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218 lines · 5.7 KiB

1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (c) 2021 Facebook */
3
4#include <linux/bitmap.h>
5#include <linux/bpf.h>
6#include <linux/btf.h>
7#include <linux/err.h>
8#include <linux/jhash.h>
9#include <linux/random.h>
10#include <linux/btf_ids.h>
11
12#define BLOOM_CREATE_FLAG_MASK \
13 (BPF_F_NUMA_NODE | BPF_F_ZERO_SEED | BPF_F_ACCESS_MASK)
14
15struct bpf_bloom_filter {
16 struct bpf_map map;
17 u32 bitset_mask;
18 u32 hash_seed;
19 u32 nr_hash_funcs;
20 unsigned long bitset[];
21};
22
23static u32 hash(struct bpf_bloom_filter *bloom, void *value,
24 u32 value_size, u32 index)
25{
26 u32 h;
27
28 if (likely(value_size % 4 == 0))
29 h = jhash2(value, value_size / 4, bloom->hash_seed + index);
30 else
31 h = jhash(value, value_size, bloom->hash_seed + index);
32
33 return h & bloom->bitset_mask;
34}
35
36static long bloom_map_peek_elem(struct bpf_map *map, void *value)
37{
38 struct bpf_bloom_filter *bloom =
39 container_of(map, struct bpf_bloom_filter, map);
40 u32 i, h;
41
42 for (i = 0; i < bloom->nr_hash_funcs; i++) {
43 h = hash(bloom, value, map->value_size, i);
44 if (!test_bit(h % BITS_PER_LONG, bloom->bitset + BIT_WORD(h)))
45 return -ENOENT;
46 }
47
48 return 0;
49}
50
51static long bloom_map_push_elem(struct bpf_map *map, void *value, u64 flags)
52{
53 struct bpf_bloom_filter *bloom =
54 container_of(map, struct bpf_bloom_filter, map);
55 u32 i, h;
56
57 if (flags != BPF_ANY)
58 return -EINVAL;
59
60 /*
61 * On 32-bit architectures, hashes larger than INT_MAX would be
62 * treated as negative by set_bit().
63 */
64 for (i = 0; i < bloom->nr_hash_funcs; i++) {
65 h = hash(bloom, value, map->value_size, i);
66 set_bit(h % BITS_PER_LONG, bloom->bitset + BIT_WORD(h));
67 }
68
69 return 0;
70}
71
72static long bloom_map_pop_elem(struct bpf_map *map, void *value)
73{
74 return -EOPNOTSUPP;
75}
76
77static long bloom_map_delete_elem(struct bpf_map *map, void *value)
78{
79 return -EOPNOTSUPP;
80}
81
82static int bloom_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
83{
84 return -EOPNOTSUPP;
85}
86
87/* Called from syscall */
88static int bloom_map_alloc_check(union bpf_attr *attr)
89{
90 if (attr->value_size > KMALLOC_MAX_SIZE)
91 /* if value_size is bigger, the user space won't be able to
92 * access the elements.
93 */
94 return -E2BIG;
95
96 return 0;
97}
98
99static struct bpf_map *bloom_map_alloc(union bpf_attr *attr)
100{
101 u32 bitset_mask, nr_hash_funcs, nr_bits;
102 int numa_node = bpf_map_attr_numa_node(attr);
103 struct bpf_bloom_filter *bloom;
104 u64 bitset_bytes;
105
106 if (attr->key_size != 0 || attr->value_size == 0 ||
107 attr->max_entries == 0 ||
108 attr->map_flags & ~BLOOM_CREATE_FLAG_MASK ||
109 !bpf_map_flags_access_ok(attr->map_flags) ||
110 /* The lower 4 bits of map_extra (0xF) specify the number
111 * of hash functions
112 */
113 (attr->map_extra & ~0xF))
114 return ERR_PTR(-EINVAL);
115
116 nr_hash_funcs = attr->map_extra;
117 if (nr_hash_funcs == 0)
118 /* Default to using 5 hash functions if unspecified */
119 nr_hash_funcs = 5;
120
121 /* For the bloom filter, the optimal bit array size that minimizes the
122 * false positive probability is n * k / ln(2) where n is the number of
123 * expected entries in the bloom filter and k is the number of hash
124 * functions. We use 7 / 5 to approximate 1 / ln(2).
125 *
126 * We round this up to the nearest power of two to enable more efficient
127 * hashing using bitmasks. The bitmask will be the bit array size - 1.
128 *
129 * If this overflows a u32, the bit array size will have 2^32 (4
130 * GB) bits.
131 */
132 if (check_mul_overflow(attr->max_entries, nr_hash_funcs, &nr_bits) ||
133 check_mul_overflow(nr_bits / 5, (u32)7, &nr_bits) ||
134 nr_bits > (1UL << 31)) {
135 bitset_mask = U32_MAX;
136 } else {
137 if (nr_bits <= BITS_PER_LONG)
138 nr_bits = BITS_PER_LONG;
139 else
140 nr_bits = roundup_pow_of_two(nr_bits);
141 bitset_mask = nr_bits - 1;
142 }
143
144 bitset_bytes = BITS_TO_LONGS((u64)bitset_mask + 1) * sizeof(unsigned long);
145 bloom = bpf_map_area_alloc(sizeof(*bloom) + bitset_bytes, numa_node);
146
147 if (!bloom)
148 return ERR_PTR(-ENOMEM);
149
150 bpf_map_init_from_attr(&bloom->map, attr);
151
152 bloom->nr_hash_funcs = nr_hash_funcs;
153 bloom->bitset_mask = bitset_mask;
154
155 if (!(attr->map_flags & BPF_F_ZERO_SEED))
156 bloom->hash_seed = get_random_u32();
157
158 return &bloom->map;
159}
160
161static void bloom_map_free(struct bpf_map *map)
162{
163 struct bpf_bloom_filter *bloom =
164 container_of(map, struct bpf_bloom_filter, map);
165
166 bpf_map_area_free(bloom);
167}
168
169static void *bloom_map_lookup_elem(struct bpf_map *map, void *key)
170{
171 /* The eBPF program should use map_peek_elem instead */
172 return ERR_PTR(-EINVAL);
173}
174
175static long bloom_map_update_elem(struct bpf_map *map, void *key,
176 void *value, u64 flags)
177{
178 /* The eBPF program should use map_push_elem instead */
179 return -EINVAL;
180}
181
182static int bloom_map_check_btf(struct bpf_map *map,
183 const struct btf *btf,
184 const struct btf_type *key_type,
185 const struct btf_type *value_type)
186{
187 /* Bloom filter maps are keyless */
188 return btf_type_is_void(key_type) ? 0 : -EINVAL;
189}
190
191static u64 bloom_map_mem_usage(const struct bpf_map *map)
192{
193 struct bpf_bloom_filter *bloom;
194 u64 bitset_bytes;
195
196 bloom = container_of(map, struct bpf_bloom_filter, map);
197 bitset_bytes = BITS_TO_BYTES((u64)bloom->bitset_mask + 1);
198 bitset_bytes = roundup(bitset_bytes, sizeof(unsigned long));
199 return sizeof(*bloom) + bitset_bytes;
200}
201
202BTF_ID_LIST_SINGLE(bpf_bloom_map_btf_ids, struct, bpf_bloom_filter)
203const struct bpf_map_ops bloom_filter_map_ops = {
204 .map_meta_equal = bpf_map_meta_equal,
205 .map_alloc_check = bloom_map_alloc_check,
206 .map_alloc = bloom_map_alloc,
207 .map_free = bloom_map_free,
208 .map_get_next_key = bloom_map_get_next_key,
209 .map_push_elem = bloom_map_push_elem,
210 .map_peek_elem = bloom_map_peek_elem,
211 .map_pop_elem = bloom_map_pop_elem,
212 .map_lookup_elem = bloom_map_lookup_elem,
213 .map_update_elem = bloom_map_update_elem,
214 .map_delete_elem = bloom_map_delete_elem,
215 .map_check_btf = bloom_map_check_btf,
216 .map_mem_usage = bloom_map_mem_usage,
217 .map_btf_id = &bpf_bloom_map_btf_ids[0],
218};