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1b262839 ST |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
3 | * Copyright 2019 Google LLC | |
4 | */ | |
5 | ||
6 | /** | |
7 | * DOC: The Keyslot Manager | |
8 | * | |
9 | * Many devices with inline encryption support have a limited number of "slots" | |
10 | * into which encryption contexts may be programmed, and requests can be tagged | |
11 | * with a slot number to specify the key to use for en/decryption. | |
12 | * | |
13 | * As the number of slots is limited, and programming keys is expensive on | |
14 | * many inline encryption hardware, we don't want to program the same key into | |
15 | * multiple slots - if multiple requests are using the same key, we want to | |
16 | * program just one slot with that key and use that slot for all requests. | |
17 | * | |
18 | * The keyslot manager manages these keyslots appropriately, and also acts as | |
19 | * an abstraction between the inline encryption hardware and the upper layers. | |
20 | * | |
21 | * Lower layer devices will set up a keyslot manager in their request queue | |
22 | * and tell it how to perform device specific operations like programming/ | |
23 | * evicting keys from keyslots. | |
24 | * | |
25 | * Upper layers will call blk_ksm_get_slot_for_key() to program a | |
26 | * key into some slot in the inline encryption hardware. | |
27 | */ | |
d145dc23 ST |
28 | |
29 | #define pr_fmt(fmt) "blk-crypto: " fmt | |
30 | ||
1b262839 ST |
31 | #include <linux/keyslot-manager.h> |
32 | #include <linux/atomic.h> | |
33 | #include <linux/mutex.h> | |
34 | #include <linux/pm_runtime.h> | |
35 | #include <linux/wait.h> | |
36 | #include <linux/blkdev.h> | |
37 | ||
38 | struct blk_ksm_keyslot { | |
39 | atomic_t slot_refs; | |
40 | struct list_head idle_slot_node; | |
41 | struct hlist_node hash_node; | |
42 | const struct blk_crypto_key *key; | |
43 | struct blk_keyslot_manager *ksm; | |
44 | }; | |
45 | ||
46 | static inline void blk_ksm_hw_enter(struct blk_keyslot_manager *ksm) | |
47 | { | |
48 | /* | |
49 | * Calling into the driver requires ksm->lock held and the device | |
50 | * resumed. But we must resume the device first, since that can acquire | |
51 | * and release ksm->lock via blk_ksm_reprogram_all_keys(). | |
52 | */ | |
53 | if (ksm->dev) | |
54 | pm_runtime_get_sync(ksm->dev); | |
55 | down_write(&ksm->lock); | |
56 | } | |
57 | ||
58 | static inline void blk_ksm_hw_exit(struct blk_keyslot_manager *ksm) | |
59 | { | |
60 | up_write(&ksm->lock); | |
61 | if (ksm->dev) | |
62 | pm_runtime_put_sync(ksm->dev); | |
63 | } | |
64 | ||
65 | /** | |
66 | * blk_ksm_init() - Initialize a keyslot manager | |
67 | * @ksm: The keyslot_manager to initialize. | |
68 | * @num_slots: The number of key slots to manage. | |
69 | * | |
70 | * Allocate memory for keyslots and initialize a keyslot manager. Called by | |
71 | * e.g. storage drivers to set up a keyslot manager in their request_queue. | |
72 | * | |
73 | * Return: 0 on success, or else a negative error code. | |
74 | */ | |
75 | int blk_ksm_init(struct blk_keyslot_manager *ksm, unsigned int num_slots) | |
76 | { | |
77 | unsigned int slot; | |
78 | unsigned int i; | |
79 | unsigned int slot_hashtable_size; | |
80 | ||
81 | memset(ksm, 0, sizeof(*ksm)); | |
82 | ||
83 | if (num_slots == 0) | |
84 | return -EINVAL; | |
85 | ||
86 | ksm->slots = kvcalloc(num_slots, sizeof(ksm->slots[0]), GFP_KERNEL); | |
87 | if (!ksm->slots) | |
88 | return -ENOMEM; | |
89 | ||
90 | ksm->num_slots = num_slots; | |
91 | ||
92 | init_rwsem(&ksm->lock); | |
93 | ||
94 | init_waitqueue_head(&ksm->idle_slots_wait_queue); | |
95 | INIT_LIST_HEAD(&ksm->idle_slots); | |
96 | ||
97 | for (slot = 0; slot < num_slots; slot++) { | |
98 | ksm->slots[slot].ksm = ksm; | |
99 | list_add_tail(&ksm->slots[slot].idle_slot_node, | |
100 | &ksm->idle_slots); | |
101 | } | |
102 | ||
103 | spin_lock_init(&ksm->idle_slots_lock); | |
104 | ||
105 | slot_hashtable_size = roundup_pow_of_two(num_slots); | |
47a84653 EB |
106 | /* |
107 | * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2 | |
108 | * buckets. This only makes a difference when there is only 1 keyslot. | |
109 | */ | |
110 | if (slot_hashtable_size < 2) | |
111 | slot_hashtable_size = 2; | |
112 | ||
1b262839 ST |
113 | ksm->log_slot_ht_size = ilog2(slot_hashtable_size); |
114 | ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size, | |
115 | sizeof(ksm->slot_hashtable[0]), | |
116 | GFP_KERNEL); | |
117 | if (!ksm->slot_hashtable) | |
118 | goto err_destroy_ksm; | |
119 | for (i = 0; i < slot_hashtable_size; i++) | |
120 | INIT_HLIST_HEAD(&ksm->slot_hashtable[i]); | |
121 | ||
122 | return 0; | |
123 | ||
124 | err_destroy_ksm: | |
125 | blk_ksm_destroy(ksm); | |
126 | return -ENOMEM; | |
127 | } | |
128 | EXPORT_SYMBOL_GPL(blk_ksm_init); | |
129 | ||
130 | static inline struct hlist_head * | |
131 | blk_ksm_hash_bucket_for_key(struct blk_keyslot_manager *ksm, | |
132 | const struct blk_crypto_key *key) | |
133 | { | |
134 | return &ksm->slot_hashtable[hash_ptr(key, ksm->log_slot_ht_size)]; | |
135 | } | |
136 | ||
137 | static void blk_ksm_remove_slot_from_lru_list(struct blk_ksm_keyslot *slot) | |
138 | { | |
139 | struct blk_keyslot_manager *ksm = slot->ksm; | |
140 | unsigned long flags; | |
141 | ||
142 | spin_lock_irqsave(&ksm->idle_slots_lock, flags); | |
143 | list_del(&slot->idle_slot_node); | |
144 | spin_unlock_irqrestore(&ksm->idle_slots_lock, flags); | |
145 | } | |
146 | ||
147 | static struct blk_ksm_keyslot *blk_ksm_find_keyslot( | |
148 | struct blk_keyslot_manager *ksm, | |
149 | const struct blk_crypto_key *key) | |
150 | { | |
151 | const struct hlist_head *head = blk_ksm_hash_bucket_for_key(ksm, key); | |
152 | struct blk_ksm_keyslot *slotp; | |
153 | ||
154 | hlist_for_each_entry(slotp, head, hash_node) { | |
155 | if (slotp->key == key) | |
156 | return slotp; | |
157 | } | |
158 | return NULL; | |
159 | } | |
160 | ||
161 | static struct blk_ksm_keyslot *blk_ksm_find_and_grab_keyslot( | |
162 | struct blk_keyslot_manager *ksm, | |
163 | const struct blk_crypto_key *key) | |
164 | { | |
165 | struct blk_ksm_keyslot *slot; | |
166 | ||
167 | slot = blk_ksm_find_keyslot(ksm, key); | |
168 | if (!slot) | |
169 | return NULL; | |
170 | if (atomic_inc_return(&slot->slot_refs) == 1) { | |
171 | /* Took first reference to this slot; remove it from LRU list */ | |
172 | blk_ksm_remove_slot_from_lru_list(slot); | |
173 | } | |
174 | return slot; | |
175 | } | |
176 | ||
177 | unsigned int blk_ksm_get_slot_idx(struct blk_ksm_keyslot *slot) | |
178 | { | |
179 | return slot - slot->ksm->slots; | |
180 | } | |
181 | EXPORT_SYMBOL_GPL(blk_ksm_get_slot_idx); | |
182 | ||
183 | /** | |
184 | * blk_ksm_get_slot_for_key() - Program a key into a keyslot. | |
185 | * @ksm: The keyslot manager to program the key into. | |
186 | * @key: Pointer to the key object to program, including the raw key, crypto | |
187 | * mode, and data unit size. | |
188 | * @slot_ptr: A pointer to return the pointer of the allocated keyslot. | |
189 | * | |
190 | * Get a keyslot that's been programmed with the specified key. If one already | |
191 | * exists, return it with incremented refcount. Otherwise, wait for a keyslot | |
192 | * to become idle and program it. | |
193 | * | |
194 | * Context: Process context. Takes and releases ksm->lock. | |
195 | * Return: BLK_STS_OK on success (and keyslot is set to the pointer of the | |
196 | * allocated keyslot), or some other blk_status_t otherwise (and | |
197 | * keyslot is set to NULL). | |
198 | */ | |
199 | blk_status_t blk_ksm_get_slot_for_key(struct blk_keyslot_manager *ksm, | |
200 | const struct blk_crypto_key *key, | |
201 | struct blk_ksm_keyslot **slot_ptr) | |
202 | { | |
203 | struct blk_ksm_keyslot *slot; | |
204 | int slot_idx; | |
205 | int err; | |
206 | ||
207 | *slot_ptr = NULL; | |
208 | down_read(&ksm->lock); | |
209 | slot = blk_ksm_find_and_grab_keyslot(ksm, key); | |
210 | up_read(&ksm->lock); | |
211 | if (slot) | |
212 | goto success; | |
213 | ||
214 | for (;;) { | |
215 | blk_ksm_hw_enter(ksm); | |
216 | slot = blk_ksm_find_and_grab_keyslot(ksm, key); | |
217 | if (slot) { | |
218 | blk_ksm_hw_exit(ksm); | |
219 | goto success; | |
220 | } | |
221 | ||
222 | /* | |
223 | * If we're here, that means there wasn't a slot that was | |
224 | * already programmed with the key. So try to program it. | |
225 | */ | |
226 | if (!list_empty(&ksm->idle_slots)) | |
227 | break; | |
228 | ||
229 | blk_ksm_hw_exit(ksm); | |
230 | wait_event(ksm->idle_slots_wait_queue, | |
231 | !list_empty(&ksm->idle_slots)); | |
232 | } | |
233 | ||
234 | slot = list_first_entry(&ksm->idle_slots, struct blk_ksm_keyslot, | |
235 | idle_slot_node); | |
236 | slot_idx = blk_ksm_get_slot_idx(slot); | |
237 | ||
238 | err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot_idx); | |
239 | if (err) { | |
240 | wake_up(&ksm->idle_slots_wait_queue); | |
241 | blk_ksm_hw_exit(ksm); | |
242 | return errno_to_blk_status(err); | |
243 | } | |
244 | ||
245 | /* Move this slot to the hash list for the new key. */ | |
246 | if (slot->key) | |
247 | hlist_del(&slot->hash_node); | |
248 | slot->key = key; | |
249 | hlist_add_head(&slot->hash_node, blk_ksm_hash_bucket_for_key(ksm, key)); | |
250 | ||
251 | atomic_set(&slot->slot_refs, 1); | |
252 | ||
253 | blk_ksm_remove_slot_from_lru_list(slot); | |
254 | ||
255 | blk_ksm_hw_exit(ksm); | |
256 | success: | |
257 | *slot_ptr = slot; | |
258 | return BLK_STS_OK; | |
259 | } | |
260 | ||
261 | /** | |
262 | * blk_ksm_put_slot() - Release a reference to a slot | |
263 | * @slot: The keyslot to release the reference of. | |
264 | * | |
265 | * Context: Any context. | |
266 | */ | |
267 | void blk_ksm_put_slot(struct blk_ksm_keyslot *slot) | |
268 | { | |
269 | struct blk_keyslot_manager *ksm; | |
270 | unsigned long flags; | |
271 | ||
272 | if (!slot) | |
273 | return; | |
274 | ||
275 | ksm = slot->ksm; | |
276 | ||
277 | if (atomic_dec_and_lock_irqsave(&slot->slot_refs, | |
278 | &ksm->idle_slots_lock, flags)) { | |
279 | list_add_tail(&slot->idle_slot_node, &ksm->idle_slots); | |
280 | spin_unlock_irqrestore(&ksm->idle_slots_lock, flags); | |
281 | wake_up(&ksm->idle_slots_wait_queue); | |
282 | } | |
283 | } | |
284 | ||
285 | /** | |
286 | * blk_ksm_crypto_cfg_supported() - Find out if a crypto configuration is | |
287 | * supported by a ksm. | |
288 | * @ksm: The keyslot manager to check | |
289 | * @cfg: The crypto configuration to check for. | |
290 | * | |
291 | * Checks for crypto_mode/data unit size/dun bytes support. | |
292 | * | |
293 | * Return: Whether or not this ksm supports the specified crypto config. | |
294 | */ | |
295 | bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm, | |
296 | const struct blk_crypto_config *cfg) | |
297 | { | |
298 | if (!ksm) | |
299 | return false; | |
300 | if (!(ksm->crypto_modes_supported[cfg->crypto_mode] & | |
301 | cfg->data_unit_size)) | |
302 | return false; | |
303 | if (ksm->max_dun_bytes_supported < cfg->dun_bytes) | |
304 | return false; | |
305 | return true; | |
306 | } | |
307 | ||
308 | /** | |
309 | * blk_ksm_evict_key() - Evict a key from the lower layer device. | |
310 | * @ksm: The keyslot manager to evict from | |
311 | * @key: The key to evict | |
312 | * | |
313 | * Find the keyslot that the specified key was programmed into, and evict that | |
314 | * slot from the lower layer device. The slot must not be in use by any | |
315 | * in-flight IO when this function is called. | |
316 | * | |
317 | * Context: Process context. Takes and releases ksm->lock. | |
318 | * Return: 0 on success or if there's no keyslot with the specified key, -EBUSY | |
319 | * if the keyslot is still in use, or another -errno value on other | |
320 | * error. | |
321 | */ | |
322 | int blk_ksm_evict_key(struct blk_keyslot_manager *ksm, | |
323 | const struct blk_crypto_key *key) | |
324 | { | |
325 | struct blk_ksm_keyslot *slot; | |
326 | int err = 0; | |
327 | ||
328 | blk_ksm_hw_enter(ksm); | |
329 | slot = blk_ksm_find_keyslot(ksm, key); | |
330 | if (!slot) | |
331 | goto out_unlock; | |
332 | ||
333 | if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) { | |
334 | err = -EBUSY; | |
335 | goto out_unlock; | |
336 | } | |
337 | err = ksm->ksm_ll_ops.keyslot_evict(ksm, key, | |
338 | blk_ksm_get_slot_idx(slot)); | |
339 | if (err) | |
340 | goto out_unlock; | |
341 | ||
342 | hlist_del(&slot->hash_node); | |
343 | slot->key = NULL; | |
344 | err = 0; | |
345 | out_unlock: | |
346 | blk_ksm_hw_exit(ksm); | |
347 | return err; | |
348 | } | |
349 | ||
350 | /** | |
351 | * blk_ksm_reprogram_all_keys() - Re-program all keyslots. | |
352 | * @ksm: The keyslot manager | |
353 | * | |
354 | * Re-program all keyslots that are supposed to have a key programmed. This is | |
355 | * intended only for use by drivers for hardware that loses its keys on reset. | |
356 | * | |
357 | * Context: Process context. Takes and releases ksm->lock. | |
358 | */ | |
359 | void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm) | |
360 | { | |
361 | unsigned int slot; | |
362 | ||
363 | /* This is for device initialization, so don't resume the device */ | |
364 | down_write(&ksm->lock); | |
365 | for (slot = 0; slot < ksm->num_slots; slot++) { | |
366 | const struct blk_crypto_key *key = ksm->slots[slot].key; | |
367 | int err; | |
368 | ||
369 | if (!key) | |
370 | continue; | |
371 | ||
372 | err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot); | |
373 | WARN_ON(err); | |
374 | } | |
375 | up_write(&ksm->lock); | |
376 | } | |
377 | EXPORT_SYMBOL_GPL(blk_ksm_reprogram_all_keys); | |
378 | ||
379 | void blk_ksm_destroy(struct blk_keyslot_manager *ksm) | |
380 | { | |
381 | if (!ksm) | |
382 | return; | |
383 | kvfree(ksm->slot_hashtable); | |
3e20aa96 | 384 | kvfree_sensitive(ksm->slots, sizeof(ksm->slots[0]) * ksm->num_slots); |
1b262839 ST |
385 | memzero_explicit(ksm, sizeof(*ksm)); |
386 | } | |
387 | EXPORT_SYMBOL_GPL(blk_ksm_destroy); | |
d145dc23 ST |
388 | |
389 | bool blk_ksm_register(struct blk_keyslot_manager *ksm, struct request_queue *q) | |
390 | { | |
391 | if (blk_integrity_queue_supports_integrity(q)) { | |
392 | pr_warn("Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n"); | |
393 | return false; | |
394 | } | |
395 | q->ksm = ksm; | |
396 | return true; | |
397 | } | |
398 | EXPORT_SYMBOL_GPL(blk_ksm_register); | |
399 | ||
400 | void blk_ksm_unregister(struct request_queue *q) | |
401 | { | |
402 | q->ksm = NULL; | |
403 | } |