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/bootmem.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 20 #include <asm/cpufeature.h> /* boot_cpu_has, ... */ 21 #include <asm/traps.h> /* dotraplinkage, ... */ 22 #include <asm/pgalloc.h> /* pgd_*(), ... */ 23 #include <asm/fixmap.h> /* VSYSCALL_ADDR */ 24 #include <asm/vsyscall.h> /* emulate_vsyscall */ 25 #include <asm/vm86.h> /* struct vm86 */ 26 #include <asm/mmu_context.h> /* vma_pkey() */ 27 28 #define CREATE_TRACE_POINTS 29 #include <asm/trace/exceptions.h> 30 31 /* 32 * Returns 0 if mmiotrace is disabled, or if the fault is not 33 * handled by mmiotrace: 34 */ 35 static nokprobe_inline int 36 kmmio_fault(struct pt_regs *regs, unsigned long addr) 37 { 38 if (unlikely(is_kmmio_active())) 39 if (kmmio_handler(regs, addr) == 1) 40 return -1; 41 return 0; 42 } 43 44 static nokprobe_inline int kprobes_fault(struct pt_regs *regs) 45 { 46 int ret = 0; 47 48 /* kprobe_running() needs smp_processor_id() */ 49 if (kprobes_built_in() && !user_mode(regs)) { 50 preempt_disable(); 51 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 52 ret = 1; 53 preempt_enable(); 54 } 55 56 return ret; 57 } 58 59 /* 60 * Prefetch quirks: 61 * 62 * 32-bit mode: 63 * 64 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 65 * Check that here and ignore it. 66 * 67 * 64-bit mode: 68 * 69 * Sometimes the CPU reports invalid exceptions on prefetch. 70 * Check that here and ignore it. 71 * 72 * Opcode checker based on code by Richard Brunner. 73 */ 74 static inline int 75 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 76 unsigned char opcode, int *prefetch) 77 { 78 unsigned char instr_hi = opcode & 0xf0; 79 unsigned char instr_lo = opcode & 0x0f; 80 81 switch (instr_hi) { 82 case 0x20: 83 case 0x30: 84 /* 85 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 86 * In X86_64 long mode, the CPU will signal invalid 87 * opcode if some of these prefixes are present so 88 * X86_64 will never get here anyway 89 */ 90 return ((instr_lo & 7) == 0x6); 91 #ifdef CONFIG_X86_64 92 case 0x40: 93 /* 94 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 95 * Need to figure out under what instruction mode the 96 * instruction was issued. Could check the LDT for lm, 97 * but for now it's good enough to assume that long 98 * mode only uses well known segments or kernel. 99 */ 100 return (!user_mode(regs) || user_64bit_mode(regs)); 101 #endif 102 case 0x60: 103 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 104 return (instr_lo & 0xC) == 0x4; 105 case 0xF0: 106 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 107 return !instr_lo || (instr_lo>>1) == 1; 108 case 0x00: 109 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 110 if (probe_kernel_address(instr, opcode)) 111 return 0; 112 113 *prefetch = (instr_lo == 0xF) && 114 (opcode == 0x0D || opcode == 0x18); 115 return 0; 116 default: 117 return 0; 118 } 119 } 120 121 static int 122 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 123 { 124 unsigned char *max_instr; 125 unsigned char *instr; 126 int prefetch = 0; 127 128 /* 129 * If it was a exec (instruction fetch) fault on NX page, then 130 * do not ignore the fault: 131 */ 132 if (error_code & X86_PF_INSTR) 133 return 0; 134 135 instr = (void *)convert_ip_to_linear(current, regs); 136 max_instr = instr + 15; 137 138 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) 139 return 0; 140 141 while (instr < max_instr) { 142 unsigned char opcode; 143 144 if (probe_kernel_address(instr, opcode)) 145 break; 146 147 instr++; 148 149 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 150 break; 151 } 152 return prefetch; 153 } 154 155 /* 156 * A protection key fault means that the PKRU value did not allow 157 * access to some PTE. Userspace can figure out what PKRU was 158 * from the XSAVE state, and this function fills out a field in 159 * siginfo so userspace can discover which protection key was set 160 * on the PTE. 161 * 162 * If we get here, we know that the hardware signaled a X86_PF_PK 163 * fault and that there was a VMA once we got in the fault 164 * handler. It does *not* guarantee that the VMA we find here 165 * was the one that we faulted on. 166 * 167 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 168 * 2. T1 : set PKRU to deny access to pkey=4, touches page 169 * 3. T1 : faults... 170 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 171 * 5. T1 : enters fault handler, takes mmap_sem, etc... 172 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 173 * faulted on a pte with its pkey=4. 174 */ 175 static void fill_sig_info_pkey(int si_signo, int si_code, siginfo_t *info, 176 u32 *pkey) 177 { 178 /* This is effectively an #ifdef */ 179 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 180 return; 181 182 /* Fault not from Protection Keys: nothing to do */ 183 if ((si_code != SEGV_PKUERR) || (si_signo != SIGSEGV)) 184 return; 185 /* 186 * force_sig_info_fault() is called from a number of 187 * contexts, some of which have a VMA and some of which 188 * do not. The X86_PF_PK handing happens after we have a 189 * valid VMA, so we should never reach this without a 190 * valid VMA. 191 */ 192 if (!pkey) { 193 WARN_ONCE(1, "PKU fault with no VMA passed in"); 194 info->si_pkey = 0; 195 return; 196 } 197 /* 198 * si_pkey should be thought of as a strong hint, but not 199 * absolutely guranteed to be 100% accurate because of 200 * the race explained above. 201 */ 202 info->si_pkey = *pkey; 203 } 204 205 static void 206 force_sig_info_fault(int si_signo, int si_code, unsigned long address, 207 struct task_struct *tsk, u32 *pkey, int fault) 208 { 209 unsigned lsb = 0; 210 siginfo_t info; 211 212 info.si_signo = si_signo; 213 info.si_errno = 0; 214 info.si_code = si_code; 215 info.si_addr = (void __user *)address; 216 if (fault & VM_FAULT_HWPOISON_LARGE) 217 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 218 if (fault & VM_FAULT_HWPOISON) 219 lsb = PAGE_SHIFT; 220 info.si_addr_lsb = lsb; 221 222 fill_sig_info_pkey(si_signo, si_code, &info, pkey); 223 224 force_sig_info(si_signo, &info, tsk); 225 } 226 227 DEFINE_SPINLOCK(pgd_lock); 228 LIST_HEAD(pgd_list); 229 230 #ifdef CONFIG_X86_32 231 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 232 { 233 unsigned index = pgd_index(address); 234 pgd_t *pgd_k; 235 p4d_t *p4d, *p4d_k; 236 pud_t *pud, *pud_k; 237 pmd_t *pmd, *pmd_k; 238 239 pgd += index; 240 pgd_k = init_mm.pgd + index; 241 242 if (!pgd_present(*pgd_k)) 243 return NULL; 244 245 /* 246 * set_pgd(pgd, *pgd_k); here would be useless on PAE 247 * and redundant with the set_pmd() on non-PAE. As would 248 * set_p4d/set_pud. 249 */ 250 p4d = p4d_offset(pgd, address); 251 p4d_k = p4d_offset(pgd_k, address); 252 if (!p4d_present(*p4d_k)) 253 return NULL; 254 255 pud = pud_offset(p4d, address); 256 pud_k = pud_offset(p4d_k, address); 257 if (!pud_present(*pud_k)) 258 return NULL; 259 260 pmd = pmd_offset(pud, address); 261 pmd_k = pmd_offset(pud_k, address); 262 if (!pmd_present(*pmd_k)) 263 return NULL; 264 265 if (!pmd_present(*pmd)) 266 set_pmd(pmd, *pmd_k); 267 else 268 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 269 270 return pmd_k; 271 } 272 273 void vmalloc_sync_all(void) 274 { 275 unsigned long address; 276 277 if (SHARED_KERNEL_PMD) 278 return; 279 280 for (address = VMALLOC_START & PMD_MASK; 281 address >= TASK_SIZE_MAX && address < FIXADDR_TOP; 282 address += PMD_SIZE) { 283 struct page *page; 284 285 spin_lock(&pgd_lock); 286 list_for_each_entry(page, &pgd_list, lru) { 287 spinlock_t *pgt_lock; 288 pmd_t *ret; 289 290 /* the pgt_lock only for Xen */ 291 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 292 293 spin_lock(pgt_lock); 294 ret = vmalloc_sync_one(page_address(page), address); 295 spin_unlock(pgt_lock); 296 297 if (!ret) 298 break; 299 } 300 spin_unlock(&pgd_lock); 301 } 302 } 303 304 /* 305 * 32-bit: 306 * 307 * Handle a fault on the vmalloc or module mapping area 308 */ 309 static noinline int vmalloc_fault(unsigned long address) 310 { 311 unsigned long pgd_paddr; 312 pmd_t *pmd_k; 313 pte_t *pte_k; 314 315 /* Make sure we are in vmalloc area: */ 316 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 317 return -1; 318 319 WARN_ON_ONCE(in_nmi()); 320 321 /* 322 * Synchronize this task's top level page-table 323 * with the 'reference' page table. 324 * 325 * Do _not_ use "current" here. We might be inside 326 * an interrupt in the middle of a task switch.. 327 */ 328 pgd_paddr = read_cr3_pa(); 329 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 330 if (!pmd_k) 331 return -1; 332 333 if (pmd_large(*pmd_k)) 334 return 0; 335 336 pte_k = pte_offset_kernel(pmd_k, address); 337 if (!pte_present(*pte_k)) 338 return -1; 339 340 return 0; 341 } 342 NOKPROBE_SYMBOL(vmalloc_fault); 343 344 /* 345 * Did it hit the DOS screen memory VA from vm86 mode? 346 */ 347 static inline void 348 check_v8086_mode(struct pt_regs *regs, unsigned long address, 349 struct task_struct *tsk) 350 { 351 #ifdef CONFIG_VM86 352 unsigned long bit; 353 354 if (!v8086_mode(regs) || !tsk->thread.vm86) 355 return; 356 357 bit = (address - 0xA0000) >> PAGE_SHIFT; 358 if (bit < 32) 359 tsk->thread.vm86->screen_bitmap |= 1 << bit; 360 #endif 361 } 362 363 static bool low_pfn(unsigned long pfn) 364 { 365 return pfn < max_low_pfn; 366 } 367 368 static void dump_pagetable(unsigned long address) 369 { 370 pgd_t *base = __va(read_cr3_pa()); 371 pgd_t *pgd = &base[pgd_index(address)]; 372 p4d_t *p4d; 373 pud_t *pud; 374 pmd_t *pmd; 375 pte_t *pte; 376 377 #ifdef CONFIG_X86_PAE 378 pr_info("*pdpt = %016Lx ", pgd_val(*pgd)); 379 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 380 goto out; 381 #define pr_pde pr_cont 382 #else 383 #define pr_pde pr_info 384 #endif 385 p4d = p4d_offset(pgd, address); 386 pud = pud_offset(p4d, address); 387 pmd = pmd_offset(pud, address); 388 pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 389 #undef pr_pde 390 391 /* 392 * We must not directly access the pte in the highpte 393 * case if the page table is located in highmem. 394 * And let's rather not kmap-atomic the pte, just in case 395 * it's allocated already: 396 */ 397 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 398 goto out; 399 400 pte = pte_offset_kernel(pmd, address); 401 pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 402 out: 403 pr_cont("\n"); 404 } 405 406 #else /* CONFIG_X86_64: */ 407 408 void vmalloc_sync_all(void) 409 { 410 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 411 } 412 413 /* 414 * 64-bit: 415 * 416 * Handle a fault on the vmalloc area 417 */ 418 static noinline int vmalloc_fault(unsigned long address) 419 { 420 pgd_t *pgd, *pgd_k; 421 p4d_t *p4d, *p4d_k; 422 pud_t *pud; 423 pmd_t *pmd; 424 pte_t *pte; 425 426 /* Make sure we are in vmalloc area: */ 427 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 428 return -1; 429 430 WARN_ON_ONCE(in_nmi()); 431 432 /* 433 * Copy kernel mappings over when needed. This can also 434 * happen within a race in page table update. In the later 435 * case just flush: 436 */ 437 pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address); 438 pgd_k = pgd_offset_k(address); 439 if (pgd_none(*pgd_k)) 440 return -1; 441 442 if (pgtable_l5_enabled) { 443 if (pgd_none(*pgd)) { 444 set_pgd(pgd, *pgd_k); 445 arch_flush_lazy_mmu_mode(); 446 } else { 447 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k)); 448 } 449 } 450 451 /* With 4-level paging, copying happens on the p4d level. */ 452 p4d = p4d_offset(pgd, address); 453 p4d_k = p4d_offset(pgd_k, address); 454 if (p4d_none(*p4d_k)) 455 return -1; 456 457 if (p4d_none(*p4d) && !pgtable_l5_enabled) { 458 set_p4d(p4d, *p4d_k); 459 arch_flush_lazy_mmu_mode(); 460 } else { 461 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k)); 462 } 463 464 BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4); 465 466 pud = pud_offset(p4d, address); 467 if (pud_none(*pud)) 468 return -1; 469 470 if (pud_large(*pud)) 471 return 0; 472 473 pmd = pmd_offset(pud, address); 474 if (pmd_none(*pmd)) 475 return -1; 476 477 if (pmd_large(*pmd)) 478 return 0; 479 480 pte = pte_offset_kernel(pmd, address); 481 if (!pte_present(*pte)) 482 return -1; 483 484 return 0; 485 } 486 NOKPROBE_SYMBOL(vmalloc_fault); 487 488 #ifdef CONFIG_CPU_SUP_AMD 489 static const char errata93_warning[] = 490 KERN_ERR 491 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 492 "******* Working around it, but it may cause SEGVs or burn power.\n" 493 "******* Please consider a BIOS update.\n" 494 "******* Disabling USB legacy in the BIOS may also help.\n"; 495 #endif 496 497 /* 498 * No vm86 mode in 64-bit mode: 499 */ 500 static inline void 501 check_v8086_mode(struct pt_regs *regs, unsigned long address, 502 struct task_struct *tsk) 503 { 504 } 505 506 static int bad_address(void *p) 507 { 508 unsigned long dummy; 509 510 return probe_kernel_address((unsigned long *)p, dummy); 511 } 512 513 static void dump_pagetable(unsigned long address) 514 { 515 pgd_t *base = __va(read_cr3_pa()); 516 pgd_t *pgd = base + pgd_index(address); 517 p4d_t *p4d; 518 pud_t *pud; 519 pmd_t *pmd; 520 pte_t *pte; 521 522 if (bad_address(pgd)) 523 goto bad; 524 525 pr_info("PGD %lx ", pgd_val(*pgd)); 526 527 if (!pgd_present(*pgd)) 528 goto out; 529 530 p4d = p4d_offset(pgd, address); 531 if (bad_address(p4d)) 532 goto bad; 533 534 pr_cont("P4D %lx ", p4d_val(*p4d)); 535 if (!p4d_present(*p4d) || p4d_large(*p4d)) 536 goto out; 537 538 pud = pud_offset(p4d, address); 539 if (bad_address(pud)) 540 goto bad; 541 542 pr_cont("PUD %lx ", pud_val(*pud)); 543 if (!pud_present(*pud) || pud_large(*pud)) 544 goto out; 545 546 pmd = pmd_offset(pud, address); 547 if (bad_address(pmd)) 548 goto bad; 549 550 pr_cont("PMD %lx ", pmd_val(*pmd)); 551 if (!pmd_present(*pmd) || pmd_large(*pmd)) 552 goto out; 553 554 pte = pte_offset_kernel(pmd, address); 555 if (bad_address(pte)) 556 goto bad; 557 558 pr_cont("PTE %lx", pte_val(*pte)); 559 out: 560 pr_cont("\n"); 561 return; 562 bad: 563 pr_info("BAD\n"); 564 } 565 566 #endif /* CONFIG_X86_64 */ 567 568 /* 569 * Workaround for K8 erratum #93 & buggy BIOS. 570 * 571 * BIOS SMM functions are required to use a specific workaround 572 * to avoid corruption of the 64bit RIP register on C stepping K8. 573 * 574 * A lot of BIOS that didn't get tested properly miss this. 575 * 576 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 577 * Try to work around it here. 578 * 579 * Note we only handle faults in kernel here. 580 * Does nothing on 32-bit. 581 */ 582 static int is_errata93(struct pt_regs *regs, unsigned long address) 583 { 584 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 585 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 586 || boot_cpu_data.x86 != 0xf) 587 return 0; 588 589 if (address != regs->ip) 590 return 0; 591 592 if ((address >> 32) != 0) 593 return 0; 594 595 address |= 0xffffffffUL << 32; 596 if ((address >= (u64)_stext && address <= (u64)_etext) || 597 (address >= MODULES_VADDR && address <= MODULES_END)) { 598 printk_once(errata93_warning); 599 regs->ip = address; 600 return 1; 601 } 602 #endif 603 return 0; 604 } 605 606 /* 607 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 608 * to illegal addresses >4GB. 609 * 610 * We catch this in the page fault handler because these addresses 611 * are not reachable. Just detect this case and return. Any code 612 * segment in LDT is compatibility mode. 613 */ 614 static int is_errata100(struct pt_regs *regs, unsigned long address) 615 { 616 #ifdef CONFIG_X86_64 617 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 618 return 1; 619 #endif 620 return 0; 621 } 622 623 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 624 { 625 #ifdef CONFIG_X86_F00F_BUG 626 unsigned long nr; 627 628 /* 629 * Pentium F0 0F C7 C8 bug workaround: 630 */ 631 if (boot_cpu_has_bug(X86_BUG_F00F)) { 632 nr = (address - idt_descr.address) >> 3; 633 634 if (nr == 6) { 635 do_invalid_op(regs, 0); 636 return 1; 637 } 638 } 639 #endif 640 return 0; 641 } 642 643 static const char nx_warning[] = KERN_CRIT 644 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; 645 static const char smep_warning[] = KERN_CRIT 646 "unable to execute userspace code (SMEP?) (uid: %d)\n"; 647 648 static void 649 show_fault_oops(struct pt_regs *regs, unsigned long error_code, 650 unsigned long address) 651 { 652 if (!oops_may_print()) 653 return; 654 655 if (error_code & X86_PF_INSTR) { 656 unsigned int level; 657 pgd_t *pgd; 658 pte_t *pte; 659 660 pgd = __va(read_cr3_pa()); 661 pgd += pgd_index(address); 662 663 pte = lookup_address_in_pgd(pgd, address, &level); 664 665 if (pte && pte_present(*pte) && !pte_exec(*pte)) 666 printk(nx_warning, from_kuid(&init_user_ns, current_uid())); 667 if (pte && pte_present(*pte) && pte_exec(*pte) && 668 (pgd_flags(*pgd) & _PAGE_USER) && 669 (__read_cr4() & X86_CR4_SMEP)) 670 printk(smep_warning, from_kuid(&init_user_ns, current_uid())); 671 } 672 673 printk(KERN_ALERT "BUG: unable to handle kernel "); 674 if (address < PAGE_SIZE) 675 printk(KERN_CONT "NULL pointer dereference"); 676 else 677 printk(KERN_CONT "paging request"); 678 679 printk(KERN_CONT " at %px\n", (void *) address); 680 681 dump_pagetable(address); 682 } 683 684 static noinline void 685 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 686 unsigned long address) 687 { 688 struct task_struct *tsk; 689 unsigned long flags; 690 int sig; 691 692 flags = oops_begin(); 693 tsk = current; 694 sig = SIGKILL; 695 696 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 697 tsk->comm, address); 698 dump_pagetable(address); 699 700 tsk->thread.cr2 = address; 701 tsk->thread.trap_nr = X86_TRAP_PF; 702 tsk->thread.error_code = error_code; 703 704 if (__die("Bad pagetable", regs, error_code)) 705 sig = 0; 706 707 oops_end(flags, regs, sig); 708 } 709 710 static noinline void 711 no_context(struct pt_regs *regs, unsigned long error_code, 712 unsigned long address, int signal, int si_code) 713 { 714 struct task_struct *tsk = current; 715 unsigned long flags; 716 int sig; 717 718 /* Are we prepared to handle this kernel fault? */ 719 if (fixup_exception(regs, X86_TRAP_PF)) { 720 /* 721 * Any interrupt that takes a fault gets the fixup. This makes 722 * the below recursive fault logic only apply to a faults from 723 * task context. 724 */ 725 if (in_interrupt()) 726 return; 727 728 /* 729 * Per the above we're !in_interrupt(), aka. task context. 730 * 731 * In this case we need to make sure we're not recursively 732 * faulting through the emulate_vsyscall() logic. 733 */ 734 if (current->thread.sig_on_uaccess_err && signal) { 735 tsk->thread.trap_nr = X86_TRAP_PF; 736 tsk->thread.error_code = error_code | X86_PF_USER; 737 tsk->thread.cr2 = address; 738 739 /* XXX: hwpoison faults will set the wrong code. */ 740 force_sig_info_fault(signal, si_code, address, 741 tsk, NULL, 0); 742 } 743 744 /* 745 * Barring that, we can do the fixup and be happy. 746 */ 747 return; 748 } 749 750 #ifdef CONFIG_VMAP_STACK 751 /* 752 * Stack overflow? During boot, we can fault near the initial 753 * stack in the direct map, but that's not an overflow -- check 754 * that we're in vmalloc space to avoid this. 755 */ 756 if (is_vmalloc_addr((void *)address) && 757 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 758 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 759 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *); 760 /* 761 * We're likely to be running with very little stack space 762 * left. It's plausible that we'd hit this condition but 763 * double-fault even before we get this far, in which case 764 * we're fine: the double-fault handler will deal with it. 765 * 766 * We don't want to make it all the way into the oops code 767 * and then double-fault, though, because we're likely to 768 * break the console driver and lose most of the stack dump. 769 */ 770 asm volatile ("movq %[stack], %%rsp\n\t" 771 "call handle_stack_overflow\n\t" 772 "1: jmp 1b" 773 : ASM_CALL_CONSTRAINT 774 : "D" ("kernel stack overflow (page fault)"), 775 "S" (regs), "d" (address), 776 [stack] "rm" (stack)); 777 unreachable(); 778 } 779 #endif 780 781 /* 782 * 32-bit: 783 * 784 * Valid to do another page fault here, because if this fault 785 * had been triggered by is_prefetch fixup_exception would have 786 * handled it. 787 * 788 * 64-bit: 789 * 790 * Hall of shame of CPU/BIOS bugs. 791 */ 792 if (is_prefetch(regs, error_code, address)) 793 return; 794 795 if (is_errata93(regs, address)) 796 return; 797 798 /* 799 * Oops. The kernel tried to access some bad page. We'll have to 800 * terminate things with extreme prejudice: 801 */ 802 flags = oops_begin(); 803 804 show_fault_oops(regs, error_code, address); 805 806 if (task_stack_end_corrupted(tsk)) 807 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 808 809 tsk->thread.cr2 = address; 810 tsk->thread.trap_nr = X86_TRAP_PF; 811 tsk->thread.error_code = error_code; 812 813 sig = SIGKILL; 814 if (__die("Oops", regs, error_code)) 815 sig = 0; 816 817 /* Executive summary in case the body of the oops scrolled away */ 818 printk(KERN_DEFAULT "CR2: %016lx\n", address); 819 820 oops_end(flags, regs, sig); 821 } 822 823 /* 824 * Print out info about fatal segfaults, if the show_unhandled_signals 825 * sysctl is set: 826 */ 827 static inline void 828 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 829 unsigned long address, struct task_struct *tsk) 830 { 831 if (!unhandled_signal(tsk, SIGSEGV)) 832 return; 833 834 if (!printk_ratelimit()) 835 return; 836 837 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %lx", 838 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 839 tsk->comm, task_pid_nr(tsk), address, 840 (void *)regs->ip, (void *)regs->sp, error_code); 841 842 print_vma_addr(KERN_CONT " in ", regs->ip); 843 844 printk(KERN_CONT "\n"); 845 } 846 847 static void 848 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 849 unsigned long address, u32 *pkey, int si_code) 850 { 851 struct task_struct *tsk = current; 852 853 /* User mode accesses just cause a SIGSEGV */ 854 if (error_code & X86_PF_USER) { 855 /* 856 * It's possible to have interrupts off here: 857 */ 858 local_irq_enable(); 859 860 /* 861 * Valid to do another page fault here because this one came 862 * from user space: 863 */ 864 if (is_prefetch(regs, error_code, address)) 865 return; 866 867 if (is_errata100(regs, address)) 868 return; 869 870 #ifdef CONFIG_X86_64 871 /* 872 * Instruction fetch faults in the vsyscall page might need 873 * emulation. 874 */ 875 if (unlikely((error_code & X86_PF_INSTR) && 876 ((address & ~0xfff) == VSYSCALL_ADDR))) { 877 if (emulate_vsyscall(regs, address)) 878 return; 879 } 880 #endif 881 882 /* 883 * To avoid leaking information about the kernel page table 884 * layout, pretend that user-mode accesses to kernel addresses 885 * are always protection faults. 886 */ 887 if (address >= TASK_SIZE_MAX) 888 error_code |= X86_PF_PROT; 889 890 if (likely(show_unhandled_signals)) 891 show_signal_msg(regs, error_code, address, tsk); 892 893 tsk->thread.cr2 = address; 894 tsk->thread.error_code = error_code; 895 tsk->thread.trap_nr = X86_TRAP_PF; 896 897 force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0); 898 899 return; 900 } 901 902 if (is_f00f_bug(regs, address)) 903 return; 904 905 no_context(regs, error_code, address, SIGSEGV, si_code); 906 } 907 908 static noinline void 909 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 910 unsigned long address, u32 *pkey) 911 { 912 __bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR); 913 } 914 915 static void 916 __bad_area(struct pt_regs *regs, unsigned long error_code, 917 unsigned long address, struct vm_area_struct *vma, int si_code) 918 { 919 struct mm_struct *mm = current->mm; 920 u32 pkey; 921 922 if (vma) 923 pkey = vma_pkey(vma); 924 925 /* 926 * Something tried to access memory that isn't in our memory map.. 927 * Fix it, but check if it's kernel or user first.. 928 */ 929 up_read(&mm->mmap_sem); 930 931 __bad_area_nosemaphore(regs, error_code, address, 932 (vma) ? &pkey : NULL, si_code); 933 } 934 935 static noinline void 936 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 937 { 938 __bad_area(regs, error_code, address, NULL, SEGV_MAPERR); 939 } 940 941 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 942 struct vm_area_struct *vma) 943 { 944 /* This code is always called on the current mm */ 945 bool foreign = false; 946 947 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 948 return false; 949 if (error_code & X86_PF_PK) 950 return true; 951 /* this checks permission keys on the VMA: */ 952 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 953 (error_code & X86_PF_INSTR), foreign)) 954 return true; 955 return false; 956 } 957 958 static noinline void 959 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 960 unsigned long address, struct vm_area_struct *vma) 961 { 962 /* 963 * This OSPKE check is not strictly necessary at runtime. 964 * But, doing it this way allows compiler optimizations 965 * if pkeys are compiled out. 966 */ 967 if (bad_area_access_from_pkeys(error_code, vma)) 968 __bad_area(regs, error_code, address, vma, SEGV_PKUERR); 969 else 970 __bad_area(regs, error_code, address, vma, SEGV_ACCERR); 971 } 972 973 static void 974 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 975 u32 *pkey, unsigned int fault) 976 { 977 struct task_struct *tsk = current; 978 int code = BUS_ADRERR; 979 980 /* Kernel mode? Handle exceptions or die: */ 981 if (!(error_code & X86_PF_USER)) { 982 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 983 return; 984 } 985 986 /* User-space => ok to do another page fault: */ 987 if (is_prefetch(regs, error_code, address)) 988 return; 989 990 tsk->thread.cr2 = address; 991 tsk->thread.error_code = error_code; 992 tsk->thread.trap_nr = X86_TRAP_PF; 993 994 #ifdef CONFIG_MEMORY_FAILURE 995 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 996 printk(KERN_ERR 997 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 998 tsk->comm, tsk->pid, address); 999 code = BUS_MCEERR_AR; 1000 } 1001 #endif 1002 force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault); 1003 } 1004 1005 static noinline void 1006 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 1007 unsigned long address, u32 *pkey, unsigned int fault) 1008 { 1009 if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) { 1010 no_context(regs, error_code, address, 0, 0); 1011 return; 1012 } 1013 1014 if (fault & VM_FAULT_OOM) { 1015 /* Kernel mode? Handle exceptions or die: */ 1016 if (!(error_code & X86_PF_USER)) { 1017 no_context(regs, error_code, address, 1018 SIGSEGV, SEGV_MAPERR); 1019 return; 1020 } 1021 1022 /* 1023 * We ran out of memory, call the OOM killer, and return the 1024 * userspace (which will retry the fault, or kill us if we got 1025 * oom-killed): 1026 */ 1027 pagefault_out_of_memory(); 1028 } else { 1029 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1030 VM_FAULT_HWPOISON_LARGE)) 1031 do_sigbus(regs, error_code, address, pkey, fault); 1032 else if (fault & VM_FAULT_SIGSEGV) 1033 bad_area_nosemaphore(regs, error_code, address, pkey); 1034 else 1035 BUG(); 1036 } 1037 } 1038 1039 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 1040 { 1041 if ((error_code & X86_PF_WRITE) && !pte_write(*pte)) 1042 return 0; 1043 1044 if ((error_code & X86_PF_INSTR) && !pte_exec(*pte)) 1045 return 0; 1046 /* 1047 * Note: We do not do lazy flushing on protection key 1048 * changes, so no spurious fault will ever set X86_PF_PK. 1049 */ 1050 if ((error_code & X86_PF_PK)) 1051 return 1; 1052 1053 return 1; 1054 } 1055 1056 /* 1057 * Handle a spurious fault caused by a stale TLB entry. 1058 * 1059 * This allows us to lazily refresh the TLB when increasing the 1060 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1061 * eagerly is very expensive since that implies doing a full 1062 * cross-processor TLB flush, even if no stale TLB entries exist 1063 * on other processors. 1064 * 1065 * Spurious faults may only occur if the TLB contains an entry with 1066 * fewer permission than the page table entry. Non-present (P = 0) 1067 * and reserved bit (R = 1) faults are never spurious. 1068 * 1069 * There are no security implications to leaving a stale TLB when 1070 * increasing the permissions on a page. 1071 * 1072 * Returns non-zero if a spurious fault was handled, zero otherwise. 1073 * 1074 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1075 * (Optional Invalidation). 1076 */ 1077 static noinline int 1078 spurious_fault(unsigned long error_code, unsigned long address) 1079 { 1080 pgd_t *pgd; 1081 p4d_t *p4d; 1082 pud_t *pud; 1083 pmd_t *pmd; 1084 pte_t *pte; 1085 int ret; 1086 1087 /* 1088 * Only writes to RO or instruction fetches from NX may cause 1089 * spurious faults. 1090 * 1091 * These could be from user or supervisor accesses but the TLB 1092 * is only lazily flushed after a kernel mapping protection 1093 * change, so user accesses are not expected to cause spurious 1094 * faults. 1095 */ 1096 if (error_code != (X86_PF_WRITE | X86_PF_PROT) && 1097 error_code != (X86_PF_INSTR | X86_PF_PROT)) 1098 return 0; 1099 1100 pgd = init_mm.pgd + pgd_index(address); 1101 if (!pgd_present(*pgd)) 1102 return 0; 1103 1104 p4d = p4d_offset(pgd, address); 1105 if (!p4d_present(*p4d)) 1106 return 0; 1107 1108 if (p4d_large(*p4d)) 1109 return spurious_fault_check(error_code, (pte_t *) p4d); 1110 1111 pud = pud_offset(p4d, address); 1112 if (!pud_present(*pud)) 1113 return 0; 1114 1115 if (pud_large(*pud)) 1116 return spurious_fault_check(error_code, (pte_t *) pud); 1117 1118 pmd = pmd_offset(pud, address); 1119 if (!pmd_present(*pmd)) 1120 return 0; 1121 1122 if (pmd_large(*pmd)) 1123 return spurious_fault_check(error_code, (pte_t *) pmd); 1124 1125 pte = pte_offset_kernel(pmd, address); 1126 if (!pte_present(*pte)) 1127 return 0; 1128 1129 ret = spurious_fault_check(error_code, pte); 1130 if (!ret) 1131 return 0; 1132 1133 /* 1134 * Make sure we have permissions in PMD. 1135 * If not, then there's a bug in the page tables: 1136 */ 1137 ret = spurious_fault_check(error_code, (pte_t *) pmd); 1138 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1139 1140 return ret; 1141 } 1142 NOKPROBE_SYMBOL(spurious_fault); 1143 1144 int show_unhandled_signals = 1; 1145 1146 static inline int 1147 access_error(unsigned long error_code, struct vm_area_struct *vma) 1148 { 1149 /* This is only called for the current mm, so: */ 1150 bool foreign = false; 1151 1152 /* 1153 * Read or write was blocked by protection keys. This is 1154 * always an unconditional error and can never result in 1155 * a follow-up action to resolve the fault, like a COW. 1156 */ 1157 if (error_code & X86_PF_PK) 1158 return 1; 1159 1160 /* 1161 * Make sure to check the VMA so that we do not perform 1162 * faults just to hit a X86_PF_PK as soon as we fill in a 1163 * page. 1164 */ 1165 if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE), 1166 (error_code & X86_PF_INSTR), foreign)) 1167 return 1; 1168 1169 if (error_code & X86_PF_WRITE) { 1170 /* write, present and write, not present: */ 1171 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1172 return 1; 1173 return 0; 1174 } 1175 1176 /* read, present: */ 1177 if (unlikely(error_code & X86_PF_PROT)) 1178 return 1; 1179 1180 /* read, not present: */ 1181 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 1182 return 1; 1183 1184 return 0; 1185 } 1186 1187 static int fault_in_kernel_space(unsigned long address) 1188 { 1189 return address >= TASK_SIZE_MAX; 1190 } 1191 1192 static inline bool smap_violation(int error_code, struct pt_regs *regs) 1193 { 1194 if (!IS_ENABLED(CONFIG_X86_SMAP)) 1195 return false; 1196 1197 if (!static_cpu_has(X86_FEATURE_SMAP)) 1198 return false; 1199 1200 if (error_code & X86_PF_USER) 1201 return false; 1202 1203 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC)) 1204 return false; 1205 1206 return true; 1207 } 1208 1209 /* 1210 * This routine handles page faults. It determines the address, 1211 * and the problem, and then passes it off to one of the appropriate 1212 * routines. 1213 */ 1214 static noinline void 1215 __do_page_fault(struct pt_regs *regs, unsigned long error_code, 1216 unsigned long address) 1217 { 1218 struct vm_area_struct *vma; 1219 struct task_struct *tsk; 1220 struct mm_struct *mm; 1221 int fault, major = 0; 1222 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 1223 u32 pkey; 1224 1225 tsk = current; 1226 mm = tsk->mm; 1227 1228 prefetchw(&mm->mmap_sem); 1229 1230 if (unlikely(kmmio_fault(regs, address))) 1231 return; 1232 1233 /* 1234 * We fault-in kernel-space virtual memory on-demand. The 1235 * 'reference' page table is init_mm.pgd. 1236 * 1237 * NOTE! We MUST NOT take any locks for this case. We may 1238 * be in an interrupt or a critical region, and should 1239 * only copy the information from the master page table, 1240 * nothing more. 1241 * 1242 * This verifies that the fault happens in kernel space 1243 * (error_code & 4) == 0, and that the fault was not a 1244 * protection error (error_code & 9) == 0. 1245 */ 1246 if (unlikely(fault_in_kernel_space(address))) { 1247 if (!(error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) { 1248 if (vmalloc_fault(address) >= 0) 1249 return; 1250 } 1251 1252 /* Can handle a stale RO->RW TLB: */ 1253 if (spurious_fault(error_code, address)) 1254 return; 1255 1256 /* kprobes don't want to hook the spurious faults: */ 1257 if (kprobes_fault(regs)) 1258 return; 1259 /* 1260 * Don't take the mm semaphore here. If we fixup a prefetch 1261 * fault we could otherwise deadlock: 1262 */ 1263 bad_area_nosemaphore(regs, error_code, address, NULL); 1264 1265 return; 1266 } 1267 1268 /* kprobes don't want to hook the spurious faults: */ 1269 if (unlikely(kprobes_fault(regs))) 1270 return; 1271 1272 if (unlikely(error_code & X86_PF_RSVD)) 1273 pgtable_bad(regs, error_code, address); 1274 1275 if (unlikely(smap_violation(error_code, regs))) { 1276 bad_area_nosemaphore(regs, error_code, address, NULL); 1277 return; 1278 } 1279 1280 /* 1281 * If we're in an interrupt, have no user context or are running 1282 * in a region with pagefaults disabled then we must not take the fault 1283 */ 1284 if (unlikely(faulthandler_disabled() || !mm)) { 1285 bad_area_nosemaphore(regs, error_code, address, NULL); 1286 return; 1287 } 1288 1289 /* 1290 * It's safe to allow irq's after cr2 has been saved and the 1291 * vmalloc fault has been handled. 1292 * 1293 * User-mode registers count as a user access even for any 1294 * potential system fault or CPU buglet: 1295 */ 1296 if (user_mode(regs)) { 1297 local_irq_enable(); 1298 error_code |= X86_PF_USER; 1299 flags |= FAULT_FLAG_USER; 1300 } else { 1301 if (regs->flags & X86_EFLAGS_IF) 1302 local_irq_enable(); 1303 } 1304 1305 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1306 1307 if (error_code & X86_PF_WRITE) 1308 flags |= FAULT_FLAG_WRITE; 1309 if (error_code & X86_PF_INSTR) 1310 flags |= FAULT_FLAG_INSTRUCTION; 1311 1312 /* 1313 * When running in the kernel we expect faults to occur only to 1314 * addresses in user space. All other faults represent errors in 1315 * the kernel and should generate an OOPS. Unfortunately, in the 1316 * case of an erroneous fault occurring in a code path which already 1317 * holds mmap_sem we will deadlock attempting to validate the fault 1318 * against the address space. Luckily the kernel only validly 1319 * references user space from well defined areas of code, which are 1320 * listed in the exceptions table. 1321 * 1322 * As the vast majority of faults will be valid we will only perform 1323 * the source reference check when there is a possibility of a 1324 * deadlock. Attempt to lock the address space, if we cannot we then 1325 * validate the source. If this is invalid we can skip the address 1326 * space check, thus avoiding the deadlock: 1327 */ 1328 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1329 if (!(error_code & X86_PF_USER) && 1330 !search_exception_tables(regs->ip)) { 1331 bad_area_nosemaphore(regs, error_code, address, NULL); 1332 return; 1333 } 1334 retry: 1335 down_read(&mm->mmap_sem); 1336 } else { 1337 /* 1338 * The above down_read_trylock() might have succeeded in 1339 * which case we'll have missed the might_sleep() from 1340 * down_read(): 1341 */ 1342 might_sleep(); 1343 } 1344 1345 vma = find_vma(mm, address); 1346 if (unlikely(!vma)) { 1347 bad_area(regs, error_code, address); 1348 return; 1349 } 1350 if (likely(vma->vm_start <= address)) 1351 goto good_area; 1352 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1353 bad_area(regs, error_code, address); 1354 return; 1355 } 1356 if (error_code & X86_PF_USER) { 1357 /* 1358 * Accessing the stack below %sp is always a bug. 1359 * The large cushion allows instructions like enter 1360 * and pusha to work. ("enter $65535, $31" pushes 1361 * 32 pointers and then decrements %sp by 65535.) 1362 */ 1363 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { 1364 bad_area(regs, error_code, address); 1365 return; 1366 } 1367 } 1368 if (unlikely(expand_stack(vma, address))) { 1369 bad_area(regs, error_code, address); 1370 return; 1371 } 1372 1373 /* 1374 * Ok, we have a good vm_area for this memory access, so 1375 * we can handle it.. 1376 */ 1377 good_area: 1378 if (unlikely(access_error(error_code, vma))) { 1379 bad_area_access_error(regs, error_code, address, vma); 1380 return; 1381 } 1382 1383 /* 1384 * If for any reason at all we couldn't handle the fault, 1385 * make sure we exit gracefully rather than endlessly redo 1386 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1387 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. 1388 * 1389 * Note that handle_userfault() may also release and reacquire mmap_sem 1390 * (and not return with VM_FAULT_RETRY), when returning to userland to 1391 * repeat the page fault later with a VM_FAULT_NOPAGE retval 1392 * (potentially after handling any pending signal during the return to 1393 * userland). The return to userland is identified whenever 1394 * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. 1395 * Thus we have to be careful about not touching vma after handling the 1396 * fault, so we read the pkey beforehand. 1397 */ 1398 pkey = vma_pkey(vma); 1399 fault = handle_mm_fault(vma, address, flags); 1400 major |= fault & VM_FAULT_MAJOR; 1401 1402 /* 1403 * If we need to retry the mmap_sem has already been released, 1404 * and if there is a fatal signal pending there is no guarantee 1405 * that we made any progress. Handle this case first. 1406 */ 1407 if (unlikely(fault & VM_FAULT_RETRY)) { 1408 /* Retry at most once */ 1409 if (flags & FAULT_FLAG_ALLOW_RETRY) { 1410 flags &= ~FAULT_FLAG_ALLOW_RETRY; 1411 flags |= FAULT_FLAG_TRIED; 1412 if (!fatal_signal_pending(tsk)) 1413 goto retry; 1414 } 1415 1416 /* User mode? Just return to handle the fatal exception */ 1417 if (flags & FAULT_FLAG_USER) 1418 return; 1419 1420 /* Not returning to user mode? Handle exceptions or die: */ 1421 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 1422 return; 1423 } 1424 1425 up_read(&mm->mmap_sem); 1426 if (unlikely(fault & VM_FAULT_ERROR)) { 1427 mm_fault_error(regs, error_code, address, &pkey, fault); 1428 return; 1429 } 1430 1431 /* 1432 * Major/minor page fault accounting. If any of the events 1433 * returned VM_FAULT_MAJOR, we account it as a major fault. 1434 */ 1435 if (major) { 1436 tsk->maj_flt++; 1437 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 1438 } else { 1439 tsk->min_flt++; 1440 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 1441 } 1442 1443 check_v8086_mode(regs, address, tsk); 1444 } 1445 NOKPROBE_SYMBOL(__do_page_fault); 1446 1447 static nokprobe_inline void 1448 trace_page_fault_entries(unsigned long address, struct pt_regs *regs, 1449 unsigned long error_code) 1450 { 1451 if (user_mode(regs)) 1452 trace_page_fault_user(address, regs, error_code); 1453 else 1454 trace_page_fault_kernel(address, regs, error_code); 1455 } 1456 1457 /* 1458 * We must have this function blacklisted from kprobes, tagged with notrace 1459 * and call read_cr2() before calling anything else. To avoid calling any 1460 * kind of tracing machinery before we've observed the CR2 value. 1461 * 1462 * exception_{enter,exit}() contains all sorts of tracepoints. 1463 */ 1464 dotraplinkage void notrace 1465 do_page_fault(struct pt_regs *regs, unsigned long error_code) 1466 { 1467 unsigned long address = read_cr2(); /* Get the faulting address */ 1468 enum ctx_state prev_state; 1469 1470 prev_state = exception_enter(); 1471 if (trace_pagefault_enabled()) 1472 trace_page_fault_entries(address, regs, error_code); 1473 1474 __do_page_fault(regs, error_code, address); 1475 exception_exit(prev_state); 1476 } 1477 NOKPROBE_SYMBOL(do_page_fault); 1478