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
14static 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 */
28static u32 hashtab_compute_size(u32 nel)
29{
30	return nel == 0 ? 0 : roundup_pow_of_two(nel);
31}
32
33int 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
51int __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
68void 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
87int 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
107void 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
139int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
140		      int (*copy)(struct hashtab_node *new,
141				  struct hashtab_node *orig, void *args),
142		      int (*destroy)(void *k, void *d, void *args), void *args)
143{
144	struct hashtab_node *cur, *tmp, *tail;
145	u32 i;
146	int rc;
147
148	memset(new, 0, sizeof(*new));
149
150	new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
151	if (!new->htable)
152		return -ENOMEM;
153
154	new->size = orig->size;
155
156	for (i = 0; i < orig->size; i++) {
157		tail = NULL;
158		for (cur = orig->htable[i]; cur; cur = cur->next) {
159			tmp = kmem_cache_zalloc(hashtab_node_cachep,
160						GFP_KERNEL);
161			if (!tmp)
162				goto error;
163			rc = copy(tmp, cur, args);
164			if (rc) {
165				kmem_cache_free(hashtab_node_cachep, tmp);
166				goto error;
167			}
168			tmp->next = NULL;
169			if (!tail)
170				new->htable[i] = tmp;
171			else
172				tail->next = tmp;
173			tail = tmp;
174			new->nel++;
175		}
176	}
177
178	return 0;
179
180error:
181	for (i = 0; i < new->size; i++) {
182		for (cur = new->htable[i]; cur; cur = tmp) {
183			tmp = cur->next;
184			destroy(cur->key, cur->datum, args);
185			kmem_cache_free(hashtab_node_cachep, cur);
186		}
187	}
188	kfree(new->htable);
189	memset(new, 0, sizeof(*new));
190	return -ENOMEM;
191}
192
193void __init hashtab_cache_init(void)
194{
195	hashtab_node_cachep = kmem_cache_create("hashtab_node",
196						sizeof(struct hashtab_node), 0,
197						SLAB_PANIC, NULL);
198}
199