lib/crc64-rocksoft.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #include <linux/types.h>
   4 #include <linux/module.h>
   5 #include <linux/crc64.h>
   6 #include <linux/err.h>
   7 #include <linux/init.h>
   8 #include <crypto/hash.h>
   9 #include <crypto/algapi.h>
  10 #include <linux/static_key.h>
  11 #include <linux/notifier.h>
  12
  13 static struct crypto_shash __rcu *crc64_rocksoft_tfm;
  14 static DEFINE_STATIC_KEY_TRUE(crc64_rocksoft_fallback);
  15 static DEFINE_MUTEX(crc64_rocksoft_mutex);
  16 static struct work_struct crc64_rocksoft_rehash_work;
  17
  18 static int crc64_rocksoft_notify(struct notifier_block *self, unsigned long val, void *data)
  19 {
  20         struct crypto_alg *alg = data;
  21
  22         if (val != CRYPTO_MSG_ALG_LOADED ||
  23             strcmp(alg->cra_name, CRC64_ROCKSOFT_STRING))
  24                 return NOTIFY_DONE;
  25
  26         schedule_work(&crc64_rocksoft_rehash_work);
  27         return NOTIFY_OK;
  28 }
  29
  30 static void crc64_rocksoft_rehash(struct work_struct *work)
  31 {
  32         struct crypto_shash *new, *old;
  33
  34         mutex_lock(&crc64_rocksoft_mutex);
  35         old = rcu_dereference_protected(crc64_rocksoft_tfm,
  36                                         lockdep_is_held(&crc64_rocksoft_mutex));
  37         new = crypto_alloc_shash(CRC64_ROCKSOFT_STRING, 0, 0);
  38         if (IS_ERR(new)) {
  39                 mutex_unlock(&crc64_rocksoft_mutex);
  40                 return;
  41         }
  42         rcu_assign_pointer(crc64_rocksoft_tfm, new);
  43         mutex_unlock(&crc64_rocksoft_mutex);
  44
  45         if (old) {
  46                 synchronize_rcu();
  47                 crypto_free_shash(old);
  48         } else {
  49                 static_branch_disable(&crc64_rocksoft_fallback);
  50         }
  51 }
  52
  53 static struct notifier_block crc64_rocksoft_nb = {
  54         .notifier_call = crc64_rocksoft_notify,
  55 };
  56
  57 u64 crc64_rocksoft_update(u64 crc, const unsigned char *buffer, size_t len)
  58 {
  59         struct {
  60                 struct shash_desc shash;
  61                 u64 crc;
  62         } desc;
  63         int err;
  64
  65         if (static_branch_unlikely(&crc64_rocksoft_fallback))
  66                 return crc64_rocksoft_generic(crc, buffer, len);
  67
  68         rcu_read_lock();
  69         desc.shash.tfm = rcu_dereference(crc64_rocksoft_tfm);
  70         desc.crc = crc;
  71         err = crypto_shash_update(&desc.shash, buffer, len);
  72         rcu_read_unlock();
  73
  74         BUG_ON(err);
  75
  76         return desc.crc;
  77 }
  78 EXPORT_SYMBOL_GPL(crc64_rocksoft_update);
  79
  80 u64 crc64_rocksoft(const unsigned char *buffer, size_t len)
  81 {
  82         return crc64_rocksoft_update(0, buffer, len);
  83 }
  84 EXPORT_SYMBOL_GPL(crc64_rocksoft);
  85
  86 static int __init crc64_rocksoft_mod_init(void)
  87 {
  88         INIT_WORK(&crc64_rocksoft_rehash_work, crc64_rocksoft_rehash);
  89         crypto_register_notifier(&crc64_rocksoft_nb);
  90         crc64_rocksoft_rehash(&crc64_rocksoft_rehash_work);
  91         return 0;
  92 }
  93
  94 static void __exit crc64_rocksoft_mod_fini(void)
  95 {
  96         crypto_unregister_notifier(&crc64_rocksoft_nb);
  97         cancel_work_sync(&crc64_rocksoft_rehash_work);
  98         crypto_free_shash(rcu_dereference_protected(crc64_rocksoft_tfm, 1));
  99 }
 100
 101 module_init(crc64_rocksoft_mod_init);
 102 module_exit(crc64_rocksoft_mod_fini);
 103
 104 static int crc64_rocksoft_transform_show(char *buffer, const struct kernel_param *kp)
 105 {
 106         struct crypto_shash *tfm;
 107         int len;
 108
 109         if (static_branch_unlikely(&crc64_rocksoft_fallback))
 110                 return sprintf(buffer, "fallback\n");
 111
 112         rcu_read_lock();
 113         tfm = rcu_dereference(crc64_rocksoft_tfm);
 114         len = snprintf(buffer, PAGE_SIZE, "%s\n",
 115                        crypto_shash_driver_name(tfm));
 116         rcu_read_unlock();
 117
 118         return len;
 119 }
 120
 121 module_param_call(transform, NULL, crc64_rocksoft_transform_show, NULL, 0444);
 122
 123 MODULE_AUTHOR("Keith Busch <kbusch@kernel.org>");
 124 MODULE_DESCRIPTION("Rocksoft model CRC64 calculation (library API)");
 125 MODULE_LICENSE("GPL");
 126 MODULE_SOFTDEP("pre: crc64");