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/sched/task_stack.h> /* task_stack_*(), ... */ 8 #include <linux/kdebug.h> /* oops_begin/end, ... */ 9 #include <linux/extable.h> /* search_exception_tables */ 10 #include <linux/bootmem.h> /* max_low_pfn */ 11 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */ 12 #include <linux/mmiotrace.h> /* kmmio_handler, ... */ 13 #include <linux/perf_event.h> /* perf_sw_event */ 14 #include <linux/hugetlb.h> /* hstate_index_to_shift */ 15 #include <linux/prefetch.h> /* prefetchw */ 16 #include <linux/context_tracking.h> /* exception_enter(), ... */ 17 #include <linux/uaccess.h> /* faulthandler_disabled() */ 18 19 #include <asm/cpufeature.h> /* boot_cpu_has, ... */ 20 #include <asm/traps.h> /* dotraplinkage, ... */ 21 #include <asm/pgalloc.h> /* pgd_*(), ... */ 22 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */ 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 * Page fault error code bits: 33 * 34 * bit 0 == 0: no page found 1: protection fault 35 * bit 1 == 0: read access 1: write access 36 * bit 2 == 0: kernel-mode access 1: user-mode access 37 * bit 3 == 1: use of reserved bit detected 38 * bit 4 == 1: fault was an instruction fetch 39 * bit 5 == 1: protection keys block access 40 */ 41 enum x86_pf_error_code { 42 43 PF_PROT = 1 << 0, 44 PF_WRITE = 1 << 1, 45 PF_USER = 1 << 2, 46 PF_RSVD = 1 << 3, 47 PF_INSTR = 1 << 4, 48 PF_PK = 1 << 5, 49 }; 50 51 /* 52 * Returns 0 if mmiotrace is disabled, or if the fault is not 53 * handled by mmiotrace: 54 */ 55 static nokprobe_inline int 56 kmmio_fault(struct pt_regs *regs, unsigned long addr) 57 { 58 if (unlikely(is_kmmio_active())) 59 if (kmmio_handler(regs, addr) == 1) 60 return -1; 61 return 0; 62 } 63 64 static nokprobe_inline int kprobes_fault(struct pt_regs *regs) 65 { 66 int ret = 0; 67 68 /* kprobe_running() needs smp_processor_id() */ 69 if (kprobes_built_in() && !user_mode(regs)) { 70 preempt_disable(); 71 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 72 ret = 1; 73 preempt_enable(); 74 } 75 76 return ret; 77 } 78 79 /* 80 * Prefetch quirks: 81 * 82 * 32-bit mode: 83 * 84 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 85 * Check that here and ignore it. 86 * 87 * 64-bit mode: 88 * 89 * Sometimes the CPU reports invalid exceptions on prefetch. 90 * Check that here and ignore it. 91 * 92 * Opcode checker based on code by Richard Brunner. 93 */ 94 static inline int 95 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 96 unsigned char opcode, int *prefetch) 97 { 98 unsigned char instr_hi = opcode & 0xf0; 99 unsigned char instr_lo = opcode & 0x0f; 100 101 switch (instr_hi) { 102 case 0x20: 103 case 0x30: 104 /* 105 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 106 * In X86_64 long mode, the CPU will signal invalid 107 * opcode if some of these prefixes are present so 108 * X86_64 will never get here anyway 109 */ 110 return ((instr_lo & 7) == 0x6); 111 #ifdef CONFIG_X86_64 112 case 0x40: 113 /* 114 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 115 * Need to figure out under what instruction mode the 116 * instruction was issued. Could check the LDT for lm, 117 * but for now it's good enough to assume that long 118 * mode only uses well known segments or kernel. 119 */ 120 return (!user_mode(regs) || user_64bit_mode(regs)); 121 #endif 122 case 0x60: 123 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 124 return (instr_lo & 0xC) == 0x4; 125 case 0xF0: 126 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 127 return !instr_lo || (instr_lo>>1) == 1; 128 case 0x00: 129 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 130 if (probe_kernel_address(instr, opcode)) 131 return 0; 132 133 *prefetch = (instr_lo == 0xF) && 134 (opcode == 0x0D || opcode == 0x18); 135 return 0; 136 default: 137 return 0; 138 } 139 } 140 141 static int 142 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 143 { 144 unsigned char *max_instr; 145 unsigned char *instr; 146 int prefetch = 0; 147 148 /* 149 * If it was a exec (instruction fetch) fault on NX page, then 150 * do not ignore the fault: 151 */ 152 if (error_code & PF_INSTR) 153 return 0; 154 155 instr = (void *)convert_ip_to_linear(current, regs); 156 max_instr = instr + 15; 157 158 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX) 159 return 0; 160 161 while (instr < max_instr) { 162 unsigned char opcode; 163 164 if (probe_kernel_address(instr, opcode)) 165 break; 166 167 instr++; 168 169 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 170 break; 171 } 172 return prefetch; 173 } 174 175 /* 176 * A protection key fault means that the PKRU value did not allow 177 * access to some PTE. Userspace can figure out what PKRU was 178 * from the XSAVE state, and this function fills out a field in 179 * siginfo so userspace can discover which protection key was set 180 * on the PTE. 181 * 182 * If we get here, we know that the hardware signaled a PF_PK 183 * fault and that there was a VMA once we got in the fault 184 * handler. It does *not* guarantee that the VMA we find here 185 * was the one that we faulted on. 186 * 187 * 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4); 188 * 2. T1 : set PKRU to deny access to pkey=4, touches page 189 * 3. T1 : faults... 190 * 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5); 191 * 5. T1 : enters fault handler, takes mmap_sem, etc... 192 * 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really 193 * faulted on a pte with its pkey=4. 194 */ 195 static void fill_sig_info_pkey(int si_code, siginfo_t *info, 196 struct vm_area_struct *vma) 197 { 198 /* This is effectively an #ifdef */ 199 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 200 return; 201 202 /* Fault not from Protection Keys: nothing to do */ 203 if (si_code != SEGV_PKUERR) 204 return; 205 /* 206 * force_sig_info_fault() is called from a number of 207 * contexts, some of which have a VMA and some of which 208 * do not. The PF_PK handing happens after we have a 209 * valid VMA, so we should never reach this without a 210 * valid VMA. 211 */ 212 if (!vma) { 213 WARN_ONCE(1, "PKU fault with no VMA passed in"); 214 info->si_pkey = 0; 215 return; 216 } 217 /* 218 * si_pkey should be thought of as a strong hint, but not 219 * absolutely guranteed to be 100% accurate because of 220 * the race explained above. 221 */ 222 info->si_pkey = vma_pkey(vma); 223 } 224 225 static void 226 force_sig_info_fault(int si_signo, int si_code, unsigned long address, 227 struct task_struct *tsk, struct vm_area_struct *vma, 228 int fault) 229 { 230 unsigned lsb = 0; 231 siginfo_t info; 232 233 info.si_signo = si_signo; 234 info.si_errno = 0; 235 info.si_code = si_code; 236 info.si_addr = (void __user *)address; 237 if (fault & VM_FAULT_HWPOISON_LARGE) 238 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 239 if (fault & VM_FAULT_HWPOISON) 240 lsb = PAGE_SHIFT; 241 info.si_addr_lsb = lsb; 242 243 fill_sig_info_pkey(si_code, &info, vma); 244 245 force_sig_info(si_signo, &info, tsk); 246 } 247 248 DEFINE_SPINLOCK(pgd_lock); 249 LIST_HEAD(pgd_list); 250 251 #ifdef CONFIG_X86_32 252 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 253 { 254 unsigned index = pgd_index(address); 255 pgd_t *pgd_k; 256 p4d_t *p4d, *p4d_k; 257 pud_t *pud, *pud_k; 258 pmd_t *pmd, *pmd_k; 259 260 pgd += index; 261 pgd_k = init_mm.pgd + index; 262 263 if (!pgd_present(*pgd_k)) 264 return NULL; 265 266 /* 267 * set_pgd(pgd, *pgd_k); here would be useless on PAE 268 * and redundant with the set_pmd() on non-PAE. As would 269 * set_p4d/set_pud. 270 */ 271 p4d = p4d_offset(pgd, address); 272 p4d_k = p4d_offset(pgd_k, address); 273 if (!p4d_present(*p4d_k)) 274 return NULL; 275 276 pud = pud_offset(p4d, address); 277 pud_k = pud_offset(p4d_k, address); 278 if (!pud_present(*pud_k)) 279 return NULL; 280 281 pmd = pmd_offset(pud, address); 282 pmd_k = pmd_offset(pud_k, address); 283 if (!pmd_present(*pmd_k)) 284 return NULL; 285 286 if (!pmd_present(*pmd)) 287 set_pmd(pmd, *pmd_k); 288 else 289 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 290 291 return pmd_k; 292 } 293 294 void vmalloc_sync_all(void) 295 { 296 unsigned long address; 297 298 if (SHARED_KERNEL_PMD) 299 return; 300 301 for (address = VMALLOC_START & PMD_MASK; 302 address >= TASK_SIZE_MAX && address < FIXADDR_TOP; 303 address += PMD_SIZE) { 304 struct page *page; 305 306 spin_lock(&pgd_lock); 307 list_for_each_entry(page, &pgd_list, lru) { 308 spinlock_t *pgt_lock; 309 pmd_t *ret; 310 311 /* the pgt_lock only for Xen */ 312 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 313 314 spin_lock(pgt_lock); 315 ret = vmalloc_sync_one(page_address(page), address); 316 spin_unlock(pgt_lock); 317 318 if (!ret) 319 break; 320 } 321 spin_unlock(&pgd_lock); 322 } 323 } 324 325 /* 326 * 32-bit: 327 * 328 * Handle a fault on the vmalloc or module mapping area 329 */ 330 static noinline int vmalloc_fault(unsigned long address) 331 { 332 unsigned long pgd_paddr; 333 pmd_t *pmd_k; 334 pte_t *pte_k; 335 336 /* Make sure we are in vmalloc area: */ 337 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 338 return -1; 339 340 WARN_ON_ONCE(in_nmi()); 341 342 /* 343 * Synchronize this task's top level page-table 344 * with the 'reference' page table. 345 * 346 * Do _not_ use "current" here. We might be inside 347 * an interrupt in the middle of a task switch.. 348 */ 349 pgd_paddr = read_cr3_pa(); 350 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 351 if (!pmd_k) 352 return -1; 353 354 if (pmd_huge(*pmd_k)) 355 return 0; 356 357 pte_k = pte_offset_kernel(pmd_k, address); 358 if (!pte_present(*pte_k)) 359 return -1; 360 361 return 0; 362 } 363 NOKPROBE_SYMBOL(vmalloc_fault); 364 365 /* 366 * Did it hit the DOS screen memory VA from vm86 mode? 367 */ 368 static inline void 369 check_v8086_mode(struct pt_regs *regs, unsigned long address, 370 struct task_struct *tsk) 371 { 372 #ifdef CONFIG_VM86 373 unsigned long bit; 374 375 if (!v8086_mode(regs) || !tsk->thread.vm86) 376 return; 377 378 bit = (address - 0xA0000) >> PAGE_SHIFT; 379 if (bit < 32) 380 tsk->thread.vm86->screen_bitmap |= 1 << bit; 381 #endif 382 } 383 384 static bool low_pfn(unsigned long pfn) 385 { 386 return pfn < max_low_pfn; 387 } 388 389 static void dump_pagetable(unsigned long address) 390 { 391 pgd_t *base = __va(read_cr3_pa()); 392 pgd_t *pgd = &base[pgd_index(address)]; 393 p4d_t *p4d; 394 pud_t *pud; 395 pmd_t *pmd; 396 pte_t *pte; 397 398 #ifdef CONFIG_X86_PAE 399 printk("*pdpt = %016Lx ", pgd_val(*pgd)); 400 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 401 goto out; 402 #endif 403 p4d = p4d_offset(pgd, address); 404 pud = pud_offset(p4d, address); 405 pmd = pmd_offset(pud, address); 406 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 407 408 /* 409 * We must not directly access the pte in the highpte 410 * case if the page table is located in highmem. 411 * And let's rather not kmap-atomic the pte, just in case 412 * it's allocated already: 413 */ 414 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 415 goto out; 416 417 pte = pte_offset_kernel(pmd, address); 418 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 419 out: 420 printk("\n"); 421 } 422 423 #else /* CONFIG_X86_64: */ 424 425 void vmalloc_sync_all(void) 426 { 427 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 428 } 429 430 /* 431 * 64-bit: 432 * 433 * Handle a fault on the vmalloc area 434 */ 435 static noinline int vmalloc_fault(unsigned long address) 436 { 437 pgd_t *pgd, *pgd_ref; 438 p4d_t *p4d, *p4d_ref; 439 pud_t *pud, *pud_ref; 440 pmd_t *pmd, *pmd_ref; 441 pte_t *pte, *pte_ref; 442 443 /* Make sure we are in vmalloc area: */ 444 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 445 return -1; 446 447 WARN_ON_ONCE(in_nmi()); 448 449 /* 450 * Copy kernel mappings over when needed. This can also 451 * happen within a race in page table update. In the later 452 * case just flush: 453 */ 454 pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address); 455 pgd_ref = pgd_offset_k(address); 456 if (pgd_none(*pgd_ref)) 457 return -1; 458 459 if (pgd_none(*pgd)) { 460 set_pgd(pgd, *pgd_ref); 461 arch_flush_lazy_mmu_mode(); 462 } else if (CONFIG_PGTABLE_LEVELS > 4) { 463 /* 464 * With folded p4d, pgd_none() is always false, so the pgd may 465 * point to an empty page table entry and pgd_page_vaddr() 466 * will return garbage. 467 * 468 * We will do the correct sanity check on the p4d level. 469 */ 470 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 471 } 472 473 /* With 4-level paging, copying happens on the p4d level. */ 474 p4d = p4d_offset(pgd, address); 475 p4d_ref = p4d_offset(pgd_ref, address); 476 if (p4d_none(*p4d_ref)) 477 return -1; 478 479 if (p4d_none(*p4d)) { 480 set_p4d(p4d, *p4d_ref); 481 arch_flush_lazy_mmu_mode(); 482 } else { 483 BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_ref)); 484 } 485 486 /* 487 * Below here mismatches are bugs because these lower tables 488 * are shared: 489 */ 490 491 pud = pud_offset(p4d, address); 492 pud_ref = pud_offset(p4d_ref, address); 493 if (pud_none(*pud_ref)) 494 return -1; 495 496 if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref)) 497 BUG(); 498 499 if (pud_huge(*pud)) 500 return 0; 501 502 pmd = pmd_offset(pud, address); 503 pmd_ref = pmd_offset(pud_ref, address); 504 if (pmd_none(*pmd_ref)) 505 return -1; 506 507 if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref)) 508 BUG(); 509 510 if (pmd_huge(*pmd)) 511 return 0; 512 513 pte_ref = pte_offset_kernel(pmd_ref, address); 514 if (!pte_present(*pte_ref)) 515 return -1; 516 517 pte = pte_offset_kernel(pmd, address); 518 519 /* 520 * Don't use pte_page here, because the mappings can point 521 * outside mem_map, and the NUMA hash lookup cannot handle 522 * that: 523 */ 524 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) 525 BUG(); 526 527 return 0; 528 } 529 NOKPROBE_SYMBOL(vmalloc_fault); 530 531 #ifdef CONFIG_CPU_SUP_AMD 532 static const char errata93_warning[] = 533 KERN_ERR 534 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 535 "******* Working around it, but it may cause SEGVs or burn power.\n" 536 "******* Please consider a BIOS update.\n" 537 "******* Disabling USB legacy in the BIOS may also help.\n"; 538 #endif 539 540 /* 541 * No vm86 mode in 64-bit mode: 542 */ 543 static inline void 544 check_v8086_mode(struct pt_regs *regs, unsigned long address, 545 struct task_struct *tsk) 546 { 547 } 548 549 static int bad_address(void *p) 550 { 551 unsigned long dummy; 552 553 return probe_kernel_address((unsigned long *)p, dummy); 554 } 555 556 static void dump_pagetable(unsigned long address) 557 { 558 pgd_t *base = __va(read_cr3_pa()); 559 pgd_t *pgd = base + pgd_index(address); 560 p4d_t *p4d; 561 pud_t *pud; 562 pmd_t *pmd; 563 pte_t *pte; 564 565 if (bad_address(pgd)) 566 goto bad; 567 568 printk("PGD %lx ", pgd_val(*pgd)); 569 570 if (!pgd_present(*pgd)) 571 goto out; 572 573 p4d = p4d_offset(pgd, address); 574 if (bad_address(p4d)) 575 goto bad; 576 577 printk("P4D %lx ", p4d_val(*p4d)); 578 if (!p4d_present(*p4d) || p4d_large(*p4d)) 579 goto out; 580 581 pud = pud_offset(p4d, address); 582 if (bad_address(pud)) 583 goto bad; 584 585 printk("PUD %lx ", pud_val(*pud)); 586 if (!pud_present(*pud) || pud_large(*pud)) 587 goto out; 588 589 pmd = pmd_offset(pud, address); 590 if (bad_address(pmd)) 591 goto bad; 592 593 printk("PMD %lx ", pmd_val(*pmd)); 594 if (!pmd_present(*pmd) || pmd_large(*pmd)) 595 goto out; 596 597 pte = pte_offset_kernel(pmd, address); 598 if (bad_address(pte)) 599 goto bad; 600 601 printk("PTE %lx", pte_val(*pte)); 602 out: 603 printk("\n"); 604 return; 605 bad: 606 printk("BAD\n"); 607 } 608 609 #endif /* CONFIG_X86_64 */ 610 611 /* 612 * Workaround for K8 erratum #93 & buggy BIOS. 613 * 614 * BIOS SMM functions are required to use a specific workaround 615 * to avoid corruption of the 64bit RIP register on C stepping K8. 616 * 617 * A lot of BIOS that didn't get tested properly miss this. 618 * 619 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 620 * Try to work around it here. 621 * 622 * Note we only handle faults in kernel here. 623 * Does nothing on 32-bit. 624 */ 625 static int is_errata93(struct pt_regs *regs, unsigned long address) 626 { 627 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 628 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 629 || boot_cpu_data.x86 != 0xf) 630 return 0; 631 632 if (address != regs->ip) 633 return 0; 634 635 if ((address >> 32) != 0) 636 return 0; 637 638 address |= 0xffffffffUL << 32; 639 if ((address >= (u64)_stext && address <= (u64)_etext) || 640 (address >= MODULES_VADDR && address <= MODULES_END)) { 641 printk_once(errata93_warning); 642 regs->ip = address; 643 return 1; 644 } 645 #endif 646 return 0; 647 } 648 649 /* 650 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 651 * to illegal addresses >4GB. 652 * 653 * We catch this in the page fault handler because these addresses 654 * are not reachable. Just detect this case and return. Any code 655 * segment in LDT is compatibility mode. 656 */ 657 static int is_errata100(struct pt_regs *regs, unsigned long address) 658 { 659 #ifdef CONFIG_X86_64 660 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 661 return 1; 662 #endif 663 return 0; 664 } 665 666 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 667 { 668 #ifdef CONFIG_X86_F00F_BUG 669 unsigned long nr; 670 671 /* 672 * Pentium F0 0F C7 C8 bug workaround: 673 */ 674 if (boot_cpu_has_bug(X86_BUG_F00F)) { 675 nr = (address - idt_descr.address) >> 3; 676 677 if (nr == 6) { 678 do_invalid_op(regs, 0); 679 return 1; 680 } 681 } 682 #endif 683 return 0; 684 } 685 686 static const char nx_warning[] = KERN_CRIT 687 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; 688 static const char smep_warning[] = KERN_CRIT 689 "unable to execute userspace code (SMEP?) (uid: %d)\n"; 690 691 static void 692 show_fault_oops(struct pt_regs *regs, unsigned long error_code, 693 unsigned long address) 694 { 695 if (!oops_may_print()) 696 return; 697 698 if (error_code & PF_INSTR) { 699 unsigned int level; 700 pgd_t *pgd; 701 pte_t *pte; 702 703 pgd = __va(read_cr3_pa()); 704 pgd += pgd_index(address); 705 706 pte = lookup_address_in_pgd(pgd, address, &level); 707 708 if (pte && pte_present(*pte) && !pte_exec(*pte)) 709 printk(nx_warning, from_kuid(&init_user_ns, current_uid())); 710 if (pte && pte_present(*pte) && pte_exec(*pte) && 711 (pgd_flags(*pgd) & _PAGE_USER) && 712 (__read_cr4() & X86_CR4_SMEP)) 713 printk(smep_warning, from_kuid(&init_user_ns, current_uid())); 714 } 715 716 printk(KERN_ALERT "BUG: unable to handle kernel "); 717 if (address < PAGE_SIZE) 718 printk(KERN_CONT "NULL pointer dereference"); 719 else 720 printk(KERN_CONT "paging request"); 721 722 printk(KERN_CONT " at %p\n", (void *) address); 723 printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip); 724 725 dump_pagetable(address); 726 } 727 728 static noinline void 729 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 730 unsigned long address) 731 { 732 struct task_struct *tsk; 733 unsigned long flags; 734 int sig; 735 736 flags = oops_begin(); 737 tsk = current; 738 sig = SIGKILL; 739 740 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 741 tsk->comm, address); 742 dump_pagetable(address); 743 744 tsk->thread.cr2 = address; 745 tsk->thread.trap_nr = X86_TRAP_PF; 746 tsk->thread.error_code = error_code; 747 748 if (__die("Bad pagetable", regs, error_code)) 749 sig = 0; 750 751 oops_end(flags, regs, sig); 752 } 753 754 static noinline void 755 no_context(struct pt_regs *regs, unsigned long error_code, 756 unsigned long address, int signal, int si_code) 757 { 758 struct task_struct *tsk = current; 759 unsigned long flags; 760 int sig; 761 /* No context means no VMA to pass down */ 762 struct vm_area_struct *vma = NULL; 763 764 /* Are we prepared to handle this kernel fault? */ 765 if (fixup_exception(regs, X86_TRAP_PF)) { 766 /* 767 * Any interrupt that takes a fault gets the fixup. This makes 768 * the below recursive fault logic only apply to a faults from 769 * task context. 770 */ 771 if (in_interrupt()) 772 return; 773 774 /* 775 * Per the above we're !in_interrupt(), aka. task context. 776 * 777 * In this case we need to make sure we're not recursively 778 * faulting through the emulate_vsyscall() logic. 779 */ 780 if (current->thread.sig_on_uaccess_err && signal) { 781 tsk->thread.trap_nr = X86_TRAP_PF; 782 tsk->thread.error_code = error_code | PF_USER; 783 tsk->thread.cr2 = address; 784 785 /* XXX: hwpoison faults will set the wrong code. */ 786 force_sig_info_fault(signal, si_code, address, 787 tsk, vma, 0); 788 } 789 790 /* 791 * Barring that, we can do the fixup and be happy. 792 */ 793 return; 794 } 795 796 #ifdef CONFIG_VMAP_STACK 797 /* 798 * Stack overflow? During boot, we can fault near the initial 799 * stack in the direct map, but that's not an overflow -- check 800 * that we're in vmalloc space to avoid this. 801 */ 802 if (is_vmalloc_addr((void *)address) && 803 (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || 804 address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { 805 register void *__sp asm("rsp"); 806 unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *); 807 /* 808 * We're likely to be running with very little stack space 809 * left. It's plausible that we'd hit this condition but 810 * double-fault even before we get this far, in which case 811 * we're fine: the double-fault handler will deal with it. 812 * 813 * We don't want to make it all the way into the oops code 814 * and then double-fault, though, because we're likely to 815 * break the console driver and lose most of the stack dump. 816 */ 817 asm volatile ("movq %[stack], %%rsp\n\t" 818 "call handle_stack_overflow\n\t" 819 "1: jmp 1b" 820 : "+r" (__sp) 821 : "D" ("kernel stack overflow (page fault)"), 822 "S" (regs), "d" (address), 823 [stack] "rm" (stack)); 824 unreachable(); 825 } 826 #endif 827 828 /* 829 * 32-bit: 830 * 831 * Valid to do another page fault here, because if this fault 832 * had been triggered by is_prefetch fixup_exception would have 833 * handled it. 834 * 835 * 64-bit: 836 * 837 * Hall of shame of CPU/BIOS bugs. 838 */ 839 if (is_prefetch(regs, error_code, address)) 840 return; 841 842 if (is_errata93(regs, address)) 843 return; 844 845 /* 846 * Oops. The kernel tried to access some bad page. We'll have to 847 * terminate things with extreme prejudice: 848 */ 849 flags = oops_begin(); 850 851 show_fault_oops(regs, error_code, address); 852 853 if (task_stack_end_corrupted(tsk)) 854 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 855 856 tsk->thread.cr2 = address; 857 tsk->thread.trap_nr = X86_TRAP_PF; 858 tsk->thread.error_code = error_code; 859 860 sig = SIGKILL; 861 if (__die("Oops", regs, error_code)) 862 sig = 0; 863 864 /* Executive summary in case the body of the oops scrolled away */ 865 printk(KERN_DEFAULT "CR2: %016lx\n", address); 866 867 oops_end(flags, regs, sig); 868 } 869 870 /* 871 * Print out info about fatal segfaults, if the show_unhandled_signals 872 * sysctl is set: 873 */ 874 static inline void 875 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 876 unsigned long address, struct task_struct *tsk) 877 { 878 if (!unhandled_signal(tsk, SIGSEGV)) 879 return; 880 881 if (!printk_ratelimit()) 882 return; 883 884 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", 885 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 886 tsk->comm, task_pid_nr(tsk), address, 887 (void *)regs->ip, (void *)regs->sp, error_code); 888 889 print_vma_addr(KERN_CONT " in ", regs->ip); 890 891 printk(KERN_CONT "\n"); 892 } 893 894 static void 895 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 896 unsigned long address, struct vm_area_struct *vma, 897 int si_code) 898 { 899 struct task_struct *tsk = current; 900 901 /* User mode accesses just cause a SIGSEGV */ 902 if (error_code & PF_USER) { 903 /* 904 * It's possible to have interrupts off here: 905 */ 906 local_irq_enable(); 907 908 /* 909 * Valid to do another page fault here because this one came 910 * from user space: 911 */ 912 if (is_prefetch(regs, error_code, address)) 913 return; 914 915 if (is_errata100(regs, address)) 916 return; 917 918 #ifdef CONFIG_X86_64 919 /* 920 * Instruction fetch faults in the vsyscall page might need 921 * emulation. 922 */ 923 if (unlikely((error_code & PF_INSTR) && 924 ((address & ~0xfff) == VSYSCALL_ADDR))) { 925 if (emulate_vsyscall(regs, address)) 926 return; 927 } 928 #endif 929 930 /* 931 * To avoid leaking information about the kernel page table 932 * layout, pretend that user-mode accesses to kernel addresses 933 * are always protection faults. 934 */ 935 if (address >= TASK_SIZE_MAX) 936 error_code |= PF_PROT; 937 938 if (likely(show_unhandled_signals)) 939 show_signal_msg(regs, error_code, address, tsk); 940 941 tsk->thread.cr2 = address; 942 tsk->thread.error_code = error_code; 943 tsk->thread.trap_nr = X86_TRAP_PF; 944 945 force_sig_info_fault(SIGSEGV, si_code, address, tsk, vma, 0); 946 947 return; 948 } 949 950 if (is_f00f_bug(regs, address)) 951 return; 952 953 no_context(regs, error_code, address, SIGSEGV, si_code); 954 } 955 956 static noinline void 957 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 958 unsigned long address, struct vm_area_struct *vma) 959 { 960 __bad_area_nosemaphore(regs, error_code, address, vma, SEGV_MAPERR); 961 } 962 963 static void 964 __bad_area(struct pt_regs *regs, unsigned long error_code, 965 unsigned long address, struct vm_area_struct *vma, int si_code) 966 { 967 struct mm_struct *mm = current->mm; 968 969 /* 970 * Something tried to access memory that isn't in our memory map.. 971 * Fix it, but check if it's kernel or user first.. 972 */ 973 up_read(&mm->mmap_sem); 974 975 __bad_area_nosemaphore(regs, error_code, address, vma, si_code); 976 } 977 978 static noinline void 979 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 980 { 981 __bad_area(regs, error_code, address, NULL, SEGV_MAPERR); 982 } 983 984 static inline bool bad_area_access_from_pkeys(unsigned long error_code, 985 struct vm_area_struct *vma) 986 { 987 /* This code is always called on the current mm */ 988 bool foreign = false; 989 990 if (!boot_cpu_has(X86_FEATURE_OSPKE)) 991 return false; 992 if (error_code & PF_PK) 993 return true; 994 /* this checks permission keys on the VMA: */ 995 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), 996 (error_code & PF_INSTR), foreign)) 997 return true; 998 return false; 999 } 1000 1001 static noinline void 1002 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 1003 unsigned long address, struct vm_area_struct *vma) 1004 { 1005 /* 1006 * This OSPKE check is not strictly necessary at runtime. 1007 * But, doing it this way allows compiler optimizations 1008 * if pkeys are compiled out. 1009 */ 1010 if (bad_area_access_from_pkeys(error_code, vma)) 1011 __bad_area(regs, error_code, address, vma, SEGV_PKUERR); 1012 else 1013 __bad_area(regs, error_code, address, vma, SEGV_ACCERR); 1014 } 1015 1016 static void 1017 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 1018 struct vm_area_struct *vma, unsigned int fault) 1019 { 1020 struct task_struct *tsk = current; 1021 int code = BUS_ADRERR; 1022 1023 /* Kernel mode? Handle exceptions or die: */ 1024 if (!(error_code & PF_USER)) { 1025 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 1026 return; 1027 } 1028 1029 /* User-space => ok to do another page fault: */ 1030 if (is_prefetch(regs, error_code, address)) 1031 return; 1032 1033 tsk->thread.cr2 = address; 1034 tsk->thread.error_code = error_code; 1035 tsk->thread.trap_nr = X86_TRAP_PF; 1036 1037 #ifdef CONFIG_MEMORY_FAILURE 1038 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 1039 printk(KERN_ERR 1040 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 1041 tsk->comm, tsk->pid, address); 1042 code = BUS_MCEERR_AR; 1043 } 1044 #endif 1045 force_sig_info_fault(SIGBUS, code, address, tsk, vma, fault); 1046 } 1047 1048 static noinline void 1049 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 1050 unsigned long address, struct vm_area_struct *vma, 1051 unsigned int fault) 1052 { 1053 if (fatal_signal_pending(current) && !(error_code & PF_USER)) { 1054 no_context(regs, error_code, address, 0, 0); 1055 return; 1056 } 1057 1058 if (fault & VM_FAULT_OOM) { 1059 /* Kernel mode? Handle exceptions or die: */ 1060 if (!(error_code & PF_USER)) { 1061 no_context(regs, error_code, address, 1062 SIGSEGV, SEGV_MAPERR); 1063 return; 1064 } 1065 1066 /* 1067 * We ran out of memory, call the OOM killer, and return the 1068 * userspace (which will retry the fault, or kill us if we got 1069 * oom-killed): 1070 */ 1071 pagefault_out_of_memory(); 1072 } else { 1073 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 1074 VM_FAULT_HWPOISON_LARGE)) 1075 do_sigbus(regs, error_code, address, vma, fault); 1076 else if (fault & VM_FAULT_SIGSEGV) 1077 bad_area_nosemaphore(regs, error_code, address, vma); 1078 else 1079 BUG(); 1080 } 1081 } 1082 1083 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 1084 { 1085 if ((error_code & PF_WRITE) && !pte_write(*pte)) 1086 return 0; 1087 1088 if ((error_code & PF_INSTR) && !pte_exec(*pte)) 1089 return 0; 1090 /* 1091 * Note: We do not do lazy flushing on protection key 1092 * changes, so no spurious fault will ever set PF_PK. 1093 */ 1094 if ((error_code & PF_PK)) 1095 return 1; 1096 1097 return 1; 1098 } 1099 1100 /* 1101 * Handle a spurious fault caused by a stale TLB entry. 1102 * 1103 * This allows us to lazily refresh the TLB when increasing the 1104 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 1105 * eagerly is very expensive since that implies doing a full 1106 * cross-processor TLB flush, even if no stale TLB entries exist 1107 * on other processors. 1108 * 1109 * Spurious faults may only occur if the TLB contains an entry with 1110 * fewer permission than the page table entry. Non-present (P = 0) 1111 * and reserved bit (R = 1) faults are never spurious. 1112 * 1113 * There are no security implications to leaving a stale TLB when 1114 * increasing the permissions on a page. 1115 * 1116 * Returns non-zero if a spurious fault was handled, zero otherwise. 1117 * 1118 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3 1119 * (Optional Invalidation). 1120 */ 1121 static noinline int 1122 spurious_fault(unsigned long error_code, unsigned long address) 1123 { 1124 pgd_t *pgd; 1125 p4d_t *p4d; 1126 pud_t *pud; 1127 pmd_t *pmd; 1128 pte_t *pte; 1129 int ret; 1130 1131 /* 1132 * Only writes to RO or instruction fetches from NX may cause 1133 * spurious faults. 1134 * 1135 * These could be from user or supervisor accesses but the TLB 1136 * is only lazily flushed after a kernel mapping protection 1137 * change, so user accesses are not expected to cause spurious 1138 * faults. 1139 */ 1140 if (error_code != (PF_WRITE | PF_PROT) 1141 && error_code != (PF_INSTR | PF_PROT)) 1142 return 0; 1143 1144 pgd = init_mm.pgd + pgd_index(address); 1145 if (!pgd_present(*pgd)) 1146 return 0; 1147 1148 p4d = p4d_offset(pgd, address); 1149 if (!p4d_present(*p4d)) 1150 return 0; 1151 1152 if (p4d_large(*p4d)) 1153 return spurious_fault_check(error_code, (pte_t *) p4d); 1154 1155 pud = pud_offset(p4d, address); 1156 if (!pud_present(*pud)) 1157 return 0; 1158 1159 if (pud_large(*pud)) 1160 return spurious_fault_check(error_code, (pte_t *) pud); 1161 1162 pmd = pmd_offset(pud, address); 1163 if (!pmd_present(*pmd)) 1164 return 0; 1165 1166 if (pmd_large(*pmd)) 1167 return spurious_fault_check(error_code, (pte_t *) pmd); 1168 1169 pte = pte_offset_kernel(pmd, address); 1170 if (!pte_present(*pte)) 1171 return 0; 1172 1173 ret = spurious_fault_check(error_code, pte); 1174 if (!ret) 1175 return 0; 1176 1177 /* 1178 * Make sure we have permissions in PMD. 1179 * If not, then there's a bug in the page tables: 1180 */ 1181 ret = spurious_fault_check(error_code, (pte_t *) pmd); 1182 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 1183 1184 return ret; 1185 } 1186 NOKPROBE_SYMBOL(spurious_fault); 1187 1188 int show_unhandled_signals = 1; 1189 1190 static inline int 1191 access_error(unsigned long error_code, struct vm_area_struct *vma) 1192 { 1193 /* This is only called for the current mm, so: */ 1194 bool foreign = false; 1195 1196 /* 1197 * Read or write was blocked by protection keys. This is 1198 * always an unconditional error and can never result in 1199 * a follow-up action to resolve the fault, like a COW. 1200 */ 1201 if (error_code & PF_PK) 1202 return 1; 1203 1204 /* 1205 * Make sure to check the VMA so that we do not perform 1206 * faults just to hit a PF_PK as soon as we fill in a 1207 * page. 1208 */ 1209 if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE), 1210 (error_code & PF_INSTR), foreign)) 1211 return 1; 1212 1213 if (error_code & PF_WRITE) { 1214 /* write, present and write, not present: */ 1215 if (unlikely(!(vma->vm_flags & VM_WRITE))) 1216 return 1; 1217 return 0; 1218 } 1219 1220 /* read, present: */ 1221 if (unlikely(error_code & PF_PROT)) 1222 return 1; 1223 1224 /* read, not present: */ 1225 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 1226 return 1; 1227 1228 return 0; 1229 } 1230 1231 static int fault_in_kernel_space(unsigned long address) 1232 { 1233 return address >= TASK_SIZE_MAX; 1234 } 1235 1236 static inline bool smap_violation(int error_code, struct pt_regs *regs) 1237 { 1238 if (!IS_ENABLED(CONFIG_X86_SMAP)) 1239 return false; 1240 1241 if (!static_cpu_has(X86_FEATURE_SMAP)) 1242 return false; 1243 1244 if (error_code & PF_USER) 1245 return false; 1246 1247 if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC)) 1248 return false; 1249 1250 return true; 1251 } 1252 1253 /* 1254 * This routine handles page faults. It determines the address, 1255 * and the problem, and then passes it off to one of the appropriate 1256 * routines. 1257 * 1258 * This function must have noinline because both callers 1259 * {,trace_}do_page_fault() have notrace on. Having this an actual function 1260 * guarantees there's a function trace entry. 1261 */ 1262 static noinline void 1263 __do_page_fault(struct pt_regs *regs, unsigned long error_code, 1264 unsigned long address) 1265 { 1266 struct vm_area_struct *vma; 1267 struct task_struct *tsk; 1268 struct mm_struct *mm; 1269 int fault, major = 0; 1270 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 1271 1272 tsk = current; 1273 mm = tsk->mm; 1274 1275 /* 1276 * Detect and handle instructions that would cause a page fault for 1277 * both a tracked kernel page and a userspace page. 1278 */ 1279 if (kmemcheck_active(regs)) 1280 kmemcheck_hide(regs); 1281 prefetchw(&mm->mmap_sem); 1282 1283 if (unlikely(kmmio_fault(regs, address))) 1284 return; 1285 1286 /* 1287 * We fault-in kernel-space virtual memory on-demand. The 1288 * 'reference' page table is init_mm.pgd. 1289 * 1290 * NOTE! We MUST NOT take any locks for this case. We may 1291 * be in an interrupt or a critical region, and should 1292 * only copy the information from the master page table, 1293 * nothing more. 1294 * 1295 * This verifies that the fault happens in kernel space 1296 * (error_code & 4) == 0, and that the fault was not a 1297 * protection error (error_code & 9) == 0. 1298 */ 1299 if (unlikely(fault_in_kernel_space(address))) { 1300 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) { 1301 if (vmalloc_fault(address) >= 0) 1302 return; 1303 1304 if (kmemcheck_fault(regs, address, error_code)) 1305 return; 1306 } 1307 1308 /* Can handle a stale RO->RW TLB: */ 1309 if (spurious_fault(error_code, address)) 1310 return; 1311 1312 /* kprobes don't want to hook the spurious faults: */ 1313 if (kprobes_fault(regs)) 1314 return; 1315 /* 1316 * Don't take the mm semaphore here. If we fixup a prefetch 1317 * fault we could otherwise deadlock: 1318 */ 1319 bad_area_nosemaphore(regs, error_code, address, NULL); 1320 1321 return; 1322 } 1323 1324 /* kprobes don't want to hook the spurious faults: */ 1325 if (unlikely(kprobes_fault(regs))) 1326 return; 1327 1328 if (unlikely(error_code & PF_RSVD)) 1329 pgtable_bad(regs, error_code, address); 1330 1331 if (unlikely(smap_violation(error_code, regs))) { 1332 bad_area_nosemaphore(regs, error_code, address, NULL); 1333 return; 1334 } 1335 1336 /* 1337 * If we're in an interrupt, have no user context or are running 1338 * in a region with pagefaults disabled then we must not take the fault 1339 */ 1340 if (unlikely(faulthandler_disabled() || !mm)) { 1341 bad_area_nosemaphore(regs, error_code, address, NULL); 1342 return; 1343 } 1344 1345 /* 1346 * It's safe to allow irq's after cr2 has been saved and the 1347 * vmalloc fault has been handled. 1348 * 1349 * User-mode registers count as a user access even for any 1350 * potential system fault or CPU buglet: 1351 */ 1352 if (user_mode(regs)) { 1353 local_irq_enable(); 1354 error_code |= PF_USER; 1355 flags |= FAULT_FLAG_USER; 1356 } else { 1357 if (regs->flags & X86_EFLAGS_IF) 1358 local_irq_enable(); 1359 } 1360 1361 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1362 1363 if (error_code & PF_WRITE) 1364 flags |= FAULT_FLAG_WRITE; 1365 if (error_code & PF_INSTR) 1366 flags |= FAULT_FLAG_INSTRUCTION; 1367 1368 /* 1369 * When running in the kernel we expect faults to occur only to 1370 * addresses in user space. All other faults represent errors in 1371 * the kernel and should generate an OOPS. Unfortunately, in the 1372 * case of an erroneous fault occurring in a code path which already 1373 * holds mmap_sem we will deadlock attempting to validate the fault 1374 * against the address space. Luckily the kernel only validly 1375 * references user space from well defined areas of code, which are 1376 * listed in the exceptions table. 1377 * 1378 * As the vast majority of faults will be valid we will only perform 1379 * the source reference check when there is a possibility of a 1380 * deadlock. Attempt to lock the address space, if we cannot we then 1381 * validate the source. If this is invalid we can skip the address 1382 * space check, thus avoiding the deadlock: 1383 */ 1384 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1385 if ((error_code & PF_USER) == 0 && 1386 !search_exception_tables(regs->ip)) { 1387 bad_area_nosemaphore(regs, error_code, address, NULL); 1388 return; 1389 } 1390 retry: 1391 down_read(&mm->mmap_sem); 1392 } else { 1393 /* 1394 * The above down_read_trylock() might have succeeded in 1395 * which case we'll have missed the might_sleep() from 1396 * down_read(): 1397 */ 1398 might_sleep(); 1399 } 1400 1401 vma = find_vma(mm, address); 1402 if (unlikely(!vma)) { 1403 bad_area(regs, error_code, address); 1404 return; 1405 } 1406 if (likely(vma->vm_start <= address)) 1407 goto good_area; 1408 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1409 bad_area(regs, error_code, address); 1410 return; 1411 } 1412 if (error_code & PF_USER) { 1413 /* 1414 * Accessing the stack below %sp is always a bug. 1415 * The large cushion allows instructions like enter 1416 * and pusha to work. ("enter $65535, $31" pushes 1417 * 32 pointers and then decrements %sp by 65535.) 1418 */ 1419 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { 1420 bad_area(regs, error_code, address); 1421 return; 1422 } 1423 } 1424 if (unlikely(expand_stack(vma, address))) { 1425 bad_area(regs, error_code, address); 1426 return; 1427 } 1428 1429 /* 1430 * Ok, we have a good vm_area for this memory access, so 1431 * we can handle it.. 1432 */ 1433 good_area: 1434 if (unlikely(access_error(error_code, vma))) { 1435 bad_area_access_error(regs, error_code, address, vma); 1436 return; 1437 } 1438 1439 /* 1440 * If for any reason at all we couldn't handle the fault, 1441 * make sure we exit gracefully rather than endlessly redo 1442 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if 1443 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked. 1444 */ 1445 fault = handle_mm_fault(vma, address, flags); 1446 major |= fault & VM_FAULT_MAJOR; 1447 1448 /* 1449 * If we need to retry the mmap_sem has already been released, 1450 * and if there is a fatal signal pending there is no guarantee 1451 * that we made any progress. Handle this case first. 1452 */ 1453 if (unlikely(fault & VM_FAULT_RETRY)) { 1454 /* Retry at most once */ 1455 if (flags & FAULT_FLAG_ALLOW_RETRY) { 1456 flags &= ~FAULT_FLAG_ALLOW_RETRY; 1457 flags |= FAULT_FLAG_TRIED; 1458 if (!fatal_signal_pending(tsk)) 1459 goto retry; 1460 } 1461 1462 /* User mode? Just return to handle the fatal exception */ 1463 if (flags & FAULT_FLAG_USER) 1464 return; 1465 1466 /* Not returning to user mode? Handle exceptions or die: */ 1467 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 1468 return; 1469 } 1470 1471 up_read(&mm->mmap_sem); 1472 if (unlikely(fault & VM_FAULT_ERROR)) { 1473 mm_fault_error(regs, error_code, address, vma, fault); 1474 return; 1475 } 1476 1477 /* 1478 * Major/minor page fault accounting. If any of the events 1479 * returned VM_FAULT_MAJOR, we account it as a major fault. 1480 */ 1481 if (major) { 1482 tsk->maj_flt++; 1483 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address); 1484 } else { 1485 tsk->min_flt++; 1486 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address); 1487 } 1488 1489 check_v8086_mode(regs, address, tsk); 1490 } 1491 NOKPROBE_SYMBOL(__do_page_fault); 1492 1493 dotraplinkage void notrace 1494 do_page_fault(struct pt_regs *regs, unsigned long error_code) 1495 { 1496 unsigned long address = read_cr2(); /* Get the faulting address */ 1497 enum ctx_state prev_state; 1498 1499 /* 1500 * We must have this function tagged with __kprobes, notrace and call 1501 * read_cr2() before calling anything else. To avoid calling any kind 1502 * of tracing machinery before we've observed the CR2 value. 1503 * 1504 * exception_{enter,exit}() contain all sorts of tracepoints. 1505 */ 1506 1507 prev_state = exception_enter(); 1508 __do_page_fault(regs, error_code, address); 1509 exception_exit(prev_state); 1510 } 1511 NOKPROBE_SYMBOL(do_page_fault); 1512 1513 #ifdef CONFIG_TRACING 1514 static nokprobe_inline void 1515 trace_page_fault_entries(unsigned long address, struct pt_regs *regs, 1516 unsigned long error_code) 1517 { 1518 if (user_mode(regs)) 1519 trace_page_fault_user(address, regs, error_code); 1520 else 1521 trace_page_fault_kernel(address, regs, error_code); 1522 } 1523 1524 dotraplinkage void notrace 1525 trace_do_page_fault(struct pt_regs *regs, unsigned long error_code) 1526 { 1527 /* 1528 * The exception_enter and tracepoint processing could 1529 * trigger another page faults (user space callchain 1530 * reading) and destroy the original cr2 value, so read 1531 * the faulting address now. 1532 */ 1533 unsigned long address = read_cr2(); 1534 enum ctx_state prev_state; 1535 1536 prev_state = exception_enter(); 1537 trace_page_fault_entries(address, regs, error_code); 1538 __do_page_fault(regs, error_code, address); 1539 exception_exit(prev_state); 1540 } 1541 NOKPROBE_SYMBOL(trace_do_page_fault); 1542 #endif /* CONFIG_TRACING */ 1543