[PATCH v1 2/4] efi_loader: Add OS notifications for SetVariableRT in RAM

[Heinrich Schuchardt]

On 4/6/24 16:01, Ilias Apalodimas wrote:
> Previous patches enable SetVariableRT using a volatile storage backend
> using EFI_RUNTIME_SERVICES_DATA allocared memory. Since there's no
> recommendation from the spec on how to notify the OS, add a volatile
> EFI variable that contains the filename relative to the ESP. OS'es
> can use that file and update it at runtime
>
> $~ efivar -p -n b2ac5fc9-92b7-4acd-aeac-11e818c3130c-RTStorageVolatile
> GUID: b2ac5fc9-92b7-4acd-aeac-11e818c3130c
> Name: "RTStorageVolatile"
> Attributes:
> 	Boot Service Access
> 	Runtime Service Access
> Value:
> 00000000  75 62 6f 6f 74 65 66 69  2e 76 61 72 00           |ubootefi.var.   |
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
>   include/efi_loader.h          |  4 ++++
>   lib/efi_loader/efi_runtime.c  |  4 ----
>   lib/efi_loader/efi_variable.c | 20 ++++++++++++++++++++
>   3 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 7daca0afba2b..25551fe18948 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -159,6 +159,10 @@ static inline void efi_set_bootdev(const char *dev, const char *devnr,
>   #define EFICONFIG_AUTO_GENERATED_ENTRY_GUID \
>   	EFI_GUID(0x8108ac4e, 0x9f11, 0x4d59, \
>   		 0x85, 0x0e, 0xe2, 0x1a, 0x52, 0x2c, 0x59, 0xb2)
> +#define U_BOOT_EFI_RT_VAR_FILE_GUID \
> +	EFI_GUID(0xb2ac5fc9, 0x92b7, 0x4acd, \
> +		 0xae, 0xac, 0x11, 0xe8, 0x18, 0xc3, 0x13, 0x0c)
> +
>
>   /* Use internal device tree when starting UEFI application */
>   #define EFI_FDT_USE_INTERNAL NULL
> diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
> index 8ebbea7e5c69..d898ba6c268f 100644
> --- a/lib/efi_loader/efi_runtime.c
> +++ b/lib/efi_loader/efi_runtime.c
> @@ -127,10 +127,6 @@ efi_status_t efi_init_runtime_supported(void)
>   				EFI_RT_SUPPORTED_SET_VIRTUAL_ADDRESS_MAP |
>   				EFI_RT_SUPPORTED_CONVERT_POINTER;
>
> -	if (IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE))
> -		rt_table->runtime_services_supported |=
> -			EFI_RT_SUPPORTED_SET_VARIABLE;
> -

Why do you want to remove this flag?

Best regards

Heinrich

>   	/*
>   	 * This value must be synced with efi_runtime_detach_list
>   	 * as well as efi_runtime_services.
> diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
> index f79041e6bedd..f97c8c57f75c 100644
> --- a/lib/efi_loader/efi_variable.c
> +++ b/lib/efi_loader/efi_variable.c
> @@ -554,6 +554,26 @@ if (IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE)) {
>    */
>   void efi_variables_boot_exit_notify(void)
>   {
> +	const efi_guid_t efi_guid_efi_rt_var_file = U_BOOT_EFI_RT_VAR_FILE_GUID;
> +	const efi_guid_t rt_prop_guid = EFI_RT_PROPERTIES_TABLE_GUID;
> +	efi_status_t ret;
> +
> +	if (IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE)) {
> +		struct efi_rt_properties_table *rt_prop =
> +			efi_get_configuration_table(&rt_prop_guid);
> +
> +		ret = efi_set_variable_int(u"RTStorageVolatile",
> +					   &efi_guid_efi_rt_var_file,
> +					   EFI_VARIABLE_BOOTSERVICE_ACCESS |
> +					   EFI_VARIABLE_RUNTIME_ACCESS |
> +					   EFI_VARIABLE_READ_ONLY,
> +					   sizeof(EFI_VAR_FILE_NAME),
> +					   EFI_VAR_FILE_NAME, false);
> +		if (ret != EFI_SUCCESS)
> +			rt_prop->runtime_services_supported |= ~EFI_RT_SUPPORTED_SET_VARIABLE;
> +		else
> +			log_err("Can't RTStorage. SetVariableRT won't be available\n");
> +	}
>   	/* Switch variable services functions to runtime version */
>   	efi_runtime_services.get_variable = efi_get_variable_runtime;
>   	efi_runtime_services.get_next_variable_name =