16b56beb5SAlexandre Ghiti // SPDX-License-Identifier: GPL-2.0
26b56beb5SAlexandre Ghiti /*
36b56beb5SAlexandre Ghiti * Helper functions used by the EFI stub on multiple
46b56beb5SAlexandre Ghiti * architectures to deal with physical address space randomization.
56b56beb5SAlexandre Ghiti */
66b56beb5SAlexandre Ghiti #include <linux/efi.h>
76b56beb5SAlexandre Ghiti
86b56beb5SAlexandre Ghiti #include "efistub.h"
96b56beb5SAlexandre Ghiti
106b56beb5SAlexandre Ghiti /**
116b56beb5SAlexandre Ghiti * efi_kaslr_get_phys_seed() - Get random seed for physical kernel KASLR
126b56beb5SAlexandre Ghiti * @image_handle: Handle to the image
136b56beb5SAlexandre Ghiti *
146b56beb5SAlexandre Ghiti * If KASLR is not disabled, obtain a random seed using EFI_RNG_PROTOCOL
156b56beb5SAlexandre Ghiti * that will be used to move the kernel physical mapping.
166b56beb5SAlexandre Ghiti *
176b56beb5SAlexandre Ghiti * Return: the random seed
186b56beb5SAlexandre Ghiti */
efi_kaslr_get_phys_seed(efi_handle_t image_handle)196b56beb5SAlexandre Ghiti u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle)
206b56beb5SAlexandre Ghiti {
216b56beb5SAlexandre Ghiti efi_status_t status;
226b56beb5SAlexandre Ghiti u32 phys_seed;
236b56beb5SAlexandre Ghiti efi_guid_t li_fixed_proto = LINUX_EFI_LOADED_IMAGE_FIXED_GUID;
246b56beb5SAlexandre Ghiti void *p;
256b56beb5SAlexandre Ghiti
266b56beb5SAlexandre Ghiti if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
276b56beb5SAlexandre Ghiti return 0;
286b56beb5SAlexandre Ghiti
296b56beb5SAlexandre Ghiti if (efi_nokaslr) {
306b56beb5SAlexandre Ghiti efi_info("KASLR disabled on kernel command line\n");
316b56beb5SAlexandre Ghiti } else if (efi_bs_call(handle_protocol, image_handle,
326b56beb5SAlexandre Ghiti &li_fixed_proto, &p) == EFI_SUCCESS) {
336b56beb5SAlexandre Ghiti efi_info("Image placement fixed by loader\n");
346b56beb5SAlexandre Ghiti } else {
356b56beb5SAlexandre Ghiti status = efi_get_random_bytes(sizeof(phys_seed),
366b56beb5SAlexandre Ghiti (u8 *)&phys_seed);
376b56beb5SAlexandre Ghiti if (status == EFI_SUCCESS) {
386b56beb5SAlexandre Ghiti return phys_seed;
396b56beb5SAlexandre Ghiti } else if (status == EFI_NOT_FOUND) {
406b56beb5SAlexandre Ghiti efi_info("EFI_RNG_PROTOCOL unavailable\n");
416b56beb5SAlexandre Ghiti efi_nokaslr = true;
426b56beb5SAlexandre Ghiti } else if (status != EFI_SUCCESS) {
436b56beb5SAlexandre Ghiti efi_err("efi_get_random_bytes() failed (0x%lx)\n",
446b56beb5SAlexandre Ghiti status);
456b56beb5SAlexandre Ghiti efi_nokaslr = true;
466b56beb5SAlexandre Ghiti }
476b56beb5SAlexandre Ghiti }
486b56beb5SAlexandre Ghiti
496b56beb5SAlexandre Ghiti return 0;
506b56beb5SAlexandre Ghiti }
516b56beb5SAlexandre Ghiti
526b56beb5SAlexandre Ghiti /*
536b56beb5SAlexandre Ghiti * Distro versions of GRUB may ignore the BSS allocation entirely (i.e., fail
546b56beb5SAlexandre Ghiti * to provide space, and fail to zero it). Check for this condition by double
556b56beb5SAlexandre Ghiti * checking that the first and the last byte of the image are covered by the
566b56beb5SAlexandre Ghiti * same EFI memory map entry.
576b56beb5SAlexandre Ghiti */
check_image_region(u64 base,u64 size)586b56beb5SAlexandre Ghiti static bool check_image_region(u64 base, u64 size)
596b56beb5SAlexandre Ghiti {
606b56beb5SAlexandre Ghiti struct efi_boot_memmap *map;
616b56beb5SAlexandre Ghiti efi_status_t status;
626b56beb5SAlexandre Ghiti bool ret = false;
636b56beb5SAlexandre Ghiti int map_offset;
646b56beb5SAlexandre Ghiti
656b56beb5SAlexandre Ghiti status = efi_get_memory_map(&map, false);
666b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS)
676b56beb5SAlexandre Ghiti return false;
686b56beb5SAlexandre Ghiti
696b56beb5SAlexandre Ghiti for (map_offset = 0; map_offset < map->map_size; map_offset += map->desc_size) {
706b56beb5SAlexandre Ghiti efi_memory_desc_t *md = (void *)map->map + map_offset;
716b56beb5SAlexandre Ghiti u64 end = md->phys_addr + md->num_pages * EFI_PAGE_SIZE;
726b56beb5SAlexandre Ghiti
736b56beb5SAlexandre Ghiti /*
746b56beb5SAlexandre Ghiti * Find the region that covers base, and return whether
756b56beb5SAlexandre Ghiti * it covers base+size bytes.
766b56beb5SAlexandre Ghiti */
776b56beb5SAlexandre Ghiti if (base >= md->phys_addr && base < end) {
786b56beb5SAlexandre Ghiti ret = (base + size) <= end;
796b56beb5SAlexandre Ghiti break;
806b56beb5SAlexandre Ghiti }
816b56beb5SAlexandre Ghiti }
826b56beb5SAlexandre Ghiti
836b56beb5SAlexandre Ghiti efi_bs_call(free_pool, map);
846b56beb5SAlexandre Ghiti
856b56beb5SAlexandre Ghiti return ret;
866b56beb5SAlexandre Ghiti }
876b56beb5SAlexandre Ghiti
886b56beb5SAlexandre Ghiti /**
896b56beb5SAlexandre Ghiti * efi_kaslr_relocate_kernel() - Relocate the kernel (random if KASLR enabled)
906b56beb5SAlexandre Ghiti * @image_addr: Pointer to the current kernel location
916b56beb5SAlexandre Ghiti * @reserve_addr: Pointer to the relocated kernel location
926b56beb5SAlexandre Ghiti * @reserve_size: Size of the relocated kernel
936b56beb5SAlexandre Ghiti * @kernel_size: Size of the text + data
946b56beb5SAlexandre Ghiti * @kernel_codesize: Size of the text
956b56beb5SAlexandre Ghiti * @kernel_memsize: Size of the text + data + bss
966b56beb5SAlexandre Ghiti * @phys_seed: Random seed used for the relocation
976b56beb5SAlexandre Ghiti *
986b56beb5SAlexandre Ghiti * If KASLR is not enabled, this function relocates the kernel to a fixed
996b56beb5SAlexandre Ghiti * address (or leave it as its current location). If KASLR is enabled, the
1006b56beb5SAlexandre Ghiti * kernel physical location is randomized using the seed in parameter.
1016b56beb5SAlexandre Ghiti *
1026b56beb5SAlexandre Ghiti * Return: status code, EFI_SUCCESS if relocation is successful
1036b56beb5SAlexandre Ghiti */
efi_kaslr_relocate_kernel(unsigned long * image_addr,unsigned long * reserve_addr,unsigned long * reserve_size,unsigned long kernel_size,unsigned long kernel_codesize,unsigned long kernel_memsize,u32 phys_seed)1046b56beb5SAlexandre Ghiti efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
1056b56beb5SAlexandre Ghiti unsigned long *reserve_addr,
1066b56beb5SAlexandre Ghiti unsigned long *reserve_size,
1076b56beb5SAlexandre Ghiti unsigned long kernel_size,
1086b56beb5SAlexandre Ghiti unsigned long kernel_codesize,
1096b56beb5SAlexandre Ghiti unsigned long kernel_memsize,
1106b56beb5SAlexandre Ghiti u32 phys_seed)
1116b56beb5SAlexandre Ghiti {
1126b56beb5SAlexandre Ghiti efi_status_t status;
1136b56beb5SAlexandre Ghiti u64 min_kimg_align = efi_get_kimg_min_align();
1146b56beb5SAlexandre Ghiti
1156b56beb5SAlexandre Ghiti if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && phys_seed != 0) {
1166b56beb5SAlexandre Ghiti /*
1176b56beb5SAlexandre Ghiti * If KASLR is enabled, and we have some randomness available,
1186b56beb5SAlexandre Ghiti * locate the kernel at a randomized offset in physical memory.
1196b56beb5SAlexandre Ghiti */
1206b56beb5SAlexandre Ghiti status = efi_random_alloc(*reserve_size, min_kimg_align,
1216b56beb5SAlexandre Ghiti reserve_addr, phys_seed,
122*0e7ca435SArd Biesheuvel EFI_LOADER_CODE, 0, EFI_ALLOC_LIMIT);
1236b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS)
1246b56beb5SAlexandre Ghiti efi_warn("efi_random_alloc() failed: 0x%lx\n", status);
1256b56beb5SAlexandre Ghiti } else {
1266b56beb5SAlexandre Ghiti status = EFI_OUT_OF_RESOURCES;
1276b56beb5SAlexandre Ghiti }
1286b56beb5SAlexandre Ghiti
1296b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS) {
1306b56beb5SAlexandre Ghiti if (!check_image_region(*image_addr, kernel_memsize)) {
1316b56beb5SAlexandre Ghiti efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
1326b56beb5SAlexandre Ghiti } else if (IS_ALIGNED(*image_addr, min_kimg_align) &&
1333c35d1a0SAlexandre Ghiti (unsigned long)_end < EFI_ALLOC_LIMIT) {
1346b56beb5SAlexandre Ghiti /*
1356b56beb5SAlexandre Ghiti * Just execute from wherever we were loaded by the
1366b56beb5SAlexandre Ghiti * UEFI PE/COFF loader if the placement is suitable.
1376b56beb5SAlexandre Ghiti */
1386b56beb5SAlexandre Ghiti *reserve_size = 0;
1396b56beb5SAlexandre Ghiti return EFI_SUCCESS;
1406b56beb5SAlexandre Ghiti }
1416b56beb5SAlexandre Ghiti
1426b56beb5SAlexandre Ghiti status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,
1436b56beb5SAlexandre Ghiti ULONG_MAX, min_kimg_align,
1446b56beb5SAlexandre Ghiti EFI_LOADER_CODE);
1456b56beb5SAlexandre Ghiti
1466b56beb5SAlexandre Ghiti if (status != EFI_SUCCESS) {
1476b56beb5SAlexandre Ghiti efi_err("Failed to relocate kernel\n");
1486b56beb5SAlexandre Ghiti *reserve_size = 0;
1496b56beb5SAlexandre Ghiti return status;
1506b56beb5SAlexandre Ghiti }
1516b56beb5SAlexandre Ghiti }
1526b56beb5SAlexandre Ghiti
1536b56beb5SAlexandre Ghiti memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size);
1546b56beb5SAlexandre Ghiti *image_addr = *reserve_addr;
1556b56beb5SAlexandre Ghiti efi_icache_sync(*image_addr, *image_addr + kernel_codesize);
1566b56beb5SAlexandre Ghiti efi_remap_image(*image_addr, *reserve_size, kernel_codesize);
1576b56beb5SAlexandre Ghiti
1586b56beb5SAlexandre Ghiti return status;
1596b56beb5SAlexandre Ghiti }
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