1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Implementation of the hash table type.
4 *
5 * Author : Stephen Smalley, <sds@tycho.nsa.gov>
6 */
7 #include <linux/kernel.h>
8 #include <linux/slab.h>
9 #include <linux/errno.h>
10 #include "hashtab.h"
11
12 static struct kmem_cache *hashtab_node_cachep __ro_after_init;
13
14 /*
15 * Here we simply round the number of elements up to the nearest power of two.
16 * I tried also other options like rounding down or rounding to the closest
17 * power of two (up or down based on which is closer), but I was unable to
18 * find any significant difference in lookup/insert performance that would
19 * justify switching to a different (less intuitive) formula. It could be that
20 * a different formula is actually more optimal, but any future changes here
21 * should be supported with performance/memory usage data.
22 *
23 * The total memory used by the htable arrays (only) with Fedora policy loaded
24 * is approximately 163 KB at the time of writing.
25 */
hashtab_compute_size(u32 nel)26 static u32 hashtab_compute_size(u32 nel)
27 {
28 return nel == 0 ? 0 : roundup_pow_of_two(nel);
29 }
30
hashtab_init(struct hashtab * h,u32 nel_hint)31 int hashtab_init(struct hashtab *h, u32 nel_hint)
32 {
33 h->size = hashtab_compute_size(nel_hint);
34 h->nel = 0;
35 if (!h->size)
36 return 0;
37
38 h->htable = kcalloc(h->size, sizeof(*h->htable), GFP_KERNEL);
39 return h->htable ? 0 : -ENOMEM;
40 }
41
__hashtab_insert(struct hashtab * h,struct hashtab_node ** dst,void * key,void * datum)42 int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst,
43 void *key, void *datum)
44 {
45 struct hashtab_node *newnode;
46
47 newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
48 if (!newnode)
49 return -ENOMEM;
50 newnode->key = key;
51 newnode->datum = datum;
52 newnode->next = *dst;
53 *dst = newnode;
54
55 h->nel++;
56 return 0;
57 }
58
hashtab_destroy(struct hashtab * h)59 void hashtab_destroy(struct hashtab *h)
60 {
61 u32 i;
62 struct hashtab_node *cur, *temp;
63
64 for (i = 0; i < h->size; i++) {
65 cur = h->htable[i];
66 while (cur) {
67 temp = cur;
68 cur = cur->next;
69 kmem_cache_free(hashtab_node_cachep, temp);
70 }
71 h->htable[i] = NULL;
72 }
73
74 kfree(h->htable);
75 h->htable = NULL;
76 }
77
hashtab_map(struct hashtab * h,int (* apply)(void * k,void * d,void * args),void * args)78 int hashtab_map(struct hashtab *h,
79 int (*apply)(void *k, void *d, void *args),
80 void *args)
81 {
82 u32 i;
83 int ret;
84 struct hashtab_node *cur;
85
86 for (i = 0; i < h->size; i++) {
87 cur = h->htable[i];
88 while (cur) {
89 ret = apply(cur->key, cur->datum, args);
90 if (ret)
91 return ret;
92 cur = cur->next;
93 }
94 }
95 return 0;
96 }
97
98
hashtab_stat(struct hashtab * h,struct hashtab_info * info)99 void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
100 {
101 u32 i, chain_len, slots_used, max_chain_len;
102 struct hashtab_node *cur;
103
104 slots_used = 0;
105 max_chain_len = 0;
106 for (i = 0; i < h->size; i++) {
107 cur = h->htable[i];
108 if (cur) {
109 slots_used++;
110 chain_len = 0;
111 while (cur) {
112 chain_len++;
113 cur = cur->next;
114 }
115
116 if (chain_len > max_chain_len)
117 max_chain_len = chain_len;
118 }
119 }
120
121 info->slots_used = slots_used;
122 info->max_chain_len = max_chain_len;
123 }
124
hashtab_duplicate(struct hashtab * new,struct hashtab * orig,int (* copy)(struct hashtab_node * new,struct hashtab_node * orig,void * args),int (* destroy)(void * k,void * d,void * args),void * args)125 int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
126 int (*copy)(struct hashtab_node *new,
127 struct hashtab_node *orig, void *args),
128 int (*destroy)(void *k, void *d, void *args),
129 void *args)
130 {
131 struct hashtab_node *cur, *tmp, *tail;
132 int i, rc;
133
134 memset(new, 0, sizeof(*new));
135
136 new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
137 if (!new->htable)
138 return -ENOMEM;
139
140 new->size = orig->size;
141
142 for (i = 0; i < orig->size; i++) {
143 tail = NULL;
144 for (cur = orig->htable[i]; cur; cur = cur->next) {
145 tmp = kmem_cache_zalloc(hashtab_node_cachep,
146 GFP_KERNEL);
147 if (!tmp)
148 goto error;
149 rc = copy(tmp, cur, args);
150 if (rc) {
151 kmem_cache_free(hashtab_node_cachep, tmp);
152 goto error;
153 }
154 tmp->next = NULL;
155 if (!tail)
156 new->htable[i] = tmp;
157 else
158 tail->next = tmp;
159 tail = tmp;
160 new->nel++;
161 }
162 }
163
164 return 0;
165
166 error:
167 for (i = 0; i < new->size; i++) {
168 for (cur = new->htable[i]; cur; cur = tmp) {
169 tmp = cur->next;
170 destroy(cur->key, cur->datum, args);
171 kmem_cache_free(hashtab_node_cachep, cur);
172 }
173 }
174 kmem_cache_free(hashtab_node_cachep, new);
175 return -ENOMEM;
176 }
177
hashtab_cache_init(void)178 void __init hashtab_cache_init(void)
179 {
180 hashtab_node_cachep = kmem_cache_create("hashtab_node",
181 sizeof(struct hashtab_node),
182 0, SLAB_PANIC, NULL);
183 }
184
