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

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Message-ID: <CADQ0-X9XAqyavimLS=91h9HYExSCYxKCg6DsGRSgP5L9noGw_Q@mail.gmail.com>
Date:   Mon, 20 Feb 2023 19:35:27 +0900
From:   Masahisa Kojima <masahisa.kojima@...aro.org>
To:     Sumit Garg <sumit.garg@...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 Sumit,

On Mon, 20 Feb 2023 at 18:17, Sumit Garg <sumit.garg@...aro.org> wrote:
>
> 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?

You are correct.
Now this patch is not required and the StMM EFI driver should directly
register efivars ops. I will remove this patch in the next version.

Thanks,
Masahisa Kojima

>
> -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
> >