

+DEFINE_STRUCT_OPS_VALUE_TYPE(bpf_dummy_ops);
+
static void bpf_dummy_unreg(void *kdata)
{
}

-struct bpf_struct_ops bpf_bpf_dummy_ops = {
+static struct bpf_struct_ops bpf_bpf_dummy_ops = {
.verifier_ops = &bpf_dummy_verifier_ops,
.init = bpf_dummy_init,
.check_member = bpf_dummy_ops_check_member,
@@ -235,4 +237,12 @@ struct bpf_struct_ops bpf_bpf_dummy_ops = {
.reg = bpf_dummy_reg,
.unreg = bpf_dummy_unreg,
.name = "bpf_dummy_ops",
+ .owner = THIS_MODULE,
};
+
+static int __init bpf_dummy_struct_ops_init(void)
+{
+ BTF_STRUCT_OPS_TYPE_EMIT(bpf_dummy_ops);
+ return register_bpf_struct_ops(&bpf_bpf_dummy_ops);
+}
+late_initcall(bpf_dummy_struct_ops_init);
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 3c8b76578a2a..b36a19274e5b 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -12,7 +12,7 @@
#include <net/bpf_sk_storage.h>

/* "extern" is to avoid sparse warning. It is only used in bpf_struct_ops.c. */
-extern struct bpf_struct_ops bpf_tcp_congestion_ops;
+static struct bpf_struct_ops bpf_tcp_congestion_ops;

static u32 unsupported_ops[] = {
offsetof(struct tcp_congestion_ops, get_info),
@@ -277,7 +277,9 @@ static int bpf_tcp_ca_validate(void *kdata)
return tcp_validate_congestion_control(kdata);
}

-struct bpf_struct_ops bpf_tcp_congestion_ops = {
+DEFINE_STRUCT_OPS_VALUE_TYPE(tcp_congestion_ops);
+
+static struct bpf_struct_ops bpf_tcp_congestion_ops = {
.verifier_ops = &bpf_tcp_ca_verifier_ops,
.reg = bpf_tcp_ca_reg,
.unreg = bpf_tcp_ca_unreg,
@@ -287,10 +289,18 @@ struct bpf_struct_ops bpf_tcp_congestion_ops = {
.init = bpf_tcp_ca_init,
.validate = bpf_tcp_ca_validate,
.name = "tcp_congestion_ops",
+ .owner = THIS_MODULE,
};

static int __init bpf_tcp_ca_kfunc_init(void)
{
- return register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_tcp_ca_kfunc_set);
+ int ret;
+
+ BTF_STRUCT_OPS_TYPE_EMIT(tcp_congestion_ops);
+
+ ret = register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &bpf_tcp_ca_kfunc_set);
+ ret = ret ?: register_bpf_struct_ops(&bpf_tcp_congestion_ops);
+
+ return ret;
}
late_initcall(bpf_tcp_ca_kfunc_init);
--
2.34.1