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 117u64 efivar_reserved_space(void) 118{ 119 if (efi_no_storage_paranoia) 120 return 0; 121 return EFI_MIN_RESERVE; 122} 123EXPORT_SYMBOL_GPL(efivar_reserved_space); 124 125/* 126 * In the nonblocking case we do not attempt to perform garbage 127 * collection if we do not have enough free space. Rather, we do the 128 * bare minimum check and give up immediately if the available space 129 * is below EFI_MIN_RESERVE. 130 * 131 * This function is intended to be small and simple because it is 132 * invoked from crash handler paths. 133 */ 134static efi_status_t 135query_variable_store_nonblocking(u32 attributes, unsigned long size) 136{ 137 efi_status_t status; 138 u64 storage_size, remaining_size, max_size; 139 140 status = efi.query_variable_info_nonblocking(attributes, &storage_size, 141 &remaining_size, 142 &max_size); 143 if (status != EFI_SUCCESS) 144 return status; 145 146 if (remaining_size - size < EFI_MIN_RESERVE) 147 return EFI_OUT_OF_RESOURCES; 148 149 return EFI_SUCCESS; 150} 151 152/* 153 * Some firmware implementations refuse to boot if there's insufficient space 154 * in the variable store. Ensure that we never use more than a safe limit. 155 * 156 * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable 157 * store. 158 */ 159efi_status_t efi_query_variable_store(u32 attributes, unsigned long size, 160 bool nonblocking) 161{ 162 efi_status_t status; 163 u64 storage_size, remaining_size, max_size; 164 165 if (!(attributes & EFI_VARIABLE_NON_VOLATILE)) 166 return 0; 167 168 if (nonblocking) 169 return query_variable_store_nonblocking(attributes, size); 170 171 status = efi.query_variable_info(attributes, &storage_size, 172 &remaining_size, &max_size); 173 if (status != EFI_SUCCESS) 174 return status; 175 176 /* 177 * We account for that by refusing the write if permitting it would 178 * reduce the available space to under 5KB. This figure was provided by 179 * Samsung, so should be safe. 180 */ 181 if ((remaining_size - size < EFI_MIN_RESERVE) && 182 !efi_no_storage_paranoia) { 183 184 /* 185 * Triggering garbage collection may require that the firmware 186 * generate a real EFI_OUT_OF_RESOURCES error. We can force 187 * that by attempting to use more space than is available. 188 */ 189 unsigned long dummy_size = remaining_size + 1024; 190 void *dummy = kzalloc(dummy_size, GFP_KERNEL); 191 192 if (!dummy) 193 return EFI_OUT_OF_RESOURCES; 194 195 status = efi.set_variable((efi_char16_t *)efi_dummy_name, 196 &EFI_DUMMY_GUID, 197 EFI_VARIABLE_NON_VOLATILE | 198 EFI_VARIABLE_BOOTSERVICE_ACCESS | 199 EFI_VARIABLE_RUNTIME_ACCESS, 200 dummy_size, dummy); 201 202 if (status == EFI_SUCCESS) { 203 /* 204 * This should have failed, so if it didn't make sure 205 * that we delete it... 206 */ 207 efi_delete_dummy_variable(); 208 } 209 210 kfree(dummy); 211 212 /* 213 * The runtime code may now have triggered a garbage collection 214 * run, so check the variable info again 215 */ 216 status = efi.query_variable_info(attributes, &storage_size, 217 &remaining_size, &max_size); 218 219 if (status != EFI_SUCCESS) 220 return status; 221 222 /* 223 * There still isn't enough room, so return an error 224 */ 225 if (remaining_size - size < EFI_MIN_RESERVE) 226 return EFI_OUT_OF_RESOURCES; 227 } 228 229 return EFI_SUCCESS; 230} 231EXPORT_SYMBOL_GPL(efi_query_variable_store); 232 233/* 234 * The UEFI specification makes it clear that the operating system is 235 * free to do whatever it wants with boot services code after 236 * ExitBootServices() has been called. Ignoring this recommendation a 237 * significant bunch of EFI implementations continue calling into boot 238 * services code (SetVirtualAddressMap). In order to work around such 239 * buggy implementations we reserve boot services region during EFI 240 * init and make sure it stays executable. Then, after 241 * SetVirtualAddressMap(), it is discarded. 242 * 243 * However, some boot services regions contain data that is required 244 * by drivers, so we need to track which memory ranges can never be 245 * freed. This is done by tagging those regions with the 246 * EFI_MEMORY_RUNTIME attribute. 247 * 248 * Any driver that wants to mark a region as reserved must use 249 * efi_mem_reserve() which will insert a new EFI memory descriptor 250 * into efi.memmap (splitting existing regions if necessary) and tag 251 * it with EFI_MEMORY_RUNTIME. 252 */ 253void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size) 254{ 255 struct efi_memory_map_data data = { 0 }; 256 struct efi_mem_range mr; 257 efi_memory_desc_t md; 258 int num_entries; 259 void *new; 260 261 if (efi_mem_desc_lookup(addr, &md) || 262 md.type != EFI_BOOT_SERVICES_DATA) { 263 pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr); 264 return; 265 } 266 267 if (addr + size > md.phys_addr + (md.num_pages << EFI_PAGE_SHIFT)) { 268 pr_err("Region spans EFI memory descriptors, %pa\n", &addr); 269 return; 270 } 271 272 size += addr % EFI_PAGE_SIZE; 273 size = round_up(size, EFI_PAGE_SIZE); 274 addr = round_down(addr, EFI_PAGE_SIZE); 275 276 mr.range.start = addr; 277 mr.range.end = addr + size - 1; 278 mr.attribute = md.attribute | EFI_MEMORY_RUNTIME; 279 280 num_entries = efi_memmap_split_count(&md, &mr.range); 281 num_entries += efi.memmap.nr_map; 282 283 if (efi_memmap_alloc(num_entries, &data) != 0) { 284 pr_err("Could not allocate boot services memmap\n"); 285 return; 286 } 287 288 new = early_memremap_prot(data.phys_map, data.size, 289 pgprot_val(pgprot_encrypted(FIXMAP_PAGE_NORMAL))); 290 if (!new) { 291 pr_err("Failed to map new boot services memmap\n"); 292 return; 293 } 294 295 efi_memmap_insert(&efi.memmap, new, &mr); 296 early_memunmap(new, data.size); 297 298 efi_memmap_install(&data); 299 e820__range_update(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED); 300 e820__update_table(e820_table); 301} 302 303/* 304 * Helper function for efi_reserve_boot_services() to figure out if we 305 * can free regions in efi_free_boot_services(). 306 * 307 * Use this function to ensure we do not free regions owned by somebody 308 * else. We must only reserve (and then free) regions: 309 * 310 * - Not within any part of the kernel 311 * - Not the BIOS reserved area (E820_TYPE_RESERVED, E820_TYPE_NVS, etc) 312 */ 313static __init bool can_free_region(u64 start, u64 size) 314{ 315 if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end)) 316 return false; 317 318 if (!e820__mapped_all(start, start+size, E820_TYPE_RAM)) 319 return false; 320 321 return true; 322} 323 324void __init efi_reserve_boot_services(void) 325{ 326 efi_memory_desc_t *md; 327 328 if (!efi_enabled(EFI_MEMMAP)) 329 return; 330 331 for_each_efi_memory_desc(md) { 332 u64 start = md->phys_addr; 333 u64 size = md->num_pages << EFI_PAGE_SHIFT; 334 bool already_reserved; 335 336 if (md->type != EFI_BOOT_SERVICES_CODE && 337 md->type != EFI_BOOT_SERVICES_DATA) 338 continue; 339 340 already_reserved = memblock_is_region_reserved(start, size); 341 342 /* 343 * Because the following memblock_reserve() is paired 344 * with memblock_free_late() for this region in 345 * efi_free_boot_services(), we must be extremely 346 * careful not to reserve, and subsequently free, 347 * critical regions of memory (like the kernel image) or 348 * those regions that somebody else has already 349 * reserved. 350 * 351 * A good example of a critical region that must not be 352 * freed is page zero (first 4Kb of memory), which may 353 * contain boot services code/data but is marked 354 * E820_TYPE_RESERVED by trim_bios_range(). 355 */ 356 if (!already_reserved) { 357 memblock_reserve(start, size); 358 359 /* 360 * If we are the first to reserve the region, no 361 * one else cares about it. We own it and can 362 * free it later. 363 */ 364 if (can_free_region(start, size)) 365 continue; 366 } 367 368 /* 369 * We don't own the region. We must not free it. 370 * 371 * Setting this bit for a boot services region really 372 * doesn't make sense as far as the firmware is 373 * concerned, but it does provide us with a way to tag 374 * those regions that must not be paired with 375 * memblock_free_late(). 376 */ 377 md->attribute |= EFI_MEMORY_RUNTIME; 378 } 379} 380 381/* 382 * Apart from having VA mappings for EFI boot services code/data regions, 383 * (duplicate) 1:1 mappings were also created as a quirk for buggy firmware. So, 384 * unmap both 1:1 and VA mappings. 385 */ 386static void __init efi_unmap_pages(efi_memory_desc_t *md) 387{ 388 pgd_t *pgd = efi_mm.pgd; 389 u64 pa = md->phys_addr; 390 u64 va = md->virt_addr; 391 392 /* 393 * EFI mixed mode has all RAM mapped to access arguments while making 394 * EFI runtime calls, hence don't unmap EFI boot services code/data 395 * regions. 396 */ 397 if (efi_is_mixed()) 398 return; 399 400 if (kernel_unmap_pages_in_pgd(pgd, pa, md->num_pages)) 401 pr_err("Failed to unmap 1:1 mapping for 0x%llx\n", pa); 402 403 if (kernel_unmap_pages_in_pgd(pgd, va, md->num_pages)) 404 pr_err("Failed to unmap VA mapping for 0x%llx\n", va); 405} 406 407void __init efi_free_boot_services(void) 408{ 409 struct efi_memory_map_data data = { 0 }; 410 efi_memory_desc_t *md; 411 int num_entries = 0; 412 void *new, *new_md; 413 414 /* Keep all regions for /sys/kernel/debug/efi */ 415 if (efi_enabled(EFI_DBG)) 416 return; 417 418 for_each_efi_memory_desc(md) { 419 unsigned long long start = md->phys_addr; 420 unsigned long long size = md->num_pages << EFI_PAGE_SHIFT; 421 size_t rm_size; 422 423 if (md->type != EFI_BOOT_SERVICES_CODE && 424 md->type != EFI_BOOT_SERVICES_DATA) { 425 num_entries++; 426 continue; 427 } 428 429 /* Do not free, someone else owns it: */ 430 if (md->attribute & EFI_MEMORY_RUNTIME) { 431 num_entries++; 432 continue; 433 } 434 435 /* 436 * Before calling set_virtual_address_map(), EFI boot services 437 * code/data regions were mapped as a quirk for buggy firmware. 438 * Unmap them from efi_pgd before freeing them up. 439 */ 440 efi_unmap_pages(md); 441 442 /* 443 * Nasty quirk: if all sub-1MB memory is used for boot 444 * services, we can get here without having allocated the 445 * real mode trampoline. It's too late to hand boot services 446 * memory back to the memblock allocator, so instead 447 * try to manually allocate the trampoline if needed. 448 * 449 * I've seen this on a Dell XPS 13 9350 with firmware 450 * 1.4.4 with SGX enabled booting Linux via Fedora 24's 451 * grub2-efi on a hard disk. (And no, I don't know why 452 * this happened, but Linux should still try to boot rather 453 * panicking early.) 454 */ 455 rm_size = real_mode_size_needed(); 456 if (rm_size && (start + rm_size) < (1<<20) && size >= rm_size) { 457 set_real_mode_mem(start); 458 start += rm_size; 459 size -= rm_size; 460 } 461 462 /* 463 * Don't free memory under 1M for two reasons: 464 * - BIOS might clobber it 465 * - Crash kernel needs it to be reserved 466 */ 467 if (start + size < SZ_1M) 468 continue; 469 if (start < SZ_1M) { 470 size -= (SZ_1M - start); 471 start = SZ_1M; 472 } 473 474 memblock_free_late(start, size); 475 } 476 477 if (!num_entries) 478 return; 479 480 if (efi_memmap_alloc(num_entries, &data) != 0) { 481 pr_err("Failed to allocate new EFI memmap\n"); 482 return; 483 } 484 485 new = memremap(data.phys_map, data.size, MEMREMAP_WB); 486 if (!new) { 487 pr_err("Failed to map new EFI memmap\n"); 488 return; 489 } 490 491 /* 492 * Build a new EFI memmap that excludes any boot services 493 * regions that are not tagged EFI_MEMORY_RUNTIME, since those 494 * regions have now been freed. 495 */ 496 new_md = new; 497 for_each_efi_memory_desc(md) { 498 if (!(md->attribute & EFI_MEMORY_RUNTIME) && 499 (md->type == EFI_BOOT_SERVICES_CODE || 500 md->type == EFI_BOOT_SERVICES_DATA)) 501 continue; 502 503 memcpy(new_md, md, efi.memmap.desc_size); 504 new_md += efi.memmap.desc_size; 505 } 506 507 memunmap(new); 508 509 if (efi_memmap_install(&data) != 0) { 510 pr_err("Could not install new EFI memmap\n"); 511 return; 512 } 513} 514 515/* 516 * A number of config table entries get remapped to virtual addresses 517 * after entering EFI virtual mode. However, the kexec kernel requires 518 * their physical addresses therefore we pass them via setup_data and 519 * correct those entries to their respective physical addresses here. 520 * 521 * Currently only handles smbios which is necessary for some firmware 522 * implementation. 523 */ 524int __init efi_reuse_config(u64 tables, int nr_tables) 525{ 526 int i, sz, ret = 0; 527 void *p, *tablep; 528 struct efi_setup_data *data; 529 530 if (nr_tables == 0) 531 return 0; 532 533 if (!efi_setup) 534 return 0; 535 536 if (!efi_enabled(EFI_64BIT)) 537 return 0; 538 539 data = early_memremap(efi_setup, sizeof(*data)); 540 if (!data) { 541 ret = -ENOMEM; 542 goto out; 543 } 544 545 if (!data->smbios) 546 goto out_memremap; 547 548 sz = sizeof(efi_config_table_64_t); 549 550 p = tablep = early_memremap(tables, nr_tables * sz); 551 if (!p) { 552 pr_err("Could not map Configuration table!\n"); 553 ret = -ENOMEM; 554 goto out_memremap; 555 } 556 557 for (i = 0; i < nr_tables; i++) { 558 efi_guid_t guid; 559 560 guid = ((efi_config_table_64_t *)p)->guid; 561 562 if (!efi_guidcmp(guid, SMBIOS_TABLE_GUID)) 563 ((efi_config_table_64_t *)p)->table = data->smbios; 564 p += sz; 565 } 566 early_memunmap(tablep, nr_tables * sz); 567 568out_memremap: 569 early_memunmap(data, sizeof(*data)); 570out: 571 return ret; 572} 573 574void __init efi_apply_memmap_quirks(void) 575{ 576 /* 577 * Once setup is done earlier, unmap the EFI memory map on mismatched 578 * firmware/kernel architectures since there is no support for runtime 579 * services. 580 */ 581 if (!efi_runtime_supported()) { 582 pr_info("Setup done, disabling due to 32/64-bit mismatch\n"); 583 efi_memmap_unmap(); 584 } 585} 586 587/* 588 * For most modern platforms the preferred method of powering off is via 589 * ACPI. However, there are some that are known to require the use of 590 * EFI runtime services and for which ACPI does not work at all. 591 * 592 * Using EFI is a last resort, to be used only if no other option 593 * exists. 594 */ 595bool efi_reboot_required(void) 596{ 597 if (!acpi_gbl_reduced_hardware) 598 return false; 599 600 efi_reboot_quirk_mode = EFI_RESET_WARM; 601 return true; 602} 603 604bool efi_poweroff_required(void) 605{ 606 return acpi_gbl_reduced_hardware || acpi_no_s5; 607} 608 609#ifdef CONFIG_EFI_CAPSULE_QUIRK_QUARK_CSH 610 611static int qrk_capsule_setup_info(struct capsule_info *cap_info, void **pkbuff, 612 size_t hdr_bytes) 613{ 614 struct quark_security_header *csh = *pkbuff; 615 616 /* Only process data block that is larger than the security header */ 617 if (hdr_bytes < sizeof(struct quark_security_header)) 618 return 0; 619 620 if (csh->csh_signature != QUARK_CSH_SIGNATURE || 621 csh->headersize != QUARK_SECURITY_HEADER_SIZE) 622 return 1; 623 624 /* Only process data block if EFI header is included */ 625 if (hdr_bytes < QUARK_SECURITY_HEADER_SIZE + 626 sizeof(efi_capsule_header_t)) 627 return 0; 628 629 pr_debug("Quark security header detected\n"); 630 631 if (csh->rsvd_next_header != 0) { 632 pr_err("multiple Quark security headers not supported\n"); 633 return -EINVAL; 634 } 635 636 *pkbuff += csh->headersize; 637 cap_info->total_size = csh->headersize; 638 639 /* 640 * Update the first page pointer to skip over the CSH header. 641 */ 642 cap_info->phys[0] += csh->headersize; 643 644 /* 645 * cap_info->capsule should point at a virtual mapping of the entire 646 * capsule, starting at the capsule header. Our image has the Quark 647 * security header prepended, so we cannot rely on the default vmap() 648 * mapping created by the generic capsule code. 649 * Given that the Quark firmware does not appear to care about the 650 * virtual mapping, let's just point cap_info->capsule at our copy 651 * of the capsule header. 652 */ 653 cap_info->capsule = &cap_info->header; 654 655 return 1; 656} 657 658static const struct x86_cpu_id efi_capsule_quirk_ids[] = { 659 X86_MATCH_VENDOR_FAM_MODEL(INTEL, 5, INTEL_FAM5_QUARK_X1000, 660 &qrk_capsule_setup_info), 661 { } 662}; 663 664int efi_capsule_setup_info(struct capsule_info *cap_info, void *kbuff, 665 size_t hdr_bytes) 666{ 667 int (*quirk_handler)(struct capsule_info *, void **, size_t); 668 const struct x86_cpu_id *id; 669 int ret; 670 671 if (hdr_bytes < sizeof(efi_capsule_header_t)) 672 return 0; 673 674 cap_info->total_size = 0; 675 676 id = x86_match_cpu(efi_capsule_quirk_ids); 677 if (id) { 678 /* 679 * The quirk handler is supposed to return 680 * - a value > 0 if the setup should continue, after advancing 681 * kbuff as needed 682 * - 0 if not enough hdr_bytes are available yet 683 * - a negative error code otherwise 684 */ 685 quirk_handler = (typeof(quirk_handler))id->driver_data; 686 ret = quirk_handler(cap_info, &kbuff, hdr_bytes); 687 if (ret <= 0) 688 return ret; 689 } 690 691 memcpy(&cap_info->header, kbuff, sizeof(cap_info->header)); 692 693 cap_info->total_size += cap_info->header.imagesize; 694 695 return __efi_capsule_setup_info(cap_info); 696} 697 698#endif 699 700/* 701 * If any access by any efi runtime service causes a page fault, then, 702 * 1. If it's efi_reset_system(), reboot through BIOS. 703 * 2. If any other efi runtime service, then 704 * a. Return error status to the efi caller process. 705 * b. Disable EFI Runtime Services forever and 706 * c. Freeze efi_rts_wq and schedule new process. 707 * 708 * @return: Returns, if the page fault is not handled. This function 709 * will never return if the page fault is handled successfully. 710 */ 711void efi_crash_gracefully_on_page_fault(unsigned long phys_addr) 712{ 713 if (!IS_ENABLED(CONFIG_X86_64)) 714 return; 715 716 /* 717 * If we get an interrupt/NMI while processing an EFI runtime service 718 * then this is a regular OOPS, not an EFI failure. 719 */ 720 if (in_interrupt()) 721 return; 722 723 /* 724 * Make sure that an efi runtime service caused the page fault. 725 * READ_ONCE() because we might be OOPSing in a different thread, 726 * and we don't want to trip KTSAN while trying to OOPS. 727 */ 728 if (READ_ONCE(efi_rts_work.efi_rts_id) == EFI_NONE || 729 current_work() != &efi_rts_work.work) 730 return; 731 732 /* 733 * Address range 0x0000 - 0x0fff is always mapped in the efi_pgd, so 734 * page faulting on these addresses isn't expected. 735 */ 736 if (phys_addr <= 0x0fff) 737 return; 738 739 /* 740 * Print stack trace as it might be useful to know which EFI Runtime 741 * Service is buggy. 742 */ 743 WARN(1, FW_BUG "Page fault caused by firmware at PA: 0x%lx\n", 744 phys_addr); 745 746 /* 747 * Buggy efi_reset_system() is handled differently from other EFI 748 * Runtime Services as it doesn't use efi_rts_wq. Although, 749 * native_machine_emergency_restart() says that machine_real_restart() 750 * could fail, it's better not to complicate this fault handler 751 * because this case occurs *very* rarely and hence could be improved 752 * on a need by basis. 753 */ 754 if (efi_rts_work.efi_rts_id == EFI_RESET_SYSTEM) { 755 pr_info("efi_reset_system() buggy! Reboot through BIOS\n"); 756 machine_real_restart(MRR_BIOS); 757 return; 758 } 759 760 /* 761 * Before calling EFI Runtime Service, the kernel has switched the 762 * calling process to efi_mm. Hence, switch back to task_mm. 763 */ 764 arch_efi_call_virt_teardown(); 765 766 /* Signal error status to the efi caller process */ 767 efi_rts_work.status = EFI_ABORTED; 768 complete(&efi_rts_work.efi_rts_comp); 769 770 clear_bit(EFI_RUNTIME_SERVICES, &efi.flags); 771 pr_info("Froze efi_rts_wq and disabled EFI Runtime Services\n"); 772 773 /* 774 * Call schedule() in an infinite loop, so that any spurious wake ups 775 * will never run efi_rts_wq again. 776 */ 777 for (;;) { 778 set_current_state(TASK_IDLE); 779 schedule(); 780 } 781} 782