1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * kaslr.c 4 * 5 * This contains the routines needed to generate a reasonable level of 6 * entropy to choose a randomized kernel base address offset in support 7 * of Kernel Address Space Layout Randomization (KASLR). Additionally 8 * handles walking the physical memory maps (and tracking memory regions 9 * to avoid) in order to select a physical memory location that can 10 * contain the entire properly aligned running kernel image. 11 * 12 */ 13 14 /* 15 * isspace() in linux/ctype.h is expected by next_args() to filter 16 * out "space/lf/tab". While boot/ctype.h conflicts with linux/ctype.h, 17 * since isdigit() is implemented in both of them. Hence disable it 18 * here. 19 */ 20 #define BOOT_CTYPE_H 21 22 /* 23 * _ctype[] in lib/ctype.c is needed by isspace() of linux/ctype.h. 24 * While both lib/ctype.c and lib/cmdline.c will bring EXPORT_SYMBOL 25 * which is meaningless and will cause compiling error in some cases. 26 */ 27 #define __DISABLE_EXPORTS 28 29 #include "misc.h" 30 #include "error.h" 31 #include "../string.h" 32 33 #include <generated/compile.h> 34 #include <linux/module.h> 35 #include <linux/uts.h> 36 #include <linux/utsname.h> 37 #include <linux/ctype.h> 38 #include <linux/efi.h> 39 #include <generated/utsrelease.h> 40 #include <asm/efi.h> 41 42 /* Macros used by the included decompressor code below. */ 43 #define STATIC 44 #include <linux/decompress/mm.h> 45 46 #ifdef CONFIG_X86_5LEVEL 47 unsigned int __pgtable_l5_enabled; 48 unsigned int pgdir_shift __ro_after_init = 39; 49 unsigned int ptrs_per_p4d __ro_after_init = 1; 50 #endif 51 52 extern unsigned long get_cmd_line_ptr(void); 53 54 /* Used by PAGE_KERN* macros: */ 55 pteval_t __default_kernel_pte_mask __read_mostly = ~0; 56 57 /* Simplified build-specific string for starting entropy. */ 58 static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@" 59 LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION; 60 61 static unsigned long rotate_xor(unsigned long hash, const void *area, 62 size_t size) 63 { 64 size_t i; 65 unsigned long *ptr = (unsigned long *)area; 66 67 for (i = 0; i < size / sizeof(hash); i++) { 68 /* Rotate by odd number of bits and XOR. */ 69 hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); 70 hash ^= ptr[i]; 71 } 72 73 return hash; 74 } 75 76 /* Attempt to create a simple but unpredictable starting entropy. */ 77 static unsigned long get_boot_seed(void) 78 { 79 unsigned long hash = 0; 80 81 hash = rotate_xor(hash, build_str, sizeof(build_str)); 82 hash = rotate_xor(hash, boot_params, sizeof(*boot_params)); 83 84 return hash; 85 } 86 87 #define KASLR_COMPRESSED_BOOT 88 #include "../../lib/kaslr.c" 89 90 91 /* Only supporting at most 4 unusable memmap regions with kaslr */ 92 #define MAX_MEMMAP_REGIONS 4 93 94 static bool memmap_too_large; 95 96 97 /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */ 98 static unsigned long long mem_limit = ULLONG_MAX; 99 100 /* Number of immovable memory regions */ 101 static int num_immovable_mem; 102 103 enum mem_avoid_index { 104 MEM_AVOID_ZO_RANGE = 0, 105 MEM_AVOID_INITRD, 106 MEM_AVOID_CMDLINE, 107 MEM_AVOID_BOOTPARAMS, 108 MEM_AVOID_MEMMAP_BEGIN, 109 MEM_AVOID_MEMMAP_END = MEM_AVOID_MEMMAP_BEGIN + MAX_MEMMAP_REGIONS - 1, 110 MEM_AVOID_MAX, 111 }; 112 113 static struct mem_vector mem_avoid[MEM_AVOID_MAX]; 114 115 static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two) 116 { 117 /* Item one is entirely before item two. */ 118 if (one->start + one->size <= two->start) 119 return false; 120 /* Item one is entirely after item two. */ 121 if (one->start >= two->start + two->size) 122 return false; 123 return true; 124 } 125 126 char *skip_spaces(const char *str) 127 { 128 while (isspace(*str)) 129 ++str; 130 return (char *)str; 131 } 132 #include "../../../../lib/ctype.c" 133 #include "../../../../lib/cmdline.c" 134 135 enum parse_mode { 136 PARSE_MEMMAP, 137 PARSE_EFI, 138 }; 139 140 static int 141 parse_memmap(char *p, unsigned long long *start, unsigned long long *size, 142 enum parse_mode mode) 143 { 144 char *oldp; 145 146 if (!p) 147 return -EINVAL; 148 149 /* We don't care about this option here */ 150 if (!strncmp(p, "exactmap", 8)) 151 return -EINVAL; 152 153 oldp = p; 154 *size = memparse(p, &p); 155 if (p == oldp) 156 return -EINVAL; 157 158 switch (*p) { 159 case '#': 160 case '$': 161 case '!': 162 *start = memparse(p + 1, &p); 163 return 0; 164 case '@': 165 if (mode == PARSE_MEMMAP) { 166 /* 167 * memmap=nn@ss specifies usable region, should 168 * be skipped 169 */ 170 *size = 0; 171 } else { 172 unsigned long long flags; 173 174 /* 175 * efi_fake_mem=nn@ss:attr the attr specifies 176 * flags that might imply a soft-reservation. 177 */ 178 *start = memparse(p + 1, &p); 179 if (p && *p == ':') { 180 p++; 181 if (kstrtoull(p, 0, &flags) < 0) 182 *size = 0; 183 else if (flags & EFI_MEMORY_SP) 184 return 0; 185 } 186 *size = 0; 187 } 188 /* Fall through */ 189 default: 190 /* 191 * If w/o offset, only size specified, memmap=nn[KMG] has the 192 * same behaviour as mem=nn[KMG]. It limits the max address 193 * system can use. Region above the limit should be avoided. 194 */ 195 *start = 0; 196 return 0; 197 } 198 199 return -EINVAL; 200 } 201 202 static void mem_avoid_memmap(enum parse_mode mode, char *str) 203 { 204 static int i; 205 206 if (i >= MAX_MEMMAP_REGIONS) 207 return; 208 209 while (str && (i < MAX_MEMMAP_REGIONS)) { 210 int rc; 211 unsigned long long start, size; 212 char *k = strchr(str, ','); 213 214 if (k) 215 *k++ = 0; 216 217 rc = parse_memmap(str, &start, &size, mode); 218 if (rc < 0) 219 break; 220 str = k; 221 222 if (start == 0) { 223 /* Store the specified memory limit if size > 0 */ 224 if (size > 0) 225 mem_limit = size; 226 227 continue; 228 } 229 230 mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].start = start; 231 mem_avoid[MEM_AVOID_MEMMAP_BEGIN + i].size = size; 232 i++; 233 } 234 235 /* More than 4 memmaps, fail kaslr */ 236 if ((i >= MAX_MEMMAP_REGIONS) && str) 237 memmap_too_large = true; 238 } 239 240 /* Store the number of 1GB huge pages which users specified: */ 241 static unsigned long max_gb_huge_pages; 242 243 static void parse_gb_huge_pages(char *param, char *val) 244 { 245 static bool gbpage_sz; 246 char *p; 247 248 if (!strcmp(param, "hugepagesz")) { 249 p = val; 250 if (memparse(p, &p) != PUD_SIZE) { 251 gbpage_sz = false; 252 return; 253 } 254 255 if (gbpage_sz) 256 warn("Repeatedly set hugeTLB page size of 1G!\n"); 257 gbpage_sz = true; 258 return; 259 } 260 261 if (!strcmp(param, "hugepages") && gbpage_sz) { 262 p = val; 263 max_gb_huge_pages = simple_strtoull(p, &p, 0); 264 return; 265 } 266 } 267 268 static void handle_mem_options(void) 269 { 270 char *args = (char *)get_cmd_line_ptr(); 271 size_t len = strlen((char *)args); 272 char *tmp_cmdline; 273 char *param, *val; 274 u64 mem_size; 275 276 if (!strstr(args, "memmap=") && !strstr(args, "mem=") && 277 !strstr(args, "hugepages")) 278 return; 279 280 tmp_cmdline = malloc(len + 1); 281 if (!tmp_cmdline) 282 error("Failed to allocate space for tmp_cmdline"); 283 284 memcpy(tmp_cmdline, args, len); 285 tmp_cmdline[len] = 0; 286 args = tmp_cmdline; 287 288 /* Chew leading spaces */ 289 args = skip_spaces(args); 290 291 while (*args) { 292 args = next_arg(args, ¶m, &val); 293 /* Stop at -- */ 294 if (!val && strcmp(param, "--") == 0) { 295 warn("Only '--' specified in cmdline"); 296 goto out; 297 } 298 299 if (!strcmp(param, "memmap")) { 300 mem_avoid_memmap(PARSE_MEMMAP, val); 301 } else if (strstr(param, "hugepages")) { 302 parse_gb_huge_pages(param, val); 303 } else if (!strcmp(param, "mem")) { 304 char *p = val; 305 306 if (!strcmp(p, "nopentium")) 307 continue; 308 mem_size = memparse(p, &p); 309 if (mem_size == 0) 310 goto out; 311 312 mem_limit = mem_size; 313 } else if (!strcmp(param, "efi_fake_mem")) { 314 mem_avoid_memmap(PARSE_EFI, val); 315 } 316 } 317 318 out: 319 free(tmp_cmdline); 320 return; 321 } 322 323 /* 324 * In theory, KASLR can put the kernel anywhere in the range of [16M, 64T). 325 * The mem_avoid array is used to store the ranges that need to be avoided 326 * when KASLR searches for an appropriate random address. We must avoid any 327 * regions that are unsafe to overlap with during decompression, and other 328 * things like the initrd, cmdline and boot_params. This comment seeks to 329 * explain mem_avoid as clearly as possible since incorrect mem_avoid 330 * memory ranges lead to really hard to debug boot failures. 331 * 332 * The initrd, cmdline, and boot_params are trivial to identify for 333 * avoiding. They are MEM_AVOID_INITRD, MEM_AVOID_CMDLINE, and 334 * MEM_AVOID_BOOTPARAMS respectively below. 335 * 336 * What is not obvious how to avoid is the range of memory that is used 337 * during decompression (MEM_AVOID_ZO_RANGE below). This range must cover 338 * the compressed kernel (ZO) and its run space, which is used to extract 339 * the uncompressed kernel (VO) and relocs. 340 * 341 * ZO's full run size sits against the end of the decompression buffer, so 342 * we can calculate where text, data, bss, etc of ZO are positioned more 343 * easily. 344 * 345 * For additional background, the decompression calculations can be found 346 * in header.S, and the memory diagram is based on the one found in misc.c. 347 * 348 * The following conditions are already enforced by the image layouts and 349 * associated code: 350 * - input + input_size >= output + output_size 351 * - kernel_total_size <= init_size 352 * - kernel_total_size <= output_size (see Note below) 353 * - output + init_size >= output + output_size 354 * 355 * (Note that kernel_total_size and output_size have no fundamental 356 * relationship, but output_size is passed to choose_random_location 357 * as a maximum of the two. The diagram is showing a case where 358 * kernel_total_size is larger than output_size, but this case is 359 * handled by bumping output_size.) 360 * 361 * The above conditions can be illustrated by a diagram: 362 * 363 * 0 output input input+input_size output+init_size 364 * | | | | | 365 * | | | | | 366 * |-----|--------|--------|--------------|-----------|--|-------------| 367 * | | | 368 * | | | 369 * output+init_size-ZO_INIT_SIZE output+output_size output+kernel_total_size 370 * 371 * [output, output+init_size) is the entire memory range used for 372 * extracting the compressed image. 373 * 374 * [output, output+kernel_total_size) is the range needed for the 375 * uncompressed kernel (VO) and its run size (bss, brk, etc). 376 * 377 * [output, output+output_size) is VO plus relocs (i.e. the entire 378 * uncompressed payload contained by ZO). This is the area of the buffer 379 * written to during decompression. 380 * 381 * [output+init_size-ZO_INIT_SIZE, output+init_size) is the worst-case 382 * range of the copied ZO and decompression code. (i.e. the range 383 * covered backwards of size ZO_INIT_SIZE, starting from output+init_size.) 384 * 385 * [input, input+input_size) is the original copied compressed image (ZO) 386 * (i.e. it does not include its run size). This range must be avoided 387 * because it contains the data used for decompression. 388 * 389 * [input+input_size, output+init_size) is [_text, _end) for ZO. This 390 * range includes ZO's heap and stack, and must be avoided since it 391 * performs the decompression. 392 * 393 * Since the above two ranges need to be avoided and they are adjacent, 394 * they can be merged, resulting in: [input, output+init_size) which 395 * becomes the MEM_AVOID_ZO_RANGE below. 396 */ 397 static void mem_avoid_init(unsigned long input, unsigned long input_size, 398 unsigned long output) 399 { 400 unsigned long init_size = boot_params->hdr.init_size; 401 u64 initrd_start, initrd_size; 402 u64 cmd_line, cmd_line_size; 403 char *ptr; 404 405 /* 406 * Avoid the region that is unsafe to overlap during 407 * decompression. 408 */ 409 mem_avoid[MEM_AVOID_ZO_RANGE].start = input; 410 mem_avoid[MEM_AVOID_ZO_RANGE].size = (output + init_size) - input; 411 add_identity_map(mem_avoid[MEM_AVOID_ZO_RANGE].start, 412 mem_avoid[MEM_AVOID_ZO_RANGE].size); 413 414 /* Avoid initrd. */ 415 initrd_start = (u64)boot_params->ext_ramdisk_image << 32; 416 initrd_start |= boot_params->hdr.ramdisk_image; 417 initrd_size = (u64)boot_params->ext_ramdisk_size << 32; 418 initrd_size |= boot_params->hdr.ramdisk_size; 419 mem_avoid[MEM_AVOID_INITRD].start = initrd_start; 420 mem_avoid[MEM_AVOID_INITRD].size = initrd_size; 421 /* No need to set mapping for initrd, it will be handled in VO. */ 422 423 /* Avoid kernel command line. */ 424 cmd_line = (u64)boot_params->ext_cmd_line_ptr << 32; 425 cmd_line |= boot_params->hdr.cmd_line_ptr; 426 /* Calculate size of cmd_line. */ 427 ptr = (char *)(unsigned long)cmd_line; 428 for (cmd_line_size = 0; ptr[cmd_line_size++];) 429 ; 430 mem_avoid[MEM_AVOID_CMDLINE].start = cmd_line; 431 mem_avoid[MEM_AVOID_CMDLINE].size = cmd_line_size; 432 add_identity_map(mem_avoid[MEM_AVOID_CMDLINE].start, 433 mem_avoid[MEM_AVOID_CMDLINE].size); 434 435 /* Avoid boot parameters. */ 436 mem_avoid[MEM_AVOID_BOOTPARAMS].start = (unsigned long)boot_params; 437 mem_avoid[MEM_AVOID_BOOTPARAMS].size = sizeof(*boot_params); 438 add_identity_map(mem_avoid[MEM_AVOID_BOOTPARAMS].start, 439 mem_avoid[MEM_AVOID_BOOTPARAMS].size); 440 441 /* We don't need to set a mapping for setup_data. */ 442 443 /* Mark the memmap regions we need to avoid */ 444 handle_mem_options(); 445 446 /* Enumerate the immovable memory regions */ 447 num_immovable_mem = count_immovable_mem_regions(); 448 449 #ifdef CONFIG_X86_VERBOSE_BOOTUP 450 /* Make sure video RAM can be used. */ 451 add_identity_map(0, PMD_SIZE); 452 #endif 453 } 454 455 /* 456 * Does this memory vector overlap a known avoided area? If so, record the 457 * overlap region with the lowest address. 458 */ 459 static bool mem_avoid_overlap(struct mem_vector *img, 460 struct mem_vector *overlap) 461 { 462 int i; 463 struct setup_data *ptr; 464 unsigned long earliest = img->start + img->size; 465 bool is_overlapping = false; 466 467 for (i = 0; i < MEM_AVOID_MAX; i++) { 468 if (mem_overlaps(img, &mem_avoid[i]) && 469 mem_avoid[i].start < earliest) { 470 *overlap = mem_avoid[i]; 471 earliest = overlap->start; 472 is_overlapping = true; 473 } 474 } 475 476 /* Avoid all entries in the setup_data linked list. */ 477 ptr = (struct setup_data *)(unsigned long)boot_params->hdr.setup_data; 478 while (ptr) { 479 struct mem_vector avoid; 480 481 avoid.start = (unsigned long)ptr; 482 avoid.size = sizeof(*ptr) + ptr->len; 483 484 if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) { 485 *overlap = avoid; 486 earliest = overlap->start; 487 is_overlapping = true; 488 } 489 490 if (ptr->type == SETUP_INDIRECT && 491 ((struct setup_indirect *)ptr->data)->type != SETUP_INDIRECT) { 492 avoid.start = ((struct setup_indirect *)ptr->data)->addr; 493 avoid.size = ((struct setup_indirect *)ptr->data)->len; 494 495 if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) { 496 *overlap = avoid; 497 earliest = overlap->start; 498 is_overlapping = true; 499 } 500 } 501 502 ptr = (struct setup_data *)(unsigned long)ptr->next; 503 } 504 505 return is_overlapping; 506 } 507 508 struct slot_area { 509 unsigned long addr; 510 int num; 511 }; 512 513 #define MAX_SLOT_AREA 100 514 515 static struct slot_area slot_areas[MAX_SLOT_AREA]; 516 517 static unsigned long slot_max; 518 519 static unsigned long slot_area_index; 520 521 static void store_slot_info(struct mem_vector *region, unsigned long image_size) 522 { 523 struct slot_area slot_area; 524 525 if (slot_area_index == MAX_SLOT_AREA) 526 return; 527 528 slot_area.addr = region->start; 529 slot_area.num = (region->size - image_size) / 530 CONFIG_PHYSICAL_ALIGN + 1; 531 532 if (slot_area.num > 0) { 533 slot_areas[slot_area_index++] = slot_area; 534 slot_max += slot_area.num; 535 } 536 } 537 538 /* 539 * Skip as many 1GB huge pages as possible in the passed region 540 * according to the number which users specified: 541 */ 542 static void 543 process_gb_huge_pages(struct mem_vector *region, unsigned long image_size) 544 { 545 unsigned long addr, size = 0; 546 struct mem_vector tmp; 547 int i = 0; 548 549 if (!max_gb_huge_pages) { 550 store_slot_info(region, image_size); 551 return; 552 } 553 554 addr = ALIGN(region->start, PUD_SIZE); 555 /* Did we raise the address above the passed in memory entry? */ 556 if (addr < region->start + region->size) 557 size = region->size - (addr - region->start); 558 559 /* Check how many 1GB huge pages can be filtered out: */ 560 while (size > PUD_SIZE && max_gb_huge_pages) { 561 size -= PUD_SIZE; 562 max_gb_huge_pages--; 563 i++; 564 } 565 566 /* No good 1GB huge pages found: */ 567 if (!i) { 568 store_slot_info(region, image_size); 569 return; 570 } 571 572 /* 573 * Skip those 'i'*1GB good huge pages, and continue checking and 574 * processing the remaining head or tail part of the passed region 575 * if available. 576 */ 577 578 if (addr >= region->start + image_size) { 579 tmp.start = region->start; 580 tmp.size = addr - region->start; 581 store_slot_info(&tmp, image_size); 582 } 583 584 size = region->size - (addr - region->start) - i * PUD_SIZE; 585 if (size >= image_size) { 586 tmp.start = addr + i * PUD_SIZE; 587 tmp.size = size; 588 store_slot_info(&tmp, image_size); 589 } 590 } 591 592 static unsigned long slots_fetch_random(void) 593 { 594 unsigned long slot; 595 int i; 596 597 /* Handle case of no slots stored. */ 598 if (slot_max == 0) 599 return 0; 600 601 slot = kaslr_get_random_long("Physical") % slot_max; 602 603 for (i = 0; i < slot_area_index; i++) { 604 if (slot >= slot_areas[i].num) { 605 slot -= slot_areas[i].num; 606 continue; 607 } 608 return slot_areas[i].addr + slot * CONFIG_PHYSICAL_ALIGN; 609 } 610 611 if (i == slot_area_index) 612 debug_putstr("slots_fetch_random() failed!?\n"); 613 return 0; 614 } 615 616 static void __process_mem_region(struct mem_vector *entry, 617 unsigned long minimum, 618 unsigned long image_size) 619 { 620 struct mem_vector region, overlap; 621 unsigned long start_orig, end; 622 struct mem_vector cur_entry; 623 624 /* On 32-bit, ignore entries entirely above our maximum. */ 625 if (IS_ENABLED(CONFIG_X86_32) && entry->start >= KERNEL_IMAGE_SIZE) 626 return; 627 628 /* Ignore entries entirely below our minimum. */ 629 if (entry->start + entry->size < minimum) 630 return; 631 632 /* Ignore entries above memory limit */ 633 end = min(entry->size + entry->start, mem_limit); 634 if (entry->start >= end) 635 return; 636 cur_entry.start = entry->start; 637 cur_entry.size = end - entry->start; 638 639 region.start = cur_entry.start; 640 region.size = cur_entry.size; 641 642 /* Give up if slot area array is full. */ 643 while (slot_area_index < MAX_SLOT_AREA) { 644 start_orig = region.start; 645 646 /* Potentially raise address to minimum location. */ 647 if (region.start < minimum) 648 region.start = minimum; 649 650 /* Potentially raise address to meet alignment needs. */ 651 region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); 652 653 /* Did we raise the address above the passed in memory entry? */ 654 if (region.start > cur_entry.start + cur_entry.size) 655 return; 656 657 /* Reduce size by any delta from the original address. */ 658 region.size -= region.start - start_orig; 659 660 /* On 32-bit, reduce region size to fit within max size. */ 661 if (IS_ENABLED(CONFIG_X86_32) && 662 region.start + region.size > KERNEL_IMAGE_SIZE) 663 region.size = KERNEL_IMAGE_SIZE - region.start; 664 665 /* Return if region can't contain decompressed kernel */ 666 if (region.size < image_size) 667 return; 668 669 /* If nothing overlaps, store the region and return. */ 670 if (!mem_avoid_overlap(®ion, &overlap)) { 671 process_gb_huge_pages(®ion, image_size); 672 return; 673 } 674 675 /* Store beginning of region if holds at least image_size. */ 676 if (overlap.start > region.start + image_size) { 677 struct mem_vector beginning; 678 679 beginning.start = region.start; 680 beginning.size = overlap.start - region.start; 681 process_gb_huge_pages(&beginning, image_size); 682 } 683 684 /* Return if overlap extends to or past end of region. */ 685 if (overlap.start + overlap.size >= region.start + region.size) 686 return; 687 688 /* Clip off the overlapping region and start over. */ 689 region.size -= overlap.start - region.start + overlap.size; 690 region.start = overlap.start + overlap.size; 691 } 692 } 693 694 static bool process_mem_region(struct mem_vector *region, 695 unsigned long long minimum, 696 unsigned long long image_size) 697 { 698 int i; 699 /* 700 * If no immovable memory found, or MEMORY_HOTREMOVE disabled, 701 * use @region directly. 702 */ 703 if (!num_immovable_mem) { 704 __process_mem_region(region, minimum, image_size); 705 706 if (slot_area_index == MAX_SLOT_AREA) { 707 debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n"); 708 return 1; 709 } 710 return 0; 711 } 712 713 #if defined(CONFIG_MEMORY_HOTREMOVE) && defined(CONFIG_ACPI) 714 /* 715 * If immovable memory found, filter the intersection between 716 * immovable memory and @region. 717 */ 718 for (i = 0; i < num_immovable_mem; i++) { 719 unsigned long long start, end, entry_end, region_end; 720 struct mem_vector entry; 721 722 if (!mem_overlaps(region, &immovable_mem[i])) 723 continue; 724 725 start = immovable_mem[i].start; 726 end = start + immovable_mem[i].size; 727 region_end = region->start + region->size; 728 729 entry.start = clamp(region->start, start, end); 730 entry_end = clamp(region_end, start, end); 731 entry.size = entry_end - entry.start; 732 733 __process_mem_region(&entry, minimum, image_size); 734 735 if (slot_area_index == MAX_SLOT_AREA) { 736 debug_putstr("Aborted e820/efi memmap scan when walking immovable regions(slot_areas full)!\n"); 737 return 1; 738 } 739 } 740 #endif 741 return 0; 742 } 743 744 #ifdef CONFIG_EFI 745 /* 746 * Returns true if mirror region found (and must have been processed 747 * for slots adding) 748 */ 749 static bool 750 process_efi_entries(unsigned long minimum, unsigned long image_size) 751 { 752 struct efi_info *e = &boot_params->efi_info; 753 bool efi_mirror_found = false; 754 struct mem_vector region; 755 efi_memory_desc_t *md; 756 unsigned long pmap; 757 char *signature; 758 u32 nr_desc; 759 int i; 760 761 signature = (char *)&e->efi_loader_signature; 762 if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) && 763 strncmp(signature, EFI64_LOADER_SIGNATURE, 4)) 764 return false; 765 766 #ifdef CONFIG_X86_32 767 /* Can't handle data above 4GB at this time */ 768 if (e->efi_memmap_hi) { 769 warn("EFI memmap is above 4GB, can't be handled now on x86_32. EFI should be disabled.\n"); 770 return false; 771 } 772 pmap = e->efi_memmap; 773 #else 774 pmap = (e->efi_memmap | ((__u64)e->efi_memmap_hi << 32)); 775 #endif 776 777 nr_desc = e->efi_memmap_size / e->efi_memdesc_size; 778 for (i = 0; i < nr_desc; i++) { 779 md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i); 780 if (md->attribute & EFI_MEMORY_MORE_RELIABLE) { 781 efi_mirror_found = true; 782 break; 783 } 784 } 785 786 for (i = 0; i < nr_desc; i++) { 787 md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i); 788 789 /* 790 * Here we are more conservative in picking free memory than 791 * the EFI spec allows: 792 * 793 * According to the spec, EFI_BOOT_SERVICES_{CODE|DATA} are also 794 * free memory and thus available to place the kernel image into, 795 * but in practice there's firmware where using that memory leads 796 * to crashes. 797 * 798 * Only EFI_CONVENTIONAL_MEMORY is guaranteed to be free. 799 */ 800 if (md->type != EFI_CONVENTIONAL_MEMORY) 801 continue; 802 803 if (efi_soft_reserve_enabled() && 804 (md->attribute & EFI_MEMORY_SP)) 805 continue; 806 807 if (efi_mirror_found && 808 !(md->attribute & EFI_MEMORY_MORE_RELIABLE)) 809 continue; 810 811 region.start = md->phys_addr; 812 region.size = md->num_pages << EFI_PAGE_SHIFT; 813 if (process_mem_region(®ion, minimum, image_size)) 814 break; 815 } 816 return true; 817 } 818 #else 819 static inline bool 820 process_efi_entries(unsigned long minimum, unsigned long image_size) 821 { 822 return false; 823 } 824 #endif 825 826 static void process_e820_entries(unsigned long minimum, 827 unsigned long image_size) 828 { 829 int i; 830 struct mem_vector region; 831 struct boot_e820_entry *entry; 832 833 /* Verify potential e820 positions, appending to slots list. */ 834 for (i = 0; i < boot_params->e820_entries; i++) { 835 entry = &boot_params->e820_table[i]; 836 /* Skip non-RAM entries. */ 837 if (entry->type != E820_TYPE_RAM) 838 continue; 839 region.start = entry->addr; 840 region.size = entry->size; 841 if (process_mem_region(®ion, minimum, image_size)) 842 break; 843 } 844 } 845 846 static unsigned long find_random_phys_addr(unsigned long minimum, 847 unsigned long image_size) 848 { 849 /* Check if we had too many memmaps. */ 850 if (memmap_too_large) { 851 debug_putstr("Aborted memory entries scan (more than 4 memmap= args)!\n"); 852 return 0; 853 } 854 855 /* Make sure minimum is aligned. */ 856 minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); 857 858 if (process_efi_entries(minimum, image_size)) 859 return slots_fetch_random(); 860 861 process_e820_entries(minimum, image_size); 862 return slots_fetch_random(); 863 } 864 865 static unsigned long find_random_virt_addr(unsigned long minimum, 866 unsigned long image_size) 867 { 868 unsigned long slots, random_addr; 869 870 /* Make sure minimum is aligned. */ 871 minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN); 872 /* Align image_size for easy slot calculations. */ 873 image_size = ALIGN(image_size, CONFIG_PHYSICAL_ALIGN); 874 875 /* 876 * There are how many CONFIG_PHYSICAL_ALIGN-sized slots 877 * that can hold image_size within the range of minimum to 878 * KERNEL_IMAGE_SIZE? 879 */ 880 slots = (KERNEL_IMAGE_SIZE - minimum - image_size) / 881 CONFIG_PHYSICAL_ALIGN + 1; 882 883 random_addr = kaslr_get_random_long("Virtual") % slots; 884 885 return random_addr * CONFIG_PHYSICAL_ALIGN + minimum; 886 } 887 888 /* 889 * Since this function examines addresses much more numerically, 890 * it takes the input and output pointers as 'unsigned long'. 891 */ 892 void choose_random_location(unsigned long input, 893 unsigned long input_size, 894 unsigned long *output, 895 unsigned long output_size, 896 unsigned long *virt_addr) 897 { 898 unsigned long random_addr, min_addr; 899 900 if (cmdline_find_option_bool("nokaslr")) { 901 warn("KASLR disabled: 'nokaslr' on cmdline."); 902 return; 903 } 904 905 #ifdef CONFIG_X86_5LEVEL 906 if (__read_cr4() & X86_CR4_LA57) { 907 __pgtable_l5_enabled = 1; 908 pgdir_shift = 48; 909 ptrs_per_p4d = 512; 910 } 911 #endif 912 913 boot_params->hdr.loadflags |= KASLR_FLAG; 914 915 /* Prepare to add new identity pagetables on demand. */ 916 initialize_identity_maps(); 917 918 /* Record the various known unsafe memory ranges. */ 919 mem_avoid_init(input, input_size, *output); 920 921 /* 922 * Low end of the randomization range should be the 923 * smaller of 512M or the initial kernel image 924 * location: 925 */ 926 min_addr = min(*output, 512UL << 20); 927 928 /* Walk available memory entries to find a random address. */ 929 random_addr = find_random_phys_addr(min_addr, output_size); 930 if (!random_addr) { 931 warn("Physical KASLR disabled: no suitable memory region!"); 932 } else { 933 /* Update the new physical address location. */ 934 if (*output != random_addr) { 935 add_identity_map(random_addr, output_size); 936 *output = random_addr; 937 } 938 939 /* 940 * This loads the identity mapping page table. 941 * This should only be done if a new physical address 942 * is found for the kernel, otherwise we should keep 943 * the old page table to make it be like the "nokaslr" 944 * case. 945 */ 946 finalize_identity_maps(); 947 } 948 949 950 /* Pick random virtual address starting from LOAD_PHYSICAL_ADDR. */ 951 if (IS_ENABLED(CONFIG_X86_64)) 952 random_addr = find_random_virt_addr(LOAD_PHYSICAL_ADDR, output_size); 953 *virt_addr = random_addr; 954 } 955