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 #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 
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 
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)133 int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
134 		int (*copy)(struct hashtab_node *new,
135 			struct hashtab_node *orig, void *args),
136 		int (*destroy)(void *k, void *d, void *args),
137 		void *args)
138 {
139 	struct hashtab_node *cur, *tmp, *tail;
140 	int i, rc;
141 
142 	memset(new, 0, sizeof(*new));
143 
144 	new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
145 	if (!new->htable)
146 		return -ENOMEM;
147 
148 	new->size = orig->size;
149 
150 	for (i = 0; i < orig->size; i++) {
151 		tail = NULL;
152 		for (cur = orig->htable[i]; cur; cur = cur->next) {
153 			tmp = kmem_cache_zalloc(hashtab_node_cachep,
154 						GFP_KERNEL);
155 			if (!tmp)
156 				goto error;
157 			rc = copy(tmp, cur, args);
158 			if (rc) {
159 				kmem_cache_free(hashtab_node_cachep, tmp);
160 				goto error;
161 			}
162 			tmp->next = NULL;
163 			if (!tail)
164 				new->htable[i] = tmp;
165 			else
166 				tail->next = tmp;
167 			tail = tmp;
168 			new->nel++;
169 		}
170 	}
171 
172 	return 0;
173 
174  error:
175 	for (i = 0; i < new->size; i++) {
176 		for (cur = new->htable[i]; cur; cur = tmp) {
177 			tmp = cur->next;
178 			destroy(cur->key, cur->datum, args);
179 			kmem_cache_free(hashtab_node_cachep, cur);
180 		}
181 	}
182 	kfree(new->htable);
183 	memset(new, 0, sizeof(*new));
184 	return -ENOMEM;
185 }
186 
hashtab_cache_init(void)187 void __init hashtab_cache_init(void)
188 {
189 		hashtab_node_cachep = kmem_cache_create("hashtab_node",
190 			sizeof(struct hashtab_node),
191 			0, SLAB_PANIC, NULL);
192 }
193