1 files changed, 378 insertions, 0 deletions
diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
new file mode 100644
index 000000000000..fcd3fd469d7c
--- /dev/null
+++ b/block/keyslot-manager.c
@@ -0,0 +1,378 @@
+// 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.
+ */
+#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);
+	memzero_explicit(ksm->slots, sizeof(ksm->slots[0]) * ksm->num_slots);
+	kvfree(ksm->slots);
+	memzero_explicit(ksm, sizeof(*ksm));
+}
+EXPORT_SYMBOL_GPL(blk_ksm_destroy);