1 /* 2 * Copyright (C) 1995 Linus Torvalds 3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs. 4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar 5 */ 6 #include <linux/sched.h> /* test_thread_flag(), ... */ 7 #include <linux/kdebug.h> /* oops_begin/end, ... */ 8 #include <linux/extable.h> /* search_exception_tables */ 9 #include <linux/bootmem.h> /* max_low_pfn */ 10 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ 11 #include <linux/mmiotrace.h> /* kmmio_handler, ... */ 12 #include <linux/perf_event.h> /* perf_sw_event */ 13 #include <linux/hugetlb.h> /* hstate_index_to_shift */ 14 #include <linux/prefetch.h> /* prefetchw */ 15 #include <linux/context_tracking.h> /* exception_enter(), ... */ 16 #include <linux/uaccess.h> /* faulthandler_disabled() */ 17 18 #include <asm/cpufeature.h> /* boot_cpu_has, ... */ 19 #include <asm/traps.h> /* dotraplinkage, ... */ 20 #include <asm/pgalloc.h> /* pgd_*(), ... */ 21 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */ 22 #include <asm/fixmap.h> /* VSYSCALL_ADDR */ 23 #include <asm/vsyscall.h> /* emulate_vsyscall */ 24 #include <asm/vm86.h> /* struct vm86 */ 25 #include <asm/mmu_context.h> /* vma_pkey() */ 26 27 #define CREATE_TRACE_POINTS 28 #include <asm/trace/exceptions.h> 29 30 /* 31 * Page fault error code bits: 32 * 33 * bit 0 == 0: no page found 1: protection fault 34 * bit 1 == 0: read access 1: write access 35 * bit 2 == 0: kernel-mode access 1: user-mode access 36 * bit 3 == 1: use of reserved bit detected 37 * bit 4 == 1: fault was an instruction fetch 38 * bit 5 == 1: protection keys block access 39 */ 40 enum x86_pf_error_code { 41 42 PF_PROT = 1 << 0, 43 PF_WRITE = 1 << 1, 44 PF_USER = 1 << 2, 45 PF_RSVD = 1 << 3, 46 PF_INSTR = 1 << 4, 47 PF_PK = 1 << 5, 48 }; 49 50 /* 51 * Returns 0 if mmiotrace is disabled, or if the fault is not 52 * handled by mmiotrace: 53 */ 54 static nokprobe_inline int 55 kmmio_fault(struct pt_regs *regs, unsigned long addr) 56 { 57 if (unlikely(is_kmmio_active())) 58 if (kmmio_handler(regs, addr) == 1) 59 return -1; 60 return 0; 61 } 62 63 static nokprobe_inline int kprobes_fault(struct pt_regs *regs) 64 { 65 int ret = 0; 66 67 /* kprobe_running() needs smp_processor_id() */ 68 if (kprobes_built_in() && !user_mode(regs)) { 69 preempt_disable(); 70 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 71 ret = 1; 72 preempt_enable(); 73 } 74 75 return ret; 76 } 77 78 /* 79 * Prefetch quirks: 80 * 81 * 32-bit mode: 82 * 83 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 84 * Check that here and ignore it. 85 * 86 * 64-bit mode: 87 * 88 * Sometimes the CPU reports invalid exceptions on prefetch. 89 * Check that here and ignore it. 90 * 91 * Opcode checker based on code by Richard Brunner. 92 */ 93 static inline int 94 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 95 unsigned char opcode, int *prefetch) 96 { 97 unsigned char instr_hi = opcode & 0xf0; 98 unsigned char instr_lo = opcode & 0x0f; 99 100 switch (instr_hi) { 101 case 0x20: 102 case 0x30: 103 /* 104 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 105 * In X86_64 long mode, the CPU will signal invalid 106 * opcode if some of these prefixes are present so 107 * X86_64 will never get here anyway 108 */ 109 return ((instr_lo & 7) == 0x6); 110 #ifdef CONFIG_X86_64 111 case 0x40: 112 /* 113 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 114 * Need to figure out under what instruction mode the 115 * instruction was issued. Could check the LDT for lm, 116 * but for now it's good enough to assume that long 117 * mode only uses well known segments or kernel. 118 */ 119 return (!user_mode(regs) || user_64bit_mode(regs)); 120 #endif 121 case 0x60: 122 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 123 return (instr_lo & 0xC) == 0x4; 124 case 0xF0: 125 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 126 return !instr_lo || (instr_lo>>1) == 1; 127 case 0x00: 128 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 129 if (probe_kernel_address(instr, opcode)) 130 return 0; 131 132 *prefetch = (instr_lo == 0xF) && 133 (opcode == 0x0D || opcode == 0x18); 134 return 0; 135 default: 136 return 0; 137 } 138 } 139 140 static int 141 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 142 { 143 unsigned char *max_instr; 144 unsigned char *instr; 145 int prefetch = 0; 146 147 /* 148 * If it was a exec (instruction fetch) fault on NX page, then 149 * do not ignore the fault: 150 */ 151 if (error_code & PF_INSTR) 152 return 0; 153 154 instr = (void *)convert_ip_to_linear(current, regs); 155 max_instr = instr + 15; 156 157 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) 158 return 0; 159 160 while (instr < max_instr) { 161 unsigned char opcode; 162 163 if (probe_kernel_address(instr, opcode)) 164 break; 165 166 instr++; 167 168 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 169 break; 170 } 171 return prefetch; 172 } 173 174 /* 175 * A protection key fault means that the PKRU value did not allow 176 * access to some PTE. Userspace can figure out what PKRU was 177 * from the XSAVE state, and this function fills out a field in 178 * siginfo so userspace can discover which protection key was set 179 * on the PTE. 180 * 181 * If we get here, we know that the hardware signaled a PF_PK 182 * fault and that there was a VMA once we got in the fault 183 * handler. It does *not* guarantee that the VMA we find here 184 * was the one that we faulted on. 185 * 186 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 187 * 2. T1 : set PKRU to deny access to pkey=4, touches page 188 * 3. T1 : faults... 189 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 190 * 5. T1 : enters fault handler, takes mmap_sem, etc... 191 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 192 * faulted on a pte with its pkey=4. 193 */ 194 static void fill_sig_info_pkey(int si_code, siginfo_t *info, 195 struct vm_area_struct *vma) 196 { 197 /* This is effectively an #ifdef */ 198 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 199 return; 200 201 /* Fault not from Protection Keys: nothing to do */ 202 if (si_code != SEGV_PKUERR) 203 return; 204 /* 205 * force_sig_info_fault() is called from a number of 206 * contexts, some of which have a VMA and some of which 207 * do not. The PF_PK handing happens after we have a 208 * valid VMA, so we should never reach this without a 209 * valid VMA. 210 */ 211 if (!vma) { 212 WARN_ONCE(1, "PKU fault with no VMA passed in"); 213 info->si_pkey = 0; 214 return; 215 } 216 /* 217 * si_pkey should be thought of as a strong hint, but not 218 * absolutely guranteed to be 100% accurate because of 219 * the race explained above. 220 */ 221 info->si_pkey = vma_pkey(vma); 222 } 223 224 static void 225 force_sig_info_fault(int si_signo, int si_code, unsigned long address, 226 struct task_struct *tsk, struct vm_area_struct *vma, 227 int fault) 228 { 229 unsigned lsb = 0; 230 siginfo_t info; 231 232 info.si_signo = si_signo; 233 info.si_errno = 0; 234 info.si_code = si_code; 235 info.si_addr = (void __user *)address; 236 if (fault & VM_FAULT_HWPOISON_LARGE) 237 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 238 if (fault & VM_FAULT_HWPOISON) 239 lsb = PAGE_SHIFT; 240 info.si_addr_lsb = lsb; 241 242 fill_sig_info_pkey(si_code, &info, vma); 243 244 force_sig_info(si_signo, &info, tsk); 245 } 246 247 DEFINE_SPINLOCK(pgd_lock); 248 LIST_HEAD(pgd_list); 249 250 #ifdef CONFIG_X86_32 251 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 252 { 253 unsigned index = pgd_index(address); 254 pgd_t *pgd_k; 255 pud_t *pud, *pud_k; 256 pmd_t *pmd, *pmd_k; 257 258 pgd += index; 259 pgd_k = init_mm.pgd + index; 260 261 if (!pgd_present(*pgd_k)) 262 return NULL; 263 264 /* 265 * set_pgd(pgd, *pgd_k); here would be useless on PAE 266 * and redundant with the set_pmd() on non-PAE. As would 267 * set_pud. 268 */ 269 pud = pud_offset(pgd, address); 270 pud_k = pud_offset(pgd_k, address); 271 if (!pud_present(*pud_k)) 272 return NULL; 273 274 pmd = pmd_offset(pud, address); 275 pmd_k = pmd_offset(pud_k, address); 276 if (!pmd_present(*pmd_k)) 277 return NULL; 278 279 if (!pmd_present(*pmd)) 280 set_pmd(pmd, *pmd_k); 281 else 282 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 283 284 return pmd_k; 285 } 286 287 void vmalloc_sync_all(void) 288 { 289 unsigned long address; 290 291 if (SHARED_KERNEL_PMD) 292 return; 293 294 for (address = VMALLOC_START & PMD_MASK; 295 address >= TASK_SIZE_MAX && address < FIXADDR_TOP; 296 address += PMD_SIZE) { 297 struct page *page; 298 299 spin_lock(&pgd_lock); 300 list_for_each_entry(page, &pgd_list, lru) { 301 spinlock_t *pgt_lock; 302 pmd_t *ret; 303 304 /* the pgt_lock only for Xen */ 305 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 306 307 spin_lock(pgt_lock); 308 ret = vmalloc_sync_one(page_address(page), address); 309 spin_unlock(pgt_lock); 310 311 if (!ret) 312 break; 313 } 314 spin_unlock(&pgd_lock); 315 } 316 } 317 318 /* 319 * 32-bit: 320 * 321 * Handle a fault on the vmalloc or module mapping area 322 */ 323 static noinline int vmalloc_fault(unsigned long address) 324 { 325 unsigned long pgd_paddr; 326 pmd_t *pmd_k; 327 pte_t *pte_k; 328 329 /* Make sure we are in vmalloc area: */ 330 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 331 return -1; 332 333 WARN_ON_ONCE(in_nmi()); 334 335 /* 336 * Synchronize this task's top level page-table 337 * with the 'reference' page table. 338 * 339 * Do _not_ use "current" here. We might be inside 340 * an interrupt in the middle of a task switch.. 341 */ 342 pgd_paddr = read_cr3(); 343 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 344 if (!pmd_k) 345 return -1; 346 347 if (pmd_huge(*pmd_k)) 348 return 0; 349 350 pte_k = pte_offset_kernel(pmd_k, address); 351 if (!pte_present(*pte_k)) 352 return -1; 353 354 return 0; 355 } 356 NOKPROBE_SYMBOL(vmalloc_fault); 357 358 /* 359 * Did it hit the DOS screen memory VA from vm86 mode? 360 */ 361 static inline void 362 check_v8086_mode(struct pt_regs *regs, unsigned long address, 363 struct task_struct *tsk) 364 { 365 #ifdef CONFIG_VM86 366 unsigned long bit; 367 368 if (!v8086_mode(regs) || !tsk->thread.vm86) 369 return; 370 371 bit = (address - 0xA0000) >> PAGE_SHIFT; 372 if (bit < 32) 373 tsk->thread.vm86->screen_bitmap |= 1 << bit; 374 #endif 375 } 376 377 static bool low_pfn(unsigned long pfn) 378 { 379 return pfn < max_low_pfn; 380 } 381 382 static void dump_pagetable(unsigned long address) 383 { 384 pgd_t *base = __va(read_cr3()); 385 pgd_t *pgd = &base[pgd_index(address)]; 386 pmd_t *pmd; 387 pte_t *pte; 388 389 #ifdef CONFIG_X86_PAE 390 printk("*pdpt = %016Lx ", pgd_val(*pgd)); 391 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 392 goto out; 393 #endif 394 pmd = pmd_offset(pud_offset(pgd, address), address); 395 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 396 397 /* 398 * We must not directly access the pte in the highpte 399 * case if the page table is located in highmem. 400 * And let's rather not kmap-atomic the pte, just in case 401 * it's allocated already: 402 */ 403 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 404 goto out; 405 406 pte = pte_offset_kernel(pmd, address); 407 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 408 out: 409 printk("\n"); 410 } 411 412 #else /* CONFIG_X86_64: */ 413 414 void vmalloc_sync_all(void) 415 { 416 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 417 } 418 419 /* 420 * 64-bit: 421 * 422 * Handle a fault on the vmalloc area 423 */ 424 static noinline int vmalloc_fault(unsigned long address) 425 { 426 pgd_t *pgd, *pgd_ref; 427 pud_t *pud, *pud_ref; 428 pmd_t *pmd, *pmd_ref; 429 pte_t *pte, *pte_ref; 430 431 /* Make sure we are in vmalloc area: */ 432 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 433 return -1; 434 435 WARN_ON_ONCE(in_nmi()); 436 437 /* 438 * Copy kernel mappings over when needed. This can also 439 * happen within a race in page table update. In the later 440 * case just flush: 441 */ 442 pgd = (pgd_t *)__va(read_cr3()) + pgd_index(address); 443 pgd_ref = pgd_offset_k(address); 444 if (pgd_none(*pgd_ref)) 445 return -1; 446 447 if (pgd_none(*pgd)) { 448 set_pgd(pgd, *pgd_ref); 449 arch_flush_lazy_mmu_mode(); 450 } else { 451 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 452 } 453 454 /* 455 * Below here mismatches are bugs because these lower tables 456 * are shared: 457 */ 458 459 pud = pud_offset(pgd, address); 460 pud_ref = pud_offset(pgd_ref, address); 461 if (pud_none(*pud_ref)) 462 return -1; 463 464 if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref)) 465 BUG(); 466 467 if (pud_huge(*pud)) 468 return 0; 469 470 pmd = pmd_offset(pud, address); 471 pmd_ref = pmd_offset(pud_ref, address); 472 if (pmd_none(*pmd_ref)) 473 return -1; 474 475 if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref)) 476 BUG(); 477 478 if (pmd_huge(*pmd)) 479 return 0; 480 481 pte_ref = pte_offset_kernel(pmd_ref, address); 482 if (!pte_present(*pte_ref)) 483 return -1; 484 485 pte = pte_offset_kernel(pmd, address); 486 487 /* 488 * Don't use pte_page here, because the mappings can point 489 * outside mem_map, and the NUMA hash lookup cannot handle 490 * that: 491 */ 492 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) 493 BUG(); 494 495 return 0; 496 } 497 NOKPROBE_SYMBOL(vmalloc_fault); 498 499 #ifdef CONFIG_CPU_SUP_AMD 500 static const char errata93_warning[] = 501 KERN_ERR 502 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 503 "******* Working around it, but it may cause SEGVs or burn power.\n" 504 "******* Please consider a BIOS update.\n" 505 "******* Disabling USB legacy in the BIOS may also help.\n"; 506 #endif 507 508 /* 509 * No vm86 mode in 64-bit mode: 510 */ 511 static inline void 512 check_v8086_mode(struct pt_regs *regs, unsigned long address, 513 struct task_struct *tsk) 514 { 515 } 516 517 static int bad_address(void *p) 518 { 519 unsigned long dummy; 520 521 return probe_kernel_address((unsigned long *)p, dummy); 522 } 523 524 static void dump_pagetable(unsigned long address) 525 { 526 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK); 527 pgd_t *pgd = base + pgd_index(address); 528 pud_t *pud; 529 pmd_t *pmd; 530 pte_t *pte; 531 532 if (bad_address(pgd)) 533 goto bad; 534 535 printk("PGD %lx ", pgd_val(*pgd)); 536 537 if (!pgd_present(*pgd)) 538 goto out; 539 540 pud = pud_offset(pgd, address); 541 if (bad_address(pud)) 542 goto bad; 543 544 printk("PUD %lx ", pud_val(*pud)); 545 if (!pud_present(*pud) || pud_large(*pud)) 546 goto out; 547 548 pmd = pmd_offset(pud, address); 549 if (bad_address(pmd)) 550 goto bad; 551 552 printk("PMD %lx ", pmd_val(*pmd)); 553 if (!pmd_present(*pmd) || pmd_large(*pmd)) 554 goto out; 555 556 pte = pte_offset_kernel(pmd, address); 557 if (bad_address(pte)) 558 goto bad; 559 560 printk("PTE %lx", pte_val(*pte)); 561 out: 562 printk("\n"); 563 return; 564 bad: 565 printk("BAD\n"); 566 } 567 568 #endif /* CONFIG_X86_64 */ 569 570 /* 571 * Workaround for K8 erratum #93 & buggy BIOS. 572 * 573 * BIOS SMM functions are required to use a specific workaround 574 * to avoid corruption of the 64bit RIP register on C stepping K8. 575 * 576 * A lot of BIOS that didn't get tested properly miss this. 577 * 578 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 579 * Try to work around it here. 580 * 581 * Note we only handle faults in kernel here. 582 * Does nothing on 32-bit. 583 */ 584 static int is_errata93(struct pt_regs *regs, unsigned long address) 585 { 586 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 587 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 588 || boot_cpu_data.x86 != 0xf) 589 return 0; 590 591 if (address != regs->ip) 592 return 0; 593 594 if ((address >> 32) != 0) 595 return 0; 596 597 address |= 0xffffffffUL << 32; 598 if ((address >= (u64)_stext && address <= (u64)_etext) || 599 (address >= MODULES_VADDR && address <= MODULES_END)) { 600 printk_once(errata93_warning); 601 regs->ip = address; 602 return 1; 603 } 604 #endif 605 return 0; 606 } 607 608 /* 609 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 610 * to illegal addresses >4GB. 611 * 612 * We catch this in the page fault handler because these addresses 613 * are not reachable. Just detect this case and return. Any code 614 * segment in LDT is compatibility mode. 615 */ 616 static int is_errata100(struct pt_regs *regs, unsigned long address) 617 { 618 #ifdef CONFIG_X86_64 619 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 620 return 1; 621 #endif 622 return 0; 623 } 624 625 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 626 { 627 #ifdef CONFIG_X86_F00F_BUG 628 unsigned long nr; 629 630 /* 631 * Pentium F0 0F C7 C8 bug workaround: 632 */ 633 if (boot_cpu_has_bug(X86_BUG_F00F)) { 634 nr = (address - idt_descr.address) >> 3; 635 636 if (nr == 6) { 637 do_invalid_op(regs, 0); 638 return 1; 639 } 640 } 641 #endif 642 return 0; 643 } 644 645 static const char nx_warning[] = KERN_CRIT 646 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; 647 static const char smep_warning[] = KERN_CRIT 648 "unable to execute userspace code (SMEP?) (uid: %d)\n"; 649 650 static void 651 show_fault_oops(struct pt_regs *regs, unsigned long error_code, 652 unsigned long address) 653 { 654 if (!oops_may_print()) 655 return; 656 657 if (error_code & PF_INSTR) { 658 unsigned int level; 659 pgd_t *pgd; 660 pte_t *pte; 661 662 pgd = __va(read_cr3() & PHYSICAL_PAGE_MASK); 663 pgd += pgd_index(address); 664 665 pte = lookup_address_in_pgd(pgd, address, &level); 666 667 if (pte && pte_present(*pte) && !pte_exec(*pte)) 668 printk(nx_warning, from_kuid(&init_user_ns, current_uid())); 669 if (pte && pte_present(*pte) && pte_exec(*pte) && 670 (pgd_flags(*pgd) & _PAGE_USER) && 671 (__read_cr4() & X86_CR4_SMEP)) 672 printk(smep_warning, from_kuid(&init_user_ns, current_uid())); 673 } 674 675 printk(KERN_ALERT "BUG: unable to handle kernel "); 676 if (address < PAGE_SIZE) 677 printk(KERN_CONT "NULL pointer dereference"); 678 else 679 printk(KERN_CONT "paging request"); 680 681 printk(KERN_CONT " at %p\n", (void *) address); 682 printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip); 683 684 dump_pagetable(address); 685 } 686 687 static noinline void 688 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 689 unsigned long address) 690 { 691 struct task_struct *tsk; 692 unsigned long flags; 693 int sig; 694 695 flags = oops_begin(); 696 tsk = current; 697 sig = SIGKILL; 698 699 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 700 tsk->comm, address); 701 dump_pagetable(address); 702 703 tsk->thread.cr2 = address; 704 tsk->thread.trap_nr = X86_TRAP_PF; 705 tsk->thread.error_code = error_code; 706 707 if (__die("Bad pagetable", regs, error_code)) 708 sig = 0; 709 710 oops_end(flags, regs, sig); 711 } 712 713 static noinline void 714 no_context(struct pt_regs *regs, unsigned long error_code, 715 unsigned long address, int signal, int si_code) 716 { 717 struct task_struct *tsk = current; 718 unsigned long flags; 719 int sig; 720 /* No context means no VMA to pass down */ 721 struct vm_area_struct *vma = NULL; 722 723 /* Are we prepared to handle this kernel fault? */ 724 if (fixup_exception(regs, X86_TRAP_PF)) { 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 tsk->thread.trap_nr = X86_TRAP_PF; 741 tsk->thread.error_code = error_code | PF_USER; 742 tsk->thread.cr2 = address; 743 744 /* XXX: hwpoison faults will set the wrong code. */ 745 force_sig_info_fault(signal, si_code, address, 746 tsk, vma, 0); 747 } 748 749 /* 750 * Barring that, we can do the fixup and be happy. 751 */ 752 return; 753 } 754 755 #ifdef CONFIG_VMAP_STACK 756 /* 757 * Stack overflow? During boot, we can fault near the initial 758 * stack in the direct map, but that's not an overflow -- check 759 * that we're in vmalloc space to avoid this. 760 */ 761 if (is_vmalloc_addr((void *)address) && 762 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 763 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 764 register void *__sp asm("rsp"); 765 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *); 766 /* 767 * We're likely to be running with very little stack space 768 * left. It's plausible that we'd hit this condition but 769 * double-fault even before we get this far, in which case 770 * we're fine: the double-fault handler will deal with it. 771 * 772 * We don't want to make it all the way into the oops code 773 * and then double-fault, though, because we're likely to 774 * break the console driver and lose most of the stack dump. 775 */ 776 asm volatile ("movq %[stack], %%rsp\n\t" 777 "call handle_stack_overflow\n\t" 778 "1: jmp 1b" 779 : "+r" (__sp) 780 : "D" ("kernel stack overflow (page fault)"), 781 "S" (regs), "d" (address), 782 [stack] "rm" (stack)); 783 unreachable(); 784 } 785 #endif 786 787 /* 788 * 32-bit: 789 * 790 * Valid to do another page fault here, because if this fault 791 * had been triggered by is_prefetch fixup_exception would have 792 * handled it. 793 * 794 * 64-bit: 795 * 796 * Hall of shame of CPU/BIOS bugs. 797 */ 798 if (is_prefetch(regs, error_code, address)) 799 return; 800 801 if (is_errata93(regs, address)) 802 return; 803 804 /* 805 * Oops. The kernel tried to access some bad page. We'll have to 806 * terminate things with extreme prejudice: 807 */ 808 flags = oops_begin(); 809 810 show_fault_oops(regs, error_code, address); 811 812 if (task_stack_end_corrupted(tsk)) 813 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 814 815 tsk->thread.cr2 = address; 816 tsk->thread.trap_nr = X86_TRAP_PF; 817 tsk->thread.error_code = error_code; 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 if (!unhandled_signal(tsk, SIGSEGV)) 838 return; 839 840 if (!printk_ratelimit()) 841 return; 842 843 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", 844 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 845 tsk->comm, task_pid_nr(tsk), address, 846 (void *)regs->ip, (void *)regs->sp, error_code); 847 848 print_vma_addr(KERN_CONT " in ", regs->ip); 849 850 printk(KERN_CONT "\n"); 851 } 852 853 static void 854 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 855 unsigned long address, struct vm_area_struct *vma, 856 int si_code) 857 { 858 struct task_struct *tsk = current; 859 860 /* User mode accesses just cause a SIGSEGV */ 861 if (error_code & PF_USER) { 862 /* 863 * It's possible to have interrupts off here: 864 */ 865 local_irq_enable(); 866 867 /* 868 * Valid to do another page fault here because this one came 869 * from user space: 870 */ 871 if (is_prefetch(regs, error_code, address)) 872 return; 873 874 if (is_errata100(regs, address)) 875 return; 876 877 #ifdef CONFIG_X86_64 878 /* 879 * Instruction fetch faults in the vsyscall page might need 880 * emulation. 881 */ 882 if (unlikely((error_code & PF_INSTR) && 883 ((address & ~0xfff) == VSYSCALL_ADDR))) { 884 if (emulate_vsyscall(regs, address)) 885 return; 886 } 887 #endif 888 889 /* 890 * To avoid leaking information about the kernel page table 891 * layout, pretend that user-mode accesses to kernel addresses 892 * are always protection faults. 893 */ 894 if (address >= TASK_SIZE_MAX) 895 error_code |= PF_PROT; 896 897 if (likely(show_unhandled_signals)) 898 show_signal_msg(regs, error_code, address, tsk); 899 900 tsk->thread.cr2 = address; 901 tsk->thread.error_code = error_code; 902 tsk->thread.trap_nr = X86_TRAP_PF; 903 904 force_sig_info_fault(SIGSEGV, si_code, address, tsk, vma, 0); 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, struct vm_area_struct *vma) 918 { 919 __bad_area_nosemaphore(regs, error_code, address, vma, SEGV_MAPERR); 920 } 921 922 static void 923 __bad_area(struct pt_regs *regs, unsigned long error_code, 924 unsigned long address, struct vm_area_struct *vma, int si_code) 925 { 926 struct mm_struct *mm = current->mm; 927 928 /* 929 * Something tried to access memory that isn't in our memory map.. 930 * Fix it, but check if it's kernel or user first.. 931 */ 932 up_read(&mm->mmap_sem); 933 934 __bad_area_nosemaphore(regs, error_code, address, vma, si_code); 935 } 936 937 static noinline void 938 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 939 { 940 __bad_area(regs, error_code, address, NULL, SEGV_MAPERR); 941 } 942 943 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 944 struct vm_area_struct *vma) 945 { 946 /* This code is always called on the current mm */ 947 bool foreign = false; 948 949 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 950 return false; 951 if (error_code & PF_PK) 952 return true; 953 /* this checks permission keys on the VMA: */ 954 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), 955 (error_code & PF_INSTR), foreign)) 956 return true; 957 return false; 958 } 959 960 static noinline void 961 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 962 unsigned long address, struct vm_area_struct *vma) 963 { 964 /* 965 * This OSPKE check is not strictly necessary at runtime. 966 * But, doing it this way allows compiler optimizations 967 * if pkeys are compiled out. 968 */ 969 if (bad_area_access_from_pkeys(error_code, vma)) 970 __bad_area(regs, error_code, address, vma, SEGV_PKUERR); 971 else 972 __bad_area(regs, error_code, address, vma, SEGV_ACCERR); 973 } 974 975 static void 976 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 977 struct vm_area_struct *vma, unsigned int fault) 978 { 979 struct task_struct *tsk = current; 980 int code = BUS_ADRERR; 981 982 /* Kernel mode? Handle exceptions or die: */ 983 if (!(error_code & PF_USER)) { 984 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 985 return; 986 } 987 988 /* User-space => ok to do another page fault: */ 989 if (is_prefetch(regs, error_code, address)) 990 return; 991 992 tsk->thread.cr2 = address; 993 tsk->thread.error_code = error_code; 994 tsk->thread.trap_nr = X86_TRAP_PF; 995 996 #ifdef CONFIG_MEMORY_FAILURE 997 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 998 printk(KERN_ERR 999 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 1000 tsk->comm, tsk->pid, address); 1001 code = BUS_MCEERR_AR; 1002 } 1003 #endif 1004 force_sig_info_fault(SIGBUS, code, address, tsk, vma, fault); 1005 } 1006 1007 static noinline void 1008 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 1009 unsigned long address, struct vm_area_struct *vma, 1010 unsigned int fault) 1011 { 1012 if (fatal_signal_pending(current) && !(error_code & PF_USER)) { 1013 no_context(regs, error_code, address, 0, 0); 1014 return; 1015 } 1016 1017 if (fault & VM_FAULT_OOM) { 1018 /* Kernel mode? Handle exceptions or die: */ 1019 if (!(error_code & PF_USER)) { 1020 no_context(regs, error_code, address, 1021 SIGSEGV, SEGV_MAPERR); 1022 return; 1023 } 1024 1025 /* 1026 * We ran out of memory, call the OOM killer, and return the 1027 * userspace (which will retry the fault, or kill us if we got 1028 * oom-killed): 1029 */ 1030 pagefault_out_of_memory(); 1031 } else { 1032 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1033 VM_FAULT_HWPOISON_LARGE)) 1034 do_sigbus(regs, error_code, address, vma, fault); 1035 else if (fault & VM_FAULT_SIGSEGV) 1036 bad_area_nosemaphore(regs, error_code, address, vma); 1037 else 1038 BUG(); 1039 } 1040 } 1041 1042 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 1043 { 1044 if ((error_code & PF_WRITE) && !pte_write(*pte)) 1045 return 0; 1046 1047 if ((error_code & PF_INSTR) && !pte_exec(*pte)) 1048 return 0; 1049 /* 1050 * Note: We do not do lazy flushing on protection key 1051 * changes, so no spurious fault will ever set PF_PK. 1052 */ 1053 if ((error_code & PF_PK)) 1054 return 1; 1055 1056 return 1; 1057 } 1058 1059 /* 1060 * Handle a spurious fault caused by a stale TLB entry. 1061 * 1062 * This allows us to lazily refresh the TLB when increasing the 1063 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1064 * eagerly is very expensive since that implies doing a full 1065 * cross-processor TLB flush, even if no stale TLB entries exist 1066 * on other processors. 1067 * 1068 * Spurious faults may only occur if the TLB contains an entry with 1069 * fewer permission than the page table entry. Non-present (P = 0) 1070 * and reserved bit (R = 1) faults are never spurious. 1071 * 1072 * There are no security implications to leaving a stale TLB when 1073 * increasing the permissions on a page. 1074 * 1075 * Returns non-zero if a spurious fault was handled, zero otherwise. 1076 * 1077 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1078 * (Optional Invalidation). 1079 */ 1080 static noinline int 1081 spurious_fault(unsigned long error_code, unsigned long address) 1082 { 1083 pgd_t *pgd; 1084 pud_t *pud; 1085 pmd_t *pmd; 1086 pte_t *pte; 1087 int ret; 1088 1089 /* 1090 * Only writes to RO or instruction fetches from NX may cause 1091 * spurious faults. 1092 * 1093 * These could be from user or supervisor accesses but the TLB 1094 * is only lazily flushed after a kernel mapping protection 1095 * change, so user accesses are not expected to cause spurious 1096 * faults. 1097 */ 1098 if (error_code != (PF_WRITE | PF_PROT) 1099 && error_code != (PF_INSTR | PF_PROT)) 1100 return 0; 1101 1102 pgd = init_mm.pgd + pgd_index(address); 1103 if (!pgd_present(*pgd)) 1104 return 0; 1105 1106 pud = pud_offset(pgd, address); 1107 if (!pud_present(*pud)) 1108 return 0; 1109 1110 if (pud_large(*pud)) 1111 return spurious_fault_check(error_code, (pte_t *) pud); 1112 1113 pmd = pmd_offset(pud, address); 1114 if (!pmd_present(*pmd)) 1115 return 0; 1116 1117 if (pmd_large(*pmd)) 1118 return spurious_fault_check(error_code, (pte_t *) pmd); 1119 1120 pte = pte_offset_kernel(pmd, address); 1121 if (!pte_present(*pte)) 1122 return 0; 1123 1124 ret = spurious_fault_check(error_code, pte); 1125 if (!ret) 1126 return 0; 1127 1128 /* 1129 * Make sure we have permissions in PMD. 1130 * If not, then there's a bug in the page tables: 1131 */ 1132 ret = spurious_fault_check(error_code, (pte_t *) pmd); 1133 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1134 1135 return ret; 1136 } 1137 NOKPROBE_SYMBOL(spurious_fault); 1138 1139 int show_unhandled_signals = 1; 1140 1141 static inline int 1142 access_error(unsigned long error_code, struct vm_area_struct *vma) 1143 { 1144 /* This is only called for the current mm, so: */ 1145 bool foreign = false; 1146 1147 /* 1148 * Read or write was blocked by protection keys. This is 1149 * always an unconditional error and can never result in 1150 * a follow-up action to resolve the fault, like a COW. 1151 */ 1152 if (error_code & PF_PK) 1153 return 1; 1154 1155 /* 1156 * Make sure to check the VMA so that we do not perform 1157 * faults just to hit a PF_PK as soon as we fill in a 1158 * page. 1159 */ 1160 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), 1161 (error_code & PF_INSTR), foreign)) 1162 return 1; 1163 1164 if (error_code & PF_WRITE) { 1165 /* write, present and write, not present: */ 1166 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1167 return 1; 1168 return 0; 1169 } 1170 1171 /* read, present: */ 1172 if (unlikely(error_code & PF_PROT)) 1173 return 1; 1174 1175 /* read, not present: */ 1176 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 1177 return 1; 1178 1179 return 0; 1180 } 1181 1182 static int fault_in_kernel_space(unsigned long address) 1183 { 1184 return address >= TASK_SIZE_MAX; 1185 } 1186 1187 static inline bool smap_violation(int error_code, struct pt_regs *regs) 1188 { 1189 if (!IS_ENABLED(CONFIG_X86_SMAP)) 1190 return false; 1191 1192 if (!static_cpu_has(X86_FEATURE_SMAP)) 1193 return false; 1194 1195 if (error_code & PF_USER) 1196 return false; 1197 1198 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC)) 1199 return false; 1200 1201 return true; 1202 } 1203 1204 /* 1205 * This routine handles page faults. It determines the address, 1206 * and the problem, and then passes it off to one of the appropriate 1207 * routines. 1208 * 1209 * This function must have noinline because both callers 1210 * {,trace_}do_page_fault() have notrace on. Having this an actual function 1211 * guarantees there's a function trace entry. 1212 */ 1213 static noinline void 1214 __do_page_fault(struct pt_regs *regs, unsigned long error_code, 1215 unsigned long address) 1216 { 1217 struct vm_area_struct *vma; 1218 struct task_struct *tsk; 1219 struct mm_struct *mm; 1220 int fault, major = 0; 1221 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 1222 1223 tsk = current; 1224 mm = tsk->mm; 1225 1226 /* 1227 * Detect and handle instructions that would cause a page fault for 1228 * both a tracked kernel page and a userspace page. 1229 */ 1230 if (kmemcheck_active(regs)) 1231 kmemcheck_hide(regs); 1232 prefetchw(&mm->mmap_sem); 1233 1234 if (unlikely(kmmio_fault(regs, address))) 1235 return; 1236 1237 /* 1238 * We 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 * This verifies that the fault happens in kernel space 1247 * (error_code & 4) == 0, and that the fault was not a 1248 * protection error (error_code & 9) == 0. 1249 */ 1250 if (unlikely(fault_in_kernel_space(address))) { 1251 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) { 1252 if (vmalloc_fault(address) >= 0) 1253 return; 1254 1255 if (kmemcheck_fault(regs, address, error_code)) 1256 return; 1257 } 1258 1259 /* Can handle a stale RO->RW TLB: */ 1260 if (spurious_fault(error_code, address)) 1261 return; 1262 1263 /* kprobes don't want to hook the spurious faults: */ 1264 if (kprobes_fault(regs)) 1265 return; 1266 /* 1267 * Don't take the mm semaphore here. If we fixup a prefetch 1268 * fault we could otherwise deadlock: 1269 */ 1270 bad_area_nosemaphore(regs, error_code, address, NULL); 1271 1272 return; 1273 } 1274 1275 /* kprobes don't want to hook the spurious faults: */ 1276 if (unlikely(kprobes_fault(regs))) 1277 return; 1278 1279 if (unlikely(error_code & PF_RSVD)) 1280 pgtable_bad(regs, error_code, address); 1281 1282 if (unlikely(smap_violation(error_code, regs))) { 1283 bad_area_nosemaphore(regs, error_code, address, NULL); 1284 return; 1285 } 1286 1287 /* 1288 * If we're in an interrupt, have no user context or are running 1289 * in a region with pagefaults disabled then we must not take the fault 1290 */ 1291 if (unlikely(faulthandler_disabled() || !mm)) { 1292 bad_area_nosemaphore(regs, error_code, address, NULL); 1293 return; 1294 } 1295 1296 /* 1297 * It's safe to allow irq's after cr2 has been saved and the 1298 * vmalloc fault has been handled. 1299 * 1300 * User-mode registers count as a user access even for any 1301 * potential system fault or CPU buglet: 1302 */ 1303 if (user_mode(regs)) { 1304 local_irq_enable(); 1305 error_code |= PF_USER; 1306 flags |= FAULT_FLAG_USER; 1307 } else { 1308 if (regs->flags & X86_EFLAGS_IF) 1309 local_irq_enable(); 1310 } 1311 1312 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1313 1314 if (error_code & PF_WRITE) 1315 flags |= FAULT_FLAG_WRITE; 1316 if (error_code & PF_INSTR) 1317 flags |= FAULT_FLAG_INSTRUCTION; 1318 1319 /* 1320 * When running in the kernel we expect faults to occur only to 1321 * addresses in user space. All other faults represent errors in 1322 * the kernel and should generate an OOPS. Unfortunately, in the 1323 * case of an erroneous fault occurring in a code path which already 1324 * holds mmap_sem we will deadlock attempting to validate the fault 1325 * against the address space. Luckily the kernel only validly 1326 * references user space from well defined areas of code, which are 1327 * listed in the exceptions table. 1328 * 1329 * As the vast majority of faults will be valid we will only perform 1330 * the source reference check when there is a possibility of a 1331 * deadlock. Attempt to lock the address space, if we cannot we then 1332 * validate the source. If this is invalid we can skip the address 1333 * space check, thus avoiding the deadlock: 1334 */ 1335 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1336 if ((error_code & PF_USER) == 0 && 1337 !search_exception_tables(regs->ip)) { 1338 bad_area_nosemaphore(regs, error_code, address, NULL); 1339 return; 1340 } 1341 retry: 1342 down_read(&mm->mmap_sem); 1343 } else { 1344 /* 1345 * The above down_read_trylock() might have succeeded in 1346 * which case we'll have missed the might_sleep() from 1347 * down_read(): 1348 */ 1349 might_sleep(); 1350 } 1351 1352 vma = find_vma(mm, address); 1353 if (unlikely(!vma)) { 1354 bad_area(regs, error_code, address); 1355 return; 1356 } 1357 if (likely(vma->vm_start <= address)) 1358 goto good_area; 1359 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1360 bad_area(regs, error_code, address); 1361 return; 1362 } 1363 if (error_code & PF_USER) { 1364 /* 1365 * Accessing the stack below %sp is always a bug. 1366 * The large cushion allows instructions like enter 1367 * and pusha to work. ("enter $65535, $31" pushes 1368 * 32 pointers and then decrements %sp by 65535.) 1369 */ 1370 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { 1371 bad_area(regs, error_code, address); 1372 return; 1373 } 1374 } 1375 if (unlikely(expand_stack(vma, address))) { 1376 bad_area(regs, error_code, address); 1377 return; 1378 } 1379 1380 /* 1381 * Ok, we have a good vm_area for this memory access, so 1382 * we can handle it.. 1383 */ 1384 good_area: 1385 if (unlikely(access_error(error_code, vma))) { 1386 bad_area_access_error(regs, error_code, address, vma); 1387 return; 1388 } 1389 1390 /* 1391 * If for any reason at all we couldn't handle the fault, 1392 * make sure we exit gracefully rather than endlessly redo 1393 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1394 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. 1395 */ 1396 fault = handle_mm_fault(vma, address, flags); 1397 major |= fault & VM_FAULT_MAJOR; 1398 1399 /* 1400 * If we need to retry the mmap_sem has already been released, 1401 * and if there is a fatal signal pending there is no guarantee 1402 * that we made any progress. Handle this case first. 1403 */ 1404 if (unlikely(fault & VM_FAULT_RETRY)) { 1405 /* Retry at most once */ 1406 if (flags & FAULT_FLAG_ALLOW_RETRY) { 1407 flags &= ~FAULT_FLAG_ALLOW_RETRY; 1408 flags |= FAULT_FLAG_TRIED; 1409 if (!fatal_signal_pending(tsk)) 1410 goto retry; 1411 } 1412 1413 /* User mode? Just return to handle the fatal exception */ 1414 if (flags & FAULT_FLAG_USER) 1415 return; 1416 1417 /* Not returning to user mode? Handle exceptions or die: */ 1418 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 1419 return; 1420 } 1421 1422 up_read(&mm->mmap_sem); 1423 if (unlikely(fault & VM_FAULT_ERROR)) { 1424 mm_fault_error(regs, error_code, address, vma, fault); 1425 return; 1426 } 1427 1428 /* 1429 * Major/minor page fault accounting. If any of the events 1430 * returned VM_FAULT_MAJOR, we account it as a major fault. 1431 */ 1432 if (major) { 1433 tsk->maj_flt++; 1434 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 1435 } else { 1436 tsk->min_flt++; 1437 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 1438 } 1439 1440 check_v8086_mode(regs, address, tsk); 1441 } 1442 NOKPROBE_SYMBOL(__do_page_fault); 1443 1444 dotraplinkage void notrace 1445 do_page_fault(struct pt_regs *regs, unsigned long error_code) 1446 { 1447 unsigned long address = read_cr2(); /* Get the faulting address */ 1448 enum ctx_state prev_state; 1449 1450 /* 1451 * We must have this function tagged with __kprobes, notrace and call 1452 * read_cr2() before calling anything else. To avoid calling any kind 1453 * of tracing machinery before we've observed the CR2 value. 1454 * 1455 * exception_{enter,exit}() contain all sorts of tracepoints. 1456 */ 1457 1458 prev_state = exception_enter(); 1459 __do_page_fault(regs, error_code, address); 1460 exception_exit(prev_state); 1461 } 1462 NOKPROBE_SYMBOL(do_page_fault); 1463 1464 #ifdef CONFIG_TRACING 1465 static nokprobe_inline void 1466 trace_page_fault_entries(unsigned long address, struct pt_regs *regs, 1467 unsigned long error_code) 1468 { 1469 if (user_mode(regs)) 1470 trace_page_fault_user(address, regs, error_code); 1471 else 1472 trace_page_fault_kernel(address, regs, error_code); 1473 } 1474 1475 dotraplinkage void notrace 1476 trace_do_page_fault(struct pt_regs *regs, unsigned long error_code) 1477 { 1478 /* 1479 * The exception_enter and tracepoint processing could 1480 * trigger another page faults (user space callchain 1481 * reading) and destroy the original cr2 value, so read 1482 * the faulting address now. 1483 */ 1484 unsigned long address = read_cr2(); 1485 enum ctx_state prev_state; 1486 1487 prev_state = exception_enter(); 1488 trace_page_fault_entries(address, regs, error_code); 1489 __do_page_fault(regs, error_code, address); 1490 exception_exit(prev_state); 1491 } 1492 NOKPROBE_SYMBOL(trace_do_page_fault); 1493 #endif /* CONFIG_TRACING */ 1494