[RFC PATCH v3 1/4] firmware: qcom_scm: Add support for programming inline crypto keys

[Eric Biggers <ebiggers@kernel.org>]

From: Eric Biggers <ebiggers@google.com>

Add support for the Inline Crypto Engine (ICE) key programming interface
that's needed for the ufs-qcom driver to use inline encryption on
Snapdragon SoCs.  This interface consists of two SCM calls: one to
program a key into a keyslot, and one to invalidate a keyslot.

Although the UFS specification defines a standard way to do this, on
these SoCs the Linux kernel isn't permitted to access the needed crypto
configuration registers directly; these SCM calls must be used instead.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 drivers/firmware/qcom_scm.c | 101 ++++++++++++++++++++++++++++++++++++
 drivers/firmware/qcom_scm.h |   4 ++
 include/linux/qcom_scm.h    |  19 +++++++
 3 files changed, 124 insertions(+)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 059bb0fbae9e5..26909006ed220 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -926,6 +926,107 @@ int qcom_scm_ocmem_unlock(enum qcom_scm_ocmem_client id, u32 offset, u32 size)
 }
 EXPORT_SYMBOL(qcom_scm_ocmem_unlock);
 
+/**
+ * qcom_scm_ice_available() - Is the ICE key programming interface available?
+ *
+ * Return: true iff the SCM calls wrapped by qcom_scm_ice_invalidate_key() and
+ *	   qcom_scm_ice_set_key() are available.
+ */
+bool qcom_scm_ice_available(void)
+{
+	return __qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_ES,
+					    QCOM_SCM_ES_INVALIDATE_ICE_KEY) &&
+		__qcom_scm_is_call_available(__scm->dev, QCOM_SCM_SVC_ES,
+					     QCOM_SCM_ES_CONFIG_SET_ICE_KEY);
+}
+EXPORT_SYMBOL(qcom_scm_ice_available);
+
+/**
+ * qcom_scm_ice_invalidate_key() - Invalidate an inline encryption key
+ * @index: the keyslot to invalidate
+ *
+ * The UFSHCI standard defines a standard way to do this, but it doesn't work on
+ * these SoCs; only this SCM call does.
+ *
+ * Return: 0 on success; -errno on failure.
+ */
+int qcom_scm_ice_invalidate_key(u32 index)
+{
+	struct qcom_scm_desc desc = {
+		.svc = QCOM_SCM_SVC_ES,
+		.cmd = QCOM_SCM_ES_INVALIDATE_ICE_KEY,
+		.arginfo = QCOM_SCM_ARGS(1),
+		.args[0] = index,
+		.owner = ARM_SMCCC_OWNER_SIP,
+	};
+
+	return qcom_scm_call(__scm->dev, &desc, NULL);
+}
+EXPORT_SYMBOL(qcom_scm_ice_invalidate_key);
+
+/**
+ * qcom_scm_ice_set_key() - Set an inline encryption key
+ * @index: the keyslot into which to set the key
+ * @key: the key to program
+ * @key_size: the size of the key in bytes
+ * @cipher: the encryption algorithm the key is for
+ * @data_unit_size: the encryption data unit size, i.e. the size of each
+ *		    individual plaintext and ciphertext.  Given in 512-byte
+ *		    units, e.g. 1 = 512 bytes, 8 = 4096 bytes, etc.
+ *
+ * Program a key into a keyslot of Qualcomm ICE (Inline Crypto Engine), where it
+ * can then be used to encrypt/decrypt UFS I/O requests inline.
+ *
+ * The UFSHCI standard defines a standard way to do this, but it doesn't work on
+ * these SoCs; only this SCM call does.
+ *
+ * Return: 0 on success; -errno on failure.
+ */
+int qcom_scm_ice_set_key(u32 index, const u8 *key, u32 key_size,
+			 enum qcom_scm_ice_cipher cipher, u32 data_unit_size)
+{
+	struct qcom_scm_desc desc = {
+		.svc = QCOM_SCM_SVC_ES,
+		.cmd = QCOM_SCM_ES_CONFIG_SET_ICE_KEY,
+		.arginfo = QCOM_SCM_ARGS(5, QCOM_SCM_VAL, QCOM_SCM_RW,
+					 QCOM_SCM_VAL, QCOM_SCM_VAL,
+					 QCOM_SCM_VAL),
+		.args[0] = index,
+		.args[2] = key_size,
+		.args[3] = cipher,
+		.args[4] = data_unit_size,
+		.owner = ARM_SMCCC_OWNER_SIP,
+	};
+	void *keybuf;
+	dma_addr_t key_phys;
+	int ret;
+
+	/*
+	 * 'key' may point to vmalloc()'ed memory, but we need to pass a
+	 * physical address that's been properly flushed.  The sanctioned way to
+	 * do this is by using the DMA API.  But as is best practice for crypto
+	 * keys, we also must wipe the key after use.  This makes kmemdup() +
+	 * dma_map_single() not clearly correct, since the DMA API can use
+	 * bounce buffers.  Instead, just use dma_alloc_coherent().  Programming
+	 * keys is normally rare and thus not performance-critical.
+	 */
+
+	keybuf = dma_alloc_coherent(__scm->dev, key_size, &key_phys,
+				    GFP_KERNEL);
+	if (!keybuf)
+		return -ENOMEM;
+	memcpy(keybuf, key, key_size);
+	desc.args[1] = key_phys;
+
+	ret = qcom_scm_call(__scm->dev, &desc, NULL);
+
+	memset(keybuf, 0, key_size);
+
+	dma_free_coherent(__scm->dev, key_size, keybuf, key_phys);
+	return ret;
+}
+EXPORT_SYMBOL(qcom_scm_ice_set_key);
+
 /**
  * qcom_scm_hdcp_available() - Check if secure environment supports HDCP.
  *
diff --git a/drivers/firmware/qcom_scm.h b/drivers/firmware/qcom_scm.h
index d9ed670da222c..38ea614d29fea 100644
--- a/drivers/firmware/qcom_scm.h
+++ b/drivers/firmware/qcom_scm.h
@@ -103,6 +103,10 @@ extern int scm_legacy_call(struct device *dev, const struct qcom_scm_desc *desc,
 #define QCOM_SCM_OCMEM_LOCK_CMD		0x01
 #define QCOM_SCM_OCMEM_UNLOCK_CMD	0x02
 
+#define QCOM_SCM_SVC_ES			0x10	/* Enterprise Security */
+#define QCOM_SCM_ES_INVALIDATE_ICE_KEY	0x03
+#define QCOM_SCM_ES_CONFIG_SET_ICE_KEY	0x04
+
 #define QCOM_SCM_SVC_HDCP		0x11
 #define QCOM_SCM_HDCP_INVOKE		0x01
 
diff --git a/include/linux/qcom_scm.h b/include/linux/qcom_scm.h
index 3d6a246977615..2e1193a3fb5f0 100644
--- a/include/linux/qcom_scm.h
+++ b/include/linux/qcom_scm.h
@@ -44,6 +44,13 @@ enum qcom_scm_sec_dev_id {
 	QCOM_SCM_ICE_DEV_ID     = 20,
 };
 
+enum qcom_scm_ice_cipher {
+	QCOM_SCM_ICE_CIPHER_AES_128_XTS = 0,
+	QCOM_SCM_ICE_CIPHER_AES_128_CBC = 1,
+	QCOM_SCM_ICE_CIPHER_AES_256_XTS = 3,
+	QCOM_SCM_ICE_CIPHER_AES_256_CBC = 4,
+};
+
 #define QCOM_SCM_VMID_HLOS       0x3
 #define QCOM_SCM_VMID_MSS_MSA    0xF
 #define QCOM_SCM_VMID_WLAN       0x18
@@ -88,6 +95,12 @@ extern int qcom_scm_ocmem_lock(enum qcom_scm_ocmem_client id, u32 offset,
 extern int qcom_scm_ocmem_unlock(enum qcom_scm_ocmem_client id, u32 offset,
 				 u32 size);
 
+extern bool qcom_scm_ice_available(void);
+extern int qcom_scm_ice_invalidate_key(u32 index);
+extern int qcom_scm_ice_set_key(u32 index, const u8 *key, u32 key_size,
+				enum qcom_scm_ice_cipher cipher,
+				u32 data_unit_size);
+
 extern bool qcom_scm_hdcp_available(void);
 extern int qcom_scm_hdcp_req(struct qcom_scm_hdcp_req *req, u32 req_cnt,
 			     u32 *resp);
@@ -138,6 +151,12 @@ static inline int qcom_scm_ocmem_lock(enum qcom_scm_ocmem_client id, u32 offset,
 static inline int qcom_scm_ocmem_unlock(enum qcom_scm_ocmem_client id,
 		u32 offset, u32 size) { return -ENODEV; }
 
+static inline bool qcom_scm_ice_available(void) { return false; }
+static inline int qcom_scm_ice_invalidate_key(u32 index) { return -ENODEV; }
+static inline int qcom_scm_ice_set_key(u32 index, const u8 *key, u32 key_size,
+				       enum qcom_scm_ice_cipher cipher,
+				       u32 data_unit_size) { return -ENODEV; }
+
 static inline bool qcom_scm_hdcp_available(void) { return false; }
 static inline int qcom_scm_hdcp_req(struct qcom_scm_hdcp_req *req, u32 req_cnt,
 		u32 *resp) { return -ENODEV; }
-- 
2.25.1