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// SPDX-License-Identifier: GPL-2.0-only
* EFI stub implementation that is shared by arm and arm64 architectures.
* This should be #included by the EFI stub implementation files.
* Copyright (C) 2013,2014 Linaro Limited
* Roy Franz <
* Copyright (C) 2013 Red Hat, Inc.
* Mark Salter <>
#include <linux/efi.h>
#include <linux/sort.h>
#include <asm/efi.h>
#include "efistub.h"
* This is the base address at which to start allocating virtual memory ranges
* for UEFI Runtime Services. This is in the low TTBR0 range so that we can use
* any allocation we choose, and eliminate the risk of a conflict after kexec.
* The value chosen is the largest non-zero power of 2 suitable for this purpose
* both on 32-bit and 64-bit ARM CPUs, to maximize the likelihood that it can
* be mapped efficiently.
* Since 32-bit ARM could potentially execute with a 1G/3G user/kernel split,
* map everything below 1 GB. (512 MB is a reasonable upper bound for the
* entire footprint of the UEFI runtime services memory regions)
#ifdef CONFIG_ARM64
static u64 virtmap_base = EFI_RT_VIRTUAL_BASE;
void efi_char16_printk(efi_system_table_t *sys_table_arg,
efi_char16_t *str)
struct efi_simple_text_output_protocol *out;
out = (struct efi_simple_text_output_protocol *)sys_table_arg->con_out;
out->output_string(out, str);
static struct screen_info *setup_graphics(efi_system_table_t *sys_table_arg)
efi_status_t status;
unsigned long size;
void **gop_handle = NULL;
struct screen_info *si = NULL;
size = 0;
status = efi_call_early(locate_handle, EFI_LOCATE_BY_PROTOCOL,
&gop_proto, NULL, &size, gop_handle);
if (status == EFI_BUFFER_TOO_SMALL) {
si = alloc_screen_info(sys_table_arg);
if (!si)
return NULL;
efi_setup_gop(sys_table_arg, si, &gop_proto, size);
return si;
void install_memreserve_table(efi_system_table_t *sys_table_arg)
struct linux_efi_memreserve *rsv;
efi_guid_t memreserve_table_guid = LINUX_EFI_MEMRESERVE_TABLE_GUID;
efi_status_t status;
status = efi_call_early(allocate_pool, EFI_LOADER_DATA, sizeof(*rsv),
(void **)&rsv);
if (status != EFI_SUCCESS) {
pr_efi_err(sys_table_arg, "Failed to allocate memreserve entry!\n");
rsv->next = 0;
rsv->size = 0;
atomic_set(&rsv->count, 0);
status = efi_call_early(install_configuration_table,
if (status != EFI_SUCCESS)
pr_efi_err(sys_table_arg, "Failed to install memreserve config table!\n");
* This function handles the architcture specific differences between arm and
* arm64 regarding where the kernel image must be loaded and any memory that
* must be reserved. On failure it is required to free all
* all allocations it has made.
efi_status_t handle_kernel_image(efi_system_table_t *sys_table,
unsigned long *image_addr,
unsigned long *image_size,
unsigned long *reserve_addr,
unsigned long *reserve_size,
unsigned long dram_base,
efi_loaded_image_t *image);
* EFI entry point for the arm/arm64 EFI stubs. This is the entrypoint
* that is described in the PE/COFF header. Most of the code is the same
* for both archictectures, with the arch-specific code provided in the
* handle_kernel_image() function.
unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
unsigned long *image_addr)
efi_loaded_image_t *image;
efi_status_t status;
unsigned long image_size = 0;
unsigned long dram_base;
/* addr/point and size pairs for memory management*/
unsigned long initrd_addr;
u64 initrd_size = 0;
unsigned long fdt_addr = 0; /* Original DTB */
unsigned long fdt_size = 0;
char *cmdline_ptr = NULL;
int cmdline_size = 0;
unsigned long new_fdt_addr;
efi_guid_t loaded_image_proto = LOADED_IMAGE_PROTOCOL_GUID;
unsigned long reserve_addr = 0;
unsigned long reserve_size = 0;
enum efi_secureboot_mode secure_boot;
struct screen_info *si;
/* Check if we were booted by the EFI firmware */
if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
goto fail;
status = check_platform_features(sys_table);
if (status != EFI_SUCCESS)
goto fail;
* Get a handle to the loaded image protocol. This is used to get
* information about the running image, such as size and the command
* line.
status = sys_table->boottime->handle_protocol(handle,
&loaded_image_proto, (void *)&image);
if (status != EFI_SUCCESS) {
pr_efi_err(sys_table, "Failed to get loaded image protocol\n");
goto fail;
dram_base = get_dram_base(sys_table);
if (dram_base == EFI_ERROR) {
pr_efi_err(sys_table, "Failed to find DRAM base\n");
goto fail;
* Get the command line from EFI, using the LOADED_IMAGE
* protocol. We are going to copy the command line into the
* device tree, so this can be allocated anywhere.
cmdline_ptr = efi_convert_cmdline(sys_table, image, &cmdline_size);
if (!cmdline_ptr) {
pr_efi_err(sys_table, "getting command line via LOADED_IMAGE_PROTOCOL\n");
goto fail;
cmdline_size == 0)
if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && cmdline_size > 0)
pr_efi(sys_table, "Booting Linux Kernel...\n");
si = setup_graphics(sys_table);
status = handle_kernel_image(sys_table, image_addr, &image_size,
dram_base, image);
if (status != EFI_SUCCESS) {
pr_efi_err(sys_table, "Failed to relocate kernel\n");
goto fail_free_cmdline;
/* Ask the firmware to clear memory on unclean shutdown */
secure_boot = efi_get_secureboot(sys_table);
* Unauthenticated device tree data is a security hazard, so ignore
* 'dtb=' unless UEFI Secure Boot is disabled. We assume that secure
* boot is enabled if we can't determine its state.
secure_boot != efi_secureboot_mode_disabled) {
if (strstr(cmdline_ptr, "dtb="))
pr_efi(sys_table, "Ignoring DTB from command line.\n");
} else {
status = handle_cmdline_files(sys_table, image, cmdline_ptr,
~0UL, &fdt_addr, &fdt_size);
if (status != EFI_SUCCESS) {
pr_efi_err(sys_table, "Failed to load device tree!\n");
goto fail_free_image;
if (fdt_addr) {
pr_efi(sys_table, "Using DTB from command line\n");
} else {
/* Look for a device tree configuration table entry. */
fdt_addr = (uintptr_t)get_fdt(sys_table, &fdt_size);
if (fdt_addr)
pr_efi(sys_table, "Using DTB from configuration table\n");
if (!fdt_addr)
pr_efi(sys_table, "Generating empty DTB\n");
status = handle_cmdline_files(sys_table, image, cmdline_ptr, "initrd=",
(unsigned long *)&initrd_addr,
(unsigned long *)&initrd_size);
if (status != EFI_SUCCESS)
pr_efi_err(sys_table, "Failed initrd from command line!\n");
/* hibernation expects the runtime regions to stay in the same place */
if (!IS_ENABLED(CONFIG_HIBERNATION) && !nokaslr()) {
* Randomize the base of the UEFI runtime services region.
* Preserve the 2 MB alignment of the region by taking a
* shift of 21 bit positions into account when scaling
* the headroom value using a 32-bit random value.
static const u64 headroom = EFI_RT_VIRTUAL_LIMIT -
u32 rnd;
status = efi_get_random_bytes(sys_table, sizeof(rnd),
(u8 *)&rnd);
if (status == EFI_SUCCESS) {
virtmap_base = EFI_RT_VIRTUAL_BASE +
(((headroom >> 21) * rnd) >> (32 - 21));
new_fdt_addr = fdt_addr;
status = allocate_new_fdt_and_exit_boot(sys_table, handle,
&new_fdt_addr, efi_get_max_fdt_addr(dram_base),
initrd_addr, initrd_size, cmdline_ptr,
fdt_addr, fdt_size);
* If all went well, we need to return the FDT address to the
* calling function so it can be passed to kernel as part of
* the kernel boot protocol.
if (status == EFI_SUCCESS)
return new_fdt_addr;
pr_efi_err(sys_table, "Failed to update FDT and exit boot services\n");
efi_free(sys_table, initrd_size, initrd_addr);
efi_free(sys_table, fdt_size, fdt_addr);
efi_free(sys_table, image_size, *image_addr);
efi_free(sys_table, reserve_size, reserve_addr);
free_screen_info(sys_table, si);
efi_free(sys_table, cmdline_size, (unsigned long)cmdline_ptr);
return EFI_ERROR;
static int cmp_mem_desc(const void *l, const void *r)
const efi_memory_desc_t *left = l, *right = r;
return (left->phys_addr > right->phys_addr) ? 1 : -1;
* Returns whether region @left ends exactly where region @right starts,
* or false if either argument is NULL.
static bool regions_are_adjacent(efi_memory_desc_t *left,
efi_memory_desc_t *right)
u64 left_end;
if (left == NULL || right == NULL)
return false;
left_end = left->phys_addr + left->num_pages * EFI_PAGE_SIZE;
return left_end == right->phys_addr;
* Returns whether region @left and region @right have compatible memory type
* mapping attributes, and are both EFI_MEMORY_RUNTIME regions.
static bool regions_have_compatible_memory_type_attrs(efi_memory_desc_t *left,
efi_memory_desc_t *right)
static const u64 mem_type_mask = EFI_MEMORY_WB | EFI_MEMORY_WT |
return ((left->attribute ^ right->attribute) & mem_type_mask) == 0;
* efi_get_virtmap() - create a virtual mapping for the EFI memory map
* This function populates the virt_addr fields of all memory region descriptors
* in @memory_map whose EFI_MEMORY_RUNTIME attribute is set. Those descriptors
* are also copied to @runtime_map, and their total count is returned in @count.
void efi_get_virtmap(efi_memory_desc_t *memory_map, unsigned long map_size,
unsigned long desc_size, efi_memory_desc_t *runtime_map,
int *count)
u64 efi_virt_base = virtmap_base;
efi_memory_desc_t *in, *prev = NULL, *out = runtime_map;
int l;
* To work around potential issues with the Properties Table feature
* introduced in UEFI 2.5, which may split PE/COFF executable images
* in memory into several RuntimeServicesCode and RuntimeServicesData
* regions, we need to preserve the relative offsets between adjacent
* EFI_MEMORY_RUNTIME regions with the same memory type attributes.
* The easiest way to find adjacent regions is to sort the memory map
* before traversing it.
sort(memory_map, map_size / desc_size, desc_size, cmp_mem_desc,
for (l = 0; l < map_size; l += desc_size, prev = in) {
u64 paddr, size;
in = (void *)memory_map + l;
if (!(in->attribute & EFI_MEMORY_RUNTIME))
paddr = in->phys_addr;
size = in->num_pages * EFI_PAGE_SIZE;
if (novamap()) {
in->virt_addr = in->phys_addr;
* Make the mapping compatible with 64k pages: this allows
* a 4k page size kernel to kexec a 64k page size kernel and
* vice versa.
!regions_are_adjacent(prev, in)) ||
!regions_have_compatible_memory_type_attrs(prev, in)) {
paddr = round_down(in->phys_addr, SZ_64K);
size += in->phys_addr - paddr;
* Avoid wasting memory on PTEs by choosing a virtual
* base that is compatible with section mappings if this
* region has the appropriate size and physical
* alignment. (Sections are 2 MB on 4k granule kernels)
if (IS_ALIGNED(in->phys_addr, SZ_2M) && size >= SZ_2M)
efi_virt_base = round_up(efi_virt_base, SZ_2M);
efi_virt_base = round_up(efi_virt_base, SZ_64K);
in->virt_addr = efi_virt_base + in->phys_addr - paddr;
efi_virt_base += size;
memcpy(out, in, desc_size);
out = (void *)out + desc_size;