text: #define pr_fmt(fmt) "efi: " fmt
  
  #include <linux/init.h>
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/time.h>
  #include <linux/types.h>
  #include <linux/efi.h>
  #include <linux/slab.h>
  #include <linux/memblock.h>
  #include <linux/bootmem.h>
  #include <linux/acpi.h>
  #include <linux/dmi.h>
  #include <asm/efi.h>
  #include <asm/uv/uv.h>
  
  #define EFI_MIN_RESERVE 5120
  
  #define EFI_DUMMY_GUID \
  	EFI_GUID(0x4424ac57, 0xbe4b, 0x47dd, 0x9e, 0x97, 0xed, 0x50, 0xf0, 0x9f, 0x92, 0xa9)
  
  static efi_char16_t efi_dummy_name[6] = { 'D', 'U', 'M', 'M', 'Y', 0 };
  
  static bool efi_no_storage_paranoia;
  
  /*
   * Some firmware implementations refuse to boot if there's insufficient
   * space in the variable store. The implementation of garbage collection
   * in some FW versions causes stale (deleted) variables to take up space
   * longer than intended and space is only freed once the store becomes
   * almost completely full.
   *
   * Enabling this option disables the space checks in
   * efi_query_variable_store() and forces garbage collection.
   *
   * Only enable this option if deleting EFI variables does not free up
   * space in your variable store, e.g. if despite deleting variables
   * you're unable to create new ones.
   */
  static int __init setup_storage_paranoia(char *arg)
  {
  	efi_no_storage_paranoia = true;
  	return 0;
  }
  early_param("efi_no_storage_paranoia", setup_storage_paranoia);
  
  /*
   * Deleting the dummy variable which kicks off garbage collection
  */
  void efi_delete_dummy_variable(void)
  {
  	efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
  			 EFI_VARIABLE_NON_VOLATILE |
  			 EFI_VARIABLE_BOOTSERVICE_ACCESS |
  			 EFI_VARIABLE_RUNTIME_ACCESS,
  			 0, NULL);
  }
  
  /*
   * In the nonblocking case we do not attempt to perform garbage
   * collection if we do not have enough free space. Rather, we do the
   * bare minimum check and give up immediately if the available space
   * is below EFI_MIN_RESERVE.
   *
   * This function is intended to be small and simple because it is
   * invoked from crash handler paths.
   */
  static efi_status_t
  query_variable_store_nonblocking(u32 attributes, unsigned long size)
  {
  	efi_status_t status;
  	u64 storage_size, remaining_size, max_size;
  
  	status = efi.query_variable_info_nonblocking(attributes, &storage_size,
  						     &remaining_size,
  						     &max_size);
  	if (status != EFI_SUCCESS)
  		return status;
  
  	if (remaining_size - size < EFI_MIN_RESERVE)
  		return EFI_OUT_OF_RESOURCES;
  
  	return EFI_SUCCESS;
  }
  
  /*
   * Some firmware implementations refuse to boot if there's insufficient space
   * in the variable store. Ensure that we never use more than a safe limit.
   *
   * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable
   * store.
   */
  efi_status_t efi_query_variable_store(u32 attributes, unsigned long size,
  				      bool nonblocking)
  {
  	efi_status_t status;
  	u64 storage_size, remaining_size, max_size;
  
  	if (!(attributes & EFI_VARIABLE_NON_VOLATILE))
  		return 0;
  
  	if (nonblocking)
  		return query_variable_store_nonblocking(attributes, size);
  
  	status = efi.query_variable_info(attributes, &storage_size,
  					 &remaining_size, &max_size);
  	if (status != EFI_SUCCESS)
  		return status;
  
  	/*
  	 * We account for that by refusing the write if permitting it would
  	 * reduce the available space to under 5KB. This figure was provided by
  	 * Samsung, so should be safe.
  	 */
  	if ((remaining_size - size < EFI_MIN_RESERVE) &&
  		!efi_no_storage_paranoia) {
  
  		/*
  		 * Triggering garbage collection may require that the firmware
  		 * generate a real EFI_OUT_OF_RESOURCES error. We can force
  		 * that by attempting to use more space than is available.
  		 */
  		unsigned long dummy_size = remaining_size + 1024;
  		void *dummy = kzalloc(dummy_size, GFP_ATOMIC);
  
  		if (!dummy)
  			return EFI_OUT_OF_RESOURCES;
  
  		status = efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
  					  EFI_VARIABLE_NON_VOLATILE |
  					  EFI_VARIABLE_BOOTSERVICE_ACCESS |
  					  EFI_VARIABLE_RUNTIME_ACCESS,
  					  dummy_size, dummy);
  
  		if (status == EFI_SUCCESS) {
  			/*
  			 * This should have failed, so if it didn't make sure
  			 * that we delete it...
  			 */
  			efi_delete_dummy_variable();
  		}
  
  		kfree(dummy);
  
  		/*
  		 * The runtime code may now have triggered a garbage collection
  		 * run, so check the variable info again
  		 */
  		status = efi.query_variable_info(attributes, &storage_size,
  						 &remaining_size, &max_size);
  
  		if (status != EFI_SUCCESS)
  			return status;
  
  		/*
  		 * There still isn't enough room, so return an error
  		 */
  		if (remaining_size - size < EFI_MIN_RESERVE)
  			return EFI_OUT_OF_RESOURCES;
  	}
  
  	return EFI_SUCCESS;
  }
  EXPORT_SYMBOL_GPL(efi_query_variable_store);
  
  /*
   * Helper function for efi_reserve_boot_services() to figure out if we
   * can free regions in efi_free_boot_services().
   *
   * Use this function to ensure we do not free regions owned by somebody
   * else. We must only reserve (and then free) regions:
   *
   * - Not within any part of the kernel
   * - Not the BIOS reserved area (E820_RESERVED, E820_NVS, etc)
   */
  static bool can_free_region(u64 start, u64 size)
  {
  	if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end))
  		return false;
  
  	if (!e820_all_mapped(start, start+size, E820_RAM))
  		return false;
  
  	return true;
  }
  
  /*
   * The UEFI specification makes it clear that the operating system is free to do
   * whatever it wants with boot services code after ExitBootServices() has been
   * called. Ignoring this recommendation a significant bunch of EFI implementations 
   * continue calling into boot services code (SetVirtualAddressMap). In order to 
   * work around such buggy implementations we reserve boot services region during 
   * EFI init and make sure it stays executable. Then, after SetVirtualAddressMap(), it
  * is discarded.
  */
  void __init efi_reserve_boot_services(void)
  {
  	efi_memory_desc_t *md;
  
  	for_each_efi_memory_desc(md) {
  		u64 start = md->phys_addr;
  		u64 size = md->num_pages << EFI_PAGE_SHIFT;
  		bool already_reserved;
  
  		if (md->type != EFI_BOOT_SERVICES_CODE &&
  		    md->type != EFI_BOOT_SERVICES_DATA)
  			continue;
  
  		already_reserved = memblock_is_region_reserved(start, size);
  
  		/*
  		 * Because the following memblock_reserve() is paired
  		 * with free_bootmem_late() for this region in
  		 * efi_free_boot_services(), we must be extremely
  		 * careful not to reserve, and subsequently free,
  		 * critical regions of memory (like the kernel image) or
  		 * those regions that somebody else has already
  		 * reserved.
  		 *
  		 * A good example of a critical region that must not be
  		 * freed is page zero (first 4Kb of memory), which may
  		 * contain boot services code/data but is marked
  		 * E820_RESERVED by trim_bios_range().
  		 */
  		if (!already_reserved) {
  			memblock_reserve(start, size);
  
  			/*
  			 * If we are the first to reserve the region, no
  			 * one else cares about it. We own it and can
  			 * free it later.
  			 */
  			if (can_free_region(start, size))
  				continue;
  		}
  
  		/*
  		 * We don't own the region. We must not free it.
  		 *
  		 * Setting this bit for a boot services region really
  		 * doesn't make sense as far as the firmware is
  		 * concerned, but it does provide us with a way to tag
  		 * those regions that must not be paired with
  		 * free_bootmem_late().
  		 */
  		md->attribute |= EFI_MEMORY_RUNTIME;
  	}
  }
  
  void __init efi_free_boot_services(void)
  {
  	efi_memory_desc_t *md;
  
  	for_each_efi_memory_desc(md) {
  		unsigned long long start = md->phys_addr;
  		unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
  
  		if (md->type != EFI_BOOT_SERVICES_CODE &&
  		    md->type != EFI_BOOT_SERVICES_DATA)
  			continue;
  
  		/* Do not free, someone else owns it: */
  		if (md->attribute & EFI_MEMORY_RUNTIME)
  			continue;
  
  		free_bootmem_late(start, size);
  	}
  
  	efi_unmap_memmap();
  }
  
  /*
   * A number of config table entries get remapped to virtual addresses
   * after entering EFI virtual mode. However, the kexec kernel requires
   * their physical addresses therefore we pass them via setup_data and
   * correct those entries to their respective physical addresses here.
   *
   * Currently only handles smbios which is necessary for some firmware
   * implementation.
   */
  int __init efi_reuse_config(u64 tables, int nr_tables)
  {
  	int i, sz, ret = 0;
  	void *p, *tablep;
  	struct efi_setup_data *data;
  
  	if (!efi_setup)
  		return 0;
  
  	if (!efi_enabled(EFI_64BIT))
  		return 0;
  
  	data = early_memremap(efi_setup, sizeof(*data));
  	if (!data) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	if (!data->smbios)
  		goto out_memremap;
  
  	sz = sizeof(efi_config_table_64_t);
  
  	p = tablep = early_memremap(tables, nr_tables * sz);
  	if (!p) {
  		pr_err("Could not map Configuration table!\n");
  		ret = -ENOMEM;
  		goto out_memremap;
  	}
  
  	for (i = 0; i < efi.systab->nr_tables; i++) {
  		efi_guid_t guid;
  
  		guid = ((efi_config_table_64_t *)p)->guid;
  
  		if (!efi_guidcmp(guid, SMBIOS_TABLE_GUID))
  			((efi_config_table_64_t *)p)->table = data->smbios;
  		p += sz;
  	}
  	early_memunmap(tablep, nr_tables * sz);
  
  out_memremap:
  	early_memunmap(data, sizeof(*data));
  out:
  	return ret;
  }
  
  static const struct dmi_system_id sgi_uv1_dmi[] = {
  	{ NULL, "SGI UV1",
  		{	DMI_MATCH(DMI_PRODUCT_NAME,	"Stoutland Platform"),
  			DMI_MATCH(DMI_PRODUCT_VERSION,	"1.0"),
  			DMI_MATCH(DMI_BIOS_VENDOR,	"SGI.COM"),
  		}
  	},
  	{ } /* NULL entry stops DMI scanning */
  };
  
  void __init efi_apply_memmap_quirks(void)
  {
  	/*
  	 * Once setup is done earlier, unmap the EFI memory map on mismatched
  	 * firmware/kernel architectures since there is no support for runtime
  	 * services.
  	 */
  	if (!efi_runtime_supported()) {
  		pr_info("Setup done, disabling due to 32/64-bit mismatch\n");
  		efi_unmap_memmap();
  	}
  
  	/* UV2+ BIOS has a fix for this issue.  UV1 still needs the quirk. */
  	if (dmi_check_system(sgi_uv1_dmi))
  		set_bit(EFI_OLD_MEMMAP, &efi.flags);
  }
  
  /*
   * For most modern platforms the preferred method of powering off is via
   * ACPI. However, there are some that are known to require the use of
   * EFI runtime services and for which ACPI does not work at all.
   *
   * Using EFI is a last resort, to be used only if no other option
   * exists.
   */
  bool efi_reboot_required(void)
  {
  	if (!acpi_gbl_reduced_hardware)
  		return false;
  
  	efi_reboot_quirk_mode = EFI_RESET_WARM;
  	return true;
  }
  
  bool efi_poweroff_required(void)
  {
  	return acpi_gbl_reduced_hardware || acpi_no_s5;
  }
  