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
13static 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 */
27static u32 hashtab_compute_size(u32 nel)
28{
29	return nel == 0 ? 0 : roundup_pow_of_two(nel);
30}
31
32int 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
50int __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
67void 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
86int 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
107void 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
134int 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
189void __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