From 41c48f3a98231738c5ce79f6f2aa6e40ba924d18 Mon Sep 17 00:00:00 2001
From: Andrey Ignatov <rdna@fb.com>
Date: Fri, 19 Jun 2020 14:11:43 -0700
Subject: bpf: Support access to bpf map fields

There are multiple use-cases when it's convenient to have access to bpf
map fields, both `struct bpf_map` and map type specific struct-s such as
`struct bpf_array`, `struct bpf_htab`, etc.

For example while working with sock arrays it can be necessary to
calculate the key based on map->max_entries (some_hash % max_entries).
Currently this is solved by communicating max_entries via "out-of-band"
channel, e.g. via additional map with known key to get info about target
map. That works, but is not very convenient and error-prone while
working with many maps.

In other cases necessary data is dynamic (i.e. unknown at loading time)
and it's impossible to get it at all. For example while working with a
hash table it can be convenient to know how much capacity is already
used (bpf_htab.count.counter for BPF_F_NO_PREALLOC case).

At the same time kernel knows this info and can provide it to bpf
program.

Fill this gap by adding support to access bpf map fields from bpf
program for both `struct bpf_map` and map type specific fields.

Support is implemented via btf_struct_access() so that a user can define
their own `struct bpf_map` or map type specific struct in their program
with only necessary fields and preserve_access_index attribute, cast a
map to this struct and use a field.

For example:

	struct bpf_map {
		__u32 max_entries;
	} __attribute__((preserve_access_index));

	struct bpf_array {
		struct bpf_map map;
		__u32 elem_size;
	} __attribute__((preserve_access_index));

	struct {
		__uint(type, BPF_MAP_TYPE_ARRAY);
		__uint(max_entries, 4);
		__type(key, __u32);
		__type(value, __u32);
	} m_array SEC(".maps");

	SEC("cgroup_skb/egress")
	int cg_skb(void *ctx)
	{
		struct bpf_array *array = (struct bpf_array *)&m_array;
		struct bpf_map *map = (struct bpf_map *)&m_array;

		/* .. use map->max_entries or array->map.max_entries .. */
	}

Similarly to other btf_struct_access() use-cases (e.g. struct tcp_sock
in net/ipv4/bpf_tcp_ca.c) the patch allows access to any fields of
corresponding struct. Only reading from map fields is supported.

For btf_struct_access() to work there should be a way to know btf id of
a struct that corresponds to a map type. To get btf id there should be a
way to get a stringified name of map-specific struct, such as
"bpf_array", "bpf_htab", etc for a map type. Two new fields are added to
`struct bpf_map_ops` to handle it:
* .map_btf_name keeps a btf name of a struct returned by map_alloc();
* .map_btf_id is used to cache btf id of that struct.

To make btf ids calculation cheaper they're calculated once while
preparing btf_vmlinux and cached same way as it's done for btf_id field
of `struct bpf_func_proto`

While calculating btf ids, struct names are NOT checked for collision.
Collisions will be checked as a part of the work to prepare btf ids used
in verifier in compile time that should land soon. The only known
collision for `struct bpf_htab` (kernel/bpf/hashtab.c vs
net/core/sock_map.c) was fixed earlier.

Both new fields .map_btf_name and .map_btf_id must be set for a map type
for the feature to work. If neither is set for a map type, verifier will
return ENOTSUPP on a try to access map_ptr of corresponding type. If
just one of them set, it's verifier misconfiguration.

Only `struct bpf_array` for BPF_MAP_TYPE_ARRAY and `struct bpf_htab` for
BPF_MAP_TYPE_HASH are supported by this patch. Other map types will be
supported separately.

The feature is available only for CONFIG_DEBUG_INFO_BTF=y and gated by
perfmon_capable() so that unpriv programs won't have access to bpf map
fields.

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/6479686a0cd1e9067993df57b4c3eef0e276fec9.1592600985.git.rdna@fb.com
---
 kernel/bpf/arraymap.c | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'kernel/bpf/arraymap.c')

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 11584618e861..e7caa48812fb 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -494,6 +494,7 @@ static int array_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
 				   vma->vm_pgoff + pgoff);
 }
 
+static int array_map_btf_id;
 const struct bpf_map_ops array_map_ops = {
 	.map_alloc_check = array_map_alloc_check,
 	.map_alloc = array_map_alloc,
@@ -510,6 +511,8 @@ const struct bpf_map_ops array_map_ops = {
 	.map_check_btf = array_map_check_btf,
 	.map_lookup_batch = generic_map_lookup_batch,
 	.map_update_batch = generic_map_update_batch,
+	.map_btf_name = "bpf_array",
+	.map_btf_id = &array_map_btf_id,
 };
 
 const struct bpf_map_ops percpu_array_map_ops = {
-- 
cgit v1.2.3-70-g09d2


From 2872e9ac33a4440173418147351ed4f93177e763 Mon Sep 17 00:00:00 2001
From: Andrey Ignatov <rdna@fb.com>
Date: Fri, 19 Jun 2020 14:11:44 -0700
Subject: bpf: Set map_btf_{name, id} for all map types

Set map_btf_name and map_btf_id for all map types so that map fields can
be accessed by bpf programs.

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/a825f808f22af52b018dbe82f1c7d29dab5fc978.1592600985.git.rdna@fb.com
---
 kernel/bpf/arraymap.c         | 15 +++++++++++++++
 kernel/bpf/bpf_struct_ops.c   |  3 +++
 kernel/bpf/cpumap.c           |  3 +++
 kernel/bpf/devmap.c           |  6 ++++++
 kernel/bpf/hashtab.c          | 12 ++++++++++++
 kernel/bpf/local_storage.c    |  3 +++
 kernel/bpf/lpm_trie.c         |  3 +++
 kernel/bpf/queue_stack_maps.c |  6 ++++++
 kernel/bpf/reuseport_array.c  |  3 +++
 kernel/bpf/ringbuf.c          |  3 +++
 kernel/bpf/stackmap.c         |  3 +++
 net/core/bpf_sk_storage.c     |  3 +++
 net/core/sock_map.c           |  6 ++++++
 net/xdp/xskmap.c              |  3 +++
 14 files changed, 72 insertions(+)

(limited to 'kernel/bpf/arraymap.c')

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index e7caa48812fb..ec5cd11032aa 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -515,6 +515,7 @@ const struct bpf_map_ops array_map_ops = {
 	.map_btf_id = &array_map_btf_id,
 };
 
+static int percpu_array_map_btf_id;
 const struct bpf_map_ops percpu_array_map_ops = {
 	.map_alloc_check = array_map_alloc_check,
 	.map_alloc = array_map_alloc,
@@ -525,6 +526,8 @@ const struct bpf_map_ops percpu_array_map_ops = {
 	.map_delete_elem = array_map_delete_elem,
 	.map_seq_show_elem = percpu_array_map_seq_show_elem,
 	.map_check_btf = array_map_check_btf,
+	.map_btf_name = "bpf_array",
+	.map_btf_id = &percpu_array_map_btf_id,
 };
 
 static int fd_array_map_alloc_check(union bpf_attr *attr)
@@ -871,6 +874,7 @@ static void prog_array_map_free(struct bpf_map *map)
 	fd_array_map_free(map);
 }
 
+static int prog_array_map_btf_id;
 const struct bpf_map_ops prog_array_map_ops = {
 	.map_alloc_check = fd_array_map_alloc_check,
 	.map_alloc = prog_array_map_alloc,
@@ -886,6 +890,8 @@ const struct bpf_map_ops prog_array_map_ops = {
 	.map_fd_sys_lookup_elem = prog_fd_array_sys_lookup_elem,
 	.map_release_uref = prog_array_map_clear,
 	.map_seq_show_elem = prog_array_map_seq_show_elem,
+	.map_btf_name = "bpf_array",
+	.map_btf_id = &prog_array_map_btf_id,
 };
 
 static struct bpf_event_entry *bpf_event_entry_gen(struct file *perf_file,
@@ -964,6 +970,7 @@ static void perf_event_fd_array_release(struct bpf_map *map,
 	rcu_read_unlock();
 }
 
+static int perf_event_array_map_btf_id;
 const struct bpf_map_ops perf_event_array_map_ops = {
 	.map_alloc_check = fd_array_map_alloc_check,
 	.map_alloc = array_map_alloc,
@@ -975,6 +982,8 @@ const struct bpf_map_ops perf_event_array_map_ops = {
 	.map_fd_put_ptr = perf_event_fd_array_put_ptr,
 	.map_release = perf_event_fd_array_release,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "bpf_array",
+	.map_btf_id = &perf_event_array_map_btf_id,
 };
 
 #ifdef CONFIG_CGROUPS
@@ -997,6 +1006,7 @@ static void cgroup_fd_array_free(struct bpf_map *map)
 	fd_array_map_free(map);
 }
 
+static int cgroup_array_map_btf_id;
 const struct bpf_map_ops cgroup_array_map_ops = {
 	.map_alloc_check = fd_array_map_alloc_check,
 	.map_alloc = array_map_alloc,
@@ -1007,6 +1017,8 @@ const struct bpf_map_ops cgroup_array_map_ops = {
 	.map_fd_get_ptr = cgroup_fd_array_get_ptr,
 	.map_fd_put_ptr = cgroup_fd_array_put_ptr,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "bpf_array",
+	.map_btf_id = &cgroup_array_map_btf_id,
 };
 #endif
 
@@ -1080,6 +1092,7 @@ static u32 array_of_map_gen_lookup(struct bpf_map *map,
 	return insn - insn_buf;
 }
 
+static int array_of_maps_map_btf_id;
 const struct bpf_map_ops array_of_maps_map_ops = {
 	.map_alloc_check = fd_array_map_alloc_check,
 	.map_alloc = array_of_map_alloc,
@@ -1092,4 +1105,6 @@ const struct bpf_map_ops array_of_maps_map_ops = {
 	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
 	.map_gen_lookup = array_of_map_gen_lookup,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "bpf_array",
+	.map_btf_id = &array_of_maps_map_btf_id,
 };
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index c6b0decaa46a..969c5d47f81f 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -611,6 +611,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 	return map;
 }
 
+static int bpf_struct_ops_map_btf_id;
 const struct bpf_map_ops bpf_struct_ops_map_ops = {
 	.map_alloc_check = bpf_struct_ops_map_alloc_check,
 	.map_alloc = bpf_struct_ops_map_alloc,
@@ -620,6 +621,8 @@ const struct bpf_map_ops bpf_struct_ops_map_ops = {
 	.map_delete_elem = bpf_struct_ops_map_delete_elem,
 	.map_update_elem = bpf_struct_ops_map_update_elem,
 	.map_seq_show_elem = bpf_struct_ops_map_seq_show_elem,
+	.map_btf_name = "bpf_struct_ops_map",
+	.map_btf_id = &bpf_struct_ops_map_btf_id,
 };
 
 /* "const void *" because some subsystem is
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 27595fc6da56..bd8658055c16 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -543,6 +543,7 @@ static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 	return 0;
 }
 
+static int cpu_map_btf_id;
 const struct bpf_map_ops cpu_map_ops = {
 	.map_alloc		= cpu_map_alloc,
 	.map_free		= cpu_map_free,
@@ -551,6 +552,8 @@ const struct bpf_map_ops cpu_map_ops = {
 	.map_lookup_elem	= cpu_map_lookup_elem,
 	.map_get_next_key	= cpu_map_get_next_key,
 	.map_check_btf		= map_check_no_btf,
+	.map_btf_name		= "bpf_cpu_map",
+	.map_btf_id		= &cpu_map_btf_id,
 };
 
 static int bq_flush_to_queue(struct xdp_bulk_queue *bq)
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 0cbb72cdaf63..58acc46861ef 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -747,6 +747,7 @@ static int dev_map_hash_update_elem(struct bpf_map *map, void *key, void *value,
 					 map, key, value, map_flags);
 }
 
+static int dev_map_btf_id;
 const struct bpf_map_ops dev_map_ops = {
 	.map_alloc = dev_map_alloc,
 	.map_free = dev_map_free,
@@ -755,8 +756,11 @@ const struct bpf_map_ops dev_map_ops = {
 	.map_update_elem = dev_map_update_elem,
 	.map_delete_elem = dev_map_delete_elem,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "bpf_dtab",
+	.map_btf_id = &dev_map_btf_id,
 };
 
+static int dev_map_hash_map_btf_id;
 const struct bpf_map_ops dev_map_hash_ops = {
 	.map_alloc = dev_map_alloc,
 	.map_free = dev_map_free,
@@ -765,6 +769,8 @@ const struct bpf_map_ops dev_map_hash_ops = {
 	.map_update_elem = dev_map_hash_update_elem,
 	.map_delete_elem = dev_map_hash_delete_elem,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "bpf_dtab",
+	.map_btf_id = &dev_map_hash_map_btf_id,
 };
 
 static void dev_map_hash_remove_netdev(struct bpf_dtab *dtab,
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 2c5999e02060..acd06081d81d 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1630,6 +1630,7 @@ const struct bpf_map_ops htab_map_ops = {
 	.map_btf_id = &htab_map_btf_id,
 };
 
+static int htab_lru_map_btf_id;
 const struct bpf_map_ops htab_lru_map_ops = {
 	.map_alloc_check = htab_map_alloc_check,
 	.map_alloc = htab_map_alloc,
@@ -1642,6 +1643,8 @@ const struct bpf_map_ops htab_lru_map_ops = {
 	.map_gen_lookup = htab_lru_map_gen_lookup,
 	.map_seq_show_elem = htab_map_seq_show_elem,
 	BATCH_OPS(htab_lru),
+	.map_btf_name = "bpf_htab",
+	.map_btf_id = &htab_lru_map_btf_id,
 };
 
 /* Called from eBPF program */
@@ -1746,6 +1749,7 @@ static void htab_percpu_map_seq_show_elem(struct bpf_map *map, void *key,
 	rcu_read_unlock();
 }
 
+static int htab_percpu_map_btf_id;
 const struct bpf_map_ops htab_percpu_map_ops = {
 	.map_alloc_check = htab_map_alloc_check,
 	.map_alloc = htab_map_alloc,
@@ -1756,8 +1760,11 @@ const struct bpf_map_ops htab_percpu_map_ops = {
 	.map_delete_elem = htab_map_delete_elem,
 	.map_seq_show_elem = htab_percpu_map_seq_show_elem,
 	BATCH_OPS(htab_percpu),
+	.map_btf_name = "bpf_htab",
+	.map_btf_id = &htab_percpu_map_btf_id,
 };
 
+static int htab_lru_percpu_map_btf_id;
 const struct bpf_map_ops htab_lru_percpu_map_ops = {
 	.map_alloc_check = htab_map_alloc_check,
 	.map_alloc = htab_map_alloc,
@@ -1768,6 +1775,8 @@ const struct bpf_map_ops htab_lru_percpu_map_ops = {
 	.map_delete_elem = htab_lru_map_delete_elem,
 	.map_seq_show_elem = htab_percpu_map_seq_show_elem,
 	BATCH_OPS(htab_lru_percpu),
+	.map_btf_name = "bpf_htab",
+	.map_btf_id = &htab_lru_percpu_map_btf_id,
 };
 
 static int fd_htab_map_alloc_check(union bpf_attr *attr)
@@ -1890,6 +1899,7 @@ static void htab_of_map_free(struct bpf_map *map)
 	fd_htab_map_free(map);
 }
 
+static int htab_of_maps_map_btf_id;
 const struct bpf_map_ops htab_of_maps_map_ops = {
 	.map_alloc_check = fd_htab_map_alloc_check,
 	.map_alloc = htab_of_map_alloc,
@@ -1902,4 +1912,6 @@ const struct bpf_map_ops htab_of_maps_map_ops = {
 	.map_fd_sys_lookup_elem = bpf_map_fd_sys_lookup_elem,
 	.map_gen_lookup = htab_of_map_gen_lookup,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "bpf_htab",
+	.map_btf_id = &htab_of_maps_map_btf_id,
 };
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 33d01866bcc2..51bd5a8cb01b 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -409,6 +409,7 @@ static void cgroup_storage_seq_show_elem(struct bpf_map *map, void *_key,
 	rcu_read_unlock();
 }
 
+static int cgroup_storage_map_btf_id;
 const struct bpf_map_ops cgroup_storage_map_ops = {
 	.map_alloc = cgroup_storage_map_alloc,
 	.map_free = cgroup_storage_map_free,
@@ -418,6 +419,8 @@ const struct bpf_map_ops cgroup_storage_map_ops = {
 	.map_delete_elem = cgroup_storage_delete_elem,
 	.map_check_btf = cgroup_storage_check_btf,
 	.map_seq_show_elem = cgroup_storage_seq_show_elem,
+	.map_btf_name = "bpf_cgroup_storage_map",
+	.map_btf_id = &cgroup_storage_map_btf_id,
 };
 
 int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *_map)
diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index c8cc4e4cf98d..1abd4e3f906d 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -735,6 +735,7 @@ static int trie_check_btf(const struct bpf_map *map,
 	       -EINVAL : 0;
 }
 
+static int trie_map_btf_id;
 const struct bpf_map_ops trie_map_ops = {
 	.map_alloc = trie_alloc,
 	.map_free = trie_free,
@@ -743,4 +744,6 @@ const struct bpf_map_ops trie_map_ops = {
 	.map_update_elem = trie_update_elem,
 	.map_delete_elem = trie_delete_elem,
 	.map_check_btf = trie_check_btf,
+	.map_btf_name = "lpm_trie",
+	.map_btf_id = &trie_map_btf_id,
 };
diff --git a/kernel/bpf/queue_stack_maps.c b/kernel/bpf/queue_stack_maps.c
index 05c8e043b9d2..80c66a6d7c54 100644
--- a/kernel/bpf/queue_stack_maps.c
+++ b/kernel/bpf/queue_stack_maps.c
@@ -262,6 +262,7 @@ static int queue_stack_map_get_next_key(struct bpf_map *map, void *key,
 	return -EINVAL;
 }
 
+static int queue_map_btf_id;
 const struct bpf_map_ops queue_map_ops = {
 	.map_alloc_check = queue_stack_map_alloc_check,
 	.map_alloc = queue_stack_map_alloc,
@@ -273,8 +274,11 @@ const struct bpf_map_ops queue_map_ops = {
 	.map_pop_elem = queue_map_pop_elem,
 	.map_peek_elem = queue_map_peek_elem,
 	.map_get_next_key = queue_stack_map_get_next_key,
+	.map_btf_name = "bpf_queue_stack",
+	.map_btf_id = &queue_map_btf_id,
 };
 
+static int stack_map_btf_id;
 const struct bpf_map_ops stack_map_ops = {
 	.map_alloc_check = queue_stack_map_alloc_check,
 	.map_alloc = queue_stack_map_alloc,
@@ -286,4 +290,6 @@ const struct bpf_map_ops stack_map_ops = {
 	.map_pop_elem = stack_map_pop_elem,
 	.map_peek_elem = stack_map_peek_elem,
 	.map_get_next_key = queue_stack_map_get_next_key,
+	.map_btf_name = "bpf_queue_stack",
+	.map_btf_id = &stack_map_btf_id,
 };
diff --git a/kernel/bpf/reuseport_array.c b/kernel/bpf/reuseport_array.c
index 21cde24386db..a09922f656e4 100644
--- a/kernel/bpf/reuseport_array.c
+++ b/kernel/bpf/reuseport_array.c
@@ -345,6 +345,7 @@ static int reuseport_array_get_next_key(struct bpf_map *map, void *key,
 	return 0;
 }
 
+static int reuseport_array_map_btf_id;
 const struct bpf_map_ops reuseport_array_ops = {
 	.map_alloc_check = reuseport_array_alloc_check,
 	.map_alloc = reuseport_array_alloc,
@@ -352,4 +353,6 @@ const struct bpf_map_ops reuseport_array_ops = {
 	.map_lookup_elem = reuseport_array_lookup_elem,
 	.map_get_next_key = reuseport_array_get_next_key,
 	.map_delete_elem = reuseport_array_delete_elem,
+	.map_btf_name = "reuseport_array",
+	.map_btf_id = &reuseport_array_map_btf_id,
 };
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index 180414bb0d3e..dbf37aff4827 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -294,6 +294,7 @@ static __poll_t ringbuf_map_poll(struct bpf_map *map, struct file *filp,
 	return 0;
 }
 
+static int ringbuf_map_btf_id;
 const struct bpf_map_ops ringbuf_map_ops = {
 	.map_alloc = ringbuf_map_alloc,
 	.map_free = ringbuf_map_free,
@@ -303,6 +304,8 @@ const struct bpf_map_ops ringbuf_map_ops = {
 	.map_update_elem = ringbuf_map_update_elem,
 	.map_delete_elem = ringbuf_map_delete_elem,
 	.map_get_next_key = ringbuf_map_get_next_key,
+	.map_btf_name = "bpf_ringbuf_map",
+	.map_btf_id = &ringbuf_map_btf_id,
 };
 
 /* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself,
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 599488f25e40..27dc9b1b08a5 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -613,6 +613,7 @@ static void stack_map_free(struct bpf_map *map)
 	put_callchain_buffers();
 }
 
+static int stack_trace_map_btf_id;
 const struct bpf_map_ops stack_trace_map_ops = {
 	.map_alloc = stack_map_alloc,
 	.map_free = stack_map_free,
@@ -621,6 +622,8 @@ const struct bpf_map_ops stack_trace_map_ops = {
 	.map_update_elem = stack_map_update_elem,
 	.map_delete_elem = stack_map_delete_elem,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "bpf_stack_map",
+	.map_btf_id = &stack_trace_map_btf_id,
 };
 
 static int __init stack_map_init(void)
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 1dae4b543243..6f921c4ddc2c 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -919,6 +919,7 @@ BPF_CALL_2(bpf_sk_storage_delete, struct bpf_map *, map, struct sock *, sk)
 	return -ENOENT;
 }
 
+static int sk_storage_map_btf_id;
 const struct bpf_map_ops sk_storage_map_ops = {
 	.map_alloc_check = bpf_sk_storage_map_alloc_check,
 	.map_alloc = bpf_sk_storage_map_alloc,
@@ -928,6 +929,8 @@ const struct bpf_map_ops sk_storage_map_ops = {
 	.map_update_elem = bpf_fd_sk_storage_update_elem,
 	.map_delete_elem = bpf_fd_sk_storage_delete_elem,
 	.map_check_btf = bpf_sk_storage_map_check_btf,
+	.map_btf_name = "bpf_sk_storage_map",
+	.map_btf_id = &sk_storage_map_btf_id,
 };
 
 const struct bpf_func_proto bpf_sk_storage_get_proto = {
diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 2b884f2d562a..4c1123c749bb 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -643,6 +643,7 @@ const struct bpf_func_proto bpf_msg_redirect_map_proto = {
 	.arg4_type      = ARG_ANYTHING,
 };
 
+static int sock_map_btf_id;
 const struct bpf_map_ops sock_map_ops = {
 	.map_alloc		= sock_map_alloc,
 	.map_free		= sock_map_free,
@@ -653,6 +654,8 @@ const struct bpf_map_ops sock_map_ops = {
 	.map_lookup_elem	= sock_map_lookup,
 	.map_release_uref	= sock_map_release_progs,
 	.map_check_btf		= map_check_no_btf,
+	.map_btf_name		= "bpf_stab",
+	.map_btf_id		= &sock_map_btf_id,
 };
 
 struct bpf_shtab_elem {
@@ -1176,6 +1179,7 @@ const struct bpf_func_proto bpf_msg_redirect_hash_proto = {
 	.arg4_type      = ARG_ANYTHING,
 };
 
+static int sock_hash_map_btf_id;
 const struct bpf_map_ops sock_hash_ops = {
 	.map_alloc		= sock_hash_alloc,
 	.map_free		= sock_hash_free,
@@ -1186,6 +1190,8 @@ const struct bpf_map_ops sock_hash_ops = {
 	.map_lookup_elem_sys_only = sock_hash_lookup_sys,
 	.map_release_uref	= sock_hash_release_progs,
 	.map_check_btf		= map_check_no_btf,
+	.map_btf_name		= "bpf_shtab",
+	.map_btf_id		= &sock_hash_map_btf_id,
 };
 
 static struct sk_psock_progs *sock_map_progs(struct bpf_map *map)
diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
index 1dc7208c71ba..8367adbbe9df 100644
--- a/net/xdp/xskmap.c
+++ b/net/xdp/xskmap.c
@@ -254,6 +254,7 @@ void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
 	spin_unlock_bh(&map->lock);
 }
 
+static int xsk_map_btf_id;
 const struct bpf_map_ops xsk_map_ops = {
 	.map_alloc = xsk_map_alloc,
 	.map_free = xsk_map_free,
@@ -264,4 +265,6 @@ const struct bpf_map_ops xsk_map_ops = {
 	.map_update_elem = xsk_map_update_elem,
 	.map_delete_elem = xsk_map_delete_elem,
 	.map_check_btf = map_check_no_btf,
+	.map_btf_name = "xsk_map",
+	.map_btf_id = &xsk_map_btf_id,
 };
-- 
cgit v1.2.3-70-g09d2


From bba1dc0b55ac462d24ed1228ad49800c238cd6d7 Mon Sep 17 00:00:00 2001
From: Alexei Starovoitov <ast@kernel.org>
Date: Mon, 29 Jun 2020 21:33:39 -0700
Subject: bpf: Remove redundant synchronize_rcu.

bpf_free_used_maps() or close(map_fd) will trigger map_free callback.
bpf_free_used_maps() is called after bpf prog is no longer executing:
bpf_prog_put->call_rcu->bpf_prog_free->bpf_free_used_maps.
Hence there is no need to call synchronize_rcu() to protect map elements.

Note that hash_of_maps and array_of_maps update/delete inner maps via
sys_bpf() that calls maybe_wait_bpf_programs() and synchronize_rcu().

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/bpf/20200630043343.53195-2-alexei.starovoitov@gmail.com
---
 kernel/bpf/arraymap.c         | 9 ---------
 kernel/bpf/hashtab.c          | 8 +++-----
 kernel/bpf/lpm_trie.c         | 5 -----
 kernel/bpf/queue_stack_maps.c | 7 -------
 kernel/bpf/reuseport_array.c  | 2 --
 kernel/bpf/ringbuf.c          | 7 -------
 kernel/bpf/stackmap.c         | 3 ---
 7 files changed, 3 insertions(+), 38 deletions(-)

(limited to 'kernel/bpf/arraymap.c')

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index ec5cd11032aa..c66e8273fccd 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -386,13 +386,6 @@ static void array_map_free(struct bpf_map *map)
 {
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 
-	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
-	 * so the programs (can be more than one that used this map) were
-	 * disconnected from events. Wait for outstanding programs to complete
-	 * and free the array
-	 */
-	synchronize_rcu();
-
 	if (array->map.map_type == BPF_MAP_TYPE_PERCPU_ARRAY)
 		bpf_array_free_percpu(array);
 
@@ -546,8 +539,6 @@ static void fd_array_map_free(struct bpf_map *map)
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
 	int i;
 
-	synchronize_rcu();
-
 	/* make sure it's empty */
 	for (i = 0; i < array->map.max_entries; i++)
 		BUG_ON(array->ptrs[i] != NULL);
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index acd06081d81d..d4378d7d442b 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1290,12 +1290,10 @@ static void htab_map_free(struct bpf_map *map)
 {
 	struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
 
-	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
-	 * so the programs (can be more than one that used this map) were
-	 * disconnected from events. Wait for outstanding critical sections in
-	 * these programs to complete
+	/* bpf_free_used_maps() or close(map_fd) will trigger this map_free callback.
+	 * bpf_free_used_maps() is called after bpf prog is no longer executing.
+	 * There is no need to synchronize_rcu() here to protect map elements.
 	 */
-	synchronize_rcu();
 
 	/* some of free_htab_elem() callbacks for elements of this map may
 	 * not have executed. Wait for them.
diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index 1abd4e3f906d..44474bf3ab7a 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -589,11 +589,6 @@ static void trie_free(struct bpf_map *map)
 	struct lpm_trie_node __rcu **slot;
 	struct lpm_trie_node *node;
 
-	/* Wait for outstanding programs to complete
-	 * update/lookup/delete/get_next_key and free the trie.
-	 */
-	synchronize_rcu();
-
 	/* Always start at the root and walk down to a node that has no
 	 * children. Then free that node, nullify its reference in the parent
 	 * and start over.
diff --git a/kernel/bpf/queue_stack_maps.c b/kernel/bpf/queue_stack_maps.c
index 80c66a6d7c54..44184f82916a 100644
--- a/kernel/bpf/queue_stack_maps.c
+++ b/kernel/bpf/queue_stack_maps.c
@@ -101,13 +101,6 @@ static void queue_stack_map_free(struct bpf_map *map)
 {
 	struct bpf_queue_stack *qs = bpf_queue_stack(map);
 
-	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
-	 * so the programs (can be more than one that used this map) were
-	 * disconnected from events. Wait for outstanding critical sections in
-	 * these programs to complete
-	 */
-	synchronize_rcu();
-
 	bpf_map_area_free(qs);
 }
 
diff --git a/kernel/bpf/reuseport_array.c b/kernel/bpf/reuseport_array.c
index a09922f656e4..3625c4fcc65c 100644
--- a/kernel/bpf/reuseport_array.c
+++ b/kernel/bpf/reuseport_array.c
@@ -96,8 +96,6 @@ static void reuseport_array_free(struct bpf_map *map)
 	struct sock *sk;
 	u32 i;
 
-	synchronize_rcu();
-
 	/*
 	 * ops->map_*_elem() will not be able to access this
 	 * array now. Hence, this function only races with
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index dbf37aff4827..13a8d3967e07 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -215,13 +215,6 @@ static void ringbuf_map_free(struct bpf_map *map)
 {
 	struct bpf_ringbuf_map *rb_map;
 
-	/* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
-	 * so the programs (can be more than one that used this map) were
-	 * disconnected from events. Wait for outstanding critical sections in
-	 * these programs to complete
-	 */
-	synchronize_rcu();
-
 	rb_map = container_of(map, struct bpf_ringbuf_map, map);
 	bpf_ringbuf_free(rb_map->rb);
 	kfree(rb_map);
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 27dc9b1b08a5..071f98d0f7c6 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -604,9 +604,6 @@ static void stack_map_free(struct bpf_map *map)
 {
 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 
-	/* wait for bpf programs to complete before freeing stack map */
-	synchronize_rcu();
-
 	bpf_map_area_free(smap->elems);
 	pcpu_freelist_destroy(&smap->freelist);
 	bpf_map_area_free(smap);
-- 
cgit v1.2.3-70-g09d2