mmc: cqhci: add support for inline encryption

Add support for eMMC inline encryption using the blk-crypto framework
(Documentation/block/inline-encryption.rst).

eMMC inline encryption support is specified by the upcoming JEDEC eMMC
v5.2 specification.  It is only specified for the CQ interface, not the
non-CQ interface.  Although the eMMC v5.2 specification hasn't been
officially released yet, the crypto support was already agreed on
several years ago, and it was already implemented by at least two major
hardware vendors.  Lots of hardware in the field already supports and
uses it, e.g. Snapdragon 630 to give one example.

eMMC inline encryption support is very similar to the UFS inline
encryption support which was standardized in the UFS v2.1 specification
and was already upstreamed.  The only major difference is that eMMC
limits data unit numbers to 32 bits, unlike UFS's 64 bits.

Like we did with UFS, make the crypto support opt-in by individual
drivers; don't enable it automatically whenever the hardware declares
crypto support.  This is necessary because in every case we've seen,
some extra vendor-specific logic is needed to use the crypto support.

Co-developed-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Satya Tangirala <satyat@google.com>
Reviewed-and-tested-by: Peng Zhou <peng.zhou@mediatek.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20210125183810.198008-5-ebiggers@kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

1 files changed, 238 insertions, 0 deletions

diff --git a/drivers/mmc/host/cqhci-crypto.c b/drivers/mmc/host/cqhci-crypto.c
new file mode 100644
index 000000000000..0e2a9dcac630
--- /dev/null
+++ b/drivers/mmc/host/cqhci-crypto.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * CQHCI crypto engine (inline encryption) support
+ *
+ * Copyright 2020 Google LLC
+ */
+
+#include <linux/blk-crypto.h>
+#include <linux/keyslot-manager.h>
+#include <linux/mmc/host.h>
+
+#include "cqhci-crypto.h"
+
+/* Map from blk-crypto modes to CQHCI crypto algorithm IDs and key sizes */
+static const struct cqhci_crypto_alg_entry {
+	enum cqhci_crypto_alg alg;
+	enum cqhci_crypto_key_size key_size;
+} cqhci_crypto_algs[BLK_ENCRYPTION_MODE_MAX] = {
+	[BLK_ENCRYPTION_MODE_AES_256_XTS] = {
+		.alg = CQHCI_CRYPTO_ALG_AES_XTS,
+		.key_size = CQHCI_CRYPTO_KEY_SIZE_256,
+	},
+};
+
+static inline struct cqhci_host *
+cqhci_host_from_ksm(struct blk_keyslot_manager *ksm)
+{
+	struct mmc_host *mmc = container_of(ksm, struct mmc_host, ksm);
+
+	return mmc->cqe_private;
+}
+
+static void cqhci_crypto_program_key(struct cqhci_host *cq_host,
+				     const union cqhci_crypto_cfg_entry *cfg,
+				     int slot)
+{
+	u32 slot_offset = cq_host->crypto_cfg_register + slot * sizeof(*cfg);
+	int i;
+
+	/* Clear CFGE */
+	cqhci_writel(cq_host, 0, slot_offset + 16 * sizeof(cfg->reg_val[0]));
+
+	/* Write the key */
+	for (i = 0; i < 16; i++) {
+		cqhci_writel(cq_host, le32_to_cpu(cfg->reg_val[i]),
+			     slot_offset + i * sizeof(cfg->reg_val[0]));
+	}
+	/* Write dword 17 */
+	cqhci_writel(cq_host, le32_to_cpu(cfg->reg_val[17]),
+		     slot_offset + 17 * sizeof(cfg->reg_val[0]));
+	/* Write dword 16, which includes the new value of CFGE */
+	cqhci_writel(cq_host, le32_to_cpu(cfg->reg_val[16]),
+		     slot_offset + 16 * sizeof(cfg->reg_val[0]));
+}
+
+static int cqhci_crypto_keyslot_program(struct blk_keyslot_manager *ksm,
+					const struct blk_crypto_key *key,
+					unsigned int slot)
+
+{
+	struct cqhci_host *cq_host = cqhci_host_from_ksm(ksm);
+	const union cqhci_crypto_cap_entry *ccap_array =
+		cq_host->crypto_cap_array;
+	const struct cqhci_crypto_alg_entry *alg =
+			&cqhci_crypto_algs[key->crypto_cfg.crypto_mode];
+	u8 data_unit_mask = key->crypto_cfg.data_unit_size / 512;
+	int i;
+	int cap_idx = -1;
+	union cqhci_crypto_cfg_entry cfg = {};
+
+	BUILD_BUG_ON(CQHCI_CRYPTO_KEY_SIZE_INVALID != 0);
+	for (i = 0; i < cq_host->crypto_capabilities.num_crypto_cap; i++) {
+		if (ccap_array[i].algorithm_id == alg->alg &&
+		    ccap_array[i].key_size == alg->key_size &&
+		    (ccap_array[i].sdus_mask & data_unit_mask)) {
+			cap_idx = i;
+			break;
+		}
+	}
+	if (WARN_ON(cap_idx < 0))
+		return -EOPNOTSUPP;
+
+	cfg.data_unit_size = data_unit_mask;
+	cfg.crypto_cap_idx = cap_idx;
+	cfg.config_enable = CQHCI_CRYPTO_CONFIGURATION_ENABLE;
+
+	if (ccap_array[cap_idx].algorithm_id == CQHCI_CRYPTO_ALG_AES_XTS) {
+		/* In XTS mode, the blk_crypto_key's size is already doubled */
+		memcpy(cfg.crypto_key, key->raw, key->size/2);
+		memcpy(cfg.crypto_key + CQHCI_CRYPTO_KEY_MAX_SIZE/2,
+		       key->raw + key->size/2, key->size/2);
+	} else {
+		memcpy(cfg.crypto_key, key->raw, key->size);
+	}
+
+	cqhci_crypto_program_key(cq_host, &cfg, slot);
+
+	memzero_explicit(&cfg, sizeof(cfg));
+	return 0;
+}
+
+static void cqhci_crypto_clear_keyslot(struct cqhci_host *cq_host, int slot)
+{
+	/*
+	 * Clear the crypto cfg on the device. Clearing CFGE
+	 * might not be sufficient, so just clear the entire cfg.
+	 */
+	union cqhci_crypto_cfg_entry cfg = {};
+
+	cqhci_crypto_program_key(cq_host, &cfg, slot);
+}
+
+static int cqhci_crypto_keyslot_evict(struct blk_keyslot_manager *ksm,
+				      const struct blk_crypto_key *key,
+				      unsigned int slot)
+{
+	struct cqhci_host *cq_host = cqhci_host_from_ksm(ksm);
+
+	cqhci_crypto_clear_keyslot(cq_host, slot);
+	return 0;
+}
+
+/*
+ * The keyslot management operations for CQHCI crypto.
+ *
+ * Note that the block layer ensures that these are never called while the host
+ * controller is runtime-suspended.  However, the CQE won't necessarily be
+ * "enabled" when these are called, i.e. CQHCI_ENABLE might not be set in the
+ * CQHCI_CFG register.  But the hardware allows that.
+ */
+static const struct blk_ksm_ll_ops cqhci_ksm_ops = {
+	.keyslot_program	= cqhci_crypto_keyslot_program,
+	.keyslot_evict		= cqhci_crypto_keyslot_evict,
+};
+
+static enum blk_crypto_mode_num
+cqhci_find_blk_crypto_mode(union cqhci_crypto_cap_entry cap)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(cqhci_crypto_algs); i++) {
+		BUILD_BUG_ON(CQHCI_CRYPTO_KEY_SIZE_INVALID != 0);
+		if (cqhci_crypto_algs[i].alg == cap.algorithm_id &&
+		    cqhci_crypto_algs[i].key_size == cap.key_size)
+			return i;
+	}
+	return BLK_ENCRYPTION_MODE_INVALID;
+}
+
+/**
+ * cqhci_crypto_init - initialize CQHCI crypto support
+ * @cq_host: a cqhci host
+ *
+ * If the driver previously set MMC_CAP2_CRYPTO and the CQE declares
+ * CQHCI_CAP_CS, initialize the crypto support.  This involves reading the
+ * crypto capability registers, initializing the keyslot manager, clearing all
+ * keyslots, and enabling 128-bit task descriptors.
+ *
+ * Return: 0 if crypto was initialized or isn't supported; whether
+ *	   MMC_CAP2_CRYPTO remains set indicates which one of those cases it is.
+ *	   Also can return a negative errno value on unexpected error.
+ */
+int cqhci_crypto_init(struct cqhci_host *cq_host)
+{
+	struct mmc_host *mmc = cq_host->mmc;
+	struct device *dev = mmc_dev(mmc);
+	struct blk_keyslot_manager *ksm = &mmc->ksm;
+	unsigned int num_keyslots;
+	unsigned int cap_idx;
+	enum blk_crypto_mode_num blk_mode_num;
+	unsigned int slot;
+	int err = 0;
+
+	if (!(mmc->caps2 & MMC_CAP2_CRYPTO) ||
+	    !(cqhci_readl(cq_host, CQHCI_CAP) & CQHCI_CAP_CS))
+		goto out;
+
+	cq_host->crypto_capabilities.reg_val =
+			cpu_to_le32(cqhci_readl(cq_host, CQHCI_CCAP));
+
+	cq_host->crypto_cfg_register =
+		(u32)cq_host->crypto_capabilities.config_array_ptr * 0x100;
+
+	cq_host->crypto_cap_array =
+		devm_kcalloc(dev, cq_host->crypto_capabilities.num_crypto_cap,
+			     sizeof(cq_host->crypto_cap_array[0]), GFP_KERNEL);
+	if (!cq_host->crypto_cap_array) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * CCAP.CFGC is off by one, so the actual number of crypto
+	 * configurations (a.k.a. keyslots) is CCAP.CFGC + 1.
+	 */
+	num_keyslots = cq_host->crypto_capabilities.config_count + 1;
+
+	err = devm_blk_ksm_init(dev, ksm, num_keyslots);
+	if (err)
+		goto out;
+
+	ksm->ksm_ll_ops = cqhci_ksm_ops;
+	ksm->dev = dev;
+
+	/* Unfortunately, CQHCI crypto only supports 32 DUN bits. */
+	ksm->max_dun_bytes_supported = 4;
+
+	/*
+	 * Cache all the crypto capabilities and advertise the supported crypto
+	 * modes and data unit sizes to the block layer.
+	 */
+	for (cap_idx = 0; cap_idx < cq_host->crypto_capabilities.num_crypto_cap;
+	     cap_idx++) {
+		cq_host->crypto_cap_array[cap_idx].reg_val =
+			cpu_to_le32(cqhci_readl(cq_host,
+						CQHCI_CRYPTOCAP +
+						cap_idx * sizeof(__le32)));
+		blk_mode_num = cqhci_find_blk_crypto_mode(
+					cq_host->crypto_cap_array[cap_idx]);
+		if (blk_mode_num == BLK_ENCRYPTION_MODE_INVALID)
+			continue;
+		ksm->crypto_modes_supported[blk_mode_num] |=
+			cq_host->crypto_cap_array[cap_idx].sdus_mask * 512;
+	}
+
+	/* Clear all the keyslots so that we start in a known state. */
+	for (slot = 0; slot < num_keyslots; slot++)
+		cqhci_crypto_clear_keyslot(cq_host, slot);
+
+	/* CQHCI crypto requires the use of 128-bit task descriptors. */
+	cq_host->caps |= CQHCI_TASK_DESC_SZ_128;
+
+	return 0;
+
+out:
+	mmc->caps2 &= ~MMC_CAP2_CRYPTO;
+	return err;
+}