1 // SPDX-License-Identifier: GPL-2.0-only 2 #define pr_fmt(fmt) "efi: " fmt 3 4 #include <linux/init.h> 5 #include <linux/kernel.h> 6 #include <linux/string.h> 7 #include <linux/time.h> 8 #include <linux/types.h> 9 #include <linux/efi.h> 10 #include <linux/slab.h> 11 #include <linux/memblock.h> 12 #include <linux/acpi.h> 13 #include <linux/dmi.h> 14 15 #include <asm/e820/api.h> 16 #include <asm/efi.h> 17 #include <asm/uv/uv.h> 18 #include <asm/cpu_device_id.h> 19 #include <asm/reboot.h> 20 21 #define EFI_MIN_RESERVE 5120 22 23 #define EFI_DUMMY_GUID \ 24 EFI_GUID(0x4424ac57, 0xbe4b, 0x47dd, 0x9e, 0x97, 0xed, 0x50, 0xf0, 0x9f, 0x92, 0xa9) 25 26 #define QUARK_CSH_SIGNATURE 0x5f435348 /* _CSH */ 27 #define QUARK_SECURITY_HEADER_SIZE 0x400 28 29 /* 30 * Header prepended to the standard EFI capsule on Quark systems the are based 31 * on Intel firmware BSP. 32 * @csh_signature: Unique identifier to sanity check signed module 33 * presence ("_CSH"). 34 * @version: Current version of CSH used. Should be one for Quark A0. 35 * @modulesize: Size of the entire module including the module header 36 * and payload. 37 * @security_version_number_index: Index of SVN to use for validation of signed 38 * module. 39 * @security_version_number: Used to prevent against roll back of modules. 40 * @rsvd_module_id: Currently unused for Clanton (Quark). 41 * @rsvd_module_vendor: Vendor Identifier. For Intel products value is 42 * 0x00008086. 43 * @rsvd_date: BCD representation of build date as yyyymmdd, where 44 * yyyy=4 digit year, mm=1-12, dd=1-31. 45 * @headersize: Total length of the header including including any 46 * padding optionally added by the signing tool. 47 * @hash_algo: What Hash is used in the module signing. 48 * @cryp_algo: What Crypto is used in the module signing. 49 * @keysize: Total length of the key data including including any 50 * padding optionally added by the signing tool. 51 * @signaturesize: Total length of the signature including including any 52 * padding optionally added by the signing tool. 53 * @rsvd_next_header: 32-bit pointer to the next Secure Boot Module in the 54 * chain, if there is a next header. 55 * @rsvd: Reserved, padding structure to required size. 56 * 57 * See also QuartSecurityHeader_t in 58 * Quark_EDKII_v1.2.1.1/QuarkPlatformPkg/Include/QuarkBootRom.h 59 * from https://downloadcenter.intel.com/download/23197/Intel-Quark-SoC-X1000-Board-Support-Package-BSP 60 */ 61 struct quark_security_header { 62 u32 csh_signature; 63 u32 version; 64 u32 modulesize; 65 u32 security_version_number_index; 66 u32 security_version_number; 67 u32 rsvd_module_id; 68 u32 rsvd_module_vendor; 69 u32 rsvd_date; 70 u32 headersize; 71 u32 hash_algo; 72 u32 cryp_algo; 73 u32 keysize; 74 u32 signaturesize; 75 u32 rsvd_next_header; 76 u32 rsvd[2]; 77 }; 78 79 static const efi_char16_t efi_dummy_name[] = L"DUMMY"; 80 81 static bool efi_no_storage_paranoia; 82 83 /* 84 * Some firmware implementations refuse to boot if there's insufficient 85 * space in the variable store. The implementation of garbage collection 86 * in some FW versions causes stale (deleted) variables to take up space 87 * longer than intended and space is only freed once the store becomes 88 * almost completely full. 89 * 90 * Enabling this option disables the space checks in 91 * efi_query_variable_store() and forces garbage collection. 92 * 93 * Only enable this option if deleting EFI variables does not free up 94 * space in your variable store, e.g. if despite deleting variables 95 * you're unable to create new ones. 96 */ 97 static int __init setup_storage_paranoia(char *arg) 98 { 99 efi_no_storage_paranoia = true; 100 return 0; 101 } 102 early_param("efi_no_storage_paranoia", setup_storage_paranoia); 103 104 /* 105 * Deleting the dummy variable which kicks off garbage collection 106 */ 107 void efi_delete_dummy_variable(void) 108 { 109 efi.set_variable_nonblocking((efi_char16_t *)efi_dummy_name, 110 &EFI_DUMMY_GUID, 111 EFI_VARIABLE_NON_VOLATILE | 112 EFI_VARIABLE_BOOTSERVICE_ACCESS | 113 EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL); 114 } 115 116 /* 117 * In the nonblocking case we do not attempt to perform garbage 118 * collection if we do not have enough free space. Rather, we do the 119 * bare minimum check and give up immediately if the available space 120 * is below EFI_MIN_RESERVE. 121 * 122 * This function is intended to be small and simple because it is 123 * invoked from crash handler paths. 124 */ 125 static efi_status_t 126 query_variable_store_nonblocking(u32 attributes, unsigned long size) 127 { 128 efi_status_t status; 129 u64 storage_size, remaining_size, max_size; 130 131 status = efi.query_variable_info_nonblocking(attributes, &storage_size, 132 &remaining_size, 133 &max_size); 134 if (status != EFI_SUCCESS) 135 return status; 136 137 if (remaining_size - size < EFI_MIN_RESERVE) 138 return EFI_OUT_OF_RESOURCES; 139 140 return EFI_SUCCESS; 141 } 142 143 /* 144 * Some firmware implementations refuse to boot if there's insufficient space 145 * in the variable store. Ensure that we never use more than a safe limit. 146 * 147 * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable 148 * store. 149 */ 150 efi_status_t efi_query_variable_store(u32 attributes, unsigned long size, 151 bool nonblocking) 152 { 153 efi_status_t status; 154 u64 storage_size, remaining_size, max_size; 155 156 if (!(attributes & EFI_VARIABLE_NON_VOLATILE)) 157 return 0; 158 159 if (nonblocking) 160 return query_variable_store_nonblocking(attributes, size); 161 162 status = efi.query_variable_info(attributes, &storage_size, 163 &remaining_size, &max_size); 164 if (status != EFI_SUCCESS) 165 return status; 166 167 /* 168 * We account for that by refusing the write if permitting it would 169 * reduce the available space to under 5KB. This figure was provided by 170 * Samsung, so should be safe. 171 */ 172 if ((remaining_size - size < EFI_MIN_RESERVE) && 173 !efi_no_storage_paranoia) { 174 175 /* 176 * Triggering garbage collection may require that the firmware 177 * generate a real EFI_OUT_OF_RESOURCES error. We can force 178 * that by attempting to use more space than is available. 179 */ 180 unsigned long dummy_size = remaining_size + 1024; 181 void *dummy = kzalloc(dummy_size, GFP_KERNEL); 182 183 if (!dummy) 184 return EFI_OUT_OF_RESOURCES; 185 186 status = efi.set_variable((efi_char16_t *)efi_dummy_name, 187 &EFI_DUMMY_GUID, 188 EFI_VARIABLE_NON_VOLATILE | 189 EFI_VARIABLE_BOOTSERVICE_ACCESS | 190 EFI_VARIABLE_RUNTIME_ACCESS, 191 dummy_size, dummy); 192 193 if (status == EFI_SUCCESS) { 194 /* 195 * This should have failed, so if it didn't make sure 196 * that we delete it... 197 */ 198 efi_delete_dummy_variable(); 199 } 200 201 kfree(dummy); 202 203 /* 204 * The runtime code may now have triggered a garbage collection 205 * run, so check the variable info again 206 */ 207 status = efi.query_variable_info(attributes, &storage_size, 208 &remaining_size, &max_size); 209 210 if (status != EFI_SUCCESS) 211 return status; 212 213 /* 214 * There still isn't enough room, so return an error 215 */ 216 if (remaining_size - size < EFI_MIN_RESERVE) 217 return EFI_OUT_OF_RESOURCES; 218 } 219 220 return EFI_SUCCESS; 221 } 222 EXPORT_SYMBOL_GPL(efi_query_variable_store); 223 224 /* 225 * The UEFI specification makes it clear that the operating system is 226 * free to do whatever it wants with boot services code after 227 * ExitBootServices() has been called. Ignoring this recommendation a 228 * significant bunch of EFI implementations continue calling into boot 229 * services code (SetVirtualAddressMap). In order to work around such 230 * buggy implementations we reserve boot services region during EFI 231 * init and make sure it stays executable. Then, after 232 * SetVirtualAddressMap(), it is discarded. 233 * 234 * However, some boot services regions contain data that is required 235 * by drivers, so we need to track which memory ranges can never be 236 * freed. This is done by tagging those regions with the 237 * EFI_MEMORY_RUNTIME attribute. 238 * 239 * Any driver that wants to mark a region as reserved must use 240 * efi_mem_reserve() which will insert a new EFI memory descriptor 241 * into efi.memmap (splitting existing regions if necessary) and tag 242 * it with EFI_MEMORY_RUNTIME. 243 */ 244 void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size) 245 { 246 phys_addr_t new_phys, new_size; 247 struct efi_mem_range mr; 248 efi_memory_desc_t md; 249 int num_entries; 250 void *new; 251 252 if (efi_mem_desc_lookup(addr, &md) || 253 md.type != EFI_BOOT_SERVICES_DATA) { 254 pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr); 255 return; 256 } 257 258 if (addr + size > md.phys_addr + (md.num_pages << EFI_PAGE_SHIFT)) { 259 pr_err("Region spans EFI memory descriptors, %pa\n", &addr); 260 return; 261 } 262 263 /* No need to reserve regions that will never be freed. */ 264 if (md.attribute & EFI_MEMORY_RUNTIME) 265 return; 266 267 size += addr % EFI_PAGE_SIZE; 268 size = round_up(size, EFI_PAGE_SIZE); 269 addr = round_down(addr, EFI_PAGE_SIZE); 270 271 mr.range.start = addr; 272 mr.range.end = addr + size - 1; 273 mr.attribute = md.attribute | EFI_MEMORY_RUNTIME; 274 275 num_entries = efi_memmap_split_count(&md, &mr.range); 276 num_entries += efi.memmap.nr_map; 277 278 new_size = efi.memmap.desc_size * num_entries; 279 280 new_phys = efi_memmap_alloc(num_entries); 281 if (!new_phys) { 282 pr_err("Could not allocate boot services memmap\n"); 283 return; 284 } 285 286 new = early_memremap(new_phys, new_size); 287 if (!new) { 288 pr_err("Failed to map new boot services memmap\n"); 289 return; 290 } 291 292 efi_memmap_insert(&efi.memmap, new, &mr); 293 early_memunmap(new, new_size); 294 295 efi_memmap_install(new_phys, num_entries); 296 } 297 298 /* 299 * Helper function for efi_reserve_boot_services() to figure out if we 300 * can free regions in efi_free_boot_services(). 301 * 302 * Use this function to ensure we do not free regions owned by somebody 303 * else. We must only reserve (and then free) regions: 304 * 305 * - Not within any part of the kernel 306 * - Not the BIOS reserved area (E820_TYPE_RESERVED, E820_TYPE_NVS, etc) 307 */ 308 static __init bool can_free_region(u64 start, u64 size) 309 { 310 if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end)) 311 return false; 312 313 if (!e820__mapped_all(start, start+size, E820_TYPE_RAM)) 314 return false; 315 316 return true; 317 } 318 319 void __init efi_reserve_boot_services(void) 320 { 321 efi_memory_desc_t *md; 322 323 if (!efi_enabled(EFI_MEMMAP)) 324 return; 325 326 for_each_efi_memory_desc(md) { 327 u64 start = md->phys_addr; 328 u64 size = md->num_pages << EFI_PAGE_SHIFT; 329 bool already_reserved; 330 331 if (md->type != EFI_BOOT_SERVICES_CODE && 332 md->type != EFI_BOOT_SERVICES_DATA) 333 continue; 334 335 already_reserved = memblock_is_region_reserved(start, size); 336 337 /* 338 * Because the following memblock_reserve() is paired 339 * with memblock_free_late() for this region in 340 * efi_free_boot_services(), we must be extremely 341 * careful not to reserve, and subsequently free, 342 * critical regions of memory (like the kernel image) or 343 * those regions that somebody else has already 344 * reserved. 345 * 346 * A good example of a critical region that must not be 347 * freed is page zero (first 4Kb of memory), which may 348 * contain boot services code/data but is marked 349 * E820_TYPE_RESERVED by trim_bios_range(). 350 */ 351 if (!already_reserved) { 352 memblock_reserve(start, size); 353 354 /* 355 * If we are the first to reserve the region, no 356 * one else cares about it. We own it and can 357 * free it later. 358 */ 359 if (can_free_region(start, size)) 360 continue; 361 } 362 363 /* 364 * We don't own the region. We must not free it. 365 * 366 * Setting this bit for a boot services region really 367 * doesn't make sense as far as the firmware is 368 * concerned, but it does provide us with a way to tag 369 * those regions that must not be paired with 370 * memblock_free_late(). 371 */ 372 md->attribute |= EFI_MEMORY_RUNTIME; 373 } 374 } 375 376 /* 377 * Apart from having VA mappings for EFI boot services code/data regions, 378 * (duplicate) 1:1 mappings were also created as a quirk for buggy firmware. So, 379 * unmap both 1:1 and VA mappings. 380 */ 381 static void __init efi_unmap_pages(efi_memory_desc_t *md) 382 { 383 pgd_t *pgd = efi_mm.pgd; 384 u64 pa = md->phys_addr; 385 u64 va = md->virt_addr; 386 387 /* 388 * To Do: Remove this check after adding functionality to unmap EFI boot 389 * services code/data regions from direct mapping area because 390 * "efi=old_map" maps EFI regions in swapper_pg_dir. 391 */ 392 if (efi_enabled(EFI_OLD_MEMMAP)) 393 return; 394 395 /* 396 * EFI mixed mode has all RAM mapped to access arguments while making 397 * EFI runtime calls, hence don't unmap EFI boot services code/data 398 * regions. 399 */ 400 if (!efi_is_native()) 401 return; 402 403 if (kernel_unmap_pages_in_pgd(pgd, pa, md->num_pages)) 404 pr_err("Failed to unmap 1:1 mapping for 0x%llx\n", pa); 405 406 if (kernel_unmap_pages_in_pgd(pgd, va, md->num_pages)) 407 pr_err("Failed to unmap VA mapping for 0x%llx\n", va); 408 } 409 410 void __init efi_free_boot_services(void) 411 { 412 phys_addr_t new_phys, new_size; 413 efi_memory_desc_t *md; 414 int num_entries = 0; 415 void *new, *new_md; 416 417 for_each_efi_memory_desc(md) { 418 unsigned long long start = md->phys_addr; 419 unsigned long long size = md->num_pages << EFI_PAGE_SHIFT; 420 size_t rm_size; 421 422 if (md->type != EFI_BOOT_SERVICES_CODE && 423 md->type != EFI_BOOT_SERVICES_DATA) { 424 num_entries++; 425 continue; 426 } 427 428 /* Do not free, someone else owns it: */ 429 if (md->attribute & EFI_MEMORY_RUNTIME) { 430 num_entries++; 431 continue; 432 } 433 434 /* 435 * Before calling set_virtual_address_map(), EFI boot services 436 * code/data regions were mapped as a quirk for buggy firmware. 437 * Unmap them from efi_pgd before freeing them up. 438 */ 439 efi_unmap_pages(md); 440 441 /* 442 * Nasty quirk: if all sub-1MB memory is used for boot 443 * services, we can get here without having allocated the 444 * real mode trampoline. It's too late to hand boot services 445 * memory back to the memblock allocator, so instead 446 * try to manually allocate the trampoline if needed. 447 * 448 * I've seen this on a Dell XPS 13 9350 with firmware 449 * 1.4.4 with SGX enabled booting Linux via Fedora 24's 450 * grub2-efi on a hard disk. (And no, I don't know why 451 * this happened, but Linux should still try to boot rather 452 * panicing early.) 453 */ 454 rm_size = real_mode_size_needed(); 455 if (rm_size && (start + rm_size) < (1<<20) && size >= rm_size) { 456 set_real_mode_mem(start); 457 start += rm_size; 458 size -= rm_size; 459 } 460 461 memblock_free_late(start, size); 462 } 463 464 if (!num_entries) 465 return; 466 467 new_size = efi.memmap.desc_size * num_entries; 468 new_phys = efi_memmap_alloc(num_entries); 469 if (!new_phys) { 470 pr_err("Failed to allocate new EFI memmap\n"); 471 return; 472 } 473 474 new = memremap(new_phys, new_size, MEMREMAP_WB); 475 if (!new) { 476 pr_err("Failed to map new EFI memmap\n"); 477 return; 478 } 479 480 /* 481 * Build a new EFI memmap that excludes any boot services 482 * regions that are not tagged EFI_MEMORY_RUNTIME, since those 483 * regions have now been freed. 484 */ 485 new_md = new; 486 for_each_efi_memory_desc(md) { 487 if (!(md->attribute & EFI_MEMORY_RUNTIME) && 488 (md->type == EFI_BOOT_SERVICES_CODE || 489 md->type == EFI_BOOT_SERVICES_DATA)) 490 continue; 491 492 memcpy(new_md, md, efi.memmap.desc_size); 493 new_md += efi.memmap.desc_size; 494 } 495 496 memunmap(new); 497 498 if (efi_memmap_install(new_phys, num_entries)) { 499 pr_err("Could not install new EFI memmap\n"); 500 return; 501 } 502 } 503 504 /* 505 * A number of config table entries get remapped to virtual addresses 506 * after entering EFI virtual mode. However, the kexec kernel requires 507 * their physical addresses therefore we pass them via setup_data and 508 * correct those entries to their respective physical addresses here. 509 * 510 * Currently only handles smbios which is necessary for some firmware 511 * implementation. 512 */ 513 int __init efi_reuse_config(u64 tables, int nr_tables) 514 { 515 int i, sz, ret = 0; 516 void *p, *tablep; 517 struct efi_setup_data *data; 518 519 if (nr_tables == 0) 520 return 0; 521 522 if (!efi_setup) 523 return 0; 524 525 if (!efi_enabled(EFI_64BIT)) 526 return 0; 527 528 data = early_memremap(efi_setup, sizeof(*data)); 529 if (!data) { 530 ret = -ENOMEM; 531 goto out; 532 } 533 534 if (!data->smbios) 535 goto out_memremap; 536 537 sz = sizeof(efi_config_table_64_t); 538 539 p = tablep = early_memremap(tables, nr_tables * sz); 540 if (!p) { 541 pr_err("Could not map Configuration table!\n"); 542 ret = -ENOMEM; 543 goto out_memremap; 544 } 545 546 for (i = 0; i < efi.systab->nr_tables; i++) { 547 efi_guid_t guid; 548 549 guid = ((efi_config_table_64_t *)p)->guid; 550 551 if (!efi_guidcmp(guid, SMBIOS_TABLE_GUID)) 552 ((efi_config_table_64_t *)p)->table = data->smbios; 553 p += sz; 554 } 555 early_memunmap(tablep, nr_tables * sz); 556 557 out_memremap: 558 early_memunmap(data, sizeof(*data)); 559 out: 560 return ret; 561 } 562 563 static const struct dmi_system_id sgi_uv1_dmi[] = { 564 { NULL, "SGI UV1", 565 { DMI_MATCH(DMI_PRODUCT_NAME, "Stoutland Platform"), 566 DMI_MATCH(DMI_PRODUCT_VERSION, "1.0"), 567 DMI_MATCH(DMI_BIOS_VENDOR, "SGI.COM"), 568 } 569 }, 570 { } /* NULL entry stops DMI scanning */ 571 }; 572 573 void __init efi_apply_memmap_quirks(void) 574 { 575 /* 576 * Once setup is done earlier, unmap the EFI memory map on mismatched 577 * firmware/kernel architectures since there is no support for runtime 578 * services. 579 */ 580 if (!efi_runtime_supported()) { 581 pr_info("Setup done, disabling due to 32/64-bit mismatch\n"); 582 efi_memmap_unmap(); 583 } 584 585 /* UV2+ BIOS has a fix for this issue. UV1 still needs the quirk. */ 586 if (dmi_check_system(sgi_uv1_dmi)) 587 set_bit(EFI_OLD_MEMMAP, &efi.flags); 588 } 589 590 /* 591 * For most modern platforms the preferred method of powering off is via 592 * ACPI. However, there are some that are known to require the use of 593 * EFI runtime services and for which ACPI does not work at all. 594 * 595 * Using EFI is a last resort, to be used only if no other option 596 * exists. 597 */ 598 bool efi_reboot_required(void) 599 { 600 if (!acpi_gbl_reduced_hardware) 601 return false; 602 603 efi_reboot_quirk_mode = EFI_RESET_WARM; 604 return true; 605 } 606 607 bool efi_poweroff_required(void) 608 { 609 return acpi_gbl_reduced_hardware || acpi_no_s5; 610 } 611 612 #ifdef CONFIG_EFI_CAPSULE_QUIRK_QUARK_CSH 613 614 static int qrk_capsule_setup_info(struct capsule_info *cap_info, void **pkbuff, 615 size_t hdr_bytes) 616 { 617 struct quark_security_header *csh = *pkbuff; 618 619 /* Only process data block that is larger than the security header */ 620 if (hdr_bytes < sizeof(struct quark_security_header)) 621 return 0; 622 623 if (csh->csh_signature != QUARK_CSH_SIGNATURE || 624 csh->headersize != QUARK_SECURITY_HEADER_SIZE) 625 return 1; 626 627 /* Only process data block if EFI header is included */ 628 if (hdr_bytes < QUARK_SECURITY_HEADER_SIZE + 629 sizeof(efi_capsule_header_t)) 630 return 0; 631 632 pr_debug("Quark security header detected\n"); 633 634 if (csh->rsvd_next_header != 0) { 635 pr_err("multiple Quark security headers not supported\n"); 636 return -EINVAL; 637 } 638 639 *pkbuff += csh->headersize; 640 cap_info->total_size = csh->headersize; 641 642 /* 643 * Update the first page pointer to skip over the CSH header. 644 */ 645 cap_info->phys[0] += csh->headersize; 646 647 /* 648 * cap_info->capsule should point at a virtual mapping of the entire 649 * capsule, starting at the capsule header. Our image has the Quark 650 * security header prepended, so we cannot rely on the default vmap() 651 * mapping created by the generic capsule code. 652 * Given that the Quark firmware does not appear to care about the 653 * virtual mapping, let's just point cap_info->capsule at our copy 654 * of the capsule header. 655 */ 656 cap_info->capsule = &cap_info->header; 657 658 return 1; 659 } 660 661 #define ICPU(family, model, quirk_handler) \ 662 { X86_VENDOR_INTEL, family, model, X86_FEATURE_ANY, \ 663 (unsigned long)&quirk_handler } 664 665 static const struct x86_cpu_id efi_capsule_quirk_ids[] = { 666 ICPU(5, 9, qrk_capsule_setup_info), /* Intel Quark X1000 */ 667 { } 668 }; 669 670 int efi_capsule_setup_info(struct capsule_info *cap_info, void *kbuff, 671 size_t hdr_bytes) 672 { 673 int (*quirk_handler)(struct capsule_info *, void **, size_t); 674 const struct x86_cpu_id *id; 675 int ret; 676 677 if (hdr_bytes < sizeof(efi_capsule_header_t)) 678 return 0; 679 680 cap_info->total_size = 0; 681 682 id = x86_match_cpu(efi_capsule_quirk_ids); 683 if (id) { 684 /* 685 * The quirk handler is supposed to return 686 * - a value > 0 if the setup should continue, after advancing 687 * kbuff as needed 688 * - 0 if not enough hdr_bytes are available yet 689 * - a negative error code otherwise 690 */ 691 quirk_handler = (typeof(quirk_handler))id->driver_data; 692 ret = quirk_handler(cap_info, &kbuff, hdr_bytes); 693 if (ret <= 0) 694 return ret; 695 } 696 697 memcpy(&cap_info->header, kbuff, sizeof(cap_info->header)); 698 699 cap_info->total_size += cap_info->header.imagesize; 700 701 return __efi_capsule_setup_info(cap_info); 702 } 703 704 #endif 705 706 /* 707 * If any access by any efi runtime service causes a page fault, then, 708 * 1. If it's efi_reset_system(), reboot through BIOS. 709 * 2. If any other efi runtime service, then 710 * a. Return error status to the efi caller process. 711 * b. Disable EFI Runtime Services forever and 712 * c. Freeze efi_rts_wq and schedule new process. 713 * 714 * @return: Returns, if the page fault is not handled. This function 715 * will never return if the page fault is handled successfully. 716 */ 717 void efi_recover_from_page_fault(unsigned long phys_addr) 718 { 719 if (!IS_ENABLED(CONFIG_X86_64)) 720 return; 721 722 /* 723 * Make sure that an efi runtime service caused the page fault. 724 * "efi_mm" cannot be used to check if the page fault had occurred 725 * in the firmware context because efi=old_map doesn't use efi_pgd. 726 */ 727 if (efi_rts_work.efi_rts_id == EFI_NONE) 728 return; 729 730 /* 731 * Address range 0x0000 - 0x0fff is always mapped in the efi_pgd, so 732 * page faulting on these addresses isn't expected. 733 */ 734 if (phys_addr <= 0x0fff) 735 return; 736 737 /* 738 * Print stack trace as it might be useful to know which EFI Runtime 739 * Service is buggy. 740 */ 741 WARN(1, FW_BUG "Page fault caused by firmware at PA: 0x%lx\n", 742 phys_addr); 743 744 /* 745 * Buggy efi_reset_system() is handled differently from other EFI 746 * Runtime Services as it doesn't use efi_rts_wq. Although, 747 * native_machine_emergency_restart() says that machine_real_restart() 748 * could fail, it's better not to compilcate this fault handler 749 * because this case occurs *very* rarely and hence could be improved 750 * on a need by basis. 751 */ 752 if (efi_rts_work.efi_rts_id == EFI_RESET_SYSTEM) { 753 pr_info("efi_reset_system() buggy! Reboot through BIOS\n"); 754 machine_real_restart(MRR_BIOS); 755 return; 756 } 757 758 /* 759 * Before calling EFI Runtime Service, the kernel has switched the 760 * calling process to efi_mm. Hence, switch back to task_mm. 761 */ 762 arch_efi_call_virt_teardown(); 763 764 /* Signal error status to the efi caller process */ 765 efi_rts_work.status = EFI_ABORTED; 766 complete(&efi_rts_work.efi_rts_comp); 767 768 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); 769 pr_info("Froze efi_rts_wq and disabled EFI Runtime Services\n"); 770 771 /* 772 * Call schedule() in an infinite loop, so that any spurious wake ups 773 * will never run efi_rts_wq again. 774 */ 775 for (;;) { 776 set_current_state(TASK_IDLE); 777 schedule(); 778 } 779 780 return; 781 } 782