404 lines
11 KiB
C
404 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright 2019 Google LLC
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*/
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/**
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* DOC: The Keyslot Manager
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*
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* Many devices with inline encryption support have a limited number of "slots"
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* into which encryption contexts may be programmed, and requests can be tagged
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* with a slot number to specify the key to use for en/decryption.
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*
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* As the number of slots is limited, and programming keys is expensive on
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* many inline encryption hardware, we don't want to program the same key into
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* multiple slots - if multiple requests are using the same key, we want to
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* program just one slot with that key and use that slot for all requests.
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*
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* The keyslot manager manages these keyslots appropriately, and also acts as
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* an abstraction between the inline encryption hardware and the upper layers.
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*
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* Lower layer devices will set up a keyslot manager in their request queue
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* and tell it how to perform device specific operations like programming/
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* evicting keys from keyslots.
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*
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* Upper layers will call blk_ksm_get_slot_for_key() to program a
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* key into some slot in the inline encryption hardware.
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*/
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#define pr_fmt(fmt) "blk-crypto: " fmt
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#include <linux/keyslot-manager.h>
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#include <linux/atomic.h>
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#include <linux/mutex.h>
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#include <linux/pm_runtime.h>
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#include <linux/wait.h>
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#include <linux/blkdev.h>
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struct blk_ksm_keyslot {
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atomic_t slot_refs;
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struct list_head idle_slot_node;
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struct hlist_node hash_node;
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const struct blk_crypto_key *key;
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struct blk_keyslot_manager *ksm;
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};
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static inline void blk_ksm_hw_enter(struct blk_keyslot_manager *ksm)
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{
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/*
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* Calling into the driver requires ksm->lock held and the device
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* resumed. But we must resume the device first, since that can acquire
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* and release ksm->lock via blk_ksm_reprogram_all_keys().
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*/
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if (ksm->dev)
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pm_runtime_get_sync(ksm->dev);
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down_write(&ksm->lock);
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}
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static inline void blk_ksm_hw_exit(struct blk_keyslot_manager *ksm)
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{
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up_write(&ksm->lock);
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if (ksm->dev)
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pm_runtime_put_sync(ksm->dev);
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}
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/**
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* blk_ksm_init() - Initialize a keyslot manager
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* @ksm: The keyslot_manager to initialize.
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* @num_slots: The number of key slots to manage.
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*
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* Allocate memory for keyslots and initialize a keyslot manager. Called by
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* e.g. storage drivers to set up a keyslot manager in their request_queue.
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*
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* Return: 0 on success, or else a negative error code.
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*/
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int blk_ksm_init(struct blk_keyslot_manager *ksm, unsigned int num_slots)
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{
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unsigned int slot;
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unsigned int i;
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unsigned int slot_hashtable_size;
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memset(ksm, 0, sizeof(*ksm));
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if (num_slots == 0)
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return -EINVAL;
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ksm->slots = kvcalloc(num_slots, sizeof(ksm->slots[0]), GFP_KERNEL);
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if (!ksm->slots)
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return -ENOMEM;
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ksm->num_slots = num_slots;
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init_rwsem(&ksm->lock);
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init_waitqueue_head(&ksm->idle_slots_wait_queue);
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INIT_LIST_HEAD(&ksm->idle_slots);
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for (slot = 0; slot < num_slots; slot++) {
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ksm->slots[slot].ksm = ksm;
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list_add_tail(&ksm->slots[slot].idle_slot_node,
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&ksm->idle_slots);
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}
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spin_lock_init(&ksm->idle_slots_lock);
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slot_hashtable_size = roundup_pow_of_two(num_slots);
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/*
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* hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
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* buckets. This only makes a difference when there is only 1 keyslot.
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*/
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if (slot_hashtable_size < 2)
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slot_hashtable_size = 2;
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ksm->log_slot_ht_size = ilog2(slot_hashtable_size);
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ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size,
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sizeof(ksm->slot_hashtable[0]),
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GFP_KERNEL);
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if (!ksm->slot_hashtable)
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goto err_destroy_ksm;
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for (i = 0; i < slot_hashtable_size; i++)
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INIT_HLIST_HEAD(&ksm->slot_hashtable[i]);
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return 0;
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err_destroy_ksm:
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blk_ksm_destroy(ksm);
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return -ENOMEM;
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}
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EXPORT_SYMBOL_GPL(blk_ksm_init);
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static inline struct hlist_head *
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blk_ksm_hash_bucket_for_key(struct blk_keyslot_manager *ksm,
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const struct blk_crypto_key *key)
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{
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return &ksm->slot_hashtable[hash_ptr(key, ksm->log_slot_ht_size)];
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}
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static void blk_ksm_remove_slot_from_lru_list(struct blk_ksm_keyslot *slot)
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{
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struct blk_keyslot_manager *ksm = slot->ksm;
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unsigned long flags;
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spin_lock_irqsave(&ksm->idle_slots_lock, flags);
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list_del(&slot->idle_slot_node);
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spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
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}
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static struct blk_ksm_keyslot *blk_ksm_find_keyslot(
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struct blk_keyslot_manager *ksm,
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const struct blk_crypto_key *key)
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{
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const struct hlist_head *head = blk_ksm_hash_bucket_for_key(ksm, key);
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struct blk_ksm_keyslot *slotp;
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hlist_for_each_entry(slotp, head, hash_node) {
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if (slotp->key == key)
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return slotp;
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}
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return NULL;
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}
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static struct blk_ksm_keyslot *blk_ksm_find_and_grab_keyslot(
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struct blk_keyslot_manager *ksm,
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const struct blk_crypto_key *key)
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{
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struct blk_ksm_keyslot *slot;
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slot = blk_ksm_find_keyslot(ksm, key);
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if (!slot)
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return NULL;
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if (atomic_inc_return(&slot->slot_refs) == 1) {
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/* Took first reference to this slot; remove it from LRU list */
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blk_ksm_remove_slot_from_lru_list(slot);
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}
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return slot;
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}
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unsigned int blk_ksm_get_slot_idx(struct blk_ksm_keyslot *slot)
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{
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return slot - slot->ksm->slots;
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}
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EXPORT_SYMBOL_GPL(blk_ksm_get_slot_idx);
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/**
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* blk_ksm_get_slot_for_key() - Program a key into a keyslot.
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* @ksm: The keyslot manager to program the key into.
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* @key: Pointer to the key object to program, including the raw key, crypto
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* mode, and data unit size.
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* @slot_ptr: A pointer to return the pointer of the allocated keyslot.
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*
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* Get a keyslot that's been programmed with the specified key. If one already
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* exists, return it with incremented refcount. Otherwise, wait for a keyslot
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* to become idle and program it.
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*
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* Context: Process context. Takes and releases ksm->lock.
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* Return: BLK_STS_OK on success (and keyslot is set to the pointer of the
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* allocated keyslot), or some other blk_status_t otherwise (and
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* keyslot is set to NULL).
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*/
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blk_status_t blk_ksm_get_slot_for_key(struct blk_keyslot_manager *ksm,
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const struct blk_crypto_key *key,
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struct blk_ksm_keyslot **slot_ptr)
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{
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struct blk_ksm_keyslot *slot;
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int slot_idx;
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int err;
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*slot_ptr = NULL;
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down_read(&ksm->lock);
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slot = blk_ksm_find_and_grab_keyslot(ksm, key);
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up_read(&ksm->lock);
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if (slot)
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goto success;
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for (;;) {
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blk_ksm_hw_enter(ksm);
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slot = blk_ksm_find_and_grab_keyslot(ksm, key);
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if (slot) {
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blk_ksm_hw_exit(ksm);
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goto success;
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}
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/*
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* If we're here, that means there wasn't a slot that was
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* already programmed with the key. So try to program it.
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*/
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if (!list_empty(&ksm->idle_slots))
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break;
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blk_ksm_hw_exit(ksm);
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wait_event(ksm->idle_slots_wait_queue,
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!list_empty(&ksm->idle_slots));
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}
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slot = list_first_entry(&ksm->idle_slots, struct blk_ksm_keyslot,
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idle_slot_node);
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slot_idx = blk_ksm_get_slot_idx(slot);
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err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot_idx);
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if (err) {
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wake_up(&ksm->idle_slots_wait_queue);
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blk_ksm_hw_exit(ksm);
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return errno_to_blk_status(err);
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}
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/* Move this slot to the hash list for the new key. */
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if (slot->key)
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hlist_del(&slot->hash_node);
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slot->key = key;
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hlist_add_head(&slot->hash_node, blk_ksm_hash_bucket_for_key(ksm, key));
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atomic_set(&slot->slot_refs, 1);
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blk_ksm_remove_slot_from_lru_list(slot);
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blk_ksm_hw_exit(ksm);
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success:
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*slot_ptr = slot;
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return BLK_STS_OK;
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}
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/**
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* blk_ksm_put_slot() - Release a reference to a slot
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* @slot: The keyslot to release the reference of.
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*
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* Context: Any context.
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*/
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void blk_ksm_put_slot(struct blk_ksm_keyslot *slot)
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{
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struct blk_keyslot_manager *ksm;
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unsigned long flags;
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if (!slot)
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return;
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ksm = slot->ksm;
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if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
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&ksm->idle_slots_lock, flags)) {
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list_add_tail(&slot->idle_slot_node, &ksm->idle_slots);
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spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
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wake_up(&ksm->idle_slots_wait_queue);
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}
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}
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/**
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* blk_ksm_crypto_cfg_supported() - Find out if a crypto configuration is
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* supported by a ksm.
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* @ksm: The keyslot manager to check
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* @cfg: The crypto configuration to check for.
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*
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* Checks for crypto_mode/data unit size/dun bytes support.
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*
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* Return: Whether or not this ksm supports the specified crypto config.
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*/
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bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
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const struct blk_crypto_config *cfg)
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{
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if (!ksm)
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return false;
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if (!(ksm->crypto_modes_supported[cfg->crypto_mode] &
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cfg->data_unit_size))
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return false;
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if (ksm->max_dun_bytes_supported < cfg->dun_bytes)
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return false;
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return true;
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}
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/**
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* blk_ksm_evict_key() - Evict a key from the lower layer device.
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* @ksm: The keyslot manager to evict from
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* @key: The key to evict
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*
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* Find the keyslot that the specified key was programmed into, and evict that
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* slot from the lower layer device. The slot must not be in use by any
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* in-flight IO when this function is called.
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*
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* Context: Process context. Takes and releases ksm->lock.
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* Return: 0 on success or if there's no keyslot with the specified key, -EBUSY
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* if the keyslot is still in use, or another -errno value on other
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* error.
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*/
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int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
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const struct blk_crypto_key *key)
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{
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struct blk_ksm_keyslot *slot;
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int err = 0;
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blk_ksm_hw_enter(ksm);
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slot = blk_ksm_find_keyslot(ksm, key);
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if (!slot)
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goto out_unlock;
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if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
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err = -EBUSY;
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goto out_unlock;
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}
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err = ksm->ksm_ll_ops.keyslot_evict(ksm, key,
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blk_ksm_get_slot_idx(slot));
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if (err)
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goto out_unlock;
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hlist_del(&slot->hash_node);
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slot->key = NULL;
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err = 0;
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out_unlock:
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blk_ksm_hw_exit(ksm);
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return err;
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}
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/**
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* blk_ksm_reprogram_all_keys() - Re-program all keyslots.
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* @ksm: The keyslot manager
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*
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* Re-program all keyslots that are supposed to have a key programmed. This is
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* intended only for use by drivers for hardware that loses its keys on reset.
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*
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* Context: Process context. Takes and releases ksm->lock.
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*/
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void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm)
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{
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unsigned int slot;
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/* This is for device initialization, so don't resume the device */
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down_write(&ksm->lock);
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for (slot = 0; slot < ksm->num_slots; slot++) {
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const struct blk_crypto_key *key = ksm->slots[slot].key;
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int err;
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if (!key)
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continue;
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err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot);
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WARN_ON(err);
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}
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up_write(&ksm->lock);
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}
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EXPORT_SYMBOL_GPL(blk_ksm_reprogram_all_keys);
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void blk_ksm_destroy(struct blk_keyslot_manager *ksm)
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{
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if (!ksm)
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return;
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kvfree(ksm->slot_hashtable);
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kvfree_sensitive(ksm->slots, sizeof(ksm->slots[0]) * ksm->num_slots);
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memzero_explicit(ksm, sizeof(*ksm));
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}
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EXPORT_SYMBOL_GPL(blk_ksm_destroy);
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bool blk_ksm_register(struct blk_keyslot_manager *ksm, struct request_queue *q)
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{
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if (blk_integrity_queue_supports_integrity(q)) {
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pr_warn("Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n");
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return false;
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}
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q->ksm = ksm;
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return true;
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}
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EXPORT_SYMBOL_GPL(blk_ksm_register);
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void blk_ksm_unregister(struct request_queue *q)
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{
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q->ksm = NULL;
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}
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