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/realmode.h> 20#include <asm/reboot.h> 21 22#define EFI_MIN_RESERVE 5120 23 24#define EFI_DUMMY_GUID \ 25 EFI_GUID(0x4424ac57, 0xbe4b, 0x47dd, 0x9e, 0x97, 0xed, 0x50, 0xf0, 0x9f, 0x92, 0xa9) 26 27#define QUARK_CSH_SIGNATURE 0x5f435348 /* _CSH */ 28#define QUARK_SECURITY_HEADER_SIZE 0x400 29 30/* 31 * Header prepended to the standard EFI capsule on Quark systems the are based 32 * on Intel firmware BSP. 33 * @csh_signature: Unique identifier to sanity check signed module 34 * presence ("_CSH"). 35 * @version: Current version of CSH used. Should be one for Quark A0. 36 * @modulesize: Size of the entire module including the module header 37 * and payload. 38 * @security_version_number_index: Index of SVN to use for validation of signed 39 * module. 40 * @security_version_number: Used to prevent against roll back of modules. 41 * @rsvd_module_id: Currently unused for Clanton (Quark). 42 * @rsvd_module_vendor: Vendor Identifier. For Intel products value is 43 * 0x00008086. 44 * @rsvd_date: BCD representation of build date as yyyymmdd, where 45 * yyyy=4 digit year, mm=1-12, dd=1-31. 46 * @headersize: Total length of the header including including any 47 * padding optionally added by the signing tool. 48 * @hash_algo: What Hash is used in the module signing. 49 * @cryp_algo: What Crypto is used in the module signing. 50 * @keysize: Total length of the key data including including any 51 * padding optionally added by the signing tool. 52 * @signaturesize: Total length of the signature including including any 53 * padding optionally added by the signing tool. 54 * @rsvd_next_header: 32-bit pointer to the next Secure Boot Module in the 55 * chain, if there is a next header. 56 * @rsvd: Reserved, padding structure to required size. 57 * 58 * See also QuartSecurityHeader_t in 59 * Quark_EDKII_v1.2.1.1/QuarkPlatformPkg/Include/QuarkBootRom.h 60 * from https://downloadcenter.intel.com/download/23197/Intel-Quark-SoC-X1000-Board-Support-Package-BSP 61 */ 62struct quark_security_header { 63 u32 csh_signature; 64 u32 version; 65 u32 modulesize; 66 u32 security_version_number_index; 67 u32 security_version_number; 68 u32 rsvd_module_id; 69 u32 rsvd_module_vendor; 70 u32 rsvd_date; 71 u32 headersize; 72 u32 hash_algo; 73 u32 cryp_algo; 74 u32 keysize; 75 u32 signaturesize; 76 u32 rsvd_next_header; 77 u32 rsvd[2]; 78}; 79 80static const efi_char16_t efi_dummy_name[] = L"DUMMY"; 81 82static bool efi_no_storage_paranoia; 83 84/* 85 * Some firmware implementations refuse to boot if there's insufficient 86 * space in the variable store. The implementation of garbage collection 87 * in some FW versions causes stale (deleted) variables to take up space 88 * longer than intended and space is only freed once the store becomes 89 * almost completely full. 90 * 91 * Enabling this option disables the space checks in 92 * efi_query_variable_store() and forces garbage collection. 93 * 94 * Only enable this option if deleting EFI variables does not free up 95 * space in your variable store, e.g. if despite deleting variables 96 * you're unable to create new ones. 97 */ 98static int __init setup_storage_paranoia(char *arg) 99{ 100 efi_no_storage_paranoia = true; 101 return 0; 102} 103early_param("efi_no_storage_paranoia", setup_storage_paranoia); 104 105/* 106 * Deleting the dummy variable which kicks off garbage collection 107*/ 108void efi_delete_dummy_variable(void) 109{ 110 efi.set_variable_nonblocking((efi_char16_t *)efi_dummy_name, 111 &EFI_DUMMY_GUID, 112 EFI_VARIABLE_NON_VOLATILE | 113 EFI_VARIABLE_BOOTSERVICE_ACCESS | 114 EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL); 115} 116 117/* 118 * In the nonblocking case we do not attempt to perform garbage 119 * collection if we do not have enough free space. Rather, we do the 120 * bare minimum check and give up immediately if the available space 121 * is below EFI_MIN_RESERVE. 122 * 123 * This function is intended to be small and simple because it is 124 * invoked from crash handler paths. 125 */ 126static efi_status_t 127query_variable_store_nonblocking(u32 attributes, unsigned long size) 128{ 129 efi_status_t status; 130 u64 storage_size, remaining_size, max_size; 131 132 status = efi.query_variable_info_nonblocking(attributes, &storage_size, 133 &remaining_size, 134 &max_size); 135 if (status != EFI_SUCCESS) 136 return status; 137 138 if (remaining_size - size < EFI_MIN_RESERVE) 139 return EFI_OUT_OF_RESOURCES; 140 141 return EFI_SUCCESS; 142} 143 144/* 145 * Some firmware implementations refuse to boot if there's insufficient space 146 * in the variable store. Ensure that we never use more than a safe limit. 147 * 148 * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable 149 * store. 150 */ 151efi_status_t efi_query_variable_store(u32 attributes, unsigned long size, 152 bool nonblocking) 153{ 154 efi_status_t status; 155 u64 storage_size, remaining_size, max_size; 156 157 if (!(attributes & EFI_VARIABLE_NON_VOLATILE)) 158 return 0; 159 160 if (nonblocking) 161 return query_variable_store_nonblocking(attributes, size); 162 163 status = efi.query_variable_info(attributes, &storage_size, 164 &remaining_size, &max_size); 165 if (status != EFI_SUCCESS) 166 return status; 167 168 /* 169 * We account for that by refusing the write if permitting it would 170 * reduce the available space to under 5KB. This figure was provided by 171 * Samsung, so should be safe. 172 */ 173 if ((remaining_size - size < EFI_MIN_RESERVE) && 174 !efi_no_storage_paranoia) { 175 176 /* 177 * Triggering garbage collection may require that the firmware 178 * generate a real EFI_OUT_OF_RESOURCES error. We can force 179 * that by attempting to use more space than is available. 180 */ 181 unsigned long dummy_size = remaining_size + 1024; 182 void *dummy = kzalloc(dummy_size, GFP_KERNEL); 183 184 if (!dummy) 185 return EFI_OUT_OF_RESOURCES; 186 187 status = efi.set_variable((efi_char16_t *)efi_dummy_name, 188 &EFI_DUMMY_GUID, 189 EFI_VARIABLE_NON_VOLATILE | 190 EFI_VARIABLE_BOOTSERVICE_ACCESS | 191 EFI_VARIABLE_RUNTIME_ACCESS, 192 dummy_size, dummy); 193 194 if (status == EFI_SUCCESS) { 195 /* 196 * This should have failed, so if it didn't make sure 197 * that we delete it... 198 */ 199 efi_delete_dummy_variable(); 200 } 201 202 kfree(dummy); 203 204 /* 205 * The runtime code may now have triggered a garbage collection 206 * run, so check the variable info again 207 */ 208 status = efi.query_variable_info(attributes, &storage_size, 209 &remaining_size, &max_size); 210 211 if (status != EFI_SUCCESS) 212 return status; 213 214 /* 215 * There still isn't enough room, so return an error 216 */ 217 if (remaining_size - size < EFI_MIN_RESERVE) 218 return EFI_OUT_OF_RESOURCES; 219 } 220 221 return EFI_SUCCESS; 222} 223EXPORT_SYMBOL_GPL(efi_query_variable_store); 224 225/* 226 * The UEFI specification makes it clear that the operating system is 227 * free to do whatever it wants with boot services code after 228 * ExitBootServices() has been called. Ignoring this recommendation a 229 * significant bunch of EFI implementations continue calling into boot 230 * services code (SetVirtualAddressMap). In order to work around such 231 * buggy implementations we reserve boot services region during EFI 232 * init and make sure it stays executable. Then, after 233 * SetVirtualAddressMap(), it is discarded. 234 * 235 * However, some boot services regions contain data that is required 236 * by drivers, so we need to track which memory ranges can never be 237 * freed. This is done by tagging those regions with the 238 * EFI_MEMORY_RUNTIME attribute. 239 * 240 * Any driver that wants to mark a region as reserved must use 241 * efi_mem_reserve() which will insert a new EFI memory descriptor 242 * into efi.memmap (splitting existing regions if necessary) and tag 243 * it with EFI_MEMORY_RUNTIME. 244 */ 245void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size) 246{ 247 struct efi_memory_map_data data = { 0 }; 248 struct efi_mem_range mr; 249 efi_memory_desc_t md; 250 int num_entries; 251 void *new; 252 253 if (efi_mem_desc_lookup(addr, &md) || 254 md.type != EFI_BOOT_SERVICES_DATA) { 255 pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr); 256 return; 257 } 258 259 if (addr + size > md.phys_addr + (md.num_pages << EFI_PAGE_SHIFT)) { 260 pr_err("Region spans EFI memory descriptors, %pa\n", &addr); 261 return; 262 } 263 264 size += addr % EFI_PAGE_SIZE; 265 size = round_up(size, EFI_PAGE_SIZE); 266 addr = round_down(addr, EFI_PAGE_SIZE); 267 268 mr.range.start = addr; 269 mr.range.end = addr + size - 1; 270 mr.attribute = md.attribute | EFI_MEMORY_RUNTIME; 271 272 num_entries = efi_memmap_split_count(&md, &mr.range); 273 num_entries += efi.memmap.nr_map; 274 275 if (efi_memmap_alloc(num_entries, &data) != 0) { 276 pr_err("Could not allocate boot services memmap\n"); 277 return; 278 } 279 280 new = early_memremap_prot(data.phys_map, data.size, 281 pgprot_val(pgprot_encrypted(FIXMAP_PAGE_NORMAL))); 282 if (!new) { 283 pr_err("Failed to map new boot services memmap\n"); 284 return; 285 } 286 287 efi_memmap_insert(&efi.memmap, new, &mr); 288 early_memunmap(new, data.size); 289 290 efi_memmap_install(&data); 291 e820__range_update(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED); 292 e820__update_table(e820_table); 293} 294 295/* 296 * Helper function for efi_reserve_boot_services() to figure out if we 297 * can free regions in efi_free_boot_services(). 298 * 299 * Use this function to ensure we do not free regions owned by somebody 300 * else. We must only reserve (and then free) regions: 301 * 302 * - Not within any part of the kernel 303 * - Not the BIOS reserved area (E820_TYPE_RESERVED, E820_TYPE_NVS, etc) 304 */ 305static __init bool can_free_region(u64 start, u64 size) 306{ 307 if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end)) 308 return false; 309 310 if (!e820__mapped_all(start, start+size, E820_TYPE_RAM)) 311 return false; 312 313 return true; 314} 315 316void __init efi_reserve_boot_services(void) 317{ 318 efi_memory_desc_t *md; 319 320 if (!efi_enabled(EFI_MEMMAP)) 321 return; 322 323 for_each_efi_memory_desc(md) { 324 u64 start = md->phys_addr; 325 u64 size = md->num_pages << EFI_PAGE_SHIFT; 326 bool already_reserved; 327 328 if (md->type != EFI_BOOT_SERVICES_CODE && 329 md->type != EFI_BOOT_SERVICES_DATA) 330 continue; 331 332 already_reserved = memblock_is_region_reserved(start, size); 333 334 /* 335 * Because the following memblock_reserve() is paired 336 * with memblock_free_late() for this region in 337 * efi_free_boot_services(), we must be extremely 338 * careful not to reserve, and subsequently free, 339 * critical regions of memory (like the kernel image) or 340 * those regions that somebody else has already 341 * reserved. 342 * 343 * A good example of a critical region that must not be 344 * freed is page zero (first 4Kb of memory), which may 345 * contain boot services code/data but is marked 346 * E820_TYPE_RESERVED by trim_bios_range(). 347 */ 348 if (!already_reserved) { 349 memblock_reserve(start, size); 350 351 /* 352 * If we are the first to reserve the region, no 353 * one else cares about it. We own it and can 354 * free it later. 355 */ 356 if (can_free_region(start, size)) 357 continue; 358 } 359 360 /* 361 * We don't own the region. We must not free it. 362 * 363 * Setting this bit for a boot services region really 364 * doesn't make sense as far as the firmware is 365 * concerned, but it does provide us with a way to tag 366 * those regions that must not be paired with 367 * memblock_free_late(). 368 */ 369 md->attribute |= EFI_MEMORY_RUNTIME; 370 } 371} 372 373/* 374 * Apart from having VA mappings for EFI boot services code/data regions, 375 * (duplicate) 1:1 mappings were also created as a quirk for buggy firmware. So, 376 * unmap both 1:1 and VA mappings. 377 */ 378static void __init efi_unmap_pages(efi_memory_desc_t *md) 379{ 380 pgd_t *pgd = efi_mm.pgd; 381 u64 pa = md->phys_addr; 382 u64 va = md->virt_addr; 383 384 /* 385 * EFI mixed mode has all RAM mapped to access arguments while making 386 * EFI runtime calls, hence don't unmap EFI boot services code/data 387 * regions. 388 */ 389 if (efi_is_mixed()) 390 return; 391 392 if (kernel_unmap_pages_in_pgd(pgd, pa, md->num_pages)) 393 pr_err("Failed to unmap 1:1 mapping for 0x%llx\n", pa); 394 395 if (kernel_unmap_pages_in_pgd(pgd, va, md->num_pages)) 396 pr_err("Failed to unmap VA mapping for 0x%llx\n", va); 397} 398 399void __init efi_free_boot_services(void) 400{ 401 struct efi_memory_map_data data = { 0 }; 402 efi_memory_desc_t *md; 403 int num_entries = 0; 404 void *new, *new_md; 405 406 /* Keep all regions for /sys/kernel/debug/efi */ 407 if (efi_enabled(EFI_DBG)) 408 return; 409 410 for_each_efi_memory_desc(md) { 411 unsigned long long start = md->phys_addr; 412 unsigned long long size = md->num_pages << EFI_PAGE_SHIFT; 413 size_t rm_size; 414 415 if (md->type != EFI_BOOT_SERVICES_CODE && 416 md->type != EFI_BOOT_SERVICES_DATA) { 417 num_entries++; 418 continue; 419 } 420 421 /* Do not free, someone else owns it: */ 422 if (md->attribute & EFI_MEMORY_RUNTIME) { 423 num_entries++; 424 continue; 425 } 426 427 /* 428 * Before calling set_virtual_address_map(), EFI boot services 429 * code/data regions were mapped as a quirk for buggy firmware. 430 * Unmap them from efi_pgd before freeing them up. 431 */ 432 efi_unmap_pages(md); 433 434 /* 435 * Nasty quirk: if all sub-1MB memory is used for boot 436 * services, we can get here without having allocated the 437 * real mode trampoline. It's too late to hand boot services 438 * memory back to the memblock allocator, so instead 439 * try to manually allocate the trampoline if needed. 440 * 441 * I've seen this on a Dell XPS 13 9350 with firmware 442 * 1.4.4 with SGX enabled booting Linux via Fedora 24's 443 * grub2-efi on a hard disk. (And no, I don't know why 444 * this happened, but Linux should still try to boot rather 445 * panicing early.) 446 */ 447 rm_size = real_mode_size_needed(); 448 if (rm_size && (start + rm_size) < (1<<20) && size >= rm_size) { 449 set_real_mode_mem(start); 450 start += rm_size; 451 size -= rm_size; 452 } 453 454 memblock_free_late(start, size); 455 } 456 457 if (!num_entries) 458 return; 459 460 if (efi_memmap_alloc(num_entries, &data) != 0) { 461 pr_err("Failed to allocate new EFI memmap\n"); 462 return; 463 } 464 465 new = memremap(data.phys_map, data.size, MEMREMAP_WB); 466 if (!new) { 467 pr_err("Failed to map new EFI memmap\n"); 468 return; 469 } 470 471 /* 472 * Build a new EFI memmap that excludes any boot services 473 * regions that are not tagged EFI_MEMORY_RUNTIME, since those 474 * regions have now been freed. 475 */ 476 new_md = new; 477 for_each_efi_memory_desc(md) { 478 if (!(md->attribute & EFI_MEMORY_RUNTIME) && 479 (md->type == EFI_BOOT_SERVICES_CODE || 480 md->type == EFI_BOOT_SERVICES_DATA)) 481 continue; 482 483 memcpy(new_md, md, efi.memmap.desc_size); 484 new_md += efi.memmap.desc_size; 485 } 486 487 memunmap(new); 488 489 if (efi_memmap_install(&data) != 0) { 490 pr_err("Could not install new EFI memmap\n"); 491 return; 492 } 493} 494 495/* 496 * A number of config table entries get remapped to virtual addresses 497 * after entering EFI virtual mode. However, the kexec kernel requires 498 * their physical addresses therefore we pass them via setup_data and 499 * correct those entries to their respective physical addresses here. 500 * 501 * Currently only handles smbios which is necessary for some firmware 502 * implementation. 503 */ 504int __init efi_reuse_config(u64 tables, int nr_tables) 505{ 506 int i, sz, ret = 0; 507 void *p, *tablep; 508 struct efi_setup_data *data; 509 510 if (nr_tables == 0) 511 return 0; 512 513 if (!efi_setup) 514 return 0; 515 516 if (!efi_enabled(EFI_64BIT)) 517 return 0; 518 519 data = early_memremap(efi_setup, sizeof(*data)); 520 if (!data) { 521 ret = -ENOMEM; 522 goto out; 523 } 524 525 if (!data->smbios) 526 goto out_memremap; 527 528 sz = sizeof(efi_config_table_64_t); 529 530 p = tablep = early_memremap(tables, nr_tables * sz); 531 if (!p) { 532 pr_err("Could not map Configuration table!\n"); 533 ret = -ENOMEM; 534 goto out_memremap; 535 } 536 537 for (i = 0; i < nr_tables; i++) { 538 efi_guid_t guid; 539 540 guid = ((efi_config_table_64_t *)p)->guid; 541 542 if (!efi_guidcmp(guid, SMBIOS_TABLE_GUID)) 543 ((efi_config_table_64_t *)p)->table = data->smbios; 544 p += sz; 545 } 546 early_memunmap(tablep, nr_tables * sz); 547 548out_memremap: 549 early_memunmap(data, sizeof(*data)); 550out: 551 return ret; 552} 553 554void __init efi_apply_memmap_quirks(void) 555{ 556 /* 557 * Once setup is done earlier, unmap the EFI memory map on mismatched 558 * firmware/kernel architectures since there is no support for runtime 559 * services. 560 */ 561 if (!efi_runtime_supported()) { 562 pr_info("Setup done, disabling due to 32/64-bit mismatch\n"); 563 efi_memmap_unmap(); 564 } 565} 566 567/* 568 * For most modern platforms the preferred method of powering off is via 569 * ACPI. However, there are some that are known to require the use of 570 * EFI runtime services and for which ACPI does not work at all. 571 * 572 * Using EFI is a last resort, to be used only if no other option 573 * exists. 574 */ 575bool efi_reboot_required(void) 576{ 577 if (!acpi_gbl_reduced_hardware) 578 return false; 579 580 efi_reboot_quirk_mode = EFI_RESET_WARM; 581 return true; 582} 583 584bool efi_poweroff_required(void) 585{ 586 return acpi_gbl_reduced_hardware || acpi_no_s5; 587} 588 589#ifdef CONFIG_EFI_CAPSULE_QUIRK_QUARK_CSH 590 591static int qrk_capsule_setup_info(struct capsule_info *cap_info, void **pkbuff, 592 size_t hdr_bytes) 593{ 594 struct quark_security_header *csh = *pkbuff; 595 596 /* Only process data block that is larger than the security header */ 597 if (hdr_bytes < sizeof(struct quark_security_header)) 598 return 0; 599 600 if (csh->csh_signature != QUARK_CSH_SIGNATURE || 601 csh->headersize != QUARK_SECURITY_HEADER_SIZE) 602 return 1; 603 604 /* Only process data block if EFI header is included */ 605 if (hdr_bytes < QUARK_SECURITY_HEADER_SIZE + 606 sizeof(efi_capsule_header_t)) 607 return 0; 608 609 pr_debug("Quark security header detected\n"); 610 611 if (csh->rsvd_next_header != 0) { 612 pr_err("multiple Quark security headers not supported\n"); 613 return -EINVAL; 614 } 615 616 *pkbuff += csh->headersize; 617 cap_info->total_size = csh->headersize; 618 619 /* 620 * Update the first page pointer to skip over the CSH header. 621 */ 622 cap_info->phys[0] += csh->headersize; 623 624 /* 625 * cap_info->capsule should point at a virtual mapping of the entire 626 * capsule, starting at the capsule header. Our image has the Quark 627 * security header prepended, so we cannot rely on the default vmap() 628 * mapping created by the generic capsule code. 629 * Given that the Quark firmware does not appear to care about the 630 * virtual mapping, let's just point cap_info->capsule at our copy 631 * of the capsule header. 632 */ 633 cap_info->capsule = &cap_info->header; 634 635 return 1; 636} 637 638static const struct x86_cpu_id efi_capsule_quirk_ids[] = { 639 X86_MATCH_VENDOR_FAM_MODEL(INTEL, 5, INTEL_FAM5_QUARK_X1000, 640 &qrk_capsule_setup_info), 641 { } 642}; 643 644int efi_capsule_setup_info(struct capsule_info *cap_info, void *kbuff, 645 size_t hdr_bytes) 646{ 647 int (*quirk_handler)(struct capsule_info *, void **, size_t); 648 const struct x86_cpu_id *id; 649 int ret; 650 651 if (hdr_bytes < sizeof(efi_capsule_header_t)) 652 return 0; 653 654 cap_info->total_size = 0; 655 656 id = x86_match_cpu(efi_capsule_quirk_ids); 657 if (id) { 658 /* 659 * The quirk handler is supposed to return 660 * - a value > 0 if the setup should continue, after advancing 661 * kbuff as needed 662 * - 0 if not enough hdr_bytes are available yet 663 * - a negative error code otherwise 664 */ 665 quirk_handler = (typeof(quirk_handler))id->driver_data; 666 ret = quirk_handler(cap_info, &kbuff, hdr_bytes); 667 if (ret <= 0) 668 return ret; 669 } 670 671 memcpy(&cap_info->header, kbuff, sizeof(cap_info->header)); 672 673 cap_info->total_size += cap_info->header.imagesize; 674 675 return __efi_capsule_setup_info(cap_info); 676} 677 678#endif 679 680/* 681 * If any access by any efi runtime service causes a page fault, then, 682 * 1. If it's efi_reset_system(), reboot through BIOS. 683 * 2. If any other efi runtime service, then 684 * a. Return error status to the efi caller process. 685 * b. Disable EFI Runtime Services forever and 686 * c. Freeze efi_rts_wq and schedule new process. 687 * 688 * @return: Returns, if the page fault is not handled. This function 689 * will never return if the page fault is handled successfully. 690 */ 691void efi_recover_from_page_fault(unsigned long phys_addr) 692{ 693 if (!IS_ENABLED(CONFIG_X86_64)) 694 return; 695 696 /* 697 * Make sure that an efi runtime service caused the page fault. 698 */ 699 if (efi_rts_work.efi_rts_id == EFI_NONE) 700 return; 701 702 /* 703 * Address range 0x0000 - 0x0fff is always mapped in the efi_pgd, so 704 * page faulting on these addresses isn't expected. 705 */ 706 if (phys_addr <= 0x0fff) 707 return; 708 709 /* 710 * Print stack trace as it might be useful to know which EFI Runtime 711 * Service is buggy. 712 */ 713 WARN(1, FW_BUG "Page fault caused by firmware at PA: 0x%lx\n", 714 phys_addr); 715 716 /* 717 * Buggy efi_reset_system() is handled differently from other EFI 718 * Runtime Services as it doesn't use efi_rts_wq. Although, 719 * native_machine_emergency_restart() says that machine_real_restart() 720 * could fail, it's better not to compilcate this fault handler 721 * because this case occurs *very* rarely and hence could be improved 722 * on a need by basis. 723 */ 724 if (efi_rts_work.efi_rts_id == EFI_RESET_SYSTEM) { 725 pr_info("efi_reset_system() buggy! Reboot through BIOS\n"); 726 machine_real_restart(MRR_BIOS); 727 return; 728 } 729 730 /* 731 * Before calling EFI Runtime Service, the kernel has switched the 732 * calling process to efi_mm. Hence, switch back to task_mm. 733 */ 734 arch_efi_call_virt_teardown(); 735 736 /* Signal error status to the efi caller process */ 737 efi_rts_work.status = EFI_ABORTED; 738 complete(&efi_rts_work.efi_rts_comp); 739 740 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); 741 pr_info("Froze efi_rts_wq and disabled EFI Runtime Services\n"); 742 743 /* 744 * Call schedule() in an infinite loop, so that any spurious wake ups 745 * will never run efi_rts_wq again. 746 */ 747 for (;;) { 748 set_current_state(TASK_IDLE); 749 schedule(); 750 } 751 752 return; 753} 754