int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
{
	unsigned long pfn, text, pf;
	struct page *page;
	unsigned npages;
	pgd_t *pgd = efi_mm.pgd;

	if (efi_enabled(EFI_OLD_MEMMAP))
		return 0;

	/*
	 * It can happen that the physical address of new_memmap lands in memory
	 * which is not mapped in the EFI page table. Therefore we need to go
	 * and ident-map those pages containing the map before calling
	 * phys_efi_set_virtual_address_map().
	 */
	pfn = pa_memmap >> PAGE_SHIFT;
	pf = _PAGE_NX | _PAGE_RW | _PAGE_ENC;
	if (kernel_map_pages_in_pgd(pgd, pfn, pa_memmap, num_pages, pf)) {
		pr_err("Error ident-mapping new memmap (0x%lx)!\n", pa_memmap);
		return 1;
	}

	/*
	 * Certain firmware versions are way too sentimential and still believe
	 * they are exclusive and unquestionable owners of the first physical page,
	 * even though they explicitly mark it as EFI_CONVENTIONAL_MEMORY
	 * (but then write-access it later during SetVirtualAddressMap()).
	 *
	 * Create a 1:1 mapping for this page, to avoid triple faults during early
	 * boot with such firmware. We are free to hand this page to the BIOS,
	 * as trim_bios_range() will reserve the first page and isolate it away
	 * from memory allocators anyway.
	 */
	pf = _PAGE_RW;
	if (sev_active())
		pf |= _PAGE_ENC;

	if (kernel_map_pages_in_pgd(pgd, 0x0, 0x0, 1, pf)) {
		pr_err("Failed to create 1:1 mapping for the first page!\n");
		return 1;
	}

	/*
	 * When making calls to the firmware everything needs to be 1:1
	 * mapped and addressable with 32-bit pointers. Map the kernel
	 * text and allocate a new stack because we can't rely on the
	 * stack pointer being < 4GB.
	 */
	if (!IS_ENABLED(CONFIG_EFI_MIXED) || efi_is_native())
		return 0;

	page = alloc_page(GFP_KERNEL|__GFP_DMA32);
	if (!page)
		panic("Unable to allocate EFI runtime stack < 4GB\n");

	efi_scratch.phys_stack = virt_to_phys(page_address(page));
	efi_scratch.phys_stack += PAGE_SIZE; /* stack grows down */

	npages = (_etext - _text) >> PAGE_SHIFT;
	text = __pa(_text);
	pfn = text >> PAGE_SHIFT;

	pf = _PAGE_RW | _PAGE_ENC;
	if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, pf)) {
		pr_err("Failed to map kernel text 1:1\n");
		return 1;
	}

	return 0;
}
Unknown