// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright 2019 Google LLC
 */

/**
 * DOC: blk-crypto profiles
 *
 * 'struct blk_crypto_profile' contains all generic inline encryption-related
 * state for a particular inline encryption device.  blk_crypto_profile serves
 * as the way that drivers for inline encryption hardware expose their crypto
 * capabilities and certain functions (e.g., functions to program and evict
 * keys) to upper layers.  Device drivers that want to support inline encryption
 * construct a crypto profile, then associate it with the disk's request_queue.
 *
 * If the device has keyslots, then its blk_crypto_profile also handles managing
 * these keyslots in a device-independent way, using the driver-provided
 * functions to program and evict keys as needed.  This includes keeping track
 * of which key and how many I/O requests are using each keyslot, getting
 * keyslots for I/O requests, and handling key eviction requests.
 *
 * For more information, see Documentation/block/inline-encryption.rst.
 */

#define pr_fmt(fmt) "blk-crypto: " fmt

#include <linux/blk-crypto-profile.h>
#include <linux/device.h>
#include <linux/atomic.h>
#include <linux/mutex.h>
#include <linux/pm_runtime.h>
#include <linux/wait.h>
#include <linux/blkdev.h>
#include <linux/blk-integrity.h>
#include "blk-crypto-internal.h"

struct blk_crypto_keyslot {
        atomic_t slot_refs;
        struct list_head idle_slot_node;
        struct hlist_node hash_node;
        const struct blk_crypto_key *key;
        struct blk_crypto_profile *profile;
};

static inline void blk_crypto_hw_enter(struct blk_crypto_profile *profile)
{
        /*
         * Calling into the driver requires profile->lock held and the device
         * resumed.  But we must resume the device first, since that can acquire
         * and release profile->lock via blk_crypto_reprogram_all_keys().
         */
        if (profile->dev)
                pm_runtime_get_sync(profile->dev);
        down_write(&profile->lock);
}

static inline void blk_crypto_hw_exit(struct blk_crypto_profile *profile)
{
        up_write(&profile->lock);
        if (profile->dev)
                pm_runtime_put_sync(profile->dev);
}

/**
 * blk_crypto_profile_init() - Initialize a blk_crypto_profile
 * @profile: the blk_crypto_profile to initialize
 * @num_slots: the number of keyslots
 *
 * Storage drivers must call this when starting to set up a blk_crypto_profile,
 * before filling in additional fields.
 *
 * Return: 0 on success, or else a negative error code.
 */
int blk_crypto_profile_init(struct blk_crypto_profile *profile,
                            unsigned int num_slots)
{
        unsigned int slot;
        unsigned int i;
        unsigned int slot_hashtable_size;

        memset(profile, 0, sizeof(*profile));

        /*
         * profile->lock of an underlying device can nest inside profile->lock
         * of a device-mapper device, so use a dynamic lock class to avoid
         * false-positive lockdep reports.
         */
        lockdep_register_key(&profile->lockdep_key);
        __init_rwsem(&profile->lock, "&profile->lock", &profile->lockdep_key);

        if (num_slots == 0)
                return 0;

        /* Initialize keyslot management data. */

        profile->slots = kvcalloc(num_slots, sizeof(profile->slots[0]),
                                  GFP_KERNEL);
        if (!profile->slots)
                goto err_destroy;

        profile->num_slots = num_slots;

        init_waitqueue_head(&profile->idle_slots_wait_queue);
        INIT_LIST_HEAD(&profile->idle_slots);

        for (slot = 0; slot < num_slots; slot++) {
                profile->slots[slot].profile = profile;
                list_add_tail(&profile->slots[slot].idle_slot_node,
                              &profile->idle_slots);
        }

        spin_lock_init(&profile->idle_slots_lock);

        slot_hashtable_size = roundup_pow_of_two(num_slots);
        /*
         * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
         * buckets.  This only makes a difference when there is only 1 keyslot.
         */
        if (slot_hashtable_size < 2)
                slot_hashtable_size = 2;

        profile->log_slot_ht_size = ilog2(slot_hashtable_size);
        profile->slot_hashtable =
                kvmalloc_array(slot_hashtable_size,
                               sizeof(profile->slot_hashtable[0]), GFP_KERNEL);
        if (!profile->slot_hashtable)
                goto err_destroy;
        for (i = 0; i < slot_hashtable_size; i++)
                INIT_HLIST_HEAD(&profile->slot_hashtable[i]);

        return 0;

err_destroy:
        blk_crypto_profile_destroy(profile);
        return -ENOMEM;
}
EXPORT_SYMBOL_GPL(blk_crypto_profile_init);

static void blk_crypto_profile_destroy_callback(void *profile)
{
        blk_crypto_profile_destroy(profile);
}

/**
 * devm_blk_crypto_profile_init() - Resource-managed blk_crypto_profile_init()
 * @dev: the device which owns the blk_crypto_profile
 * @profile: the blk_crypto_profile to initialize
 * @num_slots: the number of keyslots
 *
 * Like blk_crypto_profile_init(), but causes blk_crypto_profile_destroy() to be
 * called automatically on driver detach.
 *
 * Return: 0 on success, or else a negative error code.
 */
int devm_blk_crypto_profile_init(struct device *dev,
                                 struct blk_crypto_profile *profile,
                                 unsigned int num_slots)
{
        int err = blk_crypto_profile_init(profile, num_slots);

        if (err)
                return err;

        return devm_add_action_or_reset(dev,
                                        blk_crypto_profile_destroy_callback,
                                        profile);
}
EXPORT_SYMBOL_GPL(devm_blk_crypto_profile_init);

static inline struct hlist_head *
blk_crypto_hash_bucket_for_key(struct blk_crypto_profile *profile,
                               const struct blk_crypto_key *key)
{
        return &profile->slot_hashtable[
                        hash_ptr(key, profile->log_slot_ht_size)];
}

static void
blk_crypto_remove_slot_from_lru_list(struct blk_crypto_keyslot *slot)
{
        struct blk_crypto_profile *profile = slot->profile;
        unsigned long flags;

        spin_lock_irqsave(&profile->idle_slots_lock, flags);
        list_del(&slot->idle_slot_node);
        spin_unlock_irqrestore(&profile->idle_slots_lock, flags);
}

static struct blk_crypto_keyslot *
blk_crypto_find_keyslot(struct blk_crypto_profile *profile,
                        const struct blk_crypto_key *key)
{
        const struct hlist_head *head =
                blk_crypto_hash_bucket_for_key(profile, key);
        struct blk_crypto_keyslot *slotp;

        hlist_for_each_entry(slotp, head, hash_node) {
                if (slotp->key == key)
                        return slotp;
        }
        return NULL;
}

static struct blk_crypto_keyslot *
blk_crypto_find_and_grab_keyslot(struct blk_crypto_profile *profile,
                                 const struct blk_crypto_key *key)
{
        struct blk_crypto_keyslot *slot;

        slot = blk_crypto_find_keyslot(profile, 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_crypto_remove_slot_from_lru_list(slot);
        }
        return slot;
}

/**
 * blk_crypto_keyslot_index() - Get the index of a keyslot
 * @slot: a keyslot that blk_crypto_get_keyslot() returned
 *
 * Return: the 0-based index of the keyslot within the device's keyslots.
 */
unsigned int blk_crypto_keyslot_index(struct blk_crypto_keyslot *slot)
{
        return slot - slot->profile->slots;
}
EXPORT_SYMBOL_GPL(blk_crypto_keyslot_index);

/**
 * blk_crypto_get_keyslot() - Get a keyslot for a key, if needed.
 * @profile: the crypto profile of the device the key will be used on
 * @key: the key that will be used
 * @slot_ptr: If a keyslot is allocated, an opaque pointer to the keyslot struct
 *            will be stored here.  blk_crypto_put_keyslot() must be called
 *            later to release it.  Otherwise, NULL will be stored here.
 *
 * If the device has keyslots, this gets a keyslot that's been programmed with
 * the specified key.  If the key is already in a slot, this reuses it;
 * otherwise this waits for a slot to become idle and programs the key into it.
 *
 * Context: Process context. Takes and releases profile->lock.
 * Return: BLK_STS_OK on success, meaning that either a keyslot was allocated or
 *         one wasn't needed; or a blk_status_t error on failure.
 */
blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,
                                    const struct blk_crypto_key *key,
                                    struct blk_crypto_keyslot **slot_ptr)
{
        struct blk_crypto_keyslot *slot;
        int slot_idx;
        int err;

        *slot_ptr = NULL;

        /*
         * If the device has no concept of "keyslots", then there is no need to
         * get one.
         */
        if (profile->num_slots == 0)
                return BLK_STS_OK;

        down_read(&profile->lock);
        slot = blk_crypto_find_and_grab_keyslot(profile, key);
        up_read(&profile->lock);
        if (slot)
                goto success;

        for (;;) {
                blk_crypto_hw_enter(profile);
                slot = blk_crypto_find_and_grab_keyslot(profile, key);
                if (slot) {
                        blk_crypto_hw_exit(profile);
                        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(&profile->idle_slots))
                        break;

                blk_crypto_hw_exit(profile);
                wait_event(profile->idle_slots_wait_queue,
                           !list_empty(&profile->idle_slots));
        }

        slot = list_first_entry(&profile->idle_slots, struct blk_crypto_keyslot,
                                idle_slot_node);
        slot_idx = blk_crypto_keyslot_index(slot);

        err = profile->ll_ops.keyslot_program(profile, key, slot_idx);
        if (err) {
                wake_up(&profile->idle_slots_wait_queue);
                blk_crypto_hw_exit(profile);
                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_crypto_hash_bucket_for_key(profile, key));

        atomic_set(&slot->slot_refs, 1);

        blk_crypto_remove_slot_from_lru_list(slot);

        blk_crypto_hw_exit(profile);
success:
        *slot_ptr = slot;
        return BLK_STS_OK;
}

/**
 * blk_crypto_put_keyslot() - Release a reference to a keyslot
 * @slot: The keyslot to release the reference of
 *
 * Context: Any context.
 */
void blk_crypto_put_keyslot(struct blk_crypto_keyslot *slot)
{
        struct blk_crypto_profile *profile = slot->profile;
        unsigned long flags;

        if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
                                        &profile->idle_slots_lock, flags)) {
                list_add_tail(&slot->idle_slot_node, &profile->idle_slots);
                spin_unlock_irqrestore(&profile->idle_slots_lock, flags);
                wake_up(&profile->idle_slots_wait_queue);
        }
}

/**
 * __blk_crypto_cfg_supported() - Check whether the given crypto profile
 *                                supports the given crypto configuration.
 * @profile: the crypto profile to check
 * @cfg: the crypto configuration to check for
 *
 * Return: %true if @profile supports the given @cfg.
 */
bool __blk_crypto_cfg_supported(struct blk_crypto_profile *profile,
                                const struct blk_crypto_config *cfg)
{
        if (!profile)
                return false;
        if (!(profile->modes_supported[cfg->crypto_mode] & cfg->data_unit_size))
                return false;
        if (profile->max_dun_bytes_supported < cfg->dun_bytes)
                return false;
        return true;
}

/*
 * This is an internal function that evicts a key from an inline encryption
 * device that can be either a real device or the blk-crypto-fallback "device".
 * It is used only by blk_crypto_evict_key(); see that function for details.
 */
int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
                           const struct blk_crypto_key *key)
{
        struct blk_crypto_keyslot *slot;
        int err;

        if (profile->num_slots == 0) {
                if (profile->ll_ops.keyslot_evict) {
                        blk_crypto_hw_enter(profile);
                        err = profile->ll_ops.keyslot_evict(profile, key, -1);
                        blk_crypto_hw_exit(profile);
                        return err;
                }
                return 0;
        }

        blk_crypto_hw_enter(profile);
        slot = blk_crypto_find_keyslot(profile, key);
        if (!slot) {
                /*
                 * Not an error, since a key not in use by I/O is not guaranteed
                 * to be in a keyslot.  There can be more keys than keyslots.
                 */
                err = 0;
                goto out;
        }

        if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
                /* BUG: key is still in use by I/O */
                err = -EBUSY;
                goto out_remove;
        }
        err = profile->ll_ops.keyslot_evict(profile, key,
                                            blk_crypto_keyslot_index(slot));
out_remove:
        /*
         * Callers free the key even on error, so unlink the key from the hash
         * table and clear slot->key even on error.
         */
        hlist_del(&slot->hash_node);
        slot->key = NULL;
out:
        blk_crypto_hw_exit(profile);
        return err;
}

/**
 * blk_crypto_reprogram_all_keys() - Re-program all keyslots.
 * @profile: The crypto profile
 *
 * 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 profile->lock.
 */
void blk_crypto_reprogram_all_keys(struct blk_crypto_profile *profile)
{
        unsigned int slot;

        if (profile->num_slots == 0)
                return;

        /* This is for device initialization, so don't resume the device */
        down_write(&profile->lock);
        for (slot = 0; slot < profile->num_slots; slot++) {
                const struct blk_crypto_key *key = profile->slots[slot].key;
                int err;

                if (!key)
                        continue;

                err = profile->ll_ops.keyslot_program(profile, key, slot);
                WARN_ON(err);
        }
        up_write(&profile->lock);
}
EXPORT_SYMBOL_GPL(blk_crypto_reprogram_all_keys);

void blk_crypto_profile_destroy(struct blk_crypto_profile *profile)
{
        if (!profile)
                return;
        lockdep_unregister_key(&profile->lockdep_key);
        kvfree(profile->slot_hashtable);
        kvfree_sensitive(profile->slots,
                         sizeof(profile->slots[0]) * profile->num_slots);
        memzero_explicit(profile, sizeof(*profile));
}
EXPORT_SYMBOL_GPL(blk_crypto_profile_destroy);

bool blk_crypto_register(struct blk_crypto_profile *profile,
                         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->crypto_profile = profile;
        return true;
}
EXPORT_SYMBOL_GPL(blk_crypto_register);

/**
 * blk_crypto_intersect_capabilities() - restrict supported crypto capabilities
 *                                       by child device
 * @parent: the crypto profile for the parent device
 * @child: the crypto profile for the child device, or NULL
 *
 * This clears all crypto capabilities in @parent that aren't set in @child.  If
 * @child is NULL, then this clears all parent capabilities.
 *
 * Only use this when setting up the crypto profile for a layered device, before
 * it's been exposed yet.
 */
void blk_crypto_intersect_capabilities(struct blk_crypto_profile *parent,
                                       const struct blk_crypto_profile *child)
{
        if (child) {
                unsigned int i;

                parent->max_dun_bytes_supported =
                        min(parent->max_dun_bytes_supported,
                            child->max_dun_bytes_supported);
                for (i = 0; i < ARRAY_SIZE(child->modes_supported); i++)
                        parent->modes_supported[i] &= child->modes_supported[i];
        } else {
                parent->max_dun_bytes_supported = 0;
                memset(parent->modes_supported, 0,
                       sizeof(parent->modes_supported));
        }
}
EXPORT_SYMBOL_GPL(blk_crypto_intersect_capabilities);

/**
 * blk_crypto_has_capabilities() - Check whether @target supports at least all
 *                                 the crypto capabilities that @reference does.
 * @target: the target profile
 * @reference: the reference profile
 *
 * Return: %true if @target supports all the crypto capabilities of @reference.
 */
bool blk_crypto_has_capabilities(const struct blk_crypto_profile *target,
                                 const struct blk_crypto_profile *reference)
{
        int i;

        if (!reference)
                return true;

        if (!target)
                return false;

        for (i = 0; i < ARRAY_SIZE(target->modes_supported); i++) {
                if (reference->modes_supported[i] & ~target->modes_supported[i])
                        return false;
        }

        if (reference->max_dun_bytes_supported >
            target->max_dun_bytes_supported)
                return false;

        return true;
}
EXPORT_SYMBOL_GPL(blk_crypto_has_capabilities);

/**
 * blk_crypto_update_capabilities() - Update the capabilities of a crypto
 *                                    profile to match those of another crypto
 *                                    profile.
 * @dst: The crypto profile whose capabilities to update.
 * @src: The crypto profile whose capabilities this function will update @dst's
 *       capabilities to.
 *
 * Blk-crypto requires that crypto capabilities that were
 * advertised when a bio was created continue to be supported by the
 * device until that bio is ended. This is turn means that a device cannot
 * shrink its advertised crypto capabilities without any explicit
 * synchronization with upper layers. So if there's no such explicit
 * synchronization, @src must support all the crypto capabilities that
 * @dst does (i.e. we need blk_crypto_has_capabilities(@src, @dst)).
 *
 * Note also that as long as the crypto capabilities are being expanded, the
 * order of updates becoming visible is not important because it's alright
 * for blk-crypto to see stale values - they only cause blk-crypto to
 * believe that a crypto capability isn't supported when it actually is (which
 * might result in blk-crypto-fallback being used if available, or the bio being
 * failed).
 */
void blk_crypto_update_capabilities(struct blk_crypto_profile *dst,
                                    const struct blk_crypto_profile *src)
{
        memcpy(dst->modes_supported, src->modes_supported,
               sizeof(dst->modes_supported));

        dst->max_dun_bytes_supported = src->max_dun_bytes_supported;
}
EXPORT_SYMBOL_GPL(blk_crypto_update_capabilities);