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, <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
  12 static struct kmem_cache *hashtab_node_cachep;
  13
  14 /*
  15  * Here we simply round the number of elements up to the nearest power of two.
  16  * I tried also other options like rouding down or rounding to the closest
  17  * power of two (up or down based on which is closer), but I was unable to
  18  * find any significant difference in lookup/insert performance that would
  19  * justify switching to a different (less intuitive) formula. It could be that
  20  * a different formula is actually more optimal, but any future changes here
  21  * should be supported with performance/memory usage data.
  22  *
  23  * The total memory used by the htable arrays (only) with Fedora policy loaded
  24  * is approximately 163 KB at the time of writing.
  25  */
  26 static u32 hashtab_compute_size(u32 nel)
  27 {
  28         return nel == 0 ? 0 : roundup_pow_of_two(nel);
  29 }
  30
  31 int hashtab_init(struct hashtab *h, u32 nel_hint)
  32 {
  33         u32 size = hashtab_compute_size(nel_hint);
  34
  35         /* should already be zeroed, but better be safe */
  36         h->nel = 0;
  37         h->size = 0;
  38         h->htable = NULL;
  39
  40         if (size) {
  41                 h->htable = kcalloc(size, sizeof(*h->htable), GFP_KERNEL);
  42                 if (!h->htable)
  43                         return -ENOMEM;
  44                 h->size = size;
  45         }
  46         return 0;
  47 }
  48
  49 int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst,
  50                      void *key, void *datum)
  51 {
  52         struct hashtab_node *newnode;
  53
  54         newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
  55         if (!newnode)
  56                 return -ENOMEM;
  57         newnode->key = key;
  58         newnode->datum = datum;
  59         newnode->next = *dst;
  60         *dst = newnode;
  61
  62         h->nel++;
  63         return 0;
  64 }
  65
  66 void hashtab_destroy(struct hashtab *h)
  67 {
  68         u32 i;
  69         struct hashtab_node *cur, *temp;
  70
  71         for (i = 0; i < h->size; i++) {
  72                 cur = h->htable[i];
  73                 while (cur) {
  74                         temp = cur;
  75                         cur = cur->next;
  76                         kmem_cache_free(hashtab_node_cachep, temp);
  77                 }
  78                 h->htable[i] = NULL;
  79         }
  80
  81         kfree(h->htable);
  82         h->htable = NULL;
  83 }
  84
  85 int hashtab_map(struct hashtab *h,
  86                 int (*apply)(void *k, void *d, void *args),
  87                 void *args)
  88 {
  89         u32 i;
  90         int ret;
  91         struct hashtab_node *cur;
  92
  93         for (i = 0; i < h->size; i++) {
  94                 cur = h->htable[i];
  95                 while (cur) {
  96                         ret = apply(cur->key, cur->datum, args);
  97                         if (ret)
  98                                 return ret;
  99                         cur = cur->next;
 100                 }
 101         }
 102         return 0;
 103 }
 104
 105
 106 void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
 107 {
 108         u32 i, chain_len, slots_used, max_chain_len;
 109         struct hashtab_node *cur;
 110
 111         slots_used = 0;
 112         max_chain_len = 0;
 113         for (i = 0; i < h->size; i++) {
 114                 cur = h->htable[i];
 115                 if (cur) {
 116                         slots_used++;
 117                         chain_len = 0;
 118                         while (cur) {
 119                                 chain_len++;
 120                                 cur = cur->next;
 121                         }
 122
 123                         if (chain_len > max_chain_len)
 124                                 max_chain_len = chain_len;
 125                 }
 126         }
 127
 128         info->slots_used = slots_used;
 129         info->max_chain_len = max_chain_len;
 130 }
 131
 132 int hashtab_duplicate(struct hashtab *new, struct hashtab *orig,
 133                 int (*copy)(struct hashtab_node *new,
 134                         struct hashtab_node *orig, void *args),
 135                 int (*destroy)(void *k, void *d, void *args),
 136                 void *args)
 137 {
 138         struct hashtab_node *cur, *tmp, *tail;
 139         int i, rc;
 140
 141         memset(new, 0, sizeof(*new));
 142
 143         new->htable = kcalloc(orig->size, sizeof(*new->htable), GFP_KERNEL);
 144         if (!new->htable)
 145                 return -ENOMEM;
 146
 147         new->size = orig->size;
 148
 149         for (i = 0; i < orig->size; i++) {
 150                 tail = NULL;
 151                 for (cur = orig->htable[i]; cur; cur = cur->next) {
 152                         tmp = kmem_cache_zalloc(hashtab_node_cachep,
 153                                                 GFP_KERNEL);
 154                         if (!tmp)
 155                                 goto error;
 156                         rc = copy(tmp, cur, args);
 157                         if (rc) {
 158                                 kmem_cache_free(hashtab_node_cachep, tmp);
 159                                 goto error;
 160                         }
 161                         tmp->next = NULL;
 162                         if (!tail)
 163                                 new->htable[i] = tmp;
 164                         else
 165                                 tail->next = tmp;
 166                         tail = tmp;
 167                         new->nel++;
 168                 }
 169         }
 170
 171         return 0;
 172
 173  error:
 174         for (i = 0; i < new->size; i++) {
 175                 for (cur = new->htable[i]; cur; cur = tmp) {
 176                         tmp = cur->next;
 177                         destroy(cur->key, cur->datum, args);
 178                         kmem_cache_free(hashtab_node_cachep, cur);
 179                 }
 180         }
 181         kfree(new->htable);
 182         memset(new, 0, sizeof(*new));
 183         return -ENOMEM;
 184 }
 185
 186 void __init hashtab_cache_init(void)
 187 {
 188                 hashtab_node_cachep = kmem_cache_create("hashtab_node",
 189                         sizeof(struct hashtab_node),
 190                         0, SLAB_PANIC, NULL);
 191 }