[PATCH 1/1] efi_loader: provide variable BootOptionSupport

[Mark Kettenis]

> From: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> Date: Fri, 11 Oct 2024 19:33:40 +0200

Hi Heinrich,

> The UEFI variable BootOptionSupport is required by the UEFI specification
> [1]. It reports if specific types of boot options are honored.
> 
> We don't support any of these extras. So we should set the value 0.

It also says:

  "If the global variable is not present, then an installer or
   application must act as if a value of 0 was returned."

So until we support any of those extras, we don't have to provide that
variable.

> [1] 3.1.4 Boot Manager Capabilities, UEFI Specification 2.10 Errata A,
> 
> Cc: Vincent Stehlé <vincent.stehle at arm.com>
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> ---
>  lib/efi_loader/efi_setup.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/lib/efi_loader/efi_setup.c b/lib/efi_loader/efi_setup.c
> index a610e032d2f..05d035f4eb5 100644
> --- a/lib/efi_loader/efi_setup.c
> +++ b/lib/efi_loader/efi_setup.c
> @@ -179,6 +179,22 @@ static efi_status_t efi_init_os_indications(void)
>  				    &os_indications_supported, false);
>  }
>  
> +/**
> + * efi_init_boot_options_support() - indicate supported boot option types
> + */
> +static efi_status_t efi_init_boot_options_support(void)
> +{
> +	u32 boot_options_support = 0;
> +
> +	return efi_set_variable_int(u"BootOptionSupport",
> +				    &efi_global_variable_guid,
> +				    EFI_VARIABLE_BOOTSERVICE_ACCESS |
> +				    EFI_VARIABLE_RUNTIME_ACCESS |
> +				    EFI_VARIABLE_READ_ONLY,
> +				    sizeof(boot_options_support),
> +				    &boot_options_support, false);
> +}
> +
>  /**
>   * efi_init_early() - handle initialization at early stage
>   *
> @@ -261,6 +277,13 @@ efi_status_t efi_init_obj_list(void)
>  	if (ret != EFI_SUCCESS)
>  		goto out;
>  
> +	/* Indicate supported boot option types */
> +	if (IS_ENABLED(CONFIG_EFI_BOOTMGR)) {
> +		ret = efi_init_boot_options_support();
> +		if (ret != EFI_SUCCESS)
> +			goto out;
> +	}
> +
>  	/* Initialize system table */
>  	ret = efi_initialize_system_table();
>  	if (ret != EFI_SUCCESS)
> -- 
> 2.45.2
> 
>