1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * Copyright (c) 2019 Facebook
4 * Copyright 2020 Google LLC.
5 */
6
7 #ifndef _BPF_LOCAL_STORAGE_H
8 #define _BPF_LOCAL_STORAGE_H
9
10 #include <linux/bpf.h>
11 #include <linux/filter.h>
12 #include <linux/rculist.h>
13 #include <linux/list.h>
14 #include <linux/hash.h>
15 #include <linux/types.h>
16 #include <linux/bpf_mem_alloc.h>
17 #include <uapi/linux/btf.h>
18 #include <asm/rqspinlock.h>
19
20 #define BPF_LOCAL_STORAGE_CACHE_SIZE 16
21
22 struct bpf_local_storage_map_bucket {
23 struct hlist_head list;
24 rqspinlock_t lock;
25 };
26
27 /* Thp map is not the primary owner of a bpf_local_storage_elem.
28 * Instead, the container object (eg. sk->sk_bpf_storage) is.
29 *
30 * The map (bpf_local_storage_map) is for two purposes
31 * 1. Define the size of the "local storage". It is
32 * the map's value_size.
33 *
34 * 2. Maintain a list to keep track of all elems such
35 * that they can be cleaned up during the map destruction.
36 *
37 * When a bpf local storage is being looked up for a
38 * particular object, the "bpf_map" pointer is actually used
39 * as the "key" to search in the list of elem in
40 * the respective bpf_local_storage owned by the object.
41 *
42 * e.g. sk->sk_bpf_storage is the mini-map with the "bpf_map" pointer
43 * as the searching key.
44 */
45 struct bpf_local_storage_map {
46 struct bpf_map map;
47 /* Lookup elem does not require accessing the map.
48 *
49 * Updating/Deleting requires a bucket lock to
50 * link/unlink the elem from the map. Having
51 * multiple buckets to improve contention.
52 */
53 struct bpf_local_storage_map_bucket *buckets;
54 u32 bucket_log;
55 u16 elem_size;
56 u16 cache_idx;
57 };
58
59 struct bpf_local_storage_data {
60 /* smap is used as the searching key when looking up
61 * from the object's bpf_local_storage.
62 *
63 * Put it in the same cacheline as the data to minimize
64 * the number of cachelines accessed during the cache hit case.
65 */
66 struct bpf_local_storage_map __rcu *smap;
67 u8 data[] __aligned(8);
68 };
69
70 #define SELEM_MAP_UNLINKED (1 << 0)
71 #define SELEM_STORAGE_UNLINKED (1 << 1)
72 #define SELEM_UNLINKED (SELEM_MAP_UNLINKED | SELEM_STORAGE_UNLINKED)
73 #define SELEM_TOFREE (1 << 2)
74
75 /* Linked to bpf_local_storage and bpf_local_storage_map */
76 struct bpf_local_storage_elem {
77 struct hlist_node map_node; /* Linked to bpf_local_storage_map */
78 struct hlist_node snode; /* Linked to bpf_local_storage */
79 struct bpf_local_storage __rcu *local_storage;
80 union {
81 struct rcu_head rcu;
82 struct hlist_node free_node; /* used to postpone
83 * bpf_selem_free
84 * after raw_spin_unlock
85 */
86 };
87 atomic_t state;
88 /* 4 bytes hole */
89 /* The data is stored in another cacheline to minimize
90 * the number of cachelines access during a cache hit.
91 */
92 struct bpf_local_storage_data sdata ____cacheline_aligned;
93 };
94
95 struct bpf_local_storage {
96 struct bpf_local_storage_data __rcu *cache[BPF_LOCAL_STORAGE_CACHE_SIZE];
97 struct hlist_head list; /* List of bpf_local_storage_elem */
98 void *owner; /* The object that owns the above "list" of
99 * bpf_local_storage_elem.
100 */
101 struct rcu_head rcu;
102 rqspinlock_t lock; /* Protect adding/removing from the "list" */
103 u64 mem_charge; /* Copy of mem charged to owner. Protected by "lock" */
104 refcount_t owner_refcnt;/* Used to pin owner when map_free is uncharging */
105 };
106
107 /* U16_MAX is much more than enough for sk local storage
108 * considering a tcp_sock is ~2k.
109 */
110 #define BPF_LOCAL_STORAGE_MAX_VALUE_SIZE \
111 min_t(u32, \
112 (KMALLOC_MAX_SIZE - MAX_BPF_STACK - \
113 sizeof(struct bpf_local_storage_elem)), \
114 (U16_MAX - sizeof(struct bpf_local_storage_elem)))
115
116 #define SELEM(_SDATA) \
117 container_of((_SDATA), struct bpf_local_storage_elem, sdata)
118 #define SDATA(_SELEM) (&(_SELEM)->sdata)
119
120 #define BPF_LOCAL_STORAGE_CACHE_SIZE 16
121
122 struct bpf_local_storage_cache {
123 spinlock_t idx_lock;
124 u64 idx_usage_counts[BPF_LOCAL_STORAGE_CACHE_SIZE];
125 };
126
127 #define DEFINE_BPF_STORAGE_CACHE(name) \
128 static struct bpf_local_storage_cache name = { \
129 .idx_lock = __SPIN_LOCK_UNLOCKED(name.idx_lock), \
130 }
131
132 /* Helper functions for bpf_local_storage */
133 int bpf_local_storage_map_alloc_check(union bpf_attr *attr);
134
135 struct bpf_map *
136 bpf_local_storage_map_alloc(union bpf_attr *attr,
137 struct bpf_local_storage_cache *cache);
138
139 void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage,
140 struct bpf_local_storage_map *smap,
141 struct bpf_local_storage_elem *selem);
142 /* If cacheit_lockit is false, this lookup function is lockless */
143 static inline struct bpf_local_storage_data *
bpf_local_storage_lookup(struct bpf_local_storage * local_storage,struct bpf_local_storage_map * smap,bool cacheit_lockit)144 bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
145 struct bpf_local_storage_map *smap,
146 bool cacheit_lockit)
147 {
148 struct bpf_local_storage_data *sdata;
149 struct bpf_local_storage_elem *selem;
150
151 /* Fast path (cache hit) */
152 sdata = rcu_dereference_check(local_storage->cache[smap->cache_idx],
153 bpf_rcu_lock_held());
154 if (sdata && rcu_access_pointer(sdata->smap) == smap)
155 return sdata;
156
157 /* Slow path (cache miss) */
158 hlist_for_each_entry_rcu(selem, &local_storage->list, snode,
159 rcu_read_lock_trace_held())
160 if (rcu_access_pointer(SDATA(selem)->smap) == smap)
161 break;
162
163 if (!selem)
164 return NULL;
165 if (cacheit_lockit)
166 __bpf_local_storage_insert_cache(local_storage, smap, selem);
167 return SDATA(selem);
168 }
169
170 u32 bpf_local_storage_destroy(struct bpf_local_storage *local_storage);
171
172 void bpf_local_storage_map_free(struct bpf_map *map,
173 struct bpf_local_storage_cache *cache);
174
175 int bpf_local_storage_map_check_btf(struct bpf_map *map,
176 const struct btf *btf,
177 const struct btf_type *key_type,
178 const struct btf_type *value_type);
179
180 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
181 struct bpf_local_storage_elem *selem);
182
183 int bpf_selem_unlink(struct bpf_local_storage_elem *selem);
184
185 int bpf_selem_link_map(struct bpf_local_storage_map *smap,
186 struct bpf_local_storage *local_storage,
187 struct bpf_local_storage_elem *selem);
188
189 struct bpf_local_storage_elem *
190 bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, void *value,
191 bool swap_uptrs);
192
193 void bpf_selem_free(struct bpf_local_storage_elem *selem,
194 bool reuse_now);
195
196 int
197 bpf_local_storage_alloc(void *owner,
198 struct bpf_local_storage_map *smap,
199 struct bpf_local_storage_elem *first_selem);
200
201 struct bpf_local_storage_data *
202 bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
203 void *value, u64 map_flags, bool swap_uptrs);
204
205 u64 bpf_local_storage_map_mem_usage(const struct bpf_map *map);
206
207 #endif /* _BPF_LOCAL_STORAGE_H */
208