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1// SPDX-License-Identifier: GPL-2.02/*3 * Helper functions used by the EFI stub on multiple4 * architectures to deal with physical address space randomization.5 */6#include <linux/efi.h>7 8#include "efistub.h"9 10/**11 * efi_kaslr_get_phys_seed() - Get random seed for physical kernel KASLR12 * @image_handle: Handle to the image13 *14 * If KASLR is not disabled, obtain a random seed using EFI_RNG_PROTOCOL15 * that will be used to move the kernel physical mapping.16 *17 * Return: the random seed18 */19u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle)20{21 efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID;22 void *p;23 24 if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))25 return 0;26 27 if (efi_nokaslr) {28 efi_info("KASLR disabled on kernel command line\n");29 } else if (efi_bs_call(handle_protocol, image_handle,30 &li_fixed_proto, &p) == EFI_SUCCESS) {31 efi_info("Image placement fixed by loader\n");32 } else {33 efi_status_t status;34 u32 phys_seed;35 36 status = efi_get_random_bytes(sizeof(phys_seed),37 (u8 *)&phys_seed);38 if (status == EFI_SUCCESS)39 return phys_seed;40 41 if (status == EFI_NOT_FOUND)42 efi_info("EFI_RNG_PROTOCOL unavailable\n");43 else44 efi_err("efi_get_random_bytes() failed (0x%lx)\n", status);45 46 efi_nokaslr = true;47 }48 49 return 0;50}51 52/*53 * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail54 * to provide space, and fail to zero it). Check for this condition by double55 * checking that the first and the last byte of the image are covered by the56 * same EFI memory map entry.57 */58static bool check_image_region(u64 base, u64 size)59{60 struct efi_boot_memmap *map;61 efi_status_t status;62 bool ret = false;63 int map_offset;64 65 status = efi_get_memory_map(&map, false);66 if (status != EFI_SUCCESS)67 return false;68 69 for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {70 efi_memory_desc_t *md = (void *)map->map + map_offset;71 u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;72 73 /*74 * Find the region that covers base, and return whether75 * it covers base+size bytes.76 */77 if (base >= md->phys_addr && base < end) {78 ret = (base + size) <= end;79 break;80 }81 }82 83 efi_bs_call(free_pool, map);84 85 return ret;86}87 88/**89 * efi_kaslr_relocate_kernel() - Relocate the kernel (random if KASLR enabled)90 * @image_addr: Pointer to the current kernel location91 * @reserve_addr: Pointer to the relocated kernel location92 * @reserve_size: Size of the relocated kernel93 * @kernel_size: Size of the text + data94 * @kernel_codesize: Size of the text95 * @kernel_memsize: Size of the text + data + bss96 * @phys_seed: Random seed used for the relocation97 *98 * If KASLR is not enabled, this function relocates the kernel to a fixed99 * address (or leave it as its current location). If KASLR is enabled, the100 * kernel physical location is randomized using the seed in parameter.101 *102 * Return: status code, EFI_SUCCESS if relocation is successful103 */104efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,105 unsigned long *reserve_addr,106 unsigned long *reserve_size,107 unsigned long kernel_size,108 unsigned long kernel_codesize,109 unsigned long kernel_memsize,110 u32 phys_seed)111{112 efi_status_t status;113 u64 min_kimg_align = efi_get_kimg_min_align();114 115 if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {116 /*117 * If KASLR is enabled, and we have some randomness available,118 * locate the kernel at a randomized offset in physical memory.119 */120 status = efi_random_alloc(*reserve_size, min_kimg_align,121 reserve_addr, phys_seed,122 EFI_LOADER_CODE, 0, EFI_ALLOC_LIMIT);123 if (status != EFI_SUCCESS)124 efi_warn("efi_random_alloc() failed: 0x%lx\n", status);125 } else {126 status = EFI_OUT_OF_RESOURCES;127 }128 129 if (status != EFI_SUCCESS) {130 if (!check_image_region(*image_addr, kernel_memsize)) {131 efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");132 } else if (IS_ALIGNED(*image_addr, min_kimg_align) &&133 (unsigned long)_end < EFI_ALLOC_LIMIT) {134 /*135 * Just execute from wherever we were loaded by the136 * UEFI PE/COFF loader if the placement is suitable.137 */138 *reserve_size = 0;139 return EFI_SUCCESS;140 }141 142 status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,143 ULONG_MAX, min_kimg_align,144 EFI_LOADER_CODE);145 146 if (status != EFI_SUCCESS) {147 efi_err("Failed to relocate kernel\n");148 *reserve_size = 0;149 return status;150 }151 }152 153 memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size);154 *image_addr = *reserve_addr;155 efi_icache_sync(*image_addr, *image_addr + kernel_codesize);156 efi_remap_image(*image_addr, *reserve_size, kernel_codesize);157 158 return status;159}160