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