1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1995 Linus Torvalds 4 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. 5 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar 6 */ 7 #include <linux/sched.h> /* test_thread_flag(), ... */ 8 #include <linux/sched/task_stack.h> /* task_stack_*(), ... */ 9 #include <linux/kdebug.h> /* oops_begin/end, ... */ 10 #include <linux/extable.h> /* search_exception_tables */ 11 #include <linux/memblock.h> /* max_low_pfn */ 12 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ 13 #include <linux/mmiotrace.h> /* kmmio_handler, ... */ 14 #include <linux/perf_event.h> /* perf_sw_event */ 15 #include <linux/hugetlb.h> /* hstate_index_to_shift */ 16 #include <linux/prefetch.h> /* prefetchw */ 17 #include <linux/context_tracking.h> /* exception_enter(), ... */ 18 #include <linux/uaccess.h> /* faulthandler_disabled() */ 19 #include <linux/efi.h> /* efi_recover_from_page_fault()*/ 20 #include <linux/mm_types.h> 21 22 #include <asm/cpufeature.h> /* boot_cpu_has, ... */ 23 #include <asm/traps.h> /* dotraplinkage, ... */ 24 #include <asm/pgalloc.h> /* pgd_*(), ... */ 25 #include <asm/fixmap.h> /* VSYSCALL_ADDR */ 26 #include <asm/vsyscall.h> /* emulate_vsyscall */ 27 #include <asm/vm86.h> /* struct vm86 */ 28 #include <asm/mmu_context.h> /* vma_pkey() */ 29 #include <asm/efi.h> /* efi_recover_from_page_fault()*/ 30 #include <asm/desc.h> /* store_idt(), ... */ 31 #include <asm/cpu_entry_area.h> /* exception stack */ 32 33 #define CREATE_TRACE_POINTS 34 #include <asm/trace/exceptions.h> 35 36 /* 37 * Returns 0 if mmiotrace is disabled, or if the fault is not 38 * handled by mmiotrace: 39 */ 40 static nokprobe_inline int 41 kmmio_fault(struct pt_regs *regs, unsigned long addr) 42 { 43 if (unlikely(is_kmmio_active())) 44 if (kmmio_handler(regs, addr) == 1) 45 return -1; 46 return 0; 47 } 48 49 static nokprobe_inline int kprobes_fault(struct pt_regs *regs) 50 { 51 if (!kprobes_built_in()) 52 return 0; 53 if (user_mode(regs)) 54 return 0; 55 /* 56 * To be potentially processing a kprobe fault and to be allowed to call 57 * kprobe_running(), we have to be non-preemptible. 58 */ 59 if (preemptible()) 60 return 0; 61 if (!kprobe_running()) 62 return 0; 63 return kprobe_fault_handler(regs, X86_TRAP_PF); 64 } 65 66 /* 67 * Prefetch quirks: 68 * 69 * 32-bit mode: 70 * 71 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 72 * Check that here and ignore it. 73 * 74 * 64-bit mode: 75 * 76 * Sometimes the CPU reports invalid exceptions on prefetch. 77 * Check that here and ignore it. 78 * 79 * Opcode checker based on code by Richard Brunner. 80 */ 81 static inline int 82 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 83 unsigned char opcode, int *prefetch) 84 { 85 unsigned char instr_hi = opcode & 0xf0; 86 unsigned char instr_lo = opcode & 0x0f; 87 88 switch (instr_hi) { 89 case 0x20: 90 case 0x30: 91 /* 92 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 93 * In X86_64 long mode, the CPU will signal invalid 94 * opcode if some of these prefixes are present so 95 * X86_64 will never get here anyway 96 */ 97 return ((instr_lo & 7) == 0x6); 98 #ifdef CONFIG_X86_64 99 case 0x40: 100 /* 101 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 102 * Need to figure out under what instruction mode the 103 * instruction was issued. Could check the LDT for lm, 104 * but for now it's good enough to assume that long 105 * mode only uses well known segments or kernel. 106 */ 107 return (!user_mode(regs) || user_64bit_mode(regs)); 108 #endif 109 case 0x60: 110 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 111 return (instr_lo & 0xC) == 0x4; 112 case 0xF0: 113 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 114 return !instr_lo || (instr_lo>>1) == 1; 115 case 0x00: 116 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 117 if (probe_kernel_address(instr, opcode)) 118 return 0; 119 120 *prefetch = (instr_lo == 0xF) && 121 (opcode == 0x0D || opcode == 0x18); 122 return 0; 123 default: 124 return 0; 125 } 126 } 127 128 static int 129 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 130 { 131 unsigned char *max_instr; 132 unsigned char *instr; 133 int prefetch = 0; 134 135 /* 136 * If it was a exec (instruction fetch) fault on NX page, then 137 * do not ignore the fault: 138 */ 139 if (error_code & X86_PF_INSTR) 140 return 0; 141 142 instr = (void *)convert_ip_to_linear(current, regs); 143 max_instr = instr + 15; 144 145 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) 146 return 0; 147 148 while (instr < max_instr) { 149 unsigned char opcode; 150 151 if (probe_kernel_address(instr, opcode)) 152 break; 153 154 instr++; 155 156 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 157 break; 158 } 159 return prefetch; 160 } 161 162 DEFINE_SPINLOCK(pgd_lock); 163 LIST_HEAD(pgd_list); 164 165 #ifdef CONFIG_X86_32 166 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 167 { 168 unsigned index = pgd_index(address); 169 pgd_t *pgd_k; 170 p4d_t *p4d, *p4d_k; 171 pud_t *pud, *pud_k; 172 pmd_t *pmd, *pmd_k; 173 174 pgd += index; 175 pgd_k = init_mm.pgd + index; 176 177 if (!pgd_present(*pgd_k)) 178 return NULL; 179 180 /* 181 * set_pgd(pgd, *pgd_k); here would be useless on PAE 182 * and redundant with the set_pmd() on non-PAE. As would 183 * set_p4d/set_pud. 184 */ 185 p4d = p4d_offset(pgd, address); 186 p4d_k = p4d_offset(pgd_k, address); 187 if (!p4d_present(*p4d_k)) 188 return NULL; 189 190 pud = pud_offset(p4d, address); 191 pud_k = pud_offset(p4d_k, address); 192 if (!pud_present(*pud_k)) 193 return NULL; 194 195 pmd = pmd_offset(pud, address); 196 pmd_k = pmd_offset(pud_k, address); 197 if (!pmd_present(*pmd_k)) 198 return NULL; 199 200 if (!pmd_present(*pmd)) 201 set_pmd(pmd, *pmd_k); 202 else 203 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 204 205 return pmd_k; 206 } 207 208 void vmalloc_sync_all(void) 209 { 210 unsigned long address; 211 212 if (SHARED_KERNEL_PMD) 213 return; 214 215 for (address = VMALLOC_START & PMD_MASK; 216 address >= TASK_SIZE_MAX && address < FIXADDR_TOP; 217 address += PMD_SIZE) { 218 struct page *page; 219 220 spin_lock(&pgd_lock); 221 list_for_each_entry(page, &pgd_list, lru) { 222 spinlock_t *pgt_lock; 223 pmd_t *ret; 224 225 /* the pgt_lock only for Xen */ 226 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 227 228 spin_lock(pgt_lock); 229 ret = vmalloc_sync_one(page_address(page), address); 230 spin_unlock(pgt_lock); 231 232 if (!ret) 233 break; 234 } 235 spin_unlock(&pgd_lock); 236 } 237 } 238 239 /* 240 * 32-bit: 241 * 242 * Handle a fault on the vmalloc or module mapping area 243 */ 244 static noinline int vmalloc_fault(unsigned long address) 245 { 246 unsigned long pgd_paddr; 247 pmd_t *pmd_k; 248 pte_t *pte_k; 249 250 /* Make sure we are in vmalloc area: */ 251 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 252 return -1; 253 254 /* 255 * Synchronize this task's top level page-table 256 * with the 'reference' page table. 257 * 258 * Do _not_ use "current" here. We might be inside 259 * an interrupt in the middle of a task switch.. 260 */ 261 pgd_paddr = read_cr3_pa(); 262 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 263 if (!pmd_k) 264 return -1; 265 266 if (pmd_large(*pmd_k)) 267 return 0; 268 269 pte_k = pte_offset_kernel(pmd_k, address); 270 if (!pte_present(*pte_k)) 271 return -1; 272 273 return 0; 274 } 275 NOKPROBE_SYMBOL(vmalloc_fault); 276 277 /* 278 * Did it hit the DOS screen memory VA from vm86 mode? 279 */ 280 static inline void 281 check_v8086_mode(struct pt_regs *regs, unsigned long address, 282 struct task_struct *tsk) 283 { 284 #ifdef CONFIG_VM86 285 unsigned long bit; 286 287 if (!v8086_mode(regs) || !tsk->thread.vm86) 288 return; 289 290 bit = (address - 0xA0000) >> PAGE_SHIFT; 291 if (bit < 32) 292 tsk->thread.vm86->screen_bitmap |= 1 << bit; 293 #endif 294 } 295 296 static bool low_pfn(unsigned long pfn) 297 { 298 return pfn < max_low_pfn; 299 } 300 301 static void dump_pagetable(unsigned long address) 302 { 303 pgd_t *base = __va(read_cr3_pa()); 304 pgd_t *pgd = &base[pgd_index(address)]; 305 p4d_t *p4d; 306 pud_t *pud; 307 pmd_t *pmd; 308 pte_t *pte; 309 310 #ifdef CONFIG_X86_PAE 311 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 312 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 313 goto out; 314 #define pr_pde pr_cont 315 #else 316 #define pr_pde pr_info 317 #endif 318 p4d = p4d_offset(pgd, address); 319 pud = pud_offset(p4d, address); 320 pmd = pmd_offset(pud, address); 321 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 322 #undef pr_pde 323 324 /* 325 * We must not directly access the pte in the highpte 326 * case if the page table is located in highmem. 327 * And let's rather not kmap-atomic the pte, just in case 328 * it's allocated already: 329 */ 330 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 331 goto out; 332 333 pte = pte_offset_kernel(pmd, address); 334 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 335 out: 336 pr_cont("\n"); 337 } 338 339 #else /* CONFIG_X86_64: */ 340 341 void vmalloc_sync_all(void) 342 { 343 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 344 } 345 346 /* 347 * 64-bit: 348 * 349 * Handle a fault on the vmalloc area 350 */ 351 static noinline int vmalloc_fault(unsigned long address) 352 { 353 pgd_t *pgd, *pgd_k; 354 p4d_t *p4d, *p4d_k; 355 pud_t *pud; 356 pmd_t *pmd; 357 pte_t *pte; 358 359 /* Make sure we are in vmalloc area: */ 360 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 361 return -1; 362 363 /* 364 * Copy kernel mappings over when needed. This can also 365 * happen within a race in page table update. In the later 366 * case just flush: 367 */ 368 pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address); 369 pgd_k = pgd_offset_k(address); 370 if (pgd_none(*pgd_k)) 371 return -1; 372 373 if (pgtable_l5_enabled()) { 374 if (pgd_none(*pgd)) { 375 set_pgd(pgd, *pgd_k); 376 arch_flush_lazy_mmu_mode(); 377 } else { 378 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k)); 379 } 380 } 381 382 /* With 4-level paging, copying happens on the p4d level. */ 383 p4d = p4d_offset(pgd, address); 384 p4d_k = p4d_offset(pgd_k, address); 385 if (p4d_none(*p4d_k)) 386 return -1; 387 388 if (p4d_none(*p4d) && !pgtable_l5_enabled()) { 389 set_p4d(p4d, *p4d_k); 390 arch_flush_lazy_mmu_mode(); 391 } else { 392 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k)); 393 } 394 395 BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4); 396 397 pud = pud_offset(p4d, address); 398 if (pud_none(*pud)) 399 return -1; 400 401 if (pud_large(*pud)) 402 return 0; 403 404 pmd = pmd_offset(pud, address); 405 if (pmd_none(*pmd)) 406 return -1; 407 408 if (pmd_large(*pmd)) 409 return 0; 410 411 pte = pte_offset_kernel(pmd, address); 412 if (!pte_present(*pte)) 413 return -1; 414 415 return 0; 416 } 417 NOKPROBE_SYMBOL(vmalloc_fault); 418 419 #ifdef CONFIG_CPU_SUP_AMD 420 static const char errata93_warning[] = 421 KERN_ERR 422 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 423 "******* Working around it, but it may cause SEGVs or burn power.\n" 424 "******* Please consider a BIOS update.\n" 425 "******* Disabling USB legacy in the BIOS may also help.\n"; 426 #endif 427 428 /* 429 * No vm86 mode in 64-bit mode: 430 */ 431 static inline void 432 check_v8086_mode(struct pt_regs *regs, unsigned long address, 433 struct task_struct *tsk) 434 { 435 } 436 437 static int bad_address(void *p) 438 { 439 unsigned long dummy; 440 441 return probe_kernel_address((unsigned long *)p, dummy); 442 } 443 444 static void dump_pagetable(unsigned long address) 445 { 446 pgd_t *base = __va(read_cr3_pa()); 447 pgd_t *pgd = base + pgd_index(address); 448 p4d_t *p4d; 449 pud_t *pud; 450 pmd_t *pmd; 451 pte_t *pte; 452 453 if (bad_address(pgd)) 454 goto bad; 455 456 pr_info("PGD %lx ", pgd_val(*pgd)); 457 458 if (!pgd_present(*pgd)) 459 goto out; 460 461 p4d = p4d_offset(pgd, address); 462 if (bad_address(p4d)) 463 goto bad; 464 465 pr_cont("P4D %lx ", p4d_val(*p4d)); 466 if (!p4d_present(*p4d) || p4d_large(*p4d)) 467 goto out; 468 469 pud = pud_offset(p4d, address); 470 if (bad_address(pud)) 471 goto bad; 472 473 pr_cont("PUD %lx ", pud_val(*pud)); 474 if (!pud_present(*pud) || pud_large(*pud)) 475 goto out; 476 477 pmd = pmd_offset(pud, address); 478 if (bad_address(pmd)) 479 goto bad; 480 481 pr_cont("PMD %lx ", pmd_val(*pmd)); 482 if (!pmd_present(*pmd) || pmd_large(*pmd)) 483 goto out; 484 485 pte = pte_offset_kernel(pmd, address); 486 if (bad_address(pte)) 487 goto bad; 488 489 pr_cont("PTE %lx", pte_val(*pte)); 490 out: 491 pr_cont("\n"); 492 return; 493 bad: 494 pr_info("BAD\n"); 495 } 496 497 #endif /* CONFIG_X86_64 */ 498 499 /* 500 * Workaround for K8 erratum #93 & buggy BIOS. 501 * 502 * BIOS SMM functions are required to use a specific workaround 503 * to avoid corruption of the 64bit RIP register on C stepping K8. 504 * 505 * A lot of BIOS that didn't get tested properly miss this. 506 * 507 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 508 * Try to work around it here. 509 * 510 * Note we only handle faults in kernel here. 511 * Does nothing on 32-bit. 512 */ 513 static int is_errata93(struct pt_regs *regs, unsigned long address) 514 { 515 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 516 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 517 || boot_cpu_data.x86 != 0xf) 518 return 0; 519 520 if (address != regs->ip) 521 return 0; 522 523 if ((address >> 32) != 0) 524 return 0; 525 526 address |= 0xffffffffUL << 32; 527 if ((address >= (u64)_stext && address <= (u64)_etext) || 528 (address >= MODULES_VADDR && address <= MODULES_END)) { 529 printk_once(errata93_warning); 530 regs->ip = address; 531 return 1; 532 } 533 #endif 534 return 0; 535 } 536 537 /* 538 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 539 * to illegal addresses >4GB. 540 * 541 * We catch this in the page fault handler because these addresses 542 * are not reachable. Just detect this case and return. Any code 543 * segment in LDT is compatibility mode. 544 */ 545 static int is_errata100(struct pt_regs *regs, unsigned long address) 546 { 547 #ifdef CONFIG_X86_64 548 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 549 return 1; 550 #endif 551 return 0; 552 } 553 554 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 555 { 556 #ifdef CONFIG_X86_F00F_BUG 557 unsigned long nr; 558 559 /* 560 * Pentium F0 0F C7 C8 bug workaround: 561 */ 562 if (boot_cpu_has_bug(X86_BUG_F00F)) { 563 nr = (address - idt_descr.address) >> 3; 564 565 if (nr == 6) { 566 do_invalid_op(regs, 0); 567 return 1; 568 } 569 } 570 #endif 571 return 0; 572 } 573 574 static void show_ldttss(const struct desc_ptr *gdt, const char *name, u16 index) 575 { 576 u32 offset = (index >> 3) * sizeof(struct desc_struct); 577 unsigned long addr; 578 struct ldttss_desc desc; 579 580 if (index == 0) { 581 pr_alert("%s: NULL\n", name); 582 return; 583 } 584 585 if (offset + sizeof(struct ldttss_desc) >= gdt->size) { 586 pr_alert("%s: 0x%hx -- out of bounds\n", name, index); 587 return; 588 } 589 590 if (probe_kernel_read(&desc, (void *)(gdt->address + offset), 591 sizeof(struct ldttss_desc))) { 592 pr_alert("%s: 0x%hx -- GDT entry is not readable\n", 593 name, index); 594 return; 595 } 596 597 addr = desc.base0 | (desc.base1 << 16) | ((unsigned long)desc.base2 << 24); 598 #ifdef CONFIG_X86_64 599 addr |= ((u64)desc.base3 << 32); 600 #endif 601 pr_alert("%s: 0x%hx -- base=0x%lx limit=0x%x\n", 602 name, index, addr, (desc.limit0 | (desc.limit1 << 16))); 603 } 604 605 static void 606 show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long address) 607 { 608 if (!oops_may_print()) 609 return; 610 611 if (error_code & X86_PF_INSTR) { 612 unsigned int level; 613 pgd_t *pgd; 614 pte_t *pte; 615 616 pgd = __va(read_cr3_pa()); 617 pgd += pgd_index(address); 618 619 pte = lookup_address_in_pgd(pgd, address, &level); 620 621 if (pte && pte_present(*pte) && !pte_exec(*pte)) 622 pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", 623 from_kuid(&init_user_ns, current_uid())); 624 if (pte && pte_present(*pte) && pte_exec(*pte) && 625 (pgd_flags(*pgd) & _PAGE_USER) && 626 (__read_cr4() & X86_CR4_SMEP)) 627 pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n", 628 from_kuid(&init_user_ns, current_uid())); 629 } 630 631 if (address < PAGE_SIZE && !user_mode(regs)) 632 pr_alert("BUG: kernel NULL pointer dereference, address: %px\n", 633 (void *)address); 634 else 635 pr_alert("BUG: unable to handle page fault for address: %px\n", 636 (void *)address); 637 638 pr_alert("#PF: %s %s in %s mode\n", 639 (error_code & X86_PF_USER) ? "user" : "supervisor", 640 (error_code & X86_PF_INSTR) ? "instruction fetch" : 641 (error_code & X86_PF_WRITE) ? "write access" : 642 "read access", 643 user_mode(regs) ? "user" : "kernel"); 644 pr_alert("#PF: error_code(0x%04lx) - %s\n", error_code, 645 !(error_code & X86_PF_PROT) ? "not-present page" : 646 (error_code & X86_PF_RSVD) ? "reserved bit violation" : 647 (error_code & X86_PF_PK) ? "protection keys violation" : 648 "permissions violation"); 649 650 if (!(error_code & X86_PF_USER) && user_mode(regs)) { 651 struct desc_ptr idt, gdt; 652 u16 ldtr, tr; 653 654 /* 655 * This can happen for quite a few reasons. The more obvious 656 * ones are faults accessing the GDT, or LDT. Perhaps 657 * surprisingly, if the CPU tries to deliver a benign or 658 * contributory exception from user code and gets a page fault 659 * during delivery, the page fault can be delivered as though 660 * it originated directly from user code. This could happen 661 * due to wrong permissions on the IDT, GDT, LDT, TSS, or 662 * kernel or IST stack. 663 */ 664 store_idt(&idt); 665 666 /* Usable even on Xen PV -- it's just slow. */ 667 native_store_gdt(&gdt); 668 669 pr_alert("IDT: 0x%lx (limit=0x%hx) GDT: 0x%lx (limit=0x%hx)\n", 670 idt.address, idt.size, gdt.address, gdt.size); 671 672 store_ldt(ldtr); 673 show_ldttss(&gdt, "LDTR", ldtr); 674 675 store_tr(tr); 676 show_ldttss(&gdt, "TR", tr); 677 } 678 679 dump_pagetable(address); 680 } 681 682 static noinline void 683 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 684 unsigned long address) 685 { 686 struct task_struct *tsk; 687 unsigned long flags; 688 int sig; 689 690 flags = oops_begin(); 691 tsk = current; 692 sig = SIGKILL; 693 694 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 695 tsk->comm, address); 696 dump_pagetable(address); 697 698 if (__die("Bad pagetable", regs, error_code)) 699 sig = 0; 700 701 oops_end(flags, regs, sig); 702 } 703 704 static void set_signal_archinfo(unsigned long address, 705 unsigned long error_code) 706 { 707 struct task_struct *tsk = current; 708 709 /* 710 * To avoid leaking information about the kernel page 711 * table layout, pretend that user-mode accesses to 712 * kernel addresses are always protection faults. 713 */ 714 if (address >= TASK_SIZE_MAX) 715 error_code |= X86_PF_PROT; 716 717 tsk->thread.trap_nr = X86_TRAP_PF; 718 tsk->thread.error_code = error_code | X86_PF_USER; 719 tsk->thread.cr2 = address; 720 } 721 722 static noinline void 723 no_context(struct pt_regs *regs, unsigned long error_code, 724 unsigned long address, int signal, int si_code) 725 { 726 struct task_struct *tsk = current; 727 unsigned long flags; 728 int sig; 729 730 if (user_mode(regs)) { 731 /* 732 * This is an implicit supervisor-mode access from user 733 * mode. Bypass all the kernel-mode recovery code and just 734 * OOPS. 735 */ 736 goto oops; 737 } 738 739 /* Are we prepared to handle this kernel fault? */ 740 if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { 741 /* 742 * Any interrupt that takes a fault gets the fixup. This makes 743 * the below recursive fault logic only apply to a faults from 744 * task context. 745 */ 746 if (in_interrupt()) 747 return; 748 749 /* 750 * Per the above we're !in_interrupt(), aka. task context. 751 * 752 * In this case we need to make sure we're not recursively 753 * faulting through the emulate_vsyscall() logic. 754 */ 755 if (current->thread.sig_on_uaccess_err && signal) { 756 set_signal_archinfo(address, error_code); 757 758 /* XXX: hwpoison faults will set the wrong code. */ 759 force_sig_fault(signal, si_code, (void __user *)address, 760 tsk); 761 } 762 763 /* 764 * Barring that, we can do the fixup and be happy. 765 */ 766 return; 767 } 768 769 #ifdef CONFIG_VMAP_STACK 770 /* 771 * Stack overflow? During boot, we can fault near the initial 772 * stack in the direct map, but that's not an overflow -- check 773 * that we're in vmalloc space to avoid this. 774 */ 775 if (is_vmalloc_addr((void *)address) && 776 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 777 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 778 unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *); 779 /* 780 * We're likely to be running with very little stack space 781 * left. It's plausible that we'd hit this condition but 782 * double-fault even before we get this far, in which case 783 * we're fine: the double-fault handler will deal with it. 784 * 785 * We don't want to make it all the way into the oops code 786 * and then double-fault, though, because we're likely to 787 * break the console driver and lose most of the stack dump. 788 */ 789 asm volatile ("movq %[stack], %%rsp\n\t" 790 "call handle_stack_overflow\n\t" 791 "1: jmp 1b" 792 : ASM_CALL_CONSTRAINT 793 : "D" ("kernel stack overflow (page fault)"), 794 "S" (regs), "d" (address), 795 [stack] "rm" (stack)); 796 unreachable(); 797 } 798 #endif 799 800 /* 801 * 32-bit: 802 * 803 * Valid to do another page fault here, because if this fault 804 * had been triggered by is_prefetch fixup_exception would have 805 * handled it. 806 * 807 * 64-bit: 808 * 809 * Hall of shame of CPU/BIOS bugs. 810 */ 811 if (is_prefetch(regs, error_code, address)) 812 return; 813 814 if (is_errata93(regs, address)) 815 return; 816 817 /* 818 * Buggy firmware could access regions which might page fault, try to 819 * recover from such faults. 820 */ 821 if (IS_ENABLED(CONFIG_EFI)) 822 efi_recover_from_page_fault(address); 823 824 oops: 825 /* 826 * Oops. The kernel tried to access some bad page. We'll have to 827 * terminate things with extreme prejudice: 828 */ 829 flags = oops_begin(); 830 831 show_fault_oops(regs, error_code, address); 832 833 if (task_stack_end_corrupted(tsk)) 834 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 835 836 sig = SIGKILL; 837 if (__die("Oops", regs, error_code)) 838 sig = 0; 839 840 /* Executive summary in case the body of the oops scrolled away */ 841 printk(KERN_DEFAULT "CR2: %016lx\n", address); 842 843 oops_end(flags, regs, sig); 844 } 845 846 /* 847 * Print out info about fatal segfaults, if the show_unhandled_signals 848 * sysctl is set: 849 */ 850 static inline void 851 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 852 unsigned long address, struct task_struct *tsk) 853 { 854 const char *loglvl = task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG; 855 856 if (!unhandled_signal(tsk, SIGSEGV)) 857 return; 858 859 if (!printk_ratelimit()) 860 return; 861 862 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 863 loglvl, tsk->comm, task_pid_nr(tsk), address, 864 (void *)regs->ip, (void *)regs->sp, error_code); 865 866 print_vma_addr(KERN_CONT " in ", regs->ip); 867 868 printk(KERN_CONT "\n"); 869 870 show_opcodes(regs, loglvl); 871 } 872 873 /* 874 * The (legacy) vsyscall page is the long page in the kernel portion 875 * of the address space that has user-accessible permissions. 876 */ 877 static bool is_vsyscall_vaddr(unsigned long vaddr) 878 { 879 return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR); 880 } 881 882 static void 883 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 884 unsigned long address, u32 pkey, int si_code) 885 { 886 struct task_struct *tsk = current; 887 888 /* User mode accesses just cause a SIGSEGV */ 889 if (user_mode(regs) && (error_code & X86_PF_USER)) { 890 /* 891 * It's possible to have interrupts off here: 892 */ 893 local_irq_enable(); 894 895 /* 896 * Valid to do another page fault here because this one came 897 * from user space: 898 */ 899 if (is_prefetch(regs, error_code, address)) 900 return; 901 902 if (is_errata100(regs, address)) 903 return; 904 905 /* 906 * To avoid leaking information about the kernel page table 907 * layout, pretend that user-mode accesses to kernel addresses 908 * are always protection faults. 909 */ 910 if (address >= TASK_SIZE_MAX) 911 error_code |= X86_PF_PROT; 912 913 if (likely(show_unhandled_signals)) 914 show_signal_msg(regs, error_code, address, tsk); 915 916 set_signal_archinfo(address, error_code); 917 918 if (si_code == SEGV_PKUERR) 919 force_sig_pkuerr((void __user *)address, pkey); 920 921 force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk); 922 923 return; 924 } 925 926 if (is_f00f_bug(regs, address)) 927 return; 928 929 no_context(regs, error_code, address, SIGSEGV, si_code); 930 } 931 932 static noinline void 933 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 934 unsigned long address) 935 { 936 __bad_area_nosemaphore(regs, error_code, address, 0, SEGV_MAPERR); 937 } 938 939 static void 940 __bad_area(struct pt_regs *regs, unsigned long error_code, 941 unsigned long address, u32 pkey, int si_code) 942 { 943 struct mm_struct *mm = current->mm; 944 /* 945 * Something tried to access memory that isn't in our memory map.. 946 * Fix it, but check if it's kernel or user first.. 947 */ 948 up_read(&mm->mmap_sem); 949 950 __bad_area_nosemaphore(regs, error_code, address, pkey, si_code); 951 } 952 953 static noinline void 954 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 955 { 956 __bad_area(regs, error_code, address, 0, SEGV_MAPERR); 957 } 958 959 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 960 struct vm_area_struct *vma) 961 { 962 /* This code is always called on the current mm */ 963 bool foreign = false; 964 965 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 966 return false; 967 if (error_code & X86_PF_PK) 968 return true; 969 /* this checks permission keys on the VMA: */ 970 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 971 (error_code & X86_PF_INSTR), foreign)) 972 return true; 973 return false; 974 } 975 976 static noinline void 977 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 978 unsigned long address, struct vm_area_struct *vma) 979 { 980 /* 981 * This OSPKE check is not strictly necessary at runtime. 982 * But, doing it this way allows compiler optimizations 983 * if pkeys are compiled out. 984 */ 985 if (bad_area_access_from_pkeys(error_code, vma)) { 986 /* 987 * A protection key fault means that the PKRU value did not allow 988 * access to some PTE. Userspace can figure out what PKRU was 989 * from the XSAVE state. This function captures the pkey from 990 * the vma and passes it to userspace so userspace can discover 991 * which protection key was set on the PTE. 992 * 993 * If we get here, we know that the hardware signaled a X86_PF_PK 994 * fault and that there was a VMA once we got in the fault 995 * handler. It does *not* guarantee that the VMA we find here 996 * was the one that we faulted on. 997 * 998 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 999 * 2. T1 : set PKRU to deny access to pkey=4, touches page 1000 * 3. T1 : faults... 1001 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 1002 * 5. T1 : enters fault handler, takes mmap_sem, etc... 1003 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 1004 * faulted on a pte with its pkey=4. 1005 */ 1006 u32 pkey = vma_pkey(vma); 1007 1008 __bad_area(regs, error_code, address, pkey, SEGV_PKUERR); 1009 } else { 1010 __bad_area(regs, error_code, address, 0, SEGV_ACCERR); 1011 } 1012 } 1013 1014 static void 1015 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 1016 vm_fault_t fault) 1017 { 1018 struct task_struct *tsk = current; 1019 1020 /* Kernel mode? Handle exceptions or die: */ 1021 if (!(error_code & X86_PF_USER)) { 1022 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 1023 return; 1024 } 1025 1026 /* User-space => ok to do another page fault: */ 1027 if (is_prefetch(regs, error_code, address)) 1028 return; 1029 1030 set_signal_archinfo(address, error_code); 1031 1032 #ifdef CONFIG_MEMORY_FAILURE 1033 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 1034 unsigned lsb = 0; 1035 1036 pr_err( 1037 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 1038 tsk->comm, tsk->pid, address); 1039 if (fault & VM_FAULT_HWPOISON_LARGE) 1040 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 1041 if (fault & VM_FAULT_HWPOISON) 1042 lsb = PAGE_SHIFT; 1043 force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb, tsk); 1044 return; 1045 } 1046 #endif 1047 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk); 1048 } 1049 1050 static noinline void 1051 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 1052 unsigned long address, vm_fault_t fault) 1053 { 1054 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) { 1055 no_context(regs, error_code, address, 0, 0); 1056 return; 1057 } 1058 1059 if (fault & VM_FAULT_OOM) { 1060 /* Kernel mode? Handle exceptions or die: */ 1061 if (!(error_code & X86_PF_USER)) { 1062 no_context(regs, error_code, address, 1063 SIGSEGV, SEGV_MAPERR); 1064 return; 1065 } 1066 1067 /* 1068 * We ran out of memory, call the OOM killer, and return the 1069 * userspace (which will retry the fault, or kill us if we got 1070 * oom-killed): 1071 */ 1072 pagefault_out_of_memory(); 1073 } else { 1074 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1075 VM_FAULT_HWPOISON_LARGE)) 1076 do_sigbus(regs, error_code, address, fault); 1077 else if (fault & VM_FAULT_SIGSEGV) 1078 bad_area_nosemaphore(regs, error_code, address); 1079 else 1080 BUG(); 1081 } 1082 } 1083 1084 static int spurious_kernel_fault_check(unsigned long error_code, pte_t *pte) 1085 { 1086 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 1087 return 0; 1088 1089 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 1090 return 0; 1091 1092 return 1; 1093 } 1094 1095 /* 1096 * Handle a spurious fault caused by a stale TLB entry. 1097 * 1098 * This allows us to lazily refresh the TLB when increasing the 1099 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1100 * eagerly is very expensive since that implies doing a full 1101 * cross-processor TLB flush, even if no stale TLB entries exist 1102 * on other processors. 1103 * 1104 * Spurious faults may only occur if the TLB contains an entry with 1105 * fewer permission than the page table entry. Non-present (P = 0) 1106 * and reserved bit (R = 1) faults are never spurious. 1107 * 1108 * There are no security implications to leaving a stale TLB when 1109 * increasing the permissions on a page. 1110 * 1111 * Returns non-zero if a spurious fault was handled, zero otherwise. 1112 * 1113 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1114 * (Optional Invalidation). 1115 */ 1116 static noinline int 1117 spurious_kernel_fault(unsigned long error_code, unsigned long address) 1118 { 1119 pgd_t *pgd; 1120 p4d_t *p4d; 1121 pud_t *pud; 1122 pmd_t *pmd; 1123 pte_t *pte; 1124 int ret; 1125 1126 /* 1127 * Only writes to RO or instruction fetches from NX may cause 1128 * spurious faults. 1129 * 1130 * These could be from user or supervisor accesses but the TLB 1131 * is only lazily flushed after a kernel mapping protection 1132 * change, so user accesses are not expected to cause spurious 1133 * faults. 1134 */ 1135 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1136 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1137 return 0; 1138 1139 pgd = init_mm.pgd + pgd_index(address); 1140 if (!pgd_present(*pgd)) 1141 return 0; 1142 1143 p4d = p4d_offset(pgd, address); 1144 if (!p4d_present(*p4d)) 1145 return 0; 1146 1147 if (p4d_large(*p4d)) 1148 return spurious_kernel_fault_check(error_code, (pte_t *) p4d); 1149 1150 pud = pud_offset(p4d, address); 1151 if (!pud_present(*pud)) 1152 return 0; 1153 1154 if (pud_large(*pud)) 1155 return spurious_kernel_fault_check(error_code, (pte_t *) pud); 1156 1157 pmd = pmd_offset(pud, address); 1158 if (!pmd_present(*pmd)) 1159 return 0; 1160 1161 if (pmd_large(*pmd)) 1162 return spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1163 1164 pte = pte_offset_kernel(pmd, address); 1165 if (!pte_present(*pte)) 1166 return 0; 1167 1168 ret = spurious_kernel_fault_check(error_code, pte); 1169 if (!ret) 1170 return 0; 1171 1172 /* 1173 * Make sure we have permissions in PMD. 1174 * If not, then there's a bug in the page tables: 1175 */ 1176 ret = spurious_kernel_fault_check(error_code, (pte_t *) pmd); 1177 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1178 1179 return ret; 1180 } 1181 NOKPROBE_SYMBOL(spurious_kernel_fault); 1182 1183 int show_unhandled_signals = 1; 1184 1185 static inline int 1186 access_error(unsigned long error_code, struct vm_area_struct *vma) 1187 { 1188 /* This is only called for the current mm, so: */ 1189 bool foreign = false; 1190 1191 /* 1192 * Read or write was blocked by protection keys. This is 1193 * always an unconditional error and can never result in 1194 * a follow-up action to resolve the fault, like a COW. 1195 */ 1196 if (error_code & X86_PF_PK) 1197 return 1; 1198 1199 /* 1200 * Make sure to check the VMA so that we do not perform 1201 * faults just to hit a X86_PF_PK as soon as we fill in a 1202 * page. 1203 */ 1204 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1205 (error_code & X86_PF_INSTR), foreign)) 1206 return 1; 1207 1208 if (error_code & X86_PF_WRITE) { 1209 /* write, present and write, not present: */ 1210 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1211 return 1; 1212 return 0; 1213 } 1214 1215 /* read, present: */ 1216 if (unlikely(error_code & X86_PF_PROT)) 1217 return 1; 1218 1219 /* read, not present: */ 1220 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 1221 return 1; 1222 1223 return 0; 1224 } 1225 1226 static int fault_in_kernel_space(unsigned long address) 1227 { 1228 /* 1229 * On 64-bit systems, the vsyscall page is at an address above 1230 * TASK_SIZE_MAX, but is not considered part of the kernel 1231 * address space. 1232 */ 1233 if (IS_ENABLED(CONFIG_X86_64) && is_vsyscall_vaddr(address)) 1234 return false; 1235 1236 return address >= TASK_SIZE_MAX; 1237 } 1238 1239 /* 1240 * Called for all faults where 'address' is part of the kernel address 1241 * space. Might get called for faults that originate from *code* that 1242 * ran in userspace or the kernel. 1243 */ 1244 static void 1245 do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code, 1246 unsigned long address) 1247 { 1248 /* 1249 * Protection keys exceptions only happen on user pages. We 1250 * have no user pages in the kernel portion of the address 1251 * space, so do not expect them here. 1252 */ 1253 WARN_ON_ONCE(hw_error_code & X86_PF_PK); 1254 1255 /* 1256 * We can fault-in kernel-space virtual memory on-demand. The 1257 * 'reference' page table is init_mm.pgd. 1258 * 1259 * NOTE! We MUST NOT take any locks for this case. We may 1260 * be in an interrupt or a critical region, and should 1261 * only copy the information from the master page table, 1262 * nothing more. 1263 * 1264 * Before doing this on-demand faulting, ensure that the 1265 * fault is not any of the following: 1266 * 1. A fault on a PTE with a reserved bit set. 1267 * 2. A fault caused by a user-mode access. (Do not demand- 1268 * fault kernel memory due to user-mode accesses). 1269 * 3. A fault caused by a page-level protection violation. 1270 * (A demand fault would be on a non-present page which 1271 * would have X86_PF_PROT==0). 1272 */ 1273 if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1274 if (vmalloc_fault(address) >= 0) 1275 return; 1276 } 1277 1278 /* Was the fault spurious, caused by lazy TLB invalidation? */ 1279 if (spurious_kernel_fault(hw_error_code, address)) 1280 return; 1281 1282 /* kprobes don't want to hook the spurious faults: */ 1283 if (kprobes_fault(regs)) 1284 return; 1285 1286 /* 1287 * Note, despite being a "bad area", there are quite a few 1288 * acceptable reasons to get here, such as erratum fixups 1289 * and handling kernel code that can fault, like get_user(). 1290 * 1291 * Don't take the mm semaphore here. If we fixup a prefetch 1292 * fault we could otherwise deadlock: 1293 */ 1294 bad_area_nosemaphore(regs, hw_error_code, address); 1295 } 1296 NOKPROBE_SYMBOL(do_kern_addr_fault); 1297 1298 /* Handle faults in the user portion of the address space */ 1299 static inline 1300 void do_user_addr_fault(struct pt_regs *regs, 1301 unsigned long hw_error_code, 1302 unsigned long address) 1303 { 1304 struct vm_area_struct *vma; 1305 struct task_struct *tsk; 1306 struct mm_struct *mm; 1307 vm_fault_t fault, major = 0; 1308 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 1309 1310 tsk = current; 1311 mm = tsk->mm; 1312 1313 /* kprobes don't want to hook the spurious faults: */ 1314 if (unlikely(kprobes_fault(regs))) 1315 return; 1316 1317 /* 1318 * Reserved bits are never expected to be set on 1319 * entries in the user portion of the page tables. 1320 */ 1321 if (unlikely(hw_error_code & X86_PF_RSVD)) 1322 pgtable_bad(regs, hw_error_code, address); 1323 1324 /* 1325 * If SMAP is on, check for invalid kernel (supervisor) access to user 1326 * pages in the user address space. The odd case here is WRUSS, 1327 * which, according to the preliminary documentation, does not respect 1328 * SMAP and will have the USER bit set so, in all cases, SMAP 1329 * enforcement appears to be consistent with the USER bit. 1330 */ 1331 if (unlikely(cpu_feature_enabled(X86_FEATURE_SMAP) && 1332 !(hw_error_code & X86_PF_USER) && 1333 !(regs->flags & X86_EFLAGS_AC))) 1334 { 1335 bad_area_nosemaphore(regs, hw_error_code, address); 1336 return; 1337 } 1338 1339 /* 1340 * If we're in an interrupt, have no user context or are running 1341 * in a region with pagefaults disabled then we must not take the fault 1342 */ 1343 if (unlikely(faulthandler_disabled() || !mm)) { 1344 bad_area_nosemaphore(regs, hw_error_code, address); 1345 return; 1346 } 1347 1348 /* 1349 * It's safe to allow irq's after cr2 has been saved and the 1350 * vmalloc fault has been handled. 1351 * 1352 * User-mode registers count as a user access even for any 1353 * potential system fault or CPU buglet: 1354 */ 1355 if (user_mode(regs)) { 1356 local_irq_enable(); 1357 flags |= FAULT_FLAG_USER; 1358 } else { 1359 if (regs->flags & X86_EFLAGS_IF) 1360 local_irq_enable(); 1361 } 1362 1363 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1364 1365 if (hw_error_code & X86_PF_WRITE) 1366 flags |= FAULT_FLAG_WRITE; 1367 if (hw_error_code & X86_PF_INSTR) 1368 flags |= FAULT_FLAG_INSTRUCTION; 1369 1370 #ifdef CONFIG_X86_64 1371 /* 1372 * Instruction fetch faults in the vsyscall page might need 1373 * emulation. The vsyscall page is at a high address 1374 * (>PAGE_OFFSET), but is considered to be part of the user 1375 * address space. 1376 * 1377 * The vsyscall page does not have a "real" VMA, so do this 1378 * emulation before we go searching for VMAs. 1379 */ 1380 if ((hw_error_code & X86_PF_INSTR) && is_vsyscall_vaddr(address)) { 1381 if (emulate_vsyscall(regs, address)) 1382 return; 1383 } 1384 #endif 1385 1386 /* 1387 * Kernel-mode access to the user address space should only occur 1388 * on well-defined single instructions listed in the exception 1389 * tables. But, an erroneous kernel fault occurring outside one of 1390 * those areas which also holds mmap_sem might deadlock attempting 1391 * to validate the fault against the address space. 1392 * 1393 * Only do the expensive exception table search when we might be at 1394 * risk of a deadlock. This happens if we 1395 * 1. Failed to acquire mmap_sem, and 1396 * 2. The access did not originate in userspace. 1397 */ 1398 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1399 if (!user_mode(regs) && !search_exception_tables(regs->ip)) { 1400 /* 1401 * Fault from code in kernel from 1402 * which we do not expect faults. 1403 */ 1404 bad_area_nosemaphore(regs, hw_error_code, address); 1405 return; 1406 } 1407 retry: 1408 down_read(&mm->mmap_sem); 1409 } else { 1410 /* 1411 * The above down_read_trylock() might have succeeded in 1412 * which case we'll have missed the might_sleep() from 1413 * down_read(): 1414 */ 1415 might_sleep(); 1416 } 1417 1418 vma = find_vma(mm, address); 1419 if (unlikely(!vma)) { 1420 bad_area(regs, hw_error_code, address); 1421 return; 1422 } 1423 if (likely(vma->vm_start <= address)) 1424 goto good_area; 1425 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1426 bad_area(regs, hw_error_code, address); 1427 return; 1428 } 1429 if (unlikely(expand_stack(vma, address))) { 1430 bad_area(regs, hw_error_code, address); 1431 return; 1432 } 1433 1434 /* 1435 * Ok, we have a good vm_area for this memory access, so 1436 * we can handle it.. 1437 */ 1438 good_area: 1439 if (unlikely(access_error(hw_error_code, vma))) { 1440 bad_area_access_error(regs, hw_error_code, address, vma); 1441 return; 1442 } 1443 1444 /* 1445 * If for any reason at all we couldn't handle the fault, 1446 * make sure we exit gracefully rather than endlessly redo 1447 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1448 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. 1449 * 1450 * Note that handle_userfault() may also release and reacquire mmap_sem 1451 * (and not return with VM_FAULT_RETRY), when returning to userland to 1452 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1453 * (potentially after handling any pending signal during the return to 1454 * userland). The return to userland is identified whenever 1455 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1456 */ 1457 fault = handle_mm_fault(vma, address, flags); 1458 major |= fault & VM_FAULT_MAJOR; 1459 1460 /* 1461 * If we need to retry the mmap_sem has already been released, 1462 * and if there is a fatal signal pending there is no guarantee 1463 * that we made any progress. Handle this case first. 1464 */ 1465 if (unlikely(fault & VM_FAULT_RETRY)) { 1466 /* Retry at most once */ 1467 if (flags & FAULT_FLAG_ALLOW_RETRY) { 1468 flags &= ~FAULT_FLAG_ALLOW_RETRY; 1469 flags |= FAULT_FLAG_TRIED; 1470 if (!fatal_signal_pending(tsk)) 1471 goto retry; 1472 } 1473 1474 /* User mode? Just return to handle the fatal exception */ 1475 if (flags & FAULT_FLAG_USER) 1476 return; 1477 1478 /* Not returning to user mode? Handle exceptions or die: */ 1479 no_context(regs, hw_error_code, address, SIGBUS, BUS_ADRERR); 1480 return; 1481 } 1482 1483 up_read(&mm->mmap_sem); 1484 if (unlikely(fault & VM_FAULT_ERROR)) { 1485 mm_fault_error(regs, hw_error_code, address, fault); 1486 return; 1487 } 1488 1489 /* 1490 * Major/minor page fault accounting. If any of the events 1491 * returned VM_FAULT_MAJOR, we account it as a major fault. 1492 */ 1493 if (major) { 1494 tsk->maj_flt++; 1495 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 1496 } else { 1497 tsk->min_flt++; 1498 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 1499 } 1500 1501 check_v8086_mode(regs, address, tsk); 1502 } 1503 NOKPROBE_SYMBOL(do_user_addr_fault); 1504 1505 /* 1506 * This routine handles page faults. It determines the address, 1507 * and the problem, and then passes it off to one of the appropriate 1508 * routines. 1509 */ 1510 static noinline void 1511 __do_page_fault(struct pt_regs *regs, unsigned long hw_error_code, 1512 unsigned long address) 1513 { 1514 prefetchw(¤t->mm->mmap_sem); 1515 1516 if (unlikely(kmmio_fault(regs, address))) 1517 return; 1518 1519 /* Was the fault on kernel-controlled part of the address space? */ 1520 if (unlikely(fault_in_kernel_space(address))) 1521 do_kern_addr_fault(regs, hw_error_code, address); 1522 else 1523 do_user_addr_fault(regs, hw_error_code, address); 1524 } 1525 NOKPROBE_SYMBOL(__do_page_fault); 1526 1527 static nokprobe_inline void 1528 trace_page_fault_entries(unsigned long address, struct pt_regs *regs, 1529 unsigned long error_code) 1530 { 1531 if (user_mode(regs)) 1532 trace_page_fault_user(address, regs, error_code); 1533 else 1534 trace_page_fault_kernel(address, regs, error_code); 1535 } 1536 1537 /* 1538 * We must have this function blacklisted from kprobes, tagged with notrace 1539 * and call read_cr2() before calling anything else. To avoid calling any 1540 * kind of tracing machinery before we've observed the CR2 value. 1541 * 1542 * exception_{enter,exit}() contains all sorts of tracepoints. 1543 */ 1544 dotraplinkage void notrace 1545 do_page_fault(struct pt_regs *regs, unsigned long error_code) 1546 { 1547 unsigned long address = read_cr2(); /* Get the faulting address */ 1548 enum ctx_state prev_state; 1549 1550 prev_state = exception_enter(); 1551 if (trace_pagefault_enabled()) 1552 trace_page_fault_entries(address, regs, error_code); 1553 1554 __do_page_fault(regs, error_code, address); 1555 exception_exit(prev_state); 1556 } 1557 NOKPROBE_SYMBOL(do_page_fault); 1558