[PATCH] efi/efivars: create efivars mount point when get variable services are available

[PATCH] efi/efivars: create efivars mount point when get variable services are available

[Lee, Chun-Yi]

The efivars filesystem depends on GetVariable or GetNextVariable EFI
runtime services. So the /sys/firmware/efi/efivars does not need to be
created when GetVariable and GetNextVariable are not available.

It is useful for userland to determine the availability of efivars
filesystem.

Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
---
 drivers/firmware/efi/efi.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index fdd1db025dbf..929fbf4dfd5d 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -404,11 +404,14 @@ static int __init efisubsys_init(void)
 	if (error)
 		goto err_remove_group;
 
-	/* and the standard mountpoint for efivarfs */
-	error = sysfs_create_mount_point(efi_kobj, "efivars");
-	if (error) {
-		pr_err("efivars: Subsystem registration failed.\n");
-		goto err_remove_group;
+	if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE |
+				      EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME)) {
+		/* and the standard mountpoint for efivarfs */
+		error = sysfs_create_mount_point(efi_kobj, "efivars");
+		if (error) {
+			pr_err("efivars: Subsystem registration failed.\n");
+			goto err_remove_group;
+		}
 	}
 
 	if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
-- 
2.16.4

Re: [PATCH] efi/efivars: create efivars mount point when get variable services are available

[Ard Biesheuvel]

On Wed, 19 Aug 2020 at 11:28, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote:
>
> The efivars filesystem depends on GetVariable or GetNextVariable EFI
> runtime services. So the /sys/firmware/efi/efivars does not need to be
> created when GetVariable and GetNextVariable are not available.
>
> It is useful for userland to determine the availability of efivars
> filesystem.
>
> Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>

Hello Joey,

This is not the right check to perform here: the efivarfs code could
be instantiated using a different efivars abstraction, so whether the
RT services are implemented is not entirely relevant.

Please look at commit f88814cc2578c121e6edef686365036db72af0ed
("efi/efivars: Expose RT service availability via efivars
abstraction") for an explanation of the underlying issue, and update
your patch accordingly.


> ---
>  drivers/firmware/efi/efi.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index fdd1db025dbf..929fbf4dfd5d 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -404,11 +404,14 @@ static int __init efisubsys_init(void)
>         if (error)
>                 goto err_remove_group;
>
> -       /* and the standard mountpoint for efivarfs */
> -       error = sysfs_create_mount_point(efi_kobj, "efivars");
> -       if (error) {
> -               pr_err("efivars: Subsystem registration failed.\n");
> -               goto err_remove_group;
> +       if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE |
> +                                     EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME)) {
> +               /* and the standard mountpoint for efivarfs */
> +               error = sysfs_create_mount_point(efi_kobj, "efivars");
> +               if (error) {
> +                       pr_err("efivars: Subsystem registration failed.\n");
> +                       goto err_remove_group;
> +               }
>         }
>
>         if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
> --
> 2.16.4
>

Re: [PATCH] efi/efivars: create efivars mount point when get variable services are available

[joeyli]

Hi Ard,

On Thu, Aug 20, 2020 at 11:30:27AM +0200, Ard Biesheuvel wrote:
> On Wed, 19 Aug 2020 at 11:28, Lee, Chun-Yi <joeyli.kernel@gmail.com> wrote:
> >
> > The efivars filesystem depends on GetVariable or GetNextVariable EFI
> > runtime services. So the /sys/firmware/efi/efivars does not need to be
> > created when GetVariable and GetNextVariable are not available.
> >
> > It is useful for userland to determine the availability of efivars
> > filesystem.
> >
> > Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> > Cc: Ard Biesheuvel <ardb@kernel.org>
> > Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
> 
> Hello Joey,
> 
> This is not the right check to perform here: the efivarfs code could
> be instantiated using a different efivars abstraction, so whether the
> RT services are implemented is not entirely relevant.
> 
> Please look at commit f88814cc2578c121e6edef686365036db72af0ed
> ("efi/efivars: Expose RT service availability via efivars
> abstraction") for an explanation of the underlying issue, and update
> your patch accordingly.
>

Thanks for youre review! I will look at f88814cc257 and change my
patch for v2.

Joey Lee
 
> 
> > ---
> >  drivers/firmware/efi/efi.c | 13 ++++++++-----
> >  1 file changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> > index fdd1db025dbf..929fbf4dfd5d 100644
> > --- a/drivers/firmware/efi/efi.c
> > +++ b/drivers/firmware/efi/efi.c
> > @@ -404,11 +404,14 @@ static int __init efisubsys_init(void)
> >         if (error)
> >                 goto err_remove_group;
> >
> > -       /* and the standard mountpoint for efivarfs */
> > -       error = sysfs_create_mount_point(efi_kobj, "efivars");
> > -       if (error) {
> > -               pr_err("efivars: Subsystem registration failed.\n");
> > -               goto err_remove_group;
> > +       if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE |
> > +                                     EFI_RT_SUPPORTED_GET_NEXT_VARIABLE_NAME)) {
> > +               /* and the standard mountpoint for efivarfs */
> > +               error = sysfs_create_mount_point(efi_kobj, "efivars");
> > +               if (error) {
> > +                       pr_err("efivars: Subsystem registration failed.\n");
> > +                       goto err_remove_group;
> > +               }
> >         }
> >
> >         if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
> > --
> > 2.16.4
> >