1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright 2019 Google LLC
7 * DOC: The Keyslot Manager
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.
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.
18 * The keyslot manager manages these keyslots appropriately, and also acts as
19 * an abstraction between the inline encryption hardware and the upper layers.
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.
25 * Upper layers will call blk_ksm_get_slot_for_key() to program a
26 * key into some slot in the inline encryption hardware.
29 #define pr_fmt(fmt) "blk-crypto: " fmt
31 #include <linux/keyslot-manager.h>
32 #include <linux/device.h>
33 #include <linux/atomic.h>
34 #include <linux/mutex.h>
35 #include <linux/pm_runtime.h>
36 #include <linux/wait.h>
37 #include <linux/blkdev.h>
39 struct blk_ksm_keyslot {
41 struct list_head idle_slot_node;
42 struct hlist_node hash_node;
43 const struct blk_crypto_key *key;
44 struct blk_keyslot_manager *ksm;
47 static inline void blk_ksm_hw_enter(struct blk_keyslot_manager *ksm)
50 * Calling into the driver requires ksm->lock held and the device
51 * resumed. But we must resume the device first, since that can acquire
52 * and release ksm->lock via blk_ksm_reprogram_all_keys().
55 pm_runtime_get_sync(ksm->dev);
56 down_write(&ksm->lock);
59 static inline void blk_ksm_hw_exit(struct blk_keyslot_manager *ksm)
63 pm_runtime_put_sync(ksm->dev);
66 static inline bool blk_ksm_is_passthrough(struct blk_keyslot_manager *ksm)
68 return ksm->num_slots == 0;
72 * blk_ksm_init() - Initialize a keyslot manager
73 * @ksm: The keyslot_manager to initialize.
74 * @num_slots: The number of key slots to manage.
76 * Allocate memory for keyslots and initialize a keyslot manager. Called by
77 * e.g. storage drivers to set up a keyslot manager in their request_queue.
79 * Return: 0 on success, or else a negative error code.
81 int blk_ksm_init(struct blk_keyslot_manager *ksm, unsigned int num_slots)
85 unsigned int slot_hashtable_size;
87 memset(ksm, 0, sizeof(*ksm));
92 ksm->slots = kvcalloc(num_slots, sizeof(ksm->slots[0]), GFP_KERNEL);
96 ksm->num_slots = num_slots;
98 init_rwsem(&ksm->lock);
100 init_waitqueue_head(&ksm->idle_slots_wait_queue);
101 INIT_LIST_HEAD(&ksm->idle_slots);
103 for (slot = 0; slot < num_slots; slot++) {
104 ksm->slots[slot].ksm = ksm;
105 list_add_tail(&ksm->slots[slot].idle_slot_node,
109 spin_lock_init(&ksm->idle_slots_lock);
111 slot_hashtable_size = roundup_pow_of_two(num_slots);
113 * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
114 * buckets. This only makes a difference when there is only 1 keyslot.
116 if (slot_hashtable_size < 2)
117 slot_hashtable_size = 2;
119 ksm->log_slot_ht_size = ilog2(slot_hashtable_size);
120 ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size,
121 sizeof(ksm->slot_hashtable[0]),
123 if (!ksm->slot_hashtable)
124 goto err_destroy_ksm;
125 for (i = 0; i < slot_hashtable_size; i++)
126 INIT_HLIST_HEAD(&ksm->slot_hashtable[i]);
131 blk_ksm_destroy(ksm);
134 EXPORT_SYMBOL_GPL(blk_ksm_init);
136 static void blk_ksm_destroy_callback(void *ksm)
138 blk_ksm_destroy(ksm);
142 * devm_blk_ksm_init() - Resource-managed blk_ksm_init()
143 * @dev: The device which owns the blk_keyslot_manager.
144 * @ksm: The blk_keyslot_manager to initialize.
145 * @num_slots: The number of key slots to manage.
147 * Like blk_ksm_init(), but causes blk_ksm_destroy() to be called automatically
150 * Return: 0 on success, or else a negative error code.
152 int devm_blk_ksm_init(struct device *dev, struct blk_keyslot_manager *ksm,
153 unsigned int num_slots)
155 int err = blk_ksm_init(ksm, num_slots);
160 return devm_add_action_or_reset(dev, blk_ksm_destroy_callback, ksm);
162 EXPORT_SYMBOL_GPL(devm_blk_ksm_init);
164 static inline struct hlist_head *
165 blk_ksm_hash_bucket_for_key(struct blk_keyslot_manager *ksm,
166 const struct blk_crypto_key *key)
168 return &ksm->slot_hashtable[hash_ptr(key, ksm->log_slot_ht_size)];
171 static void blk_ksm_remove_slot_from_lru_list(struct blk_ksm_keyslot *slot)
173 struct blk_keyslot_manager *ksm = slot->ksm;
176 spin_lock_irqsave(&ksm->idle_slots_lock, flags);
177 list_del(&slot->idle_slot_node);
178 spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
181 static struct blk_ksm_keyslot *blk_ksm_find_keyslot(
182 struct blk_keyslot_manager *ksm,
183 const struct blk_crypto_key *key)
185 const struct hlist_head *head = blk_ksm_hash_bucket_for_key(ksm, key);
186 struct blk_ksm_keyslot *slotp;
188 hlist_for_each_entry(slotp, head, hash_node) {
189 if (slotp->key == key)
195 static struct blk_ksm_keyslot *blk_ksm_find_and_grab_keyslot(
196 struct blk_keyslot_manager *ksm,
197 const struct blk_crypto_key *key)
199 struct blk_ksm_keyslot *slot;
201 slot = blk_ksm_find_keyslot(ksm, key);
204 if (atomic_inc_return(&slot->slot_refs) == 1) {
205 /* Took first reference to this slot; remove it from LRU list */
206 blk_ksm_remove_slot_from_lru_list(slot);
211 unsigned int blk_ksm_get_slot_idx(struct blk_ksm_keyslot *slot)
213 return slot - slot->ksm->slots;
215 EXPORT_SYMBOL_GPL(blk_ksm_get_slot_idx);
218 * blk_ksm_get_slot_for_key() - Program a key into a keyslot.
219 * @ksm: The keyslot manager to program the key into.
220 * @key: Pointer to the key object to program, including the raw key, crypto
221 * mode, and data unit size.
222 * @slot_ptr: A pointer to return the pointer of the allocated keyslot.
224 * Get a keyslot that's been programmed with the specified key. If one already
225 * exists, return it with incremented refcount. Otherwise, wait for a keyslot
226 * to become idle and program it.
228 * Context: Process context. Takes and releases ksm->lock.
229 * Return: BLK_STS_OK on success (and keyslot is set to the pointer of the
230 * allocated keyslot), or some other blk_status_t otherwise (and
231 * keyslot is set to NULL).
233 blk_status_t blk_ksm_get_slot_for_key(struct blk_keyslot_manager *ksm,
234 const struct blk_crypto_key *key,
235 struct blk_ksm_keyslot **slot_ptr)
237 struct blk_ksm_keyslot *slot;
243 if (blk_ksm_is_passthrough(ksm))
246 down_read(&ksm->lock);
247 slot = blk_ksm_find_and_grab_keyslot(ksm, key);
253 blk_ksm_hw_enter(ksm);
254 slot = blk_ksm_find_and_grab_keyslot(ksm, key);
256 blk_ksm_hw_exit(ksm);
261 * If we're here, that means there wasn't a slot that was
262 * already programmed with the key. So try to program it.
264 if (!list_empty(&ksm->idle_slots))
267 blk_ksm_hw_exit(ksm);
268 wait_event(ksm->idle_slots_wait_queue,
269 !list_empty(&ksm->idle_slots));
272 slot = list_first_entry(&ksm->idle_slots, struct blk_ksm_keyslot,
274 slot_idx = blk_ksm_get_slot_idx(slot);
276 err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot_idx);
278 wake_up(&ksm->idle_slots_wait_queue);
279 blk_ksm_hw_exit(ksm);
280 return errno_to_blk_status(err);
283 /* Move this slot to the hash list for the new key. */
285 hlist_del(&slot->hash_node);
287 hlist_add_head(&slot->hash_node, blk_ksm_hash_bucket_for_key(ksm, key));
289 atomic_set(&slot->slot_refs, 1);
291 blk_ksm_remove_slot_from_lru_list(slot);
293 blk_ksm_hw_exit(ksm);
300 * blk_ksm_put_slot() - Release a reference to a slot
301 * @slot: The keyslot to release the reference of.
303 * Context: Any context.
305 void blk_ksm_put_slot(struct blk_ksm_keyslot *slot)
307 struct blk_keyslot_manager *ksm;
315 if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
316 &ksm->idle_slots_lock, flags)) {
317 list_add_tail(&slot->idle_slot_node, &ksm->idle_slots);
318 spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
319 wake_up(&ksm->idle_slots_wait_queue);
324 * blk_ksm_crypto_cfg_supported() - Find out if a crypto configuration is
325 * supported by a ksm.
326 * @ksm: The keyslot manager to check
327 * @cfg: The crypto configuration to check for.
329 * Checks for crypto_mode/data unit size/dun bytes support.
331 * Return: Whether or not this ksm supports the specified crypto config.
333 bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
334 const struct blk_crypto_config *cfg)
338 if (!(ksm->crypto_modes_supported[cfg->crypto_mode] &
339 cfg->data_unit_size))
341 if (ksm->max_dun_bytes_supported < cfg->dun_bytes)
347 * This is an internal function that evicts a key from an inline encryption
348 * device that can be either a real device or the blk-crypto-fallback "device".
349 * It is used only by blk_crypto_evict_key(); see that function for details.
351 int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
352 const struct blk_crypto_key *key)
354 struct blk_ksm_keyslot *slot;
357 if (blk_ksm_is_passthrough(ksm)) {
358 if (ksm->ksm_ll_ops.keyslot_evict) {
359 blk_ksm_hw_enter(ksm);
360 err = ksm->ksm_ll_ops.keyslot_evict(ksm, key, -1);
361 blk_ksm_hw_exit(ksm);
367 blk_ksm_hw_enter(ksm);
368 slot = blk_ksm_find_keyslot(ksm, key);
371 * Not an error, since a key not in use by I/O is not guaranteed
372 * to be in a keyslot. There can be more keys than keyslots.
378 if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
379 /* BUG: key is still in use by I/O */
383 err = ksm->ksm_ll_ops.keyslot_evict(ksm, key,
384 blk_ksm_get_slot_idx(slot));
387 * Callers free the key even on error, so unlink the key from the hash
388 * table and clear slot->key even on error.
390 hlist_del(&slot->hash_node);
393 blk_ksm_hw_exit(ksm);
398 * blk_ksm_reprogram_all_keys() - Re-program all keyslots.
399 * @ksm: The keyslot manager
401 * Re-program all keyslots that are supposed to have a key programmed. This is
402 * intended only for use by drivers for hardware that loses its keys on reset.
404 * Context: Process context. Takes and releases ksm->lock.
406 void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm)
410 if (blk_ksm_is_passthrough(ksm))
413 /* This is for device initialization, so don't resume the device */
414 down_write(&ksm->lock);
415 for (slot = 0; slot < ksm->num_slots; slot++) {
416 const struct blk_crypto_key *key = ksm->slots[slot].key;
422 err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot);
425 up_write(&ksm->lock);
427 EXPORT_SYMBOL_GPL(blk_ksm_reprogram_all_keys);
429 void blk_ksm_destroy(struct blk_keyslot_manager *ksm)
433 kvfree(ksm->slot_hashtable);
434 kvfree_sensitive(ksm->slots, sizeof(ksm->slots[0]) * ksm->num_slots);
435 memzero_explicit(ksm, sizeof(*ksm));
437 EXPORT_SYMBOL_GPL(blk_ksm_destroy);
439 bool blk_ksm_register(struct blk_keyslot_manager *ksm, struct request_queue *q)
441 if (blk_integrity_queue_supports_integrity(q)) {
442 pr_warn("Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n");
448 EXPORT_SYMBOL_GPL(blk_ksm_register);
450 void blk_ksm_unregister(struct request_queue *q)
456 * blk_ksm_intersect_modes() - restrict supported modes by child device
457 * @parent: The keyslot manager for parent device
458 * @child: The keyslot manager for child device, or NULL
460 * Clear any crypto mode support bits in @parent that aren't set in @child.
461 * If @child is NULL, then all parent bits are cleared.
463 * Only use this when setting up the keyslot manager for a layered device,
464 * before it's been exposed yet.
466 void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
467 const struct blk_keyslot_manager *child)
472 parent->max_dun_bytes_supported =
473 min(parent->max_dun_bytes_supported,
474 child->max_dun_bytes_supported);
475 for (i = 0; i < ARRAY_SIZE(child->crypto_modes_supported);
477 parent->crypto_modes_supported[i] &=
478 child->crypto_modes_supported[i];
481 parent->max_dun_bytes_supported = 0;
482 memset(parent->crypto_modes_supported, 0,
483 sizeof(parent->crypto_modes_supported));
486 EXPORT_SYMBOL_GPL(blk_ksm_intersect_modes);
489 * blk_ksm_is_superset() - Check if a KSM supports a superset of crypto modes
490 * and DUN bytes that another KSM supports. Here,
491 * "superset" refers to the mathematical meaning of the
492 * word - i.e. if two KSMs have the *same* capabilities,
493 * they *are* considered supersets of each other.
494 * @ksm_superset: The KSM that we want to verify is a superset
495 * @ksm_subset: The KSM that we want to verify is a subset
497 * Return: True if @ksm_superset supports a superset of the crypto modes and DUN
498 * bytes that @ksm_subset supports.
500 bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
501 struct blk_keyslot_manager *ksm_subset)
511 for (i = 0; i < ARRAY_SIZE(ksm_superset->crypto_modes_supported); i++) {
512 if (ksm_subset->crypto_modes_supported[i] &
513 (~ksm_superset->crypto_modes_supported[i])) {
518 if (ksm_subset->max_dun_bytes_supported >
519 ksm_superset->max_dun_bytes_supported) {
525 EXPORT_SYMBOL_GPL(blk_ksm_is_superset);
528 * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
530 * @target_ksm: The KSM whose restrictions to update.
531 * @reference_ksm: The KSM to whose restrictions this function will update
532 * @target_ksm's restrictions to.
534 * Blk-crypto requires that crypto capabilities that were
535 * advertised when a bio was created continue to be supported by the
536 * device until that bio is ended. This is turn means that a device cannot
537 * shrink its advertised crypto capabilities without any explicit
538 * synchronization with upper layers. So if there's no such explicit
539 * synchronization, @reference_ksm must support all the crypto capabilities that
541 * (i.e. we need blk_ksm_is_superset(@reference_ksm, @target_ksm) == true).
543 * Note also that as long as the crypto capabilities are being expanded, the
544 * order of updates becoming visible is not important because it's alright
545 * for blk-crypto to see stale values - they only cause blk-crypto to
546 * believe that a crypto capability isn't supported when it actually is (which
547 * might result in blk-crypto-fallback being used if available, or the bio being
550 void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
551 struct blk_keyslot_manager *reference_ksm)
553 memcpy(target_ksm->crypto_modes_supported,
554 reference_ksm->crypto_modes_supported,
555 sizeof(target_ksm->crypto_modes_supported));
557 target_ksm->max_dun_bytes_supported =
558 reference_ksm->max_dun_bytes_supported;
560 EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
563 * blk_ksm_init_passthrough() - Init a passthrough keyslot manager
564 * @ksm: The keyslot manager to init
566 * Initialize a passthrough keyslot manager.
567 * Called by e.g. storage drivers to set up a keyslot manager in their
568 * request_queue, when the storage driver wants to manage its keys by itself.
569 * This is useful for inline encryption hardware that doesn't have the concept
570 * of keyslots, and for layered devices.
572 void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm)
574 memset(ksm, 0, sizeof(*ksm));
575 init_rwsem(&ksm->lock);
577 EXPORT_SYMBOL_GPL(blk_ksm_init_passthrough);