[PATCH v2 2/4] efi_loader: Add OS notifications for SetVariable at runtime

[Heinrich Schuchardt]

On 17.04.24 12:19, Ilias Apalodimas wrote:
> Previous patches enable SetVariable at runtime 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>

Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>

> ---
>   include/efi_loader.h         |  4 ++++
>   lib/efi_loader/efi_runtime.c | 19 ++++++++++++++++---
>   2 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index bb51c0281774..69442f4e58de 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 dde083b09665..c8f7a88ba8db 100644
> --- a/lib/efi_loader/efi_runtime.c
> +++ b/lib/efi_loader/efi_runtime.c
> @@ -10,6 +10,7 @@
>   #include <dm.h>
>   #include <elf.h>
>   #include <efi_loader.h>
> +#include <efi_variable.h>
>   #include <log.h>
>   #include <malloc.h>
>   #include <rtc.h>
> @@ -110,6 +111,7 @@ static __efi_runtime_data efi_uintn_t efi_descriptor_size;
>    */
>   efi_status_t efi_init_runtime_supported(void)
>   {
> +	const efi_guid_t efi_guid_efi_rt_var_file = U_BOOT_EFI_RT_VAR_FILE_GUID;
>   	efi_status_t ret;
>   	struct efi_rt_properties_table *rt_table;
>   
> @@ -127,9 +129,20 @@ 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;
> +	if (IS_ENABLED(CONFIG_EFI_RT_VOLATILE_STORE)) {
> +		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) {
> +			log_err("Failed to set RTStorageVolatile\n");
> +			return ret;
> +		}
> +		rt_table->runtime_services_supported |= EFI_RT_SUPPORTED_SET_VARIABLE;
> +	}
>   
>   	/*
>   	 * This value must be synced with efi_runtime_detach_list