1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Implementation of the hash table type.
4 *
5 * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
6 */
7
8 #include <linux/kernel.h>
9 #include <linux/slab.h>
10 #include <linux/errno.h>
11 #include "hashtab.h"
12 #include "security.h"
13
14 static struct kmem_cache *hashtab_node_cachep __ro_after_init;
15
16 /*
17 * Here we simply round the number of elements up to the nearest power of two.
18 * I tried also other options like rounding down or rounding to the closest
19 * power of two (up or down based on which is closer), but I was unable to
20 * find any significant difference in lookup/insert performance that would
21 * justify switching to a different (less intuitive) formula. It could be that
22 * a different formula is actually more optimal, but any future changes here
23 * should be supported with performance/memory usage data.
24 *
25 * The total memory used by the htable arrays (only) with Fedora policy loaded
26 * is approximately 163 KB at the time of writing.
27 */
28 static u32 hashtab_compute_size(u32 nel)
29 {
30 return nel == 0 ? 0 : roundup_pow_of_two(nel);
31 }
32
33 int hashtab_init(struct hashtab *h, u32 nel_hint)
34 {
35 u32 size = hashtab_compute_size(nel_hint);
36
37 /* should already be zeroed, but better be safe */
38 h->nel = 0;
39 h->size = 0;
40 h->htable = NULL;
41
42 if (size) {
43 h->htable = kcalloc(size, sizeof(*h->htable), GFP_KERNEL);
44 if (!h->htable)
45 return -ENOMEM;
46 h->size = size;
47 }
48 return 0;
49 }
50
51 int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst, void *key,
52 void *datum)
53 {
54 struct hashtab_node *newnode;
55
56 newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
57 if (!newnode)
58 return -ENOMEM;
59 newnode->key = key;
60 newnode->datum = datum;
61 newnode->next = *dst;
62 *dst = newnode;
63
64 h->nel++;
65 return 0;
66 }
67
68 void hashtab_destroy(struct hashtab *h)
69 {
70 u32 i;
71 struct hashtab_node *cur, *temp;
72
73 for (i = 0; i < h->size; i++) {
74 cur = h->htable[i];
75 while (cur) {
76 temp = cur;
77 cur = cur->next;
78 kmem_cache_free(hashtab_node_cachep, temp);
79 }
80 h->htable[i] = NULL;
81 }
82
83 kfree(h->htable);
84 h->htable = NULL;
85 }
86
87 int hashtab_map(struct hashtab *h, int (*apply)(void *k, void *d, void *args),
88 void *args)
89 {
90 u32 i;
91 int ret;
92 struct hashtab_node *cur;
93
94 for (i = 0; i < h->size; i++) {
95 cur = h->htable[i];
96 while (cur) {
97 ret = apply(cur->key, cur->datum, args);
98 if (ret)
99 return ret;
100 cur = cur->next;
101 }
102 }
103 return 0;
104 }
105
106 #ifdef CONFIG_SECURITY_SELINUX_DEBUG
107 void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
108 {
109 u32 i, chain_len, slots_used, max_chain_len;
110 u64 chain2_len_sum;
111 struct hashtab_node *cur;
112
113 slots_used = 0;
114 max_chain_len = 0;
115 chain2_len_sum = 0;
116 for (i = 0; i < h->size; i++) {
117 cur = h->htable[i];
118 if (cur) {
119 slots_used++;
120 chain_len = 0;
121 while (cur) {
122 chain_len++;
123 cur = cur->next;
124 }
125
126 if (chain_len > max_chain_len)
127 max_chain_len = chain_len;
128
129 chain2_len_sum += (u64)chain_len * chain_len;
130 }
131 }
132
133 info->slots_used = slots_used;
134 info->max_chain_len = max_chain_len;
135 info->chain2_len_sum = chain2_len_sum;
136 }
137 #endif /* CONFIG_SECURITY_SELINUX_DEBUG */
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 const struct hashtab_node *orig_cur;
145 struct hashtab_node *cur, *tmp, *tail;
146 u32 i;
147 int rc;
148
149 memset(new, 0, sizeof(*new));
150
151 new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
152 if (!new->htable)
153 return -ENOMEM;
154
155 new->size = orig->size;
156
157 for (i = 0; i < orig->size; i++) {
158 tail = NULL;
159 for (orig_cur = orig->htable[i]; orig_cur;
160 orig_cur = orig_cur->next) {
161 tmp = kmem_cache_zalloc(hashtab_node_cachep,
162 GFP_KERNEL);
163 if (!tmp)
164 goto error;
165 rc = copy(tmp, orig_cur, args);
166 if (rc) {
167 kmem_cache_free(hashtab_node_cachep, tmp);
168 goto error;
169 }
170 tmp->next = NULL;
171 if (!tail)
172 new->htable[i] = tmp;
173 else
174 tail->next = tmp;
175 tail = tmp;
176 new->nel++;
177 }
178 }
179
180 return 0;
181
182 error:
183 for (i = 0; i < new->size; i++) {
184 for (cur = new->htable[i]; cur; cur = tmp) {
185 tmp = cur->next;
186 destroy(cur->key, cur->datum, args);
187 kmem_cache_free(hashtab_node_cachep, cur);
188 }
189 }
190 kfree(new->htable);
191 memset(new, 0, sizeof(*new));
192 return -ENOMEM;
193 }
194
195 void __init hashtab_cache_init(void)
196 {
197 hashtab_node_cachep = kmem_cache_create("hashtab_node",
198 sizeof(struct hashtab_node), 0,
199 SLAB_PANIC, NULL);
200 }
201
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