efi.c

		if ((md->phys_addr <= phys_addr) &&
		    (phys_addr < (md->phys_addr +
				  (md->num_pages << EFI_PAGE_SHIFT))))
			return md->type;
	}
	return 0;
}

u64 efi_mem_attributes(unsigned long phys_addr)
{
	efi_memory_desc_t *md;
	void *p;

	for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
		md = p;
		if ((md->phys_addr <= phys_addr) &&
		    (phys_addr < (md->phys_addr +
				  (md->num_pages << EFI_PAGE_SHIFT))))
			return md->attribute;
	}
	return 0;
}

/*
 * Some firmware has serious problems when using more than 50% of the EFI
 * variable store, i.e. it triggers bugs that can brick machines. Ensure that
 * we never use more than this 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)
{
	efi_status_t status;
	u64 storage_size, remaining_size, max_size;

	status = efi.query_variable_info(attributes, &storage_size,
					 &remaining_size, &max_size);
	if (status != EFI_SUCCESS)
		return status;

	if (!max_size && remaining_size > size)
		printk_once(KERN_ERR FW_BUG "Broken EFI implementation"
			    " is returning MaxVariableSize=0\n");

	if (!storage_size || size > remaining_size ||
	    (max_size && size > max_size) ||
	    (remaining_size - size) < (storage_size / 2))
		return EFI_OUT_OF_RESOURCES;

	return EFI_SUCCESS;
}