Re: [PATCH 2/5 v2] efi_loader: Implement EFI variable handling via OP-TEE

On 5/11/20 8:14 PM, Ilias Apalodimas wrote:

In OP-TEE we can run EDK2's StandAloneMM on a secure partition. StandAloneMM is responsible for the UEFI variable support. In combination with OP-TEE and it's U-Boot supplicant, variables are authenticated/validated in secure world and stored on an RPMB partition.

So let's add a new config option in U-Boot implementing the necessary calls to OP-TEE for the variable management.

Signed-off-by: Ilias Apalodimas ilias.apalodimas@linaro.org Signed-off-by: Pipat Methavanitpong pipat1010@gmail.com Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org

---

lib/efi_loader/Kconfig | 9 + lib/efi_loader/Makefile | 4 + lib/efi_loader/efi_variable_tee.c | 643 ++++++++++++++++++++++++++++++ 3 files changed, 656 insertions(+) create mode 100644 lib/efi_loader/efi_variable_tee.c

diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig index 1cfa24ffcf72..e385cd0b9dae 100644 --- a/lib/efi_loader/Kconfig +++ b/lib/efi_loader/Kconfig @@ -164,4 +164,13 @@ config EFI_SECURE_BOOT it is signed with a trusted key. To do that, you need to install, at least, PK, KEK and db.

+config EFI_MM_COMM_TEE

• bool "UEFI variables storage service via OP-TEE"
• depends on SUPPORT_EMMC_RPMB
• default n
• help

•  If OP-TEE is present and running StandAloneMM dispatch all UEFI variable
  

•  related operations to that. The application will verify, authenticate and
  

•  store the variables on an RPMB
  

endif diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile index eff3c25ec301..dba652121eab 100644 --- a/lib/efi_loader/Makefile +++ b/lib/efi_loader/Makefile @@ -34,7 +34,11 @@ obj-y += efi_root_node.o obj-y += efi_runtime.o obj-y += efi_setup.o obj-$(CONFIG_EFI_UNICODE_COLLATION_PROTOCOL2) += efi_unicode_collation.o +ifeq ($(CONFIG_EFI_MM_COMM_TEE),y) +obj-y += efi_variable_tee.o +else obj-y += efi_variable.o +endif obj-y += efi_watchdog.o obj-$(CONFIG_LCD) += efi_gop.o obj-$(CONFIG_DM_VIDEO) += efi_gop.o diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c new file mode 100644 index 000000000000..f8857bb81e72 --- /dev/null +++ b/lib/efi_loader/efi_variable_tee.c @@ -0,0 +1,643 @@ +// SPDX-License-Identifier: GPL-2.0+ +/*

• • EFI variable service via OP-TEE
• • Copyright (C) 2019 Linaro Ltd. sughosh.ganu@linaro.org
• • Copyright (C) 2019 Linaro Ltd. ilias.apalodimas@linaro.org
• */

+#include <common.h> +#include <efi.h> +#include <efi_api.h> +#include <efi_loader.h> +#include <tee.h> +#include <malloc.h> +#include <mm_communication.h>

+static efi_uintn_t max_buffer_size; /* comm + var + func + data */ +static efi_uintn_t max_payload_size; /* func + data */

+struct mm_connection {

• struct udevice *tee;
• u32 session;

+};

+/**

• • get_connection() - Retrieve OP-TEE session for a specific UUID.
• • @conn: session buffer to fill
• • Return: status code
• */

+static int get_connection(struct mm_connection *conn) +{

• static const struct tee_optee_ta_uuid uuid = PTA_STMM_UUID;
• struct udevice *tee = NULL;
• struct tee_open_session_arg arg;
• int rc;
• tee = tee_find_device(tee, NULL, NULL, NULL);
• if (!tee)

• return -ENODEV;
  

• memset(&arg, 0, sizeof(arg));
• tee_optee_ta_uuid_to_octets(arg.uuid, &uuid);
• rc = tee_open_session(tee, &arg, 0, NULL);
• if (!rc) {

• conn->tee = tee;
  

• conn->session = arg.session;
  

• }
• return rc;

+}

+/**

• • optee_mm_communicate() - Pass a buffer to StandaloneMM running in OP-TEE
• • @comm_buf: locally allocted communcation buffer
• • @dsize: buffer size
• • Return: status code
• */

+static efi_status_t optee_mm_communicate(void *comm_buf, ulong dsize) +{

• ulong buf_size;
• efi_status_t ret;
• struct efi_mm_communicate_header *mm_hdr;
• struct mm_connection conn = { NULL, 0 };
• struct tee_invoke_arg arg;
• struct tee_param param[2];
• struct tee_shm *shm = NULL;
• int rc;
• if (!comm_buf)

• return EFI_INVALID_PARAMETER;
  

• mm_hdr = (struct efi_mm_communicate_header *)comm_buf;
• buf_size = mm_hdr->message_len + sizeof(efi_guid_t) + sizeof(size_t);
• if (dsize != buf_size)

• return EFI_INVALID_PARAMETER;
  

• rc = get_connection(&conn);
• if (rc) {

• log_err("Unable to open OP-TEE session (err=%d)\n", rc);
  

• return EFI_UNSUPPORTED;
  

• }
• if (tee_shm_register(conn.tee, comm_buf, buf_size, 0, &shm)) {

• log_err("Unable to register shared memory\n");
  

• return EFI_UNSUPPORTED;
  

• }
• memset(&arg, 0, sizeof(arg));
• arg.func = PTA_STMM_CMDID_COMMUNICATE;
• arg.session = conn.session;
• memset(param, 0, sizeof(param));
• param[0].attr = TEE_PARAM_ATTR_TYPE_MEMREF_INOUT;
• param[0].u.memref.size = buf_size;
• param[0].u.memref.shm = shm;
• param[1].attr = TEE_PARAM_ATTR_TYPE_VALUE_OUTPUT;
• rc = tee_invoke_func(conn.tee, &arg, 2, param);
• if (rc)

• return EFI_INVALID_PARAMETER;
  

• tee_shm_free(shm);
• tee_close_session(conn.tee, conn.session);
• switch (param[1].u.value.a) {
• case ARM_SMC_MM_RET_SUCCESS:

• ret = EFI_SUCCESS;
  

• break;
  

• case ARM_SMC_MM_RET_INVALID_PARAMS:

• ret = EFI_INVALID_PARAMETER;
  

• break;
  

• case ARM_SMC_MM_RET_DENIED:

• ret = EFI_ACCESS_DENIED;
  

• break;
  

• case ARM_SMC_MM_RET_NO_MEMORY:

• ret = EFI_OUT_OF_RESOURCES;
  

• break;
  

• default:

• ret = EFI_ACCESS_DENIED;
  

• }
• return ret;

+}

+/**

• • mm_communicate() - Adjust the cmonnucation buffer to StandAlonneMM and send
• • it to OP-TEE
• • @comm_buf: locally allocted communcation buffer
• • @dsize: buffer size
• • Return: status code
• */

+static efi_status_t mm_communicate(u8 *comm_buf, efi_uintn_t dsize) +{

• efi_status_t ret;
• struct efi_mm_communicate_header *mm_hdr;
• struct smm_variable_communicate_header *var_hdr;
• dsize += MM_COMMUNICATE_HEADER_SIZE + MM_VARIABLE_COMMUNICATE_SIZE;
• mm_hdr = (struct efi_mm_communicate_header *)comm_buf;
• var_hdr = (struct smm_variable_communicate_header *)mm_hdr->data;
• ret = optee_mm_communicate(comm_buf, dsize);
• if (ret != EFI_SUCCESS) {

• log_err("%s failed!\n", __func__);
  

• return ret;
  

• }
• return var_hdr->ret_status;

+}

+/**

• • setup_mm_hdr() - Allocate a buffer for StandAloneMM and initialize the

• • 	header data.
    

• • @dptr: pointer address of the corresponding StandAloneMM

• • 	function
    

• • @payload_size: buffer size
• • @func: standAloneMM function number
• • @ret: EFI return code
• • Return: buffer or NULL
• */

+static u8 *setup_mm_hdr(void **dptr, efi_uintn_t payload_size,

• 	efi_uintn_t func, efi_status_t *ret)
  

+{

• const efi_guid_t mm_var_guid = EFI_MM_VARIABLE_GUID;
• struct efi_mm_communicate_header *mm_hdr;
• struct smm_variable_communicate_header *var_hdr;
• u8 *comm_buf;
• /* In the init function we initialize max_buffer_size with

• * get_max_payload(). So skip the test if max_buffer_size is initialized
  

• * StandAloneMM will perform similar checks and drop the buffer if it's
  

• * too long
  

• */
  

• if (max_buffer_size && max_buffer_size <

• 	(MM_COMMUNICATE_HEADER_SIZE +
  

• 	 MM_VARIABLE_COMMUNICATE_SIZE +
  

• 	 payload_size)) {
  

• *ret = EFI_INVALID_PARAMETER;
  

• return NULL;
  

• }
• comm_buf = calloc(1, MM_COMMUNICATE_HEADER_SIZE +

• 	  MM_VARIABLE_COMMUNICATE_SIZE +
  

• 	  payload_size);
  

• if (!comm_buf) {

• *ret = EFI_OUT_OF_RESOURCES;
  

• return NULL;
  

• }
• mm_hdr = (struct efi_mm_communicate_header *)comm_buf;
• guidcpy(&mm_hdr->header_guid, &mm_var_guid);
• mm_hdr->message_len = MM_VARIABLE_COMMUNICATE_SIZE + payload_size;
• var_hdr = (struct smm_variable_communicate_header *)mm_hdr->data;
• var_hdr->function = func;
• if (dptr)

• *dptr = var_hdr->data;
  

• *ret = EFI_SUCCESS;
• return comm_buf;

+}

+/**

• • get_max_payload() - Get variable payload size from StandAloneMM.
• • @size: size of the variable in storage
• • Return: status code
• */

+efi_status_t EFIAPI get_max_payload(efi_uintn_t *size) +{

• struct smm_variable_payload_size *var_payload = NULL;
• efi_uintn_t payload_size;
• efi_status_t ret;
• u8 *comm_buf;
• if (!size)

• return EFI_INVALID_PARAMETER;
  

• payload_size = sizeof(*var_payload);
• comm_buf = setup_mm_hdr((void **)&var_payload, payload_size,

• 		SMM_VARIABLE_FUNCTION_GET_PAYLOAD_SIZE, &ret);
  

• if (!comm_buf)

• return EFI_EXIT(ret);
  

• ret = mm_communicate(comm_buf, payload_size);
• if (ret != EFI_SUCCESS)

• goto out;
  

• *size = var_payload->size;

+out:

• free(comm_buf);
• return ret;

+}

+/**

• • efi_get_variable() - retrieve value of a UEFI variable
• • This function implements the GetVariable runtime service.
• • See the Unified Extensible Firmware Interface (UEFI) specification for
• • details.
• • @name: name of the variable
• • @guid: vendor GUID
• • @attr: attributes of the variable
• • @data_size: size of the buffer to which the variable value is copied
• • @data: buffer to which the variable value is copied
• • Return: status code
• */

+efi_status_t EFIAPI efi_get_variable(u16 *name, const efi_guid_t *guid,

• 		     u32 *attr, efi_uintn_t *data_size,
  

• 		     void *data)
  

+{

• struct smm_variable_access *var_acc;
• efi_uintn_t payload_size;
• efi_uintn_t name_size;
• efi_uintn_t tmp_dsize;
• efi_status_t ret;
• u8 *comm_buf;
• EFI_ENTRY(""%ls" %pUl %p %p %p", name, guid, attr, data_size, data);
• if (!name || !guid || !data_size)

• return EFI_EXIT(EFI_INVALID_PARAMETER);
  

• /* Check payload size */
• name_size = u16_strsize(name);
• if (name_size > max_payload_size - MM_VARIABLE_ACCESS_HEADER_SIZE)

• return EFI_EXIT(EFI_INVALID_PARAMETER);
  

• /* Trim output buffer size */
• tmp_dsize = *data_size;
• if (name_size + tmp_dsize >

• 	max_payload_size - MM_VARIABLE_ACCESS_HEADER_SIZE) {
  

• tmp_dsize = max_payload_size -
  

• 		MM_VARIABLE_ACCESS_HEADER_SIZE -
  

• 		name_size;
  

• }
• /* Get communication buffer and initialize header */
• payload_size = MM_VARIABLE_ACCESS_HEADER_SIZE + name_size + tmp_dsize;
• comm_buf = setup_mm_hdr((void **)&var_acc, payload_size,

• 		SMM_VARIABLE_FUNCTION_GET_VARIABLE, &ret);
  

• if (!comm_buf)

• return EFI_EXIT(ret);
  

• /* Fill in contents */
• guidcpy(&var_acc->guid, guid);
• var_acc->data_size = tmp_dsize;
• var_acc->name_size = name_size;
• var_acc->attr = attr ? *attr : 0;
• memcpy(var_acc->name, name, name_size);
• /* Communicate */
• ret = mm_communicate(comm_buf, payload_size);
• if (ret == EFI_SUCCESS || ret == EFI_BUFFER_TOO_SMALL) {

• /* Update with reported data size for trimmed case */
  

• *data_size = var_acc->data_size;
  

• }
• if (ret != EFI_SUCCESS)

• goto done;
  

• if (attr)

• *attr = var_acc->attr;
  

• if (data)

• memcpy(data, (u8 *)var_acc->name + var_acc->name_size,
  

•        var_acc->data_size);
  

• else

• ret = EFI_INVALID_PARAMETER;
  

+done:

• free(comm_buf);
• return EFI_EXIT(ret);

+}

+/**

• • efi_get_next_variable_name() - enumerate the current variable names
• • @variable_name_size: size of variable_name buffer in byte
• • @variable_name: name of uefi variable's name in u16
• • @guid: vendor's guid
• • This function implements the GetNextVariableName service.
• • See the Unified Extensible Firmware Interface (UEFI) specification for
• • details.
• • Return: status code
• */

+efi_status_t EFIAPI efi_get_next_variable_name(efi_uintn_t *variable_name_size,

• 			       u16 *variable_name,
  

• 			       efi_guid_t *guid)
  

+{

• struct smm_variable_getnext *var_getnext;
• efi_uintn_t payload_size;
• efi_uintn_t tmp_dsize;
• efi_uintn_t name_size;
• efi_status_t ret;
• efi_uintn_t out_name_size;
• efi_uintn_t in_name_size;
• u8 *comm_buf;
• EFI_ENTRY("%p "%ls" %pUl", variable_name_size, variable_name, guid);
• if (!variable_name_size || !variable_name || !guid)

• return EFI_EXIT(EFI_INVALID_PARAMETER);
  

• out_name_size = *variable_name_size;
• in_name_size = u16_strsize(variable_name);

The UEFI spec requires that EFI_INVALID_PARAMETER should be returned if there is no '\0' character in the first *variable_name_size words of variable_name. I think we should add this test here instead of using max(out_name_size, in_name_size) later in the code.

You are currently calling EFI_EXIT() in many places. Depending on the level of code optimizations done by the compiler and the debug settings this may need to unnecessary code size. I suggest to use a single exit point in each of the functions, e.g.

if (out_name_size > in_name_size) { ret = EFI_INVALID_PARAMETER; goto out; } ... out: EFI_EXIT(ret); }

Best regards

Heinrich

• name_size = u16_strsize(variable_name);
• if (name_size > max_payload_size - MM_VARIABLE_GET_NEXT_HEADER_SIZE)

• return EFI_EXIT(EFI_INVALID_PARAMETER);
  

• /* Trim output buffer size */
• tmp_dsize = *variable_name_size;
• if (name_size + tmp_dsize >

• 	max_payload_size - MM_VARIABLE_GET_NEXT_HEADER_SIZE) {
  

• tmp_dsize = max_payload_size -
  

• 		MM_VARIABLE_GET_NEXT_HEADER_SIZE -
  

• 		name_size;
  

• }
• payload_size = MM_VARIABLE_GET_NEXT_HEADER_SIZE +

• 	max(out_name_size, in_name_size);
  

• comm_buf = setup_mm_hdr((void **)&var_getnext, payload_size,

• 		SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME,
  

• 		&ret);
  

• if (!comm_buf)

• return EFI_EXIT(ret);
  

• /* Fill in contents */
• guidcpy(&var_getnext->guid, guid);
• var_getnext->name_size = out_name_size;
• memcpy(var_getnext->name, variable_name, in_name_size);
• if (out_name_size > in_name_size) {

• memset((u8 *)var_getnext->name + in_name_size, 0x0,
  

•        out_name_size - in_name_size);
  

• }
• /* Communicate */
• ret = mm_communicate(comm_buf, payload_size);
• if (ret == EFI_SUCCESS || ret == EFI_BUFFER_TOO_SMALL) {

• /* Update with reported data size for trimmed case */
  

• *variable_name_size = var_getnext->name_size;
  

• }
• if (ret != EFI_SUCCESS)

• goto done;
  

• guidcpy(guid, &var_getnext->guid);
• memcpy(variable_name, (u8 *)var_getnext->name,

•       var_getnext->name_size);
  

+done:

• free(comm_buf);
• return EFI_EXIT(ret);

+}

+/**

• • efi_set_variable() - set value of a UEFI variable
• • This function implements the SetVariable runtime service.
• • See the Unified Extensible Firmware Interface (UEFI) specification for
• • details.
• • @name: name of the variable
• • @guid: vendor GUID
• • @attr: attributes of the variable
• • @data_size: size of the buffer with the variable value
• • @data: buffer with the variable value
• • Return: status code
• */

+efi_status_t EFIAPI efi_set_variable(u16 *name, const efi_guid_t *guid,

• 		     u32 attr, efi_uintn_t data_size,
  

• 		     const void *data)
  

+{

• struct smm_variable_access *var_acc;
• efi_uintn_t payload_size;
• efi_uintn_t name_size;
• efi_status_t ret;
• u8 *comm_buf;
• EFI_ENTRY(""%ls" %pUl %x %zu %p", name, guid, attr, data_size, data);
• if (!name || name[0] == 0 || !guid)

• return EFI_EXIT(EFI_INVALID_PARAMETER);
  

• if (data_size > 0 && !data)

• return EFI_EXIT(EFI_INVALID_PARAMETER);
  

• /* Check payload size */
• name_size = u16_strsize(name);
• payload_size = MM_VARIABLE_ACCESS_HEADER_SIZE + name_size + data_size;
• if (payload_size > max_payload_size)

• return EFI_EXIT(EFI_INVALID_PARAMETER);
  

• /* Get communication buffer and initialize header */
• comm_buf = setup_mm_hdr((void **)&var_acc, payload_size,

• 		SMM_VARIABLE_FUNCTION_SET_VARIABLE, &ret);
  

• if (!comm_buf)

• return EFI_EXIT(ret);
  

• /* Fill in contents */
• guidcpy(&var_acc->guid, guid);
• var_acc->data_size = data_size;
• var_acc->name_size = name_size;
• var_acc->attr = attr;
• memcpy(var_acc->name, name, name_size);
• memcpy((u8 *)var_acc->name + name_size, data, data_size);
• /* Communicate */
• ret = mm_communicate(comm_buf, payload_size);
• free(comm_buf);
• return EFI_EXIT(ret);

+}

+/**

• • efi_query_variable_info() - get information about EFI variables
• • This function implements the QueryVariableInfo() runtime service.
• • See the Unified Extensible Firmware Interface (UEFI) specification for
• • details.
• • @attributes: bitmask to select variables to be

• • 			queried
    

• • @maximum_variable_storage_size: maximum size of storage area for the

• • 			selected variable types
    

• • @remaining_variable_storage_size: remaining size of storage are for the

• • 			selected variable types
    

• • @maximum_variable_size: maximum size of a variable of the

• • 			selected type
    

• • Returns: status code
• */

+efi_status_t EFIAPI __efi_runtime +efi_query_variable_info(u32 attributes, u64 *max_variable_storage_size,

• 	u64 *remain_variable_storage_size,
  

• 	u64 *max_variable_size)
  

+{

• struct smm_variable_query_info *mm_query_info;
• efi_uintn_t payload_size;
• efi_status_t ret;
• u8 *comm_buf;
• EFI_ENTRY("%x %p %p %p", attributes, max_variable_storage_size,

•   remain_variable_storage_size, max_variable_size);
  

• payload_size = sizeof(*mm_query_info);
• comm_buf = setup_mm_hdr((void **)&mm_query_info, payload_size,

• 		SMM_VARIABLE_FUNCTION_QUERY_VARIABLE_INFO,
  

• 		&ret);
  

• if (!comm_buf)

• return EFI_EXIT(ret);
  

• mm_query_info->attr = attributes;
• ret = mm_communicate(comm_buf, payload_size);
• if (ret != EFI_SUCCESS)

• goto out;
  

• *max_variable_storage_size = mm_query_info->max_variable_storage;
• *remain_variable_storage_size =

• 	mm_query_info->remaining_variable_storage;
  

• *max_variable_size = mm_query_info->max_variable_size;

+out:

• free(comm_buf);
• return EFI_EXIT(ret);

+}

+/**

• • efi_get_variable_runtime() - runtime implementation of GetVariable()
• • @variable_name: name of the variable
• • @guid: vendor GUID
• • @attributes: attributes of the variable
• • @data_size: size of the buffer to which the variable value is copied
• • @data: buffer to which the variable value is copied
• • Return: status code
• */

+static efi_status_t __efi_runtime EFIAPI +efi_get_variable_runtime(u16 *variable_name, const efi_guid_t *guid,

• 	 u32 *attributes, efi_uintn_t *data_size, void *data)
  

+{

• return EFI_UNSUPPORTED;

+}

+/**

• • efi_get_next_variable_name_runtime() - runtime implementation of

• • 			  GetNextVariable()
    

• • @variable_name_size: size of variable_name buffer in byte
• • @variable_name: name of uefi variable's name in u16
• • @guid: vendor's guid
• • Return: status code
• */

+static efi_status_t __efi_runtime EFIAPI +efi_get_next_variable_name_runtime(efi_uintn_t *variable_name_size,

• 		   u16 *variable_name, efi_guid_t *guid)
  

+{

• return EFI_UNSUPPORTED;

+}

+/**

• • efi_query_variable_info() - get information about EFI variables
• • This function implements the QueryVariableInfo() runtime service.
• • See the Unified Extensible Firmware Interface (UEFI) specification for
• • details.
• • @attributes: bitmask to select variables to be

• • 			queried
    

• • @maximum_variable_storage_size: maximum size of storage area for the

• • 			selected variable types
    

• • @remaining_variable_storage_size: remaining size of storage are for the

• • 			selected variable types
    

• • @maximum_variable_size: maximum size of a variable of the

• • 			selected type
    

• • Return: status code
• */

+efi_status_t EFIAPI __efi_runtime +efi_query_variable_info_runtime(u32 attributes, u64 *max_variable_storage_size,

• 		u64 *remain_variable_storage_size,
  

• 		u64 *max_variable_size)
  

+{

• return EFI_UNSUPPORTED;

+}

+/**

• • efi_set_variable_runtime() - runtime implementation of SetVariable()
• • @variable_name: name of the variable
• • @guid: vendor GUID
• • @attributes: attributes of the variable
• • @data_size: size of the buffer with the variable value
• • @data: buffer with the variable value
• • Return: status code
• */

+static efi_status_t __efi_runtime EFIAPI +efi_set_variable_runtime(u16 *variable_name, const efi_guid_t *guid,

• 	 u32 attributes, efi_uintn_t data_size,
  

• 	 const void *data)
  

+{

• return EFI_UNSUPPORTED;

+}

+/**

• • efi_variables_boot_exit_notify() - notify ExitBootServices() is called
• */

+void efi_variables_boot_exit_notify(void) +{

• u8 *comm_buf;
• efi_status_t ret;
• comm_buf = setup_mm_hdr(NULL, 0,

• 		SMM_VARIABLE_FUNCTION_EXIT_BOOT_SERVICE, &ret);
  

• if (comm_buf)

• ret = mm_communicate(comm_buf, 0);
  

• else

• ret = EFI_NOT_FOUND;
  

• if (ret != EFI_SUCCESS)

• log_err("Unable to notify StMM for ExitBootServices\n");
  

• free(comm_buf);
• /* Update runtime service table */
• efi_runtime_services.query_variable_info =

• 	efi_query_variable_info_runtime;
  

• efi_runtime_services.get_variable = efi_get_variable_runtime;
• efi_runtime_services.get_next_variable_name =

• 	efi_get_next_variable_name_runtime;
  

• efi_runtime_services.set_variable = efi_set_variable_runtime;
• efi_update_table_header_crc32(&efi_runtime_services.hdr);

+}

+/**

• • efi_init_variables() - initialize variable services
• • Return: status code
• */

+efi_status_t efi_init_variables(void) +{

• efi_status_t ret;
• ret = get_max_payload(&max_payload_size);
• if (ret != EFI_SUCCESS)

• return ret;
  

• max_buffer_size = MM_COMMUNICATE_HEADER_SIZE +

• 	  MM_VARIABLE_COMMUNICATE_SIZE +
  

• 	  max_payload_size;
  

• return EFI_SUCCESS;

+}