1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3 * A hash table (hashtab) maintains associations between
4 * key values and datum values. The type of the key values
5 * and the type of the datum values is arbitrary. The
6 * functions for hash computation and key comparison are
7 * provided by the creator of the table.
8 *
9 * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
10 */
11
12 #ifndef _SS_HASHTAB_H_
13 #define _SS_HASHTAB_H_
14
15 #include <linux/types.h>
16 #include <linux/errno.h>
17 #include <linux/sched.h>
18
19 #define HASHTAB_MAX_NODES U32_MAX
20
21 struct hashtab_key_params {
22 u32 (*hash)(const void *key); /* hash func */
23 int (*cmp)(const void *key1, const void *key2); /* comparison func */
24 };
25
26 struct hashtab_node {
27 void *key;
28 void *datum;
29 struct hashtab_node *next;
30 };
31
32 struct hashtab {
33 struct hashtab_node **htable; /* hash table */
34 u32 size; /* number of slots in hash table */
35 u32 nel; /* number of elements in hash table */
36 };
37
38 struct hashtab_info {
39 u32 slots_used;
40 u32 max_chain_len;
41 u64 chain2_len_sum;
42 };
43
44 /*
45 * Initializes a new hash table with the specified characteristics.
46 *
47 * Returns -ENOMEM if insufficient space is available or 0 otherwise.
48 */
49 int hashtab_init(struct hashtab *h, u32 nel_hint);
50
51 int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst, void *key,
52 void *datum);
53
54 /*
55 * Inserts the specified (key, datum) pair into the specified hash table.
56 *
57 * Returns -ENOMEM on memory allocation error,
58 * -EEXIST if there is already an entry with the same key,
59 * -EINVAL for general errors or
60 0 otherwise.
61 */
62 static inline int hashtab_insert(struct hashtab *h, void *key, void *datum,
63 struct hashtab_key_params key_params)
64 {
65 u32 hvalue;
66 struct hashtab_node *prev, *cur;
67
68 cond_resched();
69
70 if (!h->size || h->nel == HASHTAB_MAX_NODES)
71 return -EINVAL;
72
73 hvalue = key_params.hash(key) & (h->size - 1);
74 prev = NULL;
75 cur = h->htable[hvalue];
76 while (cur) {
77 int cmp = key_params.cmp(key, cur->key);
78
79 if (cmp == 0)
80 return -EEXIST;
81 if (cmp < 0)
82 break;
83 prev = cur;
84 cur = cur->next;
85 }
86
87 return __hashtab_insert(h, prev ? &prev->next : &h->htable[hvalue], key,
88 datum);
89 }
90
91 /*
92 * Searches for the entry with the specified key in the hash table.
93 *
94 * Returns NULL if no entry has the specified key or
95 * the datum of the entry otherwise.
96 */
97 static inline void *hashtab_search(struct hashtab *h, const void *key,
98 struct hashtab_key_params key_params)
99 {
100 u32 hvalue;
101 struct hashtab_node *cur;
102
103 if (!h->size)
104 return NULL;
105
106 hvalue = key_params.hash(key) & (h->size - 1);
107 cur = h->htable[hvalue];
108 while (cur) {
109 int cmp = key_params.cmp(key, cur->key);
110
111 if (cmp == 0)
112 return cur->datum;
113 if (cmp < 0)
114 break;
115 cur = cur->next;
116 }
117 return NULL;
118 }
119
120 /*
121 * Destroys the specified hash table.
122 */
123 void hashtab_destroy(struct hashtab *h);
124
125 /*
126 * Applies the specified apply function to (key,datum,args)
127 * for each entry in the specified hash table.
128 *
129 * The order in which the function is applied to the entries
130 * is dependent upon the internal structure of the hash table.
131 *
132 * If apply returns a non-zero status, then hashtab_map will cease
133 * iterating through the hash table and will propagate the error
134 * return to its caller.
135 */
136 int hashtab_map(struct hashtab *h, int (*apply)(void *k, void *d, void *args),
137 void *args);
138
139 int hashtab_duplicate(struct hashtab *new, const struct hashtab *orig,
140 int (*copy)(struct hashtab_node *new,
141 const struct hashtab_node *orig, void *args),
142 int (*destroy)(void *k, void *d, void *args), void *args);
143
144 #ifdef CONFIG_SECURITY_SELINUX_DEBUG
145 /* Fill info with some hash table statistics */
146 void hashtab_stat(struct hashtab *h, struct hashtab_info *info);
147 #else
148 static inline void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
149 {
150 return;
151 }
152 #endif
153
154 #endif /* _SS_HASHTAB_H */
155
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