linux-kernel - Re: [PATCH 3/4] tee: amdtee: check TEE status during driver initialization

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Message-ID: <67839c5e-32e5-a69b-5dc6-bbbdf8559bf5@amd.com>
Date:   Fri, 27 Dec 2019 12:37:49 -0600
From:   Gary R Hook <ghook@....com>
To:     Rijo Thomas <Rijo-john.Thomas@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        tee-dev@...ts.linaro.org
Cc:     Nimesh Easow <Nimesh.Easow@....com>,
        Devaraj Rangasamy <Devaraj.Rangasamy@....com>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Gary Hook <gary.hook@....com>
Subject: Re: [PATCH 3/4] tee: amdtee: check TEE status during driver
 initialization

On 12/26/19 11:24 PM, Rijo Thomas wrote:
> The AMD-TEE driver should check if TEE is available before
> registering itself with TEE subsystem. This ensures that
> there is a TEE which the driver can talk to before proceeding
> with tee device node allocation.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Acked-by: Jens Wiklander <jens.wiklander@...aro.org>
> Co-developed-by: Devaraj Rangasamy <Devaraj.Rangasamy@....com>
> Signed-off-by: Devaraj Rangasamy <Devaraj.Rangasamy@....com>
> Signed-off-by: Rijo Thomas <Rijo-john.Thomas@....com>

Reviewed-by: Gary R Hook <gary.hook@....com>

> ---
>   drivers/crypto/ccp/tee-dev.c | 11 +++++++++++
>   drivers/tee/amdtee/core.c    |  6 ++++++
>   include/linux/psp-tee.h      | 18 ++++++++++++++++++
>   3 files changed, 35 insertions(+)
> 
> diff --git a/drivers/crypto/ccp/tee-dev.c b/drivers/crypto/ccp/tee-dev.c
> index 555c8a7..5e697a9 100644
> --- a/drivers/crypto/ccp/tee-dev.c
> +++ b/drivers/crypto/ccp/tee-dev.c
> @@ -362,3 +362,14 @@ int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf, size_t len,
>   	return 0;
>   }
>   EXPORT_SYMBOL(psp_tee_process_cmd);
> +
> +int psp_check_tee_status(void)
> +{
> +	struct psp_device *psp = psp_get_master_device();
> +
> +	if (!psp || !psp->tee_data)
> +		return -ENODEV;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(psp_check_tee_status);
> diff --git a/drivers/tee/amdtee/core.c b/drivers/tee/amdtee/core.c
> index dd360f3..9d0cee1 100644
> --- a/drivers/tee/amdtee/core.c
> +++ b/drivers/tee/amdtee/core.c
> @@ -16,6 +16,7 @@
>   #include <linux/firmware.h>
>   #include "amdtee_private.h"
>   #include "../tee_private.h"
> +#include <linux/psp-tee.h>
>   
>   static struct amdtee_driver_data *drv_data;
>   static DEFINE_MUTEX(session_list_mutex);
> @@ -438,6 +439,10 @@ static int __init amdtee_driver_init(void)
>   	struct tee_shm_pool *pool = ERR_PTR(-EINVAL);
>   	int rc;
>   
> +	rc = psp_check_tee_status();
> +	if (rc)
> +		goto err_fail;
> +
>   	drv_data = kzalloc(sizeof(*drv_data), GFP_KERNEL);
>   	if (IS_ERR(drv_data))
>   		return -ENOMEM;
> @@ -485,6 +490,7 @@ static int __init amdtee_driver_init(void)
>   	kfree(drv_data);
>   	drv_data = NULL;
>   
> +err_fail:
>   	pr_err("amd-tee driver initialization failed\n");
>   	return rc;
>   }
> diff --git a/include/linux/psp-tee.h b/include/linux/psp-tee.h
> index 63bb221..cb0c95d 100644
> --- a/include/linux/psp-tee.h
> +++ b/include/linux/psp-tee.h
> @@ -62,6 +62,19 @@ enum tee_cmd_id {
>   int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf, size_t len,
>   			u32 *status);
>   
> +/**
> + * psp_check_tee_status() - Checks whether there is a TEE which a driver can
> + * talk to.
> + *
> + * This function can be used by AMD-TEE driver to query if there is TEE with
> + * which it can communicate.
> + *
> + * Returns:
> + * 0          if the device has TEE
> + * -%ENODEV   if there is no TEE available
> + */
> +int psp_check_tee_status(void);
> +
>   #else /* !CONFIG_CRYPTO_DEV_SP_PSP */
>   
>   static inline int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf,
> @@ -69,5 +82,10 @@ static inline int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf,
>   {
>   	return -ENODEV;
>   }
> +
> +static inline int psp_check_tee_status(void)
> +{
> +	return -ENODEV;
> +}
>   #endif /* CONFIG_CRYPTO_DEV_SP_PSP */
>   #endif /* __PSP_TEE_H_ */
>