linux-kernel - Re: [PATCH v2 3/4] tee: expose tee efivar register function

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Message-ID: <CAFA6WYPdhWAgkBs+ehADVB__5-C9xDmdGL=D9Q5V047yEoL2EA@mail.gmail.com>
Date:   Mon, 20 Feb 2023 14:47:10 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Masahisa Kojima <masahisa.kojima@...aro.org>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        linux-kernel@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Johan Hovold <johan+linaro@...nel.org>
Subject: Re: [PATCH v2 3/4] tee: expose tee efivar register function

Hi Masahisa,

On Mon, 20 Feb 2023 at 10:47, Masahisa Kojima
<masahisa.kojima@...aro.org> wrote:
>
> This commit adds the functions to register/unregister
> the tee-based EFI variable driver.
>

I am unsure if this commit adds any value now since the TEE StMM EFI
driver should be able to directly use efivars_{register/unregister}()
APIs. Do you expect any other TEE kernel driver to use these?

-Sumit

> Co-developed-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Masahisa Kojima <masahisa.kojima@...aro.org>
> ---
>  drivers/tee/tee_core.c  | 23 +++++++++++++++++++++++
>  include/linux/tee_drv.h | 23 +++++++++++++++++++++++
>  2 files changed, 46 insertions(+)
>
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index 98da206cd761..0dce5b135d2c 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -7,6 +7,7 @@
>
>  #include <linux/cdev.h>
>  #include <linux/cred.h>
> +#include <linux/efi.h>
>  #include <linux/fs.h>
>  #include <linux/idr.h>
>  #include <linux/module.h>
> @@ -1263,6 +1264,28 @@ static void __exit tee_exit(void)
>         tee_class = NULL;
>  }
>
> +void tee_register_efivar_ops(struct efivars *tee_efivars,
> +                            struct efivar_operations *ops)
> +{
> +       /*
> +        * If the firmware EFI runtime services support SetVariable(),
> +        * tee-based EFI variable services are not used.
> +        */
> +       if (!efivar_supports_writes()) {
> +               efivars_generic_ops_unregister();
> +               pr_info("Use tee-based EFI runtime variable services\n");
> +               efivars_register(tee_efivars, ops);
> +       }
> +}
> +EXPORT_SYMBOL_GPL(tee_register_efivar_ops);
> +
> +void tee_unregister_efivar_ops(struct efivars *tee_efivars)
> +{
> +       efivars_unregister(tee_efivars);
> +       efivars_generic_ops_register();
> +}
> +EXPORT_SYMBOL_GPL(tee_unregister_efivar_ops);
> +
>  subsys_initcall(tee_init);
>  module_exit(tee_exit);
>
> diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> index 17eb1c5205d3..def4ea6212ee 100644
> --- a/include/linux/tee_drv.h
> +++ b/include/linux/tee_drv.h
> @@ -7,6 +7,7 @@
>  #define __TEE_DRV_H
>
>  #include <linux/device.h>
> +#include <linux/efi.h>
>  #include <linux/idr.h>
>  #include <linux/kref.h>
>  #include <linux/list.h>
> @@ -507,4 +508,26 @@ struct tee_context *teedev_open(struct tee_device *teedev);
>   */
>  void teedev_close_context(struct tee_context *ctx);
>
> +/**
> + * tee_register_efivar_ops() - register the efivar ops
> + * @tee_efivars:       pointer to efivars structure
> + * @ops:               pointer to contain the efivar operation
> + *
> + * This function registers the tee-based efivar operation as an
> + * EFI Runtime Service.
> + *
> + */
> +void tee_register_efivar_ops(struct efivars *tee_efivars,
> +                            struct efivar_operations *ops);
> +
> +/**
> + * tee_unregister_efivar_ops() - unregister the efivar ops
> + * @tee_efivars:       pointer to efivars structure
> + *
> + * This function unregisters the tee-based efivar operation
> + * and reverts to the generic operation.
> + *
> + */
> +void tee_unregister_efivar_ops(struct efivars *tee_efivars);
> +
>  #endif /*__TEE_DRV_H*/
> --
> 2.30.2
>