drivers/acpi/prmt.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Author: Erik Kaneda <erik.kaneda@intel.com>
  * Copyright 2020 Intel Corporation
  *
  * prmt.c
  *
  * Each PRM service is an executable that is run in a restricted environment
  * that is invoked by writing to the PlatformRtMechanism OperationRegion from
  * AML bytecode.
  *
  * init_prmt initializes the Platform Runtime Mechanism (PRM) services by
  * processing data in the PRMT as well as registering an ACPI OperationRegion
  * handler for the PlatformRtMechanism subtype.
  *
  */
 #include <linux/kernel.h>
 #include <linux/efi.h>
 #include <linux/acpi.h>
 #include <linux/prmt.h>
 #include <asm/efi.h>

 #pragma pack(1)
 struct prm_mmio_addr_range {
 	u64 phys_addr;
 	u64 virt_addr;
 	u32 length;
 };

 struct prm_mmio_info {
 	u64 mmio_count;
 	struct prm_mmio_addr_range addr_ranges[];
 };

 struct prm_buffer {
 	u8 prm_status;
 	u64 efi_status;
 	u8 prm_cmd;
 	guid_t handler_guid;
 };

 struct prm_context_buffer {
 	char signature[ACPI_NAMESEG_SIZE];
 	u16 revision;
 	u16 reserved;
 	guid_t identifier;
 	u64 static_data_buffer;
 	struct prm_mmio_info *mmio_ranges;
 };
 #pragma pack()

 static LIST_HEAD(prm_module_list);

 struct prm_handler_info {
 	efi_guid_t guid;
 	efi_status_t (__efiapi *handler_addr)(u64, void *);
 	u64 static_data_buffer_addr;
 	u64 acpi_param_buffer_addr;

 	struct list_head handler_list;
 };

 struct prm_module_info {
 	guid_t guid;
 	u16 major_rev;
 	u16 minor_rev;
 	u16 handler_count;
 	struct prm_mmio_info *mmio_info;
 	bool updatable;

 	struct list_head module_list;
 	struct prm_handler_info handlers[] __counted_by(handler_count);
 };

 static u64 efi_pa_va_lookup(efi_guid_t *guid, u64 pa)
 {
 	efi_memory_desc_t *md;
 	u64 pa_offset = pa & ~PAGE_MASK;
 	u64 page = pa & PAGE_MASK;

 	for_each_efi_memory_desc(md) {
 		if ((md->attribute & EFI_MEMORY_RUNTIME) &&
 		    (md->phys_addr < pa && pa < md->phys_addr + PAGE_SIZE * md->num_pages)) {
 			return pa_offset + md->virt_addr + page - md->phys_addr;
 		}
 	}

 	pr_warn("Failed to find VA for GUID: %pUL, PA: 0x%llx", guid, pa);

 	return 0;
 }

 #define get_first_handler(a) ((struct acpi_prmt_handler_info *) ((char *) (a) + a->handler_info_offset))
 #define get_next_handler(a) ((struct acpi_prmt_handler_info *) (sizeof(struct acpi_prmt_handler_info) + (char *) a))

 static int __init
 acpi_parse_prmt(union acpi_subtable_headers *header, const unsigned long end)
 {
 	struct acpi_prmt_module_info *module_info;
 	struct acpi_prmt_handler_info *handler_info;
 	struct prm_handler_info *th;
 	struct prm_module_info *tm;
 	u64 *mmio_count;
 	u64 cur_handler = 0;
 	u32 module_info_size = 0;
 	u64 mmio_range_size = 0;
 	void *temp_mmio;

 	module_info = (struct acpi_prmt_module_info *) header;
 	module_info_size = struct_size(tm, handlers, module_info->handler_info_count);
 	tm = kmalloc(module_info_size, GFP_KERNEL);
 	if (!tm)
 		goto parse_prmt_out1;

 	guid_copy(&tm->guid, (guid_t *) module_info->module_guid);
 	tm->major_rev = module_info->major_rev;
 	tm->minor_rev = module_info->minor_rev;
 	tm->handler_count = module_info->handler_info_count;
 	tm->updatable = true;

 	if (module_info->mmio_list_pointer) {
 		/*
 		 * Each module is associated with a list of addr
 		 * ranges that it can use during the service
 		 */
 		mmio_count = (u64 *) memremap(module_info->mmio_list_pointer, 8, MEMREMAP_WB);
 		if (!mmio_count)
 			goto parse_prmt_out2;

 		mmio_range_size = struct_size(tm->mmio_info, addr_ranges, *mmio_count);
 		tm->mmio_info = kmalloc(mmio_range_size, GFP_KERNEL);
 		if (!tm->mmio_info)
 			goto parse_prmt_out3;

 		temp_mmio = memremap(module_info->mmio_list_pointer, mmio_range_size, MEMREMAP_WB);
 		if (!temp_mmio)
 			goto parse_prmt_out4;
 		memmove(tm->mmio_info, temp_mmio, mmio_range_size);
 	} else {
 		tm->mmio_info = kmalloc(sizeof(*tm->mmio_info), GFP_KERNEL);
 		if (!tm->mmio_info)
 			goto parse_prmt_out2;

 		tm->mmio_info->mmio_count = 0;
 	}

 	INIT_LIST_HEAD(&tm->module_list);
 	list_add(&tm->module_list, &prm_module_list);

 	handler_info = get_first_handler(module_info);
 	do {
 		th = &tm->handlers[cur_handler];

 		guid_copy(&th->guid, (guid_t *)handler_info->handler_guid);
 		th->handler_addr =
 			(void *)efi_pa_va_lookup(&th->guid, handler_info->handler_address);

 		th->static_data_buffer_addr =
 			efi_pa_va_lookup(&th->guid, handler_info->static_data_buffer_address);

 		th->acpi_param_buffer_addr =
 			efi_pa_va_lookup(&th->guid, handler_info->acpi_param_buffer_address);

 	} while (++cur_handler < tm->handler_count && (handler_info = get_next_handler(handler_info)));

 	return 0;

 parse_prmt_out4:
 	kfree(tm->mmio_info);
 parse_prmt_out3:
 	memunmap(mmio_count);
 parse_prmt_out2:
 	kfree(tm);
 parse_prmt_out1:
 	return -ENOMEM;
 }

 #define GET_MODULE	0
 #define GET_HANDLER	1

 static void *find_guid_info(const guid_t *guid, u8 mode)
 {
 	struct prm_handler_info *cur_handler;
 	struct prm_module_info *cur_module;
 	int i = 0;

 	list_for_each_entry(cur_module, &prm_module_list, module_list) {
 		for (i = 0; i < cur_module->handler_count; ++i) {
 			cur_handler = &cur_module->handlers[i];
 			if (guid_equal(guid, &cur_handler->guid)) {
 				if (mode == GET_MODULE)
 					return (void *)cur_module;
 				else
 					return (void *)cur_handler;
 			}
 		}
 	}

 	return NULL;
 }

 static struct prm_module_info *find_prm_module(const guid_t *guid)
 {
 	return (struct prm_module_info *)find_guid_info(guid, GET_MODULE);
 }

 static struct prm_handler_info *find_prm_handler(const guid_t *guid)
 {
 	return (struct prm_handler_info *) find_guid_info(guid, GET_HANDLER);
 }

 /* In-coming PRM commands */

 #define PRM_CMD_RUN_SERVICE		0
 #define PRM_CMD_START_TRANSACTION	1
 #define PRM_CMD_END_TRANSACTION		2

 /* statuses that can be passed back to ASL */

 #define PRM_HANDLER_SUCCESS 		0
 #define PRM_HANDLER_ERROR 		1
 #define INVALID_PRM_COMMAND 		2
 #define PRM_HANDLER_GUID_NOT_FOUND 	3
 #define UPDATE_LOCK_ALREADY_HELD 	4
 #define UPDATE_UNLOCK_WITHOUT_LOCK 	5

 int acpi_call_prm_handler(guid_t handler_guid, void *param_buffer)
 {
 	struct prm_handler_info *handler = find_prm_handler(&handler_guid);
 	struct prm_module_info *module = find_prm_module(&handler_guid);
 	struct prm_context_buffer context;
 	efi_status_t status;

 	if (!module || !handler)
 		return -ENODEV;

 	memset(&context, 0, sizeof(context));
 	ACPI_COPY_NAMESEG(context.signature, "PRMC");
 	context.identifier         = handler->guid;
 	context.static_data_buffer = handler->static_data_buffer_addr;
 	context.mmio_ranges        = module->mmio_info;

 	status = efi_call_acpi_prm_handler(handler->handler_addr,
 					   (u64)param_buffer,
 					   &context);

 	return efi_status_to_err(status);
 }
 EXPORT_SYMBOL_GPL(acpi_call_prm_handler);

 /*
  * This is the PlatformRtMechanism opregion space handler.
  * @function: indicates the read/write. In fact as the PlatformRtMechanism
  * message is driven by command, only write is meaningful.
  *
  * @addr   : not used
  * @bits   : not used.
  * @value  : it is an in/out parameter. It points to the PRM message buffer.
  * @handler_context: not used
  */
 static acpi_status acpi_platformrt_space_handler(u32 function,
 						 acpi_physical_address addr,
 						 u32 bits, acpi_integer *value,
 						 void *handler_context,
 						 void *region_context)
 {
 	struct prm_buffer *buffer = ACPI_CAST_PTR(struct prm_buffer, value);
 	struct prm_handler_info *handler;
 	struct prm_module_info *module;
 	efi_status_t status;
 	struct prm_context_buffer context;

 	if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
 		pr_err_ratelimited("PRM: EFI runtime services no longer available\n");
 		return AE_NO_HANDLER;
 	}

 	/*
 	 * The returned acpi_status will always be AE_OK. Error values will be
 	 * saved in the first byte of the PRM message buffer to be used by ASL.
 	 */
 	switch (buffer->prm_cmd) {
 	case PRM_CMD_RUN_SERVICE:

 		handler = find_prm_handler(&buffer->handler_guid);
 		module = find_prm_module(&buffer->handler_guid);
 		if (!handler || !module)
 			goto invalid_guid;

 		if (!handler->handler_addr ||
 		    !handler->static_data_buffer_addr ||
 		    !handler->acpi_param_buffer_addr) {
 			buffer->prm_status = PRM_HANDLER_ERROR;
 			return AE_OK;
 		}

 		ACPI_COPY_NAMESEG(context.signature, "PRMC");
 		context.revision = 0x0;
 		context.reserved = 0x0;
 		context.identifier = handler->guid;
 		context.static_data_buffer = handler->static_data_buffer_addr;
 		context.mmio_ranges = module->mmio_info;

 		status = efi_call_acpi_prm_handler(handler->handler_addr,
 						   handler->acpi_param_buffer_addr,
 						   &context);
 		if (status == EFI_SUCCESS) {
 			buffer->prm_status = PRM_HANDLER_SUCCESS;
 		} else {
 			buffer->prm_status = PRM_HANDLER_ERROR;
 			buffer->efi_status = status;
 		}
 		break;

 	case PRM_CMD_START_TRANSACTION:

 		module = find_prm_module(&buffer->handler_guid);
 		if (!module)
 			goto invalid_guid;

 		if (module->updatable)
 			module->updatable = false;
 		else
 			buffer->prm_status = UPDATE_LOCK_ALREADY_HELD;
 		break;

 	case PRM_CMD_END_TRANSACTION:

 		module = find_prm_module(&buffer->handler_guid);
 		if (!module)
 			goto invalid_guid;

 		if (module->updatable)
 			buffer->prm_status = UPDATE_UNLOCK_WITHOUT_LOCK;
 		else
 			module->updatable = true;
 		break;

 	default:

 		buffer->prm_status = INVALID_PRM_COMMAND;
 		break;
 	}

 	return AE_OK;

 invalid_guid:
 	buffer->prm_status = PRM_HANDLER_GUID_NOT_FOUND;
 	return AE_OK;
 }

 void __init init_prmt(void)
 {
 	struct acpi_table_header *tbl;
 	acpi_status status;
 	int mc;

 	status = acpi_get_table(ACPI_SIG_PRMT, 0, &tbl);
 	if (ACPI_FAILURE(status))
 		return;

 	mc = acpi_table_parse_entries(ACPI_SIG_PRMT, sizeof(struct acpi_table_prmt) +
 					  sizeof (struct acpi_table_prmt_header),
 					  0, acpi_parse_prmt, 0);
 	acpi_put_table(tbl);
 	/*
 	 * Return immediately if PRMT table is not present or no PRM module found.
 	 */
 	if (mc <= 0)
 		return;

 	pr_info("PRM: found %u modules\n", mc);

 	if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
 		pr_err("PRM: EFI runtime services unavailable\n");
 		return;
 	}

 	status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
 						    ACPI_ADR_SPACE_PLATFORM_RT,
 						    &acpi_platformrt_space_handler,
 						    NULL, NULL);
 	if (ACPI_FAILURE(status))
 		pr_alert("PRM: OperationRegion handler could not be installed\n");
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Author: Erik Kaneda <erik.kaneda@intel.com>
	* Copyright 2020 Intel Corporation
	*
	* prmt.c
	*
	* Each PRM service is an executable that is run in a restricted environment
	* that is invoked by writing to the PlatformRtMechanism OperationRegion from
	* AML bytecode.
	*
	* init_prmt initializes the Platform Runtime Mechanism (PRM) services by
	* processing data in the PRMT as well as registering an ACPI OperationRegion
	* handler for the PlatformRtMechanism subtype.
	*
	*/
	#include <linux/kernel.h>
	#include <linux/efi.h>
	#include <linux/acpi.h>
	#include <linux/prmt.h>
	#include <asm/efi.h>

	#pragma pack(1)
	struct prm_mmio_addr_range {
	u64 phys_addr;
	u64 virt_addr;
	u32 length;
	};

	struct prm_mmio_info {
	u64 mmio_count;
	struct prm_mmio_addr_range addr_ranges[];
	};

	struct prm_buffer {
	u8 prm_status;
	u64 efi_status;
	u8 prm_cmd;
	guid_t handler_guid;
	};

	struct prm_context_buffer {
	char signature[ACPI_NAMESEG_SIZE];
	u16 revision;
	u16 reserved;
	guid_t identifier;
	u64 static_data_buffer;
	struct prm_mmio_info *mmio_ranges;
	};
	#pragma pack()

	static LIST_HEAD(prm_module_list);

	struct prm_handler_info {
	efi_guid_t guid;
	efi_status_t (__efiapi handler_addr)(u64, void );
	u64 static_data_buffer_addr;
	u64 acpi_param_buffer_addr;

	struct list_head handler_list;
	};

	struct prm_module_info {
	guid_t guid;
	u16 major_rev;
	u16 minor_rev;
	u16 handler_count;
	struct prm_mmio_info *mmio_info;
	bool updatable;

	struct list_head module_list;
	struct prm_handler_info handlers[] __counted_by(handler_count);
	};

	static u64 efi_pa_va_lookup(efi_guid_t *guid, u64 pa)
	{
	efi_memory_desc_t *md;
	u64 pa_offset = pa & ~PAGE_MASK;
	u64 page = pa & PAGE_MASK;

	for_each_efi_memory_desc(md) {
	if ((md->attribute & EFI_MEMORY_RUNTIME) &&
	(md->phys_addr < pa && pa < md->phys_addr + PAGE_SIZE * md->num_pages)) {
	return pa_offset + md->virt_addr + page - md->phys_addr;
	}
	}

	pr_warn("Failed to find VA for GUID: %pUL, PA: 0x%llx", guid, pa);

	return 0;
	}

	#define get_first_handler(a) ((struct acpi_prmt_handler_info ) ((char ) (a) + a->handler_info_offset))
	#define get_next_handler(a) ((struct acpi_prmt_handler_info ) (sizeof(struct acpi_prmt_handler_info) + (char ) a))

	static int __init
	acpi_parse_prmt(union acpi_subtable_headers *header, const unsigned long end)
	{
	struct acpi_prmt_module_info *module_info;
	struct acpi_prmt_handler_info *handler_info;
	struct prm_handler_info *th;
	struct prm_module_info *tm;
	u64 *mmio_count;
	u64 cur_handler = 0;
	u32 module_info_size = 0;
	u64 mmio_range_size = 0;
	void *temp_mmio;

	module_info = (struct acpi_prmt_module_info *) header;
	module_info_size = struct_size(tm, handlers, module_info->handler_info_count);
	tm = kmalloc(module_info_size, GFP_KERNEL);
	if (!tm)
	goto parse_prmt_out1;

	guid_copy(&tm->guid, (guid_t *) module_info->module_guid);
	tm->major_rev = module_info->major_rev;
	tm->minor_rev = module_info->minor_rev;
	tm->handler_count = module_info->handler_info_count;
	tm->updatable = true;

	if (module_info->mmio_list_pointer) {
	/*
	* Each module is associated with a list of addr
	* ranges that it can use during the service
	*/
	mmio_count = (u64 *) memremap(module_info->mmio_list_pointer, 8, MEMREMAP_WB);
	if (!mmio_count)
	goto parse_prmt_out2;

	mmio_range_size = struct_size(tm->mmio_info, addr_ranges, *mmio_count);
	tm->mmio_info = kmalloc(mmio_range_size, GFP_KERNEL);
	if (!tm->mmio_info)
	goto parse_prmt_out3;

	temp_mmio = memremap(module_info->mmio_list_pointer, mmio_range_size, MEMREMAP_WB);
	if (!temp_mmio)
	goto parse_prmt_out4;
	memmove(tm->mmio_info, temp_mmio, mmio_range_size);
	} else {
	tm->mmio_info = kmalloc(sizeof(*tm->mmio_info), GFP_KERNEL);
	if (!tm->mmio_info)
	goto parse_prmt_out2;

	tm->mmio_info->mmio_count = 0;
	}

	INIT_LIST_HEAD(&tm->module_list);
	list_add(&tm->module_list, &prm_module_list);

	handler_info = get_first_handler(module_info);
	do {
	th = &tm->handlers[cur_handler];

	guid_copy(&th->guid, (guid_t *)handler_info->handler_guid);
	th->handler_addr =
	(void *)efi_pa_va_lookup(&th->guid, handler_info->handler_address);

	th->static_data_buffer_addr =
	efi_pa_va_lookup(&th->guid, handler_info->static_data_buffer_address);

	th->acpi_param_buffer_addr =
	efi_pa_va_lookup(&th->guid, handler_info->acpi_param_buffer_address);

	} while (++cur_handler < tm->handler_count && (handler_info = get_next_handler(handler_info)));

	return 0;

	parse_prmt_out4:
	kfree(tm->mmio_info);
	parse_prmt_out3:
	memunmap(mmio_count);
	parse_prmt_out2:
	kfree(tm);
	parse_prmt_out1:
	return -ENOMEM;
	}

	#define GET_MODULE 0
	#define GET_HANDLER 1

	static void find_guid_info(const guid_t guid, u8 mode)
	{
	struct prm_handler_info *cur_handler;
	struct prm_module_info *cur_module;
	int i = 0;

	list_for_each_entry(cur_module, &prm_module_list, module_list) {
	for (i = 0; i < cur_module->handler_count; ++i) {
	cur_handler = &cur_module->handlers[i];
	if (guid_equal(guid, &cur_handler->guid)) {
	if (mode == GET_MODULE)
	return (void *)cur_module;
	else
	return (void *)cur_handler;
	}
	}
	}

	return NULL;
	}

	static struct prm_module_info find_prm_module(const guid_t guid)
	{
	return (struct prm_module_info *)find_guid_info(guid, GET_MODULE);
	}

	static struct prm_handler_info find_prm_handler(const guid_t guid)
	{
	return (struct prm_handler_info *) find_guid_info(guid, GET_HANDLER);
	}

	/* In-coming PRM commands */

	#define PRM_CMD_RUN_SERVICE 0
	#define PRM_CMD_START_TRANSACTION 1
	#define PRM_CMD_END_TRANSACTION 2

	/* statuses that can be passed back to ASL */

	#define PRM_HANDLER_SUCCESS 0
	#define PRM_HANDLER_ERROR 1
	#define INVALID_PRM_COMMAND 2
	#define PRM_HANDLER_GUID_NOT_FOUND 3
	#define UPDATE_LOCK_ALREADY_HELD 4
	#define UPDATE_UNLOCK_WITHOUT_LOCK 5

	int acpi_call_prm_handler(guid_t handler_guid, void *param_buffer)
	{
	struct prm_handler_info *handler = find_prm_handler(&handler_guid);
	struct prm_module_info *module = find_prm_module(&handler_guid);
	struct prm_context_buffer context;
	efi_status_t status;

	if (!module \|\| !handler)
	return -ENODEV;

	memset(&context, 0, sizeof(context));
	ACPI_COPY_NAMESEG(context.signature, "PRMC");
	context.identifier = handler->guid;
	context.static_data_buffer = handler->static_data_buffer_addr;
	context.mmio_ranges = module->mmio_info;

	status = efi_call_acpi_prm_handler(handler->handler_addr,
	(u64)param_buffer,
	&context);

	return efi_status_to_err(status);
	}
	EXPORT_SYMBOL_GPL(acpi_call_prm_handler);

	/*
	* This is the PlatformRtMechanism opregion space handler.
	* @function: indicates the read/write. In fact as the PlatformRtMechanism
	* message is driven by command, only write is meaningful.
	*
	* @addr : not used
	* @bits : not used.
	* @value : it is an in/out parameter. It points to the PRM message buffer.
	* @handler_context: not used
	*/
	static acpi_status acpi_platformrt_space_handler(u32 function,
	acpi_physical_address addr,
	u32 bits, acpi_integer *value,
	void *handler_context,
	void *region_context)
	{
	struct prm_buffer *buffer = ACPI_CAST_PTR(struct prm_buffer, value);
	struct prm_handler_info *handler;
	struct prm_module_info *module;
	efi_status_t status;
	struct prm_context_buffer context;

	if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
	pr_err_ratelimited("PRM: EFI runtime services no longer available\n");
	return AE_NO_HANDLER;
	}

	/*
	* The returned acpi_status will always be AE_OK. Error values will be
	* saved in the first byte of the PRM message buffer to be used by ASL.
	*/
	switch (buffer->prm_cmd) {
	case PRM_CMD_RUN_SERVICE:

	handler = find_prm_handler(&buffer->handler_guid);
	module = find_prm_module(&buffer->handler_guid);
	if (!handler \|\| !module)
	goto invalid_guid;

	if (!handler->handler_addr \|\|
	!handler->static_data_buffer_addr \|\|
	!handler->acpi_param_buffer_addr) {
	buffer->prm_status = PRM_HANDLER_ERROR;
	return AE_OK;
	}

	ACPI_COPY_NAMESEG(context.signature, "PRMC");
	context.revision = 0x0;
	context.reserved = 0x0;
	context.identifier = handler->guid;
	context.static_data_buffer = handler->static_data_buffer_addr;
	context.mmio_ranges = module->mmio_info;

	status = efi_call_acpi_prm_handler(handler->handler_addr,
	handler->acpi_param_buffer_addr,
	&context);
	if (status == EFI_SUCCESS) {
	buffer->prm_status = PRM_HANDLER_SUCCESS;
	} else {
	buffer->prm_status = PRM_HANDLER_ERROR;
	buffer->efi_status = status;
	}
	break;

	case PRM_CMD_START_TRANSACTION:

	module = find_prm_module(&buffer->handler_guid);
	if (!module)
	goto invalid_guid;

	if (module->updatable)
	module->updatable = false;
	else
	buffer->prm_status = UPDATE_LOCK_ALREADY_HELD;
	break;

	case PRM_CMD_END_TRANSACTION:

	module = find_prm_module(&buffer->handler_guid);
	if (!module)
	goto invalid_guid;

	if (module->updatable)
	buffer->prm_status = UPDATE_UNLOCK_WITHOUT_LOCK;
	else
	module->updatable = true;
	break;

	default:

	buffer->prm_status = INVALID_PRM_COMMAND;
	break;
	}

	return AE_OK;

	invalid_guid:
	buffer->prm_status = PRM_HANDLER_GUID_NOT_FOUND;
	return AE_OK;
	}

	void __init init_prmt(void)
	{
	struct acpi_table_header *tbl;
	acpi_status status;
	int mc;

	status = acpi_get_table(ACPI_SIG_PRMT, 0, &tbl);
	if (ACPI_FAILURE(status))
	return;

	mc = acpi_table_parse_entries(ACPI_SIG_PRMT, sizeof(struct acpi_table_prmt) +
	sizeof (struct acpi_table_prmt_header),
	0, acpi_parse_prmt, 0);
	acpi_put_table(tbl);
	/*
	* Return immediately if PRMT table is not present or no PRM module found.
	*/
	if (mc <= 0)
	return;

	pr_info("PRM: found %u modules\n", mc);

	if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
	pr_err("PRM: EFI runtime services unavailable\n");
	return;
	}

	status = acpi_install_address_space_handler(ACPI_ROOT_OBJECT,
	ACPI_ADR_SPACE_PLATFORM_RT,
	&acpi_platformrt_space_handler,
	NULL, NULL);
	if (ACPI_FAILURE(status))
	pr_alert("PRM: OperationRegion handler could not be installed\n");
	}