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 #include <linux/kernel.h>
8 #include <linux/slab.h>
9 #include <linux/errno.h>
10 #include "hashtab.h"
11 #include "security.h"
12
13 static struct kmem_cache *hashtab_node_cachep __ro_after_init;
14
15 /*
16 * Here we simply round the number of elements up to the nearest power of two.
17 * I tried also other options like rounding down or rounding to the closest
18 * power of two (up or down based on which is closer), but I was unable to
19 * find any significant difference in lookup/insert performance that would
20 * justify switching to a different (less intuitive) formula. It could be that
21 * a different formula is actually more optimal, but any future changes here
22 * should be supported with performance/memory usage data.
23 *
24 * The total memory used by the htable arrays (only) with Fedora policy loaded
25 * is approximately 163 KB at the time of writing.
26 */
hashtab_compute_size(u32 nel)27 static u32 hashtab_compute_size(u32 nel)
28 {
29 return nel == 0 ? 0 : roundup_pow_of_two(nel);
30 }
31
hashtab_init(struct hashtab * h,u32 nel_hint)32 int hashtab_init(struct hashtab *h, u32 nel_hint)
33 {
34 u32 size = hashtab_compute_size(nel_hint);
35
36 /* should already be zeroed, but better be safe */
37 h->nel = 0;
38 h->size = 0;
39 h->htable = NULL;
40
41 if (size) {
42 h->htable = kcalloc(size, sizeof(*h->htable), GFP_KERNEL);
43 if (!h->htable)
44 return -ENOMEM;
45 h->size = size;
46 }
47 return 0;
48 }
49
__hashtab_insert(struct hashtab * h,struct hashtab_node ** dst,void * key,void * datum)50 int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst,
51 void *key, void *datum)
52 {
53 struct hashtab_node *newnode;
54
55 newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
56 if (!newnode)
57 return -ENOMEM;
58 newnode->key = key;
59 newnode->datum = datum;
60 newnode->next = *dst;
61 *dst = newnode;
62
63 h->nel++;
64 return 0;
65 }
66
hashtab_destroy(struct hashtab * h)67 void hashtab_destroy(struct hashtab *h)
68 {
69 u32 i;
70 struct hashtab_node *cur, *temp;
71
72 for (i = 0; i < h->size; i++) {
73 cur = h->htable[i];
74 while (cur) {
75 temp = cur;
76 cur = cur->next;
77 kmem_cache_free(hashtab_node_cachep, temp);
78 }
79 h->htable[i] = NULL;
80 }
81
82 kfree(h->htable);
83 h->htable = NULL;
84 }
85
hashtab_map(struct hashtab * h,int (* apply)(void * k,void * d,void * args),void * args)86 int hashtab_map(struct hashtab *h,
87 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
hashtab_stat(struct hashtab * h,struct hashtab_info * info)107 void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
108 {
109 u32 i, chain_len, slots_used, max_chain_len;
110 struct hashtab_node *cur;
111
112 slots_used = 0;
113 max_chain_len = 0;
114 for (i = 0; i < h->size; i++) {
115 cur = h->htable[i];
116 if (cur) {
117 slots_used++;
118 chain_len = 0;
119 while (cur) {
120 chain_len++;
121 cur = cur->next;
122 }
123
124 if (chain_len > max_chain_len)
125 max_chain_len = chain_len;
126 }
127 }
128
129 info->slots_used = slots_used;
130 info->max_chain_len = max_chain_len;
131 }
132 #endif /* CONFIG_SECURITY_SELINUX_DEBUG */
133
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)134 int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
135 int (*copy)(struct hashtab_node *new,
136 struct hashtab_node *orig, void *args),
137 int (*destroy)(void *k, void *d, void *args),
138 void *args)
139 {
140 struct hashtab_node *cur, *tmp, *tail;
141 u32 i;
142 int rc;
143
144 memset(new, 0, sizeof(*new));
145
146 new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
147 if (!new->htable)
148 return -ENOMEM;
149
150 new->size = orig->size;
151
152 for (i = 0; i < orig->size; i++) {
153 tail = NULL;
154 for (cur = orig->htable[i]; cur; cur = cur->next) {
155 tmp = kmem_cache_zalloc(hashtab_node_cachep,
156 GFP_KERNEL);
157 if (!tmp)
158 goto error;
159 rc = copy(tmp, cur, args);
160 if (rc) {
161 kmem_cache_free(hashtab_node_cachep, tmp);
162 goto error;
163 }
164 tmp->next = NULL;
165 if (!tail)
166 new->htable[i] = tmp;
167 else
168 tail->next = tmp;
169 tail = tmp;
170 new->nel++;
171 }
172 }
173
174 return 0;
175
176 error:
177 for (i = 0; i < new->size; i++) {
178 for (cur = new->htable[i]; cur; cur = tmp) {
179 tmp = cur->next;
180 destroy(cur->key, cur->datum, args);
181 kmem_cache_free(hashtab_node_cachep, cur);
182 }
183 }
184 kfree(new->htable);
185 memset(new, 0, sizeof(*new));
186 return -ENOMEM;
187 }
188
hashtab_cache_init(void)189 void __init hashtab_cache_init(void)
190 {
191 hashtab_node_cachep = kmem_cache_create("hashtab_node",
192 sizeof(struct hashtab_node),
193 0, SLAB_PANIC, NULL);
194 }
195