2020-08-19 09:30:56

by Chun-Yi Lee

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

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 <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Signed-off-by: "Lee, Chun-Yi" <[email protected]>
---
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

2020-08-20 13:51:24

by Ard Biesheuvel

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

On Wed, 19 Aug 2020 at 11:28, Lee, Chun-Yi <[email protected]> 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 <[email protected]>
> Cc: Ard Biesheuvel <[email protected]>
> Signed-off-by: "Lee, Chun-Yi" <[email protected]>

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
>

2020-08-24 13:06:52

by joeyli

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

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 <[email protected]> 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 <[email protected]>
> > Cc: Ard Biesheuvel <[email protected]>
> > Signed-off-by: "Lee, Chun-Yi" <[email protected]>
>
> 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
> >