Re: [RFC PATCH v4 1/4] firmware: qcom_scm: Add support for programming inline crypto keys

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Thu 30 Apr 21:51 PDT 2020, Eric Biggers wrote:

> 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>

Acked-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> ---
>  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 059bb0fbae9e5b..646f9613393612 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);
> +
> +	memzero_explicit(keybuf, 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 d9ed670da222c8..38ea614d29fea2 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 3d6a2469776153..2e1193a3fb5f06 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; }
> -- 
> 2.26.2
>