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/magic.h> /* STACK_END_MAGIC */ 7 #include <linux/sched.h> /* test_thread_flag(), ... */ 8 #include <linux/kdebug.h> /* oops_begin/end, ... */ 9 #include <linux/module.h> /* search_exception_table */ 10 #include <linux/bootmem.h> /* max_low_pfn */ 11 #include <linux/kprobes.h> /* __kprobes, ... */ 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 16 #include <asm/traps.h> /* dotraplinkage, ... */ 17 #include <asm/pgalloc.h> /* pgd_*(), ... */ 18 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */ 19 20 /* 21 * Page fault error code bits: 22 * 23 * bit 0 == 0: no page found 1: protection fault 24 * bit 1 == 0: read access 1: write access 25 * bit 2 == 0: kernel-mode access 1: user-mode access 26 * bit 3 == 1: use of reserved bit detected 27 * bit 4 == 1: fault was an instruction fetch 28 */ 29 enum x86_pf_error_code { 30 31 PF_PROT = 1 << 0, 32 PF_WRITE = 1 << 1, 33 PF_USER = 1 << 2, 34 PF_RSVD = 1 << 3, 35 PF_INSTR = 1 << 4, 36 }; 37 38 /* 39 * Returns 0 if mmiotrace is disabled, or if the fault is not 40 * handled by mmiotrace: 41 */ 42 static inline int __kprobes 43 kmmio_fault(struct pt_regs *regs, unsigned long addr) 44 { 45 if (unlikely(is_kmmio_active())) 46 if (kmmio_handler(regs, addr) == 1) 47 return -1; 48 return 0; 49 } 50 51 static inline int __kprobes notify_page_fault(struct pt_regs *regs) 52 { 53 int ret = 0; 54 55 /* kprobe_running() needs smp_processor_id() */ 56 if (kprobes_built_in() && !user_mode_vm(regs)) { 57 preempt_disable(); 58 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 59 ret = 1; 60 preempt_enable(); 61 } 62 63 return ret; 64 } 65 66 /* 67 * Prefetch quirks: 68 * 69 * 32-bit mode: 70 * 71 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 72 * Check that here and ignore it. 73 * 74 * 64-bit mode: 75 * 76 * Sometimes the CPU reports invalid exceptions on prefetch. 77 * Check that here and ignore it. 78 * 79 * Opcode checker based on code by Richard Brunner. 80 */ 81 static inline int 82 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 83 unsigned char opcode, int *prefetch) 84 { 85 unsigned char instr_hi = opcode & 0xf0; 86 unsigned char instr_lo = opcode & 0x0f; 87 88 switch (instr_hi) { 89 case 0x20: 90 case 0x30: 91 /* 92 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 93 * In X86_64 long mode, the CPU will signal invalid 94 * opcode if some of these prefixes are present so 95 * X86_64 will never get here anyway 96 */ 97 return ((instr_lo & 7) == 0x6); 98 #ifdef CONFIG_X86_64 99 case 0x40: 100 /* 101 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 102 * Need to figure out under what instruction mode the 103 * instruction was issued. Could check the LDT for lm, 104 * but for now it's good enough to assume that long 105 * mode only uses well known segments or kernel. 106 */ 107 return (!user_mode(regs)) || (regs->cs == __USER_CS); 108 #endif 109 case 0x60: 110 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 111 return (instr_lo & 0xC) == 0x4; 112 case 0xF0: 113 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 114 return !instr_lo || (instr_lo>>1) == 1; 115 case 0x00: 116 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 117 if (probe_kernel_address(instr, opcode)) 118 return 0; 119 120 *prefetch = (instr_lo == 0xF) && 121 (opcode == 0x0D || opcode == 0x18); 122 return 0; 123 default: 124 return 0; 125 } 126 } 127 128 static int 129 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 130 { 131 unsigned char *max_instr; 132 unsigned char *instr; 133 int prefetch = 0; 134 135 /* 136 * If it was a exec (instruction fetch) fault on NX page, then 137 * do not ignore the fault: 138 */ 139 if (error_code & PF_INSTR) 140 return 0; 141 142 instr = (void *)convert_ip_to_linear(current, regs); 143 max_instr = instr + 15; 144 145 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE) 146 return 0; 147 148 while (instr < max_instr) { 149 unsigned char opcode; 150 151 if (probe_kernel_address(instr, opcode)) 152 break; 153 154 instr++; 155 156 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 157 break; 158 } 159 return prefetch; 160 } 161 162 static void 163 force_sig_info_fault(int si_signo, int si_code, unsigned long address, 164 struct task_struct *tsk, int fault) 165 { 166 unsigned lsb = 0; 167 siginfo_t info; 168 169 info.si_signo = si_signo; 170 info.si_errno = 0; 171 info.si_code = si_code; 172 info.si_addr = (void __user *)address; 173 if (fault & VM_FAULT_HWPOISON_LARGE) 174 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 175 if (fault & VM_FAULT_HWPOISON) 176 lsb = PAGE_SHIFT; 177 info.si_addr_lsb = lsb; 178 179 force_sig_info(si_signo, &info, tsk); 180 } 181 182 DEFINE_SPINLOCK(pgd_lock); 183 LIST_HEAD(pgd_list); 184 185 #ifdef CONFIG_X86_32 186 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 187 { 188 unsigned index = pgd_index(address); 189 pgd_t *pgd_k; 190 pud_t *pud, *pud_k; 191 pmd_t *pmd, *pmd_k; 192 193 pgd += index; 194 pgd_k = init_mm.pgd + index; 195 196 if (!pgd_present(*pgd_k)) 197 return NULL; 198 199 /* 200 * set_pgd(pgd, *pgd_k); here would be useless on PAE 201 * and redundant with the set_pmd() on non-PAE. As would 202 * set_pud. 203 */ 204 pud = pud_offset(pgd, address); 205 pud_k = pud_offset(pgd_k, address); 206 if (!pud_present(*pud_k)) 207 return NULL; 208 209 pmd = pmd_offset(pud, address); 210 pmd_k = pmd_offset(pud_k, address); 211 if (!pmd_present(*pmd_k)) 212 return NULL; 213 214 if (!pmd_present(*pmd)) 215 set_pmd(pmd, *pmd_k); 216 else 217 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 218 219 return pmd_k; 220 } 221 222 void vmalloc_sync_all(void) 223 { 224 unsigned long address; 225 226 if (SHARED_KERNEL_PMD) 227 return; 228 229 for (address = VMALLOC_START & PMD_MASK; 230 address >= TASK_SIZE && address < FIXADDR_TOP; 231 address += PMD_SIZE) { 232 233 unsigned long flags; 234 struct page *page; 235 236 spin_lock_irqsave(&pgd_lock, flags); 237 list_for_each_entry(page, &pgd_list, lru) { 238 spinlock_t *pgt_lock; 239 pmd_t *ret; 240 241 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 242 243 spin_lock(pgt_lock); 244 ret = vmalloc_sync_one(page_address(page), address); 245 spin_unlock(pgt_lock); 246 247 if (!ret) 248 break; 249 } 250 spin_unlock_irqrestore(&pgd_lock, flags); 251 } 252 } 253 254 /* 255 * 32-bit: 256 * 257 * Handle a fault on the vmalloc or module mapping area 258 */ 259 static noinline __kprobes int vmalloc_fault(unsigned long address) 260 { 261 unsigned long pgd_paddr; 262 pmd_t *pmd_k; 263 pte_t *pte_k; 264 265 /* Make sure we are in vmalloc area: */ 266 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 267 return -1; 268 269 WARN_ON_ONCE(in_nmi()); 270 271 /* 272 * Synchronize this task's top level page-table 273 * with the 'reference' page table. 274 * 275 * Do _not_ use "current" here. We might be inside 276 * an interrupt in the middle of a task switch.. 277 */ 278 pgd_paddr = read_cr3(); 279 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 280 if (!pmd_k) 281 return -1; 282 283 pte_k = pte_offset_kernel(pmd_k, address); 284 if (!pte_present(*pte_k)) 285 return -1; 286 287 return 0; 288 } 289 290 /* 291 * Did it hit the DOS screen memory VA from vm86 mode? 292 */ 293 static inline void 294 check_v8086_mode(struct pt_regs *regs, unsigned long address, 295 struct task_struct *tsk) 296 { 297 unsigned long bit; 298 299 if (!v8086_mode(regs)) 300 return; 301 302 bit = (address - 0xA0000) >> PAGE_SHIFT; 303 if (bit < 32) 304 tsk->thread.screen_bitmap |= 1 << bit; 305 } 306 307 static bool low_pfn(unsigned long pfn) 308 { 309 return pfn < max_low_pfn; 310 } 311 312 static void dump_pagetable(unsigned long address) 313 { 314 pgd_t *base = __va(read_cr3()); 315 pgd_t *pgd = &base[pgd_index(address)]; 316 pmd_t *pmd; 317 pte_t *pte; 318 319 #ifdef CONFIG_X86_PAE 320 printk("*pdpt = %016Lx ", pgd_val(*pgd)); 321 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 322 goto out; 323 #endif 324 pmd = pmd_offset(pud_offset(pgd, address), address); 325 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 326 327 /* 328 * We must not directly access the pte in the highpte 329 * case if the page table is located in highmem. 330 * And let's rather not kmap-atomic the pte, just in case 331 * it's allocated already: 332 */ 333 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 334 goto out; 335 336 pte = pte_offset_kernel(pmd, address); 337 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 338 out: 339 printk("\n"); 340 } 341 342 #else /* CONFIG_X86_64: */ 343 344 void vmalloc_sync_all(void) 345 { 346 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 347 } 348 349 /* 350 * 64-bit: 351 * 352 * Handle a fault on the vmalloc area 353 * 354 * This assumes no large pages in there. 355 */ 356 static noinline __kprobes int vmalloc_fault(unsigned long address) 357 { 358 pgd_t *pgd, *pgd_ref; 359 pud_t *pud, *pud_ref; 360 pmd_t *pmd, *pmd_ref; 361 pte_t *pte, *pte_ref; 362 363 /* Make sure we are in vmalloc area: */ 364 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 365 return -1; 366 367 WARN_ON_ONCE(in_nmi()); 368 369 /* 370 * Copy kernel mappings over when needed. This can also 371 * happen within a race in page table update. In the later 372 * case just flush: 373 */ 374 pgd = pgd_offset(current->active_mm, address); 375 pgd_ref = pgd_offset_k(address); 376 if (pgd_none(*pgd_ref)) 377 return -1; 378 379 if (pgd_none(*pgd)) 380 set_pgd(pgd, *pgd_ref); 381 else 382 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 383 384 /* 385 * Below here mismatches are bugs because these lower tables 386 * are shared: 387 */ 388 389 pud = pud_offset(pgd, address); 390 pud_ref = pud_offset(pgd_ref, address); 391 if (pud_none(*pud_ref)) 392 return -1; 393 394 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref)) 395 BUG(); 396 397 pmd = pmd_offset(pud, address); 398 pmd_ref = pmd_offset(pud_ref, address); 399 if (pmd_none(*pmd_ref)) 400 return -1; 401 402 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref)) 403 BUG(); 404 405 pte_ref = pte_offset_kernel(pmd_ref, address); 406 if (!pte_present(*pte_ref)) 407 return -1; 408 409 pte = pte_offset_kernel(pmd, address); 410 411 /* 412 * Don't use pte_page here, because the mappings can point 413 * outside mem_map, and the NUMA hash lookup cannot handle 414 * that: 415 */ 416 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) 417 BUG(); 418 419 return 0; 420 } 421 422 static const char errata93_warning[] = 423 KERN_ERR 424 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 425 "******* Working around it, but it may cause SEGVs or burn power.\n" 426 "******* Please consider a BIOS update.\n" 427 "******* Disabling USB legacy in the BIOS may also help.\n"; 428 429 /* 430 * No vm86 mode in 64-bit mode: 431 */ 432 static inline void 433 check_v8086_mode(struct pt_regs *regs, unsigned long address, 434 struct task_struct *tsk) 435 { 436 } 437 438 static int bad_address(void *p) 439 { 440 unsigned long dummy; 441 442 return probe_kernel_address((unsigned long *)p, dummy); 443 } 444 445 static void dump_pagetable(unsigned long address) 446 { 447 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK); 448 pgd_t *pgd = base + pgd_index(address); 449 pud_t *pud; 450 pmd_t *pmd; 451 pte_t *pte; 452 453 if (bad_address(pgd)) 454 goto bad; 455 456 printk("PGD %lx ", pgd_val(*pgd)); 457 458 if (!pgd_present(*pgd)) 459 goto out; 460 461 pud = pud_offset(pgd, address); 462 if (bad_address(pud)) 463 goto bad; 464 465 printk("PUD %lx ", pud_val(*pud)); 466 if (!pud_present(*pud) || pud_large(*pud)) 467 goto out; 468 469 pmd = pmd_offset(pud, address); 470 if (bad_address(pmd)) 471 goto bad; 472 473 printk("PMD %lx ", pmd_val(*pmd)); 474 if (!pmd_present(*pmd) || pmd_large(*pmd)) 475 goto out; 476 477 pte = pte_offset_kernel(pmd, address); 478 if (bad_address(pte)) 479 goto bad; 480 481 printk("PTE %lx", pte_val(*pte)); 482 out: 483 printk("\n"); 484 return; 485 bad: 486 printk("BAD\n"); 487 } 488 489 #endif /* CONFIG_X86_64 */ 490 491 /* 492 * Workaround for K8 erratum #93 & buggy BIOS. 493 * 494 * BIOS SMM functions are required to use a specific workaround 495 * to avoid corruption of the 64bit RIP register on C stepping K8. 496 * 497 * A lot of BIOS that didn't get tested properly miss this. 498 * 499 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 500 * Try to work around it here. 501 * 502 * Note we only handle faults in kernel here. 503 * Does nothing on 32-bit. 504 */ 505 static int is_errata93(struct pt_regs *regs, unsigned long address) 506 { 507 #ifdef CONFIG_X86_64 508 if (address != regs->ip) 509 return 0; 510 511 if ((address >> 32) != 0) 512 return 0; 513 514 address |= 0xffffffffUL << 32; 515 if ((address >= (u64)_stext && address <= (u64)_etext) || 516 (address >= MODULES_VADDR && address <= MODULES_END)) { 517 printk_once(errata93_warning); 518 regs->ip = address; 519 return 1; 520 } 521 #endif 522 return 0; 523 } 524 525 /* 526 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 527 * to illegal addresses >4GB. 528 * 529 * We catch this in the page fault handler because these addresses 530 * are not reachable. Just detect this case and return. Any code 531 * segment in LDT is compatibility mode. 532 */ 533 static int is_errata100(struct pt_regs *regs, unsigned long address) 534 { 535 #ifdef CONFIG_X86_64 536 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 537 return 1; 538 #endif 539 return 0; 540 } 541 542 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 543 { 544 #ifdef CONFIG_X86_F00F_BUG 545 unsigned long nr; 546 547 /* 548 * Pentium F0 0F C7 C8 bug workaround: 549 */ 550 if (boot_cpu_data.f00f_bug) { 551 nr = (address - idt_descr.address) >> 3; 552 553 if (nr == 6) { 554 do_invalid_op(regs, 0); 555 return 1; 556 } 557 } 558 #endif 559 return 0; 560 } 561 562 static const char nx_warning[] = KERN_CRIT 563 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; 564 565 static void 566 show_fault_oops(struct pt_regs *regs, unsigned long error_code, 567 unsigned long address) 568 { 569 if (!oops_may_print()) 570 return; 571 572 if (error_code & PF_INSTR) { 573 unsigned int level; 574 575 pte_t *pte = lookup_address(address, &level); 576 577 if (pte && pte_present(*pte) && !pte_exec(*pte)) 578 printk(nx_warning, current_uid()); 579 } 580 581 printk(KERN_ALERT "BUG: unable to handle kernel "); 582 if (address < PAGE_SIZE) 583 printk(KERN_CONT "NULL pointer dereference"); 584 else 585 printk(KERN_CONT "paging request"); 586 587 printk(KERN_CONT " at %p\n", (void *) address); 588 printk(KERN_ALERT "IP:"); 589 printk_address(regs->ip, 1); 590 591 dump_pagetable(address); 592 } 593 594 static noinline void 595 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 596 unsigned long address) 597 { 598 struct task_struct *tsk; 599 unsigned long flags; 600 int sig; 601 602 flags = oops_begin(); 603 tsk = current; 604 sig = SIGKILL; 605 606 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 607 tsk->comm, address); 608 dump_pagetable(address); 609 610 tsk->thread.cr2 = address; 611 tsk->thread.trap_no = 14; 612 tsk->thread.error_code = error_code; 613 614 if (__die("Bad pagetable", regs, error_code)) 615 sig = 0; 616 617 oops_end(flags, regs, sig); 618 } 619 620 static noinline void 621 no_context(struct pt_regs *regs, unsigned long error_code, 622 unsigned long address) 623 { 624 struct task_struct *tsk = current; 625 unsigned long *stackend; 626 unsigned long flags; 627 int sig; 628 629 /* Are we prepared to handle this kernel fault? */ 630 if (fixup_exception(regs)) 631 return; 632 633 /* 634 * 32-bit: 635 * 636 * Valid to do another page fault here, because if this fault 637 * had been triggered by is_prefetch fixup_exception would have 638 * handled it. 639 * 640 * 64-bit: 641 * 642 * Hall of shame of CPU/BIOS bugs. 643 */ 644 if (is_prefetch(regs, error_code, address)) 645 return; 646 647 if (is_errata93(regs, address)) 648 return; 649 650 /* 651 * Oops. The kernel tried to access some bad page. We'll have to 652 * terminate things with extreme prejudice: 653 */ 654 flags = oops_begin(); 655 656 show_fault_oops(regs, error_code, address); 657 658 stackend = end_of_stack(tsk); 659 if (tsk != &init_task && *stackend != STACK_END_MAGIC) 660 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); 661 662 tsk->thread.cr2 = address; 663 tsk->thread.trap_no = 14; 664 tsk->thread.error_code = error_code; 665 666 sig = SIGKILL; 667 if (__die("Oops", regs, error_code)) 668 sig = 0; 669 670 /* Executive summary in case the body of the oops scrolled away */ 671 printk(KERN_EMERG "CR2: %016lx\n", address); 672 673 oops_end(flags, regs, sig); 674 } 675 676 /* 677 * Print out info about fatal segfaults, if the show_unhandled_signals 678 * sysctl is set: 679 */ 680 static inline void 681 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 682 unsigned long address, struct task_struct *tsk) 683 { 684 if (!unhandled_signal(tsk, SIGSEGV)) 685 return; 686 687 if (!printk_ratelimit()) 688 return; 689 690 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", 691 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 692 tsk->comm, task_pid_nr(tsk), address, 693 (void *)regs->ip, (void *)regs->sp, error_code); 694 695 print_vma_addr(KERN_CONT " in ", regs->ip); 696 697 printk(KERN_CONT "\n"); 698 } 699 700 static void 701 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 702 unsigned long address, int si_code) 703 { 704 struct task_struct *tsk = current; 705 706 /* User mode accesses just cause a SIGSEGV */ 707 if (error_code & PF_USER) { 708 /* 709 * It's possible to have interrupts off here: 710 */ 711 local_irq_enable(); 712 713 /* 714 * Valid to do another page fault here because this one came 715 * from user space: 716 */ 717 if (is_prefetch(regs, error_code, address)) 718 return; 719 720 if (is_errata100(regs, address)) 721 return; 722 723 if (unlikely(show_unhandled_signals)) 724 show_signal_msg(regs, error_code, address, tsk); 725 726 /* Kernel addresses are always protection faults: */ 727 tsk->thread.cr2 = address; 728 tsk->thread.error_code = error_code | (address >= TASK_SIZE); 729 tsk->thread.trap_no = 14; 730 731 force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0); 732 733 return; 734 } 735 736 if (is_f00f_bug(regs, address)) 737 return; 738 739 no_context(regs, error_code, address); 740 } 741 742 static noinline void 743 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 744 unsigned long address) 745 { 746 __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR); 747 } 748 749 static void 750 __bad_area(struct pt_regs *regs, unsigned long error_code, 751 unsigned long address, int si_code) 752 { 753 struct mm_struct *mm = current->mm; 754 755 /* 756 * Something tried to access memory that isn't in our memory map.. 757 * Fix it, but check if it's kernel or user first.. 758 */ 759 up_read(&mm->mmap_sem); 760 761 __bad_area_nosemaphore(regs, error_code, address, si_code); 762 } 763 764 static noinline void 765 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 766 { 767 __bad_area(regs, error_code, address, SEGV_MAPERR); 768 } 769 770 static noinline void 771 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 772 unsigned long address) 773 { 774 __bad_area(regs, error_code, address, SEGV_ACCERR); 775 } 776 777 /* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */ 778 static void 779 out_of_memory(struct pt_regs *regs, unsigned long error_code, 780 unsigned long address) 781 { 782 /* 783 * We ran out of memory, call the OOM killer, and return the userspace 784 * (which will retry the fault, or kill us if we got oom-killed): 785 */ 786 up_read(¤t->mm->mmap_sem); 787 788 pagefault_out_of_memory(); 789 } 790 791 static void 792 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 793 unsigned int fault) 794 { 795 struct task_struct *tsk = current; 796 struct mm_struct *mm = tsk->mm; 797 int code = BUS_ADRERR; 798 799 up_read(&mm->mmap_sem); 800 801 /* Kernel mode? Handle exceptions or die: */ 802 if (!(error_code & PF_USER)) { 803 no_context(regs, error_code, address); 804 return; 805 } 806 807 /* User-space => ok to do another page fault: */ 808 if (is_prefetch(regs, error_code, address)) 809 return; 810 811 tsk->thread.cr2 = address; 812 tsk->thread.error_code = error_code; 813 tsk->thread.trap_no = 14; 814 815 #ifdef CONFIG_MEMORY_FAILURE 816 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 817 printk(KERN_ERR 818 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 819 tsk->comm, tsk->pid, address); 820 code = BUS_MCEERR_AR; 821 } 822 #endif 823 force_sig_info_fault(SIGBUS, code, address, tsk, fault); 824 } 825 826 static noinline void 827 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 828 unsigned long address, unsigned int fault) 829 { 830 if (fault & VM_FAULT_OOM) { 831 out_of_memory(regs, error_code, address); 832 } else { 833 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 834 VM_FAULT_HWPOISON_LARGE)) 835 do_sigbus(regs, error_code, address, fault); 836 else 837 BUG(); 838 } 839 } 840 841 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 842 { 843 if ((error_code & PF_WRITE) && !pte_write(*pte)) 844 return 0; 845 846 if ((error_code & PF_INSTR) && !pte_exec(*pte)) 847 return 0; 848 849 return 1; 850 } 851 852 /* 853 * Handle a spurious fault caused by a stale TLB entry. 854 * 855 * This allows us to lazily refresh the TLB when increasing the 856 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 857 * eagerly is very expensive since that implies doing a full 858 * cross-processor TLB flush, even if no stale TLB entries exist 859 * on other processors. 860 * 861 * There are no security implications to leaving a stale TLB when 862 * increasing the permissions on a page. 863 */ 864 static noinline __kprobes int 865 spurious_fault(unsigned long error_code, unsigned long address) 866 { 867 pgd_t *pgd; 868 pud_t *pud; 869 pmd_t *pmd; 870 pte_t *pte; 871 int ret; 872 873 /* Reserved-bit violation or user access to kernel space? */ 874 if (error_code & (PF_USER | PF_RSVD)) 875 return 0; 876 877 pgd = init_mm.pgd + pgd_index(address); 878 if (!pgd_present(*pgd)) 879 return 0; 880 881 pud = pud_offset(pgd, address); 882 if (!pud_present(*pud)) 883 return 0; 884 885 if (pud_large(*pud)) 886 return spurious_fault_check(error_code, (pte_t *) pud); 887 888 pmd = pmd_offset(pud, address); 889 if (!pmd_present(*pmd)) 890 return 0; 891 892 if (pmd_large(*pmd)) 893 return spurious_fault_check(error_code, (pte_t *) pmd); 894 895 /* 896 * Note: don't use pte_present() here, since it returns true 897 * if the _PAGE_PROTNONE bit is set. However, this aliases the 898 * _PAGE_GLOBAL bit, which for kernel pages give false positives 899 * when CONFIG_DEBUG_PAGEALLOC is used. 900 */ 901 pte = pte_offset_kernel(pmd, address); 902 if (!(pte_flags(*pte) & _PAGE_PRESENT)) 903 return 0; 904 905 ret = spurious_fault_check(error_code, pte); 906 if (!ret) 907 return 0; 908 909 /* 910 * Make sure we have permissions in PMD. 911 * If not, then there's a bug in the page tables: 912 */ 913 ret = spurious_fault_check(error_code, (pte_t *) pmd); 914 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 915 916 return ret; 917 } 918 919 int show_unhandled_signals = 1; 920 921 static inline int 922 access_error(unsigned long error_code, struct vm_area_struct *vma) 923 { 924 if (error_code & PF_WRITE) { 925 /* write, present and write, not present: */ 926 if (unlikely(!(vma->vm_flags & VM_WRITE))) 927 return 1; 928 return 0; 929 } 930 931 /* read, present: */ 932 if (unlikely(error_code & PF_PROT)) 933 return 1; 934 935 /* read, not present: */ 936 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 937 return 1; 938 939 return 0; 940 } 941 942 static int fault_in_kernel_space(unsigned long address) 943 { 944 return address >= TASK_SIZE_MAX; 945 } 946 947 /* 948 * This routine handles page faults. It determines the address, 949 * and the problem, and then passes it off to one of the appropriate 950 * routines. 951 */ 952 dotraplinkage void __kprobes 953 do_page_fault(struct pt_regs *regs, unsigned long error_code) 954 { 955 struct vm_area_struct *vma; 956 struct task_struct *tsk; 957 unsigned long address; 958 struct mm_struct *mm; 959 int fault; 960 int write = error_code & PF_WRITE; 961 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | 962 (write ? FAULT_FLAG_WRITE : 0); 963 964 tsk = current; 965 mm = tsk->mm; 966 967 /* Get the faulting address: */ 968 address = read_cr2(); 969 970 /* 971 * Detect and handle instructions that would cause a page fault for 972 * both a tracked kernel page and a userspace page. 973 */ 974 if (kmemcheck_active(regs)) 975 kmemcheck_hide(regs); 976 prefetchw(&mm->mmap_sem); 977 978 if (unlikely(kmmio_fault(regs, address))) 979 return; 980 981 /* 982 * We fault-in kernel-space virtual memory on-demand. The 983 * 'reference' page table is init_mm.pgd. 984 * 985 * NOTE! We MUST NOT take any locks for this case. We may 986 * be in an interrupt or a critical region, and should 987 * only copy the information from the master page table, 988 * nothing more. 989 * 990 * This verifies that the fault happens in kernel space 991 * (error_code & 4) == 0, and that the fault was not a 992 * protection error (error_code & 9) == 0. 993 */ 994 if (unlikely(fault_in_kernel_space(address))) { 995 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) { 996 if (vmalloc_fault(address) >= 0) 997 return; 998 999 if (kmemcheck_fault(regs, address, error_code)) 1000 return; 1001 } 1002 1003 /* Can handle a stale RO->RW TLB: */ 1004 if (spurious_fault(error_code, address)) 1005 return; 1006 1007 /* kprobes don't want to hook the spurious faults: */ 1008 if (notify_page_fault(regs)) 1009 return; 1010 /* 1011 * Don't take the mm semaphore here. If we fixup a prefetch 1012 * fault we could otherwise deadlock: 1013 */ 1014 bad_area_nosemaphore(regs, error_code, address); 1015 1016 return; 1017 } 1018 1019 /* kprobes don't want to hook the spurious faults: */ 1020 if (unlikely(notify_page_fault(regs))) 1021 return; 1022 /* 1023 * It's safe to allow irq's after cr2 has been saved and the 1024 * vmalloc fault has been handled. 1025 * 1026 * User-mode registers count as a user access even for any 1027 * potential system fault or CPU buglet: 1028 */ 1029 if (user_mode_vm(regs)) { 1030 local_irq_enable(); 1031 error_code |= PF_USER; 1032 } else { 1033 if (regs->flags & X86_EFLAGS_IF) 1034 local_irq_enable(); 1035 } 1036 1037 if (unlikely(error_code & PF_RSVD)) 1038 pgtable_bad(regs, error_code, address); 1039 1040 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address); 1041 1042 /* 1043 * If we're in an interrupt, have no user context or are running 1044 * in an atomic region then we must not take the fault: 1045 */ 1046 if (unlikely(in_atomic() || !mm)) { 1047 bad_area_nosemaphore(regs, error_code, address); 1048 return; 1049 } 1050 1051 /* 1052 * When running in the kernel we expect faults to occur only to 1053 * addresses in user space. All other faults represent errors in 1054 * the kernel and should generate an OOPS. Unfortunately, in the 1055 * case of an erroneous fault occurring in a code path which already 1056 * holds mmap_sem we will deadlock attempting to validate the fault 1057 * against the address space. Luckily the kernel only validly 1058 * references user space from well defined areas of code, which are 1059 * listed in the exceptions table. 1060 * 1061 * As the vast majority of faults will be valid we will only perform 1062 * the source reference check when there is a possibility of a 1063 * deadlock. Attempt to lock the address space, if we cannot we then 1064 * validate the source. If this is invalid we can skip the address 1065 * space check, thus avoiding the deadlock: 1066 */ 1067 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1068 if ((error_code & PF_USER) == 0 && 1069 !search_exception_tables(regs->ip)) { 1070 bad_area_nosemaphore(regs, error_code, address); 1071 return; 1072 } 1073 retry: 1074 down_read(&mm->mmap_sem); 1075 } else { 1076 /* 1077 * The above down_read_trylock() might have succeeded in 1078 * which case we'll have missed the might_sleep() from 1079 * down_read(): 1080 */ 1081 might_sleep(); 1082 } 1083 1084 vma = find_vma(mm, address); 1085 if (unlikely(!vma)) { 1086 bad_area(regs, error_code, address); 1087 return; 1088 } 1089 if (likely(vma->vm_start <= address)) 1090 goto good_area; 1091 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1092 bad_area(regs, error_code, address); 1093 return; 1094 } 1095 if (error_code & PF_USER) { 1096 /* 1097 * Accessing the stack below %sp is always a bug. 1098 * The large cushion allows instructions like enter 1099 * and pusha to work. ("enter $65535, $31" pushes 1100 * 32 pointers and then decrements %sp by 65535.) 1101 */ 1102 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { 1103 bad_area(regs, error_code, address); 1104 return; 1105 } 1106 } 1107 if (unlikely(expand_stack(vma, address))) { 1108 bad_area(regs, error_code, address); 1109 return; 1110 } 1111 1112 /* 1113 * Ok, we have a good vm_area for this memory access, so 1114 * we can handle it.. 1115 */ 1116 good_area: 1117 if (unlikely(access_error(error_code, vma))) { 1118 bad_area_access_error(regs, error_code, address); 1119 return; 1120 } 1121 1122 /* 1123 * If for any reason at all we couldn't handle the fault, 1124 * make sure we exit gracefully rather than endlessly redo 1125 * the fault: 1126 */ 1127 fault = handle_mm_fault(mm, vma, address, flags); 1128 1129 if (unlikely(fault & VM_FAULT_ERROR)) { 1130 mm_fault_error(regs, error_code, address, fault); 1131 return; 1132 } 1133 1134 /* 1135 * Major/minor page fault accounting is only done on the 1136 * initial attempt. If we go through a retry, it is extremely 1137 * likely that the page will be found in page cache at that point. 1138 */ 1139 if (flags & FAULT_FLAG_ALLOW_RETRY) { 1140 if (fault & VM_FAULT_MAJOR) { 1141 tsk->maj_flt++; 1142 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0, 1143 regs, address); 1144 } else { 1145 tsk->min_flt++; 1146 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0, 1147 regs, address); 1148 } 1149 if (fault & VM_FAULT_RETRY) { 1150 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 1151 * of starvation. */ 1152 flags &= ~FAULT_FLAG_ALLOW_RETRY; 1153 goto retry; 1154 } 1155 } 1156 1157 check_v8086_mode(regs, address, tsk); 1158 1159 up_read(&mm->mmap_sem); 1160 } 1161