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