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[J-linux.git] / security / selinux / ss / hashtab.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Implementation of the hash table type.
4  *
5  * Author : Stephen Smalley, <[email protected]>
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(hashtab_node, SLAB_PANIC);
198 }
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