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