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