1*6b56beb5SAlexandre Ghiti // SPDX-License-Identifier: GPL-2.0 2*6b56beb5SAlexandre Ghiti /* 3*6b56beb5SAlexandre Ghiti * Helper functions used by the EFI stub on multiple 4*6b56beb5SAlexandre Ghiti * architectures to deal with physical address space randomization. 5*6b56beb5SAlexandre Ghiti */ 6*6b56beb5SAlexandre Ghiti #include <linux/efi.h> 7*6b56beb5SAlexandre Ghiti 8*6b56beb5SAlexandre Ghiti #include "efistub.h" 9*6b56beb5SAlexandre Ghiti 10*6b56beb5SAlexandre Ghiti /** 11*6b56beb5SAlexandre Ghiti * efi_kaslr_get_phys_seed() - Get random seed for physical kernel KASLR 12*6b56beb5SAlexandre Ghiti * @image_handle: Handle to the image 13*6b56beb5SAlexandre Ghiti * 14*6b56beb5SAlexandre Ghiti * If KASLR is not disabled, obtain a random seed using EFI_RNG_PROTOCOL 15*6b56beb5SAlexandre Ghiti * that will be used to move the kernel physical mapping. 16*6b56beb5SAlexandre Ghiti * 17*6b56beb5SAlexandre Ghiti * Return: the random seed 18*6b56beb5SAlexandre Ghiti */ 19*6b56beb5SAlexandre Ghiti u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle) 20*6b56beb5SAlexandre Ghiti { 21*6b56beb5SAlexandre Ghiti efi_status_t status; 22*6b56beb5SAlexandre Ghiti u32 phys_seed; 23*6b56beb5SAlexandre Ghiti efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID; 24*6b56beb5SAlexandre Ghiti void *p; 25*6b56beb5SAlexandre Ghiti 26*6b56beb5SAlexandre Ghiti if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE)) 27*6b56beb5SAlexandre Ghiti return 0; 28*6b56beb5SAlexandre Ghiti 29*6b56beb5SAlexandre Ghiti if (efi_nokaslr) { 30*6b56beb5SAlexandre Ghiti efi_info("KASLR disabled on kernel command line\n"); 31*6b56beb5SAlexandre Ghiti } else if (efi_bs_call(handle_protocol, image_handle, 32*6b56beb5SAlexandre Ghiti &li_fixed_proto, &p) == EFI_SUCCESS) { 33*6b56beb5SAlexandre Ghiti efi_info("Image placement fixed by loader\n"); 34*6b56beb5SAlexandre Ghiti } else { 35*6b56beb5SAlexandre Ghiti status = efi_get_random_bytes(sizeof(phys_seed), 36*6b56beb5SAlexandre Ghiti (u8 *)&phys_seed); 37*6b56beb5SAlexandre Ghiti if (status == EFI_SUCCESS) { 38*6b56beb5SAlexandre Ghiti return phys_seed; 39*6b56beb5SAlexandre Ghiti } else if (status == EFI_NOT_FOUND) { 40*6b56beb5SAlexandre Ghiti efi_info("EFI_RNG_PROTOCOL unavailable\n"); 41*6b56beb5SAlexandre Ghiti efi_nokaslr = true; 42*6b56beb5SAlexandre Ghiti } else if (status != EFI_SUCCESS) { 43*6b56beb5SAlexandre Ghiti efi_err("efi_get_random_bytes() failed (0x%lx)\n", 44*6b56beb5SAlexandre Ghiti status); 45*6b56beb5SAlexandre Ghiti efi_nokaslr = true; 46*6b56beb5SAlexandre Ghiti } 47*6b56beb5SAlexandre Ghiti } 48*6b56beb5SAlexandre Ghiti 49*6b56beb5SAlexandre Ghiti return 0; 50*6b56beb5SAlexandre Ghiti } 51*6b56beb5SAlexandre Ghiti 52*6b56beb5SAlexandre Ghiti /* 53*6b56beb5SAlexandre Ghiti * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail 54*6b56beb5SAlexandre Ghiti * to provide space, and fail to zero it). Check for this condition by double 55*6b56beb5SAlexandre Ghiti * checking that the first and the last byte of the image are covered by the 56*6b56beb5SAlexandre Ghiti * same EFI memory map entry. 57*6b56beb5SAlexandre Ghiti */ 58*6b56beb5SAlexandre Ghiti static bool check_image_region(u64 base, u64 size) 59*6b56beb5SAlexandre Ghiti { 60*6b56beb5SAlexandre Ghiti struct efi_boot_memmap *map; 61*6b56beb5SAlexandre Ghiti efi_status_t status; 62*6b56beb5SAlexandre Ghiti bool ret = false; 63*6b56beb5SAlexandre Ghiti int map_offset; 64*6b56beb5SAlexandre Ghiti 65*6b56beb5SAlexandre Ghiti status = efi_get_memory_map(&map, false); 66*6b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS) 67*6b56beb5SAlexandre Ghiti return false; 68*6b56beb5SAlexandre Ghiti 69*6b56beb5SAlexandre Ghiti for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) { 70*6b56beb5SAlexandre Ghiti efi_memory_desc_t *md = (void *)map->map + map_offset; 71*6b56beb5SAlexandre Ghiti u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE; 72*6b56beb5SAlexandre Ghiti 73*6b56beb5SAlexandre Ghiti /* 74*6b56beb5SAlexandre Ghiti * Find the region that covers base, and return whether 75*6b56beb5SAlexandre Ghiti * it covers base+size bytes. 76*6b56beb5SAlexandre Ghiti */ 77*6b56beb5SAlexandre Ghiti if (base >= md->phys_addr && base < end) { 78*6b56beb5SAlexandre Ghiti ret = (base + size) <= end; 79*6b56beb5SAlexandre Ghiti break; 80*6b56beb5SAlexandre Ghiti } 81*6b56beb5SAlexandre Ghiti } 82*6b56beb5SAlexandre Ghiti 83*6b56beb5SAlexandre Ghiti efi_bs_call(free_pool, map); 84*6b56beb5SAlexandre Ghiti 85*6b56beb5SAlexandre Ghiti return ret; 86*6b56beb5SAlexandre Ghiti } 87*6b56beb5SAlexandre Ghiti 88*6b56beb5SAlexandre Ghiti /** 89*6b56beb5SAlexandre Ghiti * efi_kaslr_relocate_kernel() - Relocate the kernel (random if KASLR enabled) 90*6b56beb5SAlexandre Ghiti * @image_addr: Pointer to the current kernel location 91*6b56beb5SAlexandre Ghiti * @reserve_addr: Pointer to the relocated kernel location 92*6b56beb5SAlexandre Ghiti * @reserve_size: Size of the relocated kernel 93*6b56beb5SAlexandre Ghiti * @kernel_size: Size of the text + data 94*6b56beb5SAlexandre Ghiti * @kernel_codesize: Size of the text 95*6b56beb5SAlexandre Ghiti * @kernel_memsize: Size of the text + data + bss 96*6b56beb5SAlexandre Ghiti * @phys_seed: Random seed used for the relocation 97*6b56beb5SAlexandre Ghiti * 98*6b56beb5SAlexandre Ghiti * If KASLR is not enabled, this function relocates the kernel to a fixed 99*6b56beb5SAlexandre Ghiti * address (or leave it as its current location). If KASLR is enabled, the 100*6b56beb5SAlexandre Ghiti * kernel physical location is randomized using the seed in parameter. 101*6b56beb5SAlexandre Ghiti * 102*6b56beb5SAlexandre Ghiti * Return: status code, EFI_SUCCESS if relocation is successful 103*6b56beb5SAlexandre Ghiti */ 104*6b56beb5SAlexandre Ghiti efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr, 105*6b56beb5SAlexandre Ghiti unsigned long *reserve_addr, 106*6b56beb5SAlexandre Ghiti unsigned long *reserve_size, 107*6b56beb5SAlexandre Ghiti unsigned long kernel_size, 108*6b56beb5SAlexandre Ghiti unsigned long kernel_codesize, 109*6b56beb5SAlexandre Ghiti unsigned long kernel_memsize, 110*6b56beb5SAlexandre Ghiti u32 phys_seed) 111*6b56beb5SAlexandre Ghiti { 112*6b56beb5SAlexandre Ghiti efi_status_t status; 113*6b56beb5SAlexandre Ghiti u64 min_kimg_align = efi_get_kimg_min_align(); 114*6b56beb5SAlexandre Ghiti 115*6b56beb5SAlexandre Ghiti if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) { 116*6b56beb5SAlexandre Ghiti /* 117*6b56beb5SAlexandre Ghiti * If KASLR is enabled, and we have some randomness available, 118*6b56beb5SAlexandre Ghiti * locate the kernel at a randomized offset in physical memory. 119*6b56beb5SAlexandre Ghiti */ 120*6b56beb5SAlexandre Ghiti status = efi_random_alloc(*reserve_size, min_kimg_align, 121*6b56beb5SAlexandre Ghiti reserve_addr, phys_seed, 122*6b56beb5SAlexandre Ghiti EFI_LOADER_CODE); 123*6b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS) 124*6b56beb5SAlexandre Ghiti efi_warn("efi_random_alloc() failed: 0x%lx\n", status); 125*6b56beb5SAlexandre Ghiti } else { 126*6b56beb5SAlexandre Ghiti status = EFI_OUT_OF_RESOURCES; 127*6b56beb5SAlexandre Ghiti } 128*6b56beb5SAlexandre Ghiti 129*6b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS) { 130*6b56beb5SAlexandre Ghiti if (!check_image_region(*image_addr, kernel_memsize)) { 131*6b56beb5SAlexandre Ghiti efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n"); 132*6b56beb5SAlexandre Ghiti } else if (IS_ALIGNED(*image_addr, min_kimg_align) && 133*6b56beb5SAlexandre Ghiti (u64)_end < EFI_ALLOC_LIMIT) { 134*6b56beb5SAlexandre Ghiti /* 135*6b56beb5SAlexandre Ghiti * Just execute from wherever we were loaded by the 136*6b56beb5SAlexandre Ghiti * UEFI PE/COFF loader if the placement is suitable. 137*6b56beb5SAlexandre Ghiti */ 138*6b56beb5SAlexandre Ghiti *reserve_size = 0; 139*6b56beb5SAlexandre Ghiti return EFI_SUCCESS; 140*6b56beb5SAlexandre Ghiti } 141*6b56beb5SAlexandre Ghiti 142*6b56beb5SAlexandre Ghiti status = efi_allocate_pages_aligned(*reserve_size, reserve_addr, 143*6b56beb5SAlexandre Ghiti ULONG_MAX, min_kimg_align, 144*6b56beb5SAlexandre Ghiti EFI_LOADER_CODE); 145*6b56beb5SAlexandre Ghiti 146*6b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS) { 147*6b56beb5SAlexandre Ghiti efi_err("Failed to relocate kernel\n"); 148*6b56beb5SAlexandre Ghiti *reserve_size = 0; 149*6b56beb5SAlexandre Ghiti return status; 150*6b56beb5SAlexandre Ghiti } 151*6b56beb5SAlexandre Ghiti } 152*6b56beb5SAlexandre Ghiti 153*6b56beb5SAlexandre Ghiti memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size); 154*6b56beb5SAlexandre Ghiti *image_addr = *reserve_addr; 155*6b56beb5SAlexandre Ghiti efi_icache_sync(*image_addr, *image_addr + kernel_codesize); 156*6b56beb5SAlexandre Ghiti efi_remap_image(*image_addr, *reserve_size, kernel_codesize); 157*6b56beb5SAlexandre Ghiti 158*6b56beb5SAlexandre Ghiti return status; 159*6b56beb5SAlexandre Ghiti } 160