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 #include <linux/prefetch.h> /* prefetchw */ 16 #include <linux/context_tracking.h> /* exception_enter(), ... */ 17 18 #include <asm/traps.h> /* dotraplinkage, ... */ 19 #include <asm/pgalloc.h> /* pgd_*(), ... */ 20 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */ 21 #include <asm/fixmap.h> /* VSYSCALL_START */ 22 23 /* 24 * Page fault error code bits: 25 * 26 * bit 0 == 0: no page found 1: protection fault 27 * bit 1 == 0: read access 1: write access 28 * bit 2 == 0: kernel-mode access 1: user-mode access 29 * bit 3 == 1: use of reserved bit detected 30 * bit 4 == 1: fault was an instruction fetch 31 */ 32 enum x86_pf_error_code { 33 34 PF_PROT = 1 << 0, 35 PF_WRITE = 1 << 1, 36 PF_USER = 1 << 2, 37 PF_RSVD = 1 << 3, 38 PF_INSTR = 1 << 4, 39 }; 40 41 /* 42 * Returns 0 if mmiotrace is disabled, or if the fault is not 43 * handled by mmiotrace: 44 */ 45 static inline int __kprobes 46 kmmio_fault(struct pt_regs *regs, unsigned long addr) 47 { 48 if (unlikely(is_kmmio_active())) 49 if (kmmio_handler(regs, addr) == 1) 50 return -1; 51 return 0; 52 } 53 54 static inline int __kprobes notify_page_fault(struct pt_regs *regs) 55 { 56 int ret = 0; 57 58 /* kprobe_running() needs smp_processor_id() */ 59 if (kprobes_built_in() && !user_mode_vm(regs)) { 60 preempt_disable(); 61 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 62 ret = 1; 63 preempt_enable(); 64 } 65 66 return ret; 67 } 68 69 /* 70 * Prefetch quirks: 71 * 72 * 32-bit mode: 73 * 74 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 75 * Check that here and ignore it. 76 * 77 * 64-bit mode: 78 * 79 * Sometimes the CPU reports invalid exceptions on prefetch. 80 * Check that here and ignore it. 81 * 82 * Opcode checker based on code by Richard Brunner. 83 */ 84 static inline int 85 check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, 86 unsigned char opcode, int *prefetch) 87 { 88 unsigned char instr_hi = opcode & 0xf0; 89 unsigned char instr_lo = opcode & 0x0f; 90 91 switch (instr_hi) { 92 case 0x20: 93 case 0x30: 94 /* 95 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 96 * In X86_64 long mode, the CPU will signal invalid 97 * opcode if some of these prefixes are present so 98 * X86_64 will never get here anyway 99 */ 100 return ((instr_lo & 7) == 0x6); 101 #ifdef CONFIG_X86_64 102 case 0x40: 103 /* 104 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 105 * Need to figure out under what instruction mode the 106 * instruction was issued. Could check the LDT for lm, 107 * but for now it's good enough to assume that long 108 * mode only uses well known segments or kernel. 109 */ 110 return (!user_mode(regs) || user_64bit_mode(regs)); 111 #endif 112 case 0x60: 113 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 114 return (instr_lo & 0xC) == 0x4; 115 case 0xF0: 116 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 117 return !instr_lo || (instr_lo>>1) == 1; 118 case 0x00: 119 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 120 if (probe_kernel_address(instr, opcode)) 121 return 0; 122 123 *prefetch = (instr_lo == 0xF) && 124 (opcode == 0x0D || opcode == 0x18); 125 return 0; 126 default: 127 return 0; 128 } 129 } 130 131 static int 132 is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) 133 { 134 unsigned char *max_instr; 135 unsigned char *instr; 136 int prefetch = 0; 137 138 /* 139 * If it was a exec (instruction fetch) fault on NX page, then 140 * do not ignore the fault: 141 */ 142 if (error_code & PF_INSTR) 143 return 0; 144 145 instr = (void *)convert_ip_to_linear(current, regs); 146 max_instr = instr + 15; 147 148 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE) 149 return 0; 150 151 while (instr < max_instr) { 152 unsigned char opcode; 153 154 if (probe_kernel_address(instr, opcode)) 155 break; 156 157 instr++; 158 159 if (!check_prefetch_opcode(regs, instr, opcode, &prefetch)) 160 break; 161 } 162 return prefetch; 163 } 164 165 static void 166 force_sig_info_fault(int si_signo, int si_code, unsigned long address, 167 struct task_struct *tsk, int fault) 168 { 169 unsigned lsb = 0; 170 siginfo_t info; 171 172 info.si_signo = si_signo; 173 info.si_errno = 0; 174 info.si_code = si_code; 175 info.si_addr = (void __user *)address; 176 if (fault & VM_FAULT_HWPOISON_LARGE) 177 lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); 178 if (fault & VM_FAULT_HWPOISON) 179 lsb = PAGE_SHIFT; 180 info.si_addr_lsb = lsb; 181 182 force_sig_info(si_signo, &info, tsk); 183 } 184 185 DEFINE_SPINLOCK(pgd_lock); 186 LIST_HEAD(pgd_list); 187 188 #ifdef CONFIG_X86_32 189 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 190 { 191 unsigned index = pgd_index(address); 192 pgd_t *pgd_k; 193 pud_t *pud, *pud_k; 194 pmd_t *pmd, *pmd_k; 195 196 pgd += index; 197 pgd_k = init_mm.pgd + index; 198 199 if (!pgd_present(*pgd_k)) 200 return NULL; 201 202 /* 203 * set_pgd(pgd, *pgd_k); here would be useless on PAE 204 * and redundant with the set_pmd() on non-PAE. As would 205 * set_pud. 206 */ 207 pud = pud_offset(pgd, address); 208 pud_k = pud_offset(pgd_k, address); 209 if (!pud_present(*pud_k)) 210 return NULL; 211 212 pmd = pmd_offset(pud, address); 213 pmd_k = pmd_offset(pud_k, address); 214 if (!pmd_present(*pmd_k)) 215 return NULL; 216 217 if (!pmd_present(*pmd)) 218 set_pmd(pmd, *pmd_k); 219 else 220 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 221 222 return pmd_k; 223 } 224 225 void vmalloc_sync_all(void) 226 { 227 unsigned long address; 228 229 if (SHARED_KERNEL_PMD) 230 return; 231 232 for (address = VMALLOC_START & PMD_MASK; 233 address >= TASK_SIZE && address < FIXADDR_TOP; 234 address += PMD_SIZE) { 235 struct page *page; 236 237 spin_lock(&pgd_lock); 238 list_for_each_entry(page, &pgd_list, lru) { 239 spinlock_t *pgt_lock; 240 pmd_t *ret; 241 242 /* the pgt_lock only for Xen */ 243 pgt_lock = &pgd_page_get_mm(page)->page_table_lock; 244 245 spin_lock(pgt_lock); 246 ret = vmalloc_sync_one(page_address(page), address); 247 spin_unlock(pgt_lock); 248 249 if (!ret) 250 break; 251 } 252 spin_unlock(&pgd_lock); 253 } 254 } 255 256 /* 257 * 32-bit: 258 * 259 * Handle a fault on the vmalloc or module mapping area 260 */ 261 static noinline __kprobes int vmalloc_fault(unsigned long address) 262 { 263 unsigned long pgd_paddr; 264 pmd_t *pmd_k; 265 pte_t *pte_k; 266 267 /* Make sure we are in vmalloc area: */ 268 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 269 return -1; 270 271 WARN_ON_ONCE(in_nmi()); 272 273 /* 274 * Synchronize this task's top level page-table 275 * with the 'reference' page table. 276 * 277 * Do _not_ use "current" here. We might be inside 278 * an interrupt in the middle of a task switch.. 279 */ 280 pgd_paddr = read_cr3(); 281 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 282 if (!pmd_k) 283 return -1; 284 285 pte_k = pte_offset_kernel(pmd_k, address); 286 if (!pte_present(*pte_k)) 287 return -1; 288 289 return 0; 290 } 291 292 /* 293 * Did it hit the DOS screen memory VA from vm86 mode? 294 */ 295 static inline void 296 check_v8086_mode(struct pt_regs *regs, unsigned long address, 297 struct task_struct *tsk) 298 { 299 unsigned long bit; 300 301 if (!v8086_mode(regs)) 302 return; 303 304 bit = (address - 0xA0000) >> PAGE_SHIFT; 305 if (bit < 32) 306 tsk->thread.screen_bitmap |= 1 << bit; 307 } 308 309 static bool low_pfn(unsigned long pfn) 310 { 311 return pfn < max_low_pfn; 312 } 313 314 static void dump_pagetable(unsigned long address) 315 { 316 pgd_t *base = __va(read_cr3()); 317 pgd_t *pgd = &base[pgd_index(address)]; 318 pmd_t *pmd; 319 pte_t *pte; 320 321 #ifdef CONFIG_X86_PAE 322 printk("*pdpt = %016Lx ", pgd_val(*pgd)); 323 if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd)) 324 goto out; 325 #endif 326 pmd = pmd_offset(pud_offset(pgd, address), address); 327 printk(KERN_CONT "*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd)); 328 329 /* 330 * We must not directly access the pte in the highpte 331 * case if the page table is located in highmem. 332 * And let's rather not kmap-atomic the pte, just in case 333 * it's allocated already: 334 */ 335 if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd)) 336 goto out; 337 338 pte = pte_offset_kernel(pmd, address); 339 printk("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte)); 340 out: 341 printk("\n"); 342 } 343 344 #else /* CONFIG_X86_64: */ 345 346 void vmalloc_sync_all(void) 347 { 348 sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); 349 } 350 351 /* 352 * 64-bit: 353 * 354 * Handle a fault on the vmalloc area 355 * 356 * This assumes no large pages in there. 357 */ 358 static noinline __kprobes int vmalloc_fault(unsigned long address) 359 { 360 pgd_t *pgd, *pgd_ref; 361 pud_t *pud, *pud_ref; 362 pmd_t *pmd, *pmd_ref; 363 pte_t *pte, *pte_ref; 364 365 /* Make sure we are in vmalloc area: */ 366 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 367 return -1; 368 369 WARN_ON_ONCE(in_nmi()); 370 371 /* 372 * Copy kernel mappings over when needed. This can also 373 * happen within a race in page table update. In the later 374 * case just flush: 375 */ 376 pgd = pgd_offset(current->active_mm, address); 377 pgd_ref = pgd_offset_k(address); 378 if (pgd_none(*pgd_ref)) 379 return -1; 380 381 if (pgd_none(*pgd)) { 382 set_pgd(pgd, *pgd_ref); 383 arch_flush_lazy_mmu_mode(); 384 } else { 385 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 386 } 387 388 /* 389 * Below here mismatches are bugs because these lower tables 390 * are shared: 391 */ 392 393 pud = pud_offset(pgd, address); 394 pud_ref = pud_offset(pgd_ref, address); 395 if (pud_none(*pud_ref)) 396 return -1; 397 398 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref)) 399 BUG(); 400 401 pmd = pmd_offset(pud, address); 402 pmd_ref = pmd_offset(pud_ref, address); 403 if (pmd_none(*pmd_ref)) 404 return -1; 405 406 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref)) 407 BUG(); 408 409 pte_ref = pte_offset_kernel(pmd_ref, address); 410 if (!pte_present(*pte_ref)) 411 return -1; 412 413 pte = pte_offset_kernel(pmd, address); 414 415 /* 416 * Don't use pte_page here, because the mappings can point 417 * outside mem_map, and the NUMA hash lookup cannot handle 418 * that: 419 */ 420 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) 421 BUG(); 422 423 return 0; 424 } 425 426 #ifdef CONFIG_CPU_SUP_AMD 427 static const char errata93_warning[] = 428 KERN_ERR 429 "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 430 "******* Working around it, but it may cause SEGVs or burn power.\n" 431 "******* Please consider a BIOS update.\n" 432 "******* Disabling USB legacy in the BIOS may also help.\n"; 433 #endif 434 435 /* 436 * No vm86 mode in 64-bit mode: 437 */ 438 static inline void 439 check_v8086_mode(struct pt_regs *regs, unsigned long address, 440 struct task_struct *tsk) 441 { 442 } 443 444 static int bad_address(void *p) 445 { 446 unsigned long dummy; 447 448 return probe_kernel_address((unsigned long *)p, dummy); 449 } 450 451 static void dump_pagetable(unsigned long address) 452 { 453 pgd_t *base = __va(read_cr3() & PHYSICAL_PAGE_MASK); 454 pgd_t *pgd = base + pgd_index(address); 455 pud_t *pud; 456 pmd_t *pmd; 457 pte_t *pte; 458 459 if (bad_address(pgd)) 460 goto bad; 461 462 printk("PGD %lx ", pgd_val(*pgd)); 463 464 if (!pgd_present(*pgd)) 465 goto out; 466 467 pud = pud_offset(pgd, address); 468 if (bad_address(pud)) 469 goto bad; 470 471 printk("PUD %lx ", pud_val(*pud)); 472 if (!pud_present(*pud) || pud_large(*pud)) 473 goto out; 474 475 pmd = pmd_offset(pud, address); 476 if (bad_address(pmd)) 477 goto bad; 478 479 printk("PMD %lx ", pmd_val(*pmd)); 480 if (!pmd_present(*pmd) || pmd_large(*pmd)) 481 goto out; 482 483 pte = pte_offset_kernel(pmd, address); 484 if (bad_address(pte)) 485 goto bad; 486 487 printk("PTE %lx", pte_val(*pte)); 488 out: 489 printk("\n"); 490 return; 491 bad: 492 printk("BAD\n"); 493 } 494 495 #endif /* CONFIG_X86_64 */ 496 497 /* 498 * Workaround for K8 erratum #93 & buggy BIOS. 499 * 500 * BIOS SMM functions are required to use a specific workaround 501 * to avoid corruption of the 64bit RIP register on C stepping K8. 502 * 503 * A lot of BIOS that didn't get tested properly miss this. 504 * 505 * The OS sees this as a page fault with the upper 32bits of RIP cleared. 506 * Try to work around it here. 507 * 508 * Note we only handle faults in kernel here. 509 * Does nothing on 32-bit. 510 */ 511 static int is_errata93(struct pt_regs *regs, unsigned long address) 512 { 513 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD) 514 if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD 515 || boot_cpu_data.x86 != 0xf) 516 return 0; 517 518 if (address != regs->ip) 519 return 0; 520 521 if ((address >> 32) != 0) 522 return 0; 523 524 address |= 0xffffffffUL << 32; 525 if ((address >= (u64)_stext && address <= (u64)_etext) || 526 (address >= MODULES_VADDR && address <= MODULES_END)) { 527 printk_once(errata93_warning); 528 regs->ip = address; 529 return 1; 530 } 531 #endif 532 return 0; 533 } 534 535 /* 536 * Work around K8 erratum #100 K8 in compat mode occasionally jumps 537 * to illegal addresses >4GB. 538 * 539 * We catch this in the page fault handler because these addresses 540 * are not reachable. Just detect this case and return. Any code 541 * segment in LDT is compatibility mode. 542 */ 543 static int is_errata100(struct pt_regs *regs, unsigned long address) 544 { 545 #ifdef CONFIG_X86_64 546 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32)) 547 return 1; 548 #endif 549 return 0; 550 } 551 552 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 553 { 554 #ifdef CONFIG_X86_F00F_BUG 555 unsigned long nr; 556 557 /* 558 * Pentium F0 0F C7 C8 bug workaround: 559 */ 560 if (boot_cpu_has_bug(X86_BUG_F00F)) { 561 nr = (address - idt_descr.address) >> 3; 562 563 if (nr == 6) { 564 do_invalid_op(regs, 0); 565 return 1; 566 } 567 } 568 #endif 569 return 0; 570 } 571 572 static const char nx_warning[] = KERN_CRIT 573 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n"; 574 575 static void 576 show_fault_oops(struct pt_regs *regs, unsigned long error_code, 577 unsigned long address) 578 { 579 if (!oops_may_print()) 580 return; 581 582 if (error_code & PF_INSTR) { 583 unsigned int level; 584 585 pte_t *pte = lookup_address(address, &level); 586 587 if (pte && pte_present(*pte) && !pte_exec(*pte)) 588 printk(nx_warning, from_kuid(&init_user_ns, current_uid())); 589 } 590 591 printk(KERN_ALERT "BUG: unable to handle kernel "); 592 if (address < PAGE_SIZE) 593 printk(KERN_CONT "NULL pointer dereference"); 594 else 595 printk(KERN_CONT "paging request"); 596 597 printk(KERN_CONT " at %p\n", (void *) address); 598 printk(KERN_ALERT "IP:"); 599 printk_address(regs->ip, 1); 600 601 dump_pagetable(address); 602 } 603 604 static noinline void 605 pgtable_bad(struct pt_regs *regs, unsigned long error_code, 606 unsigned long address) 607 { 608 struct task_struct *tsk; 609 unsigned long flags; 610 int sig; 611 612 flags = oops_begin(); 613 tsk = current; 614 sig = SIGKILL; 615 616 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 617 tsk->comm, address); 618 dump_pagetable(address); 619 620 tsk->thread.cr2 = address; 621 tsk->thread.trap_nr = X86_TRAP_PF; 622 tsk->thread.error_code = error_code; 623 624 if (__die("Bad pagetable", regs, error_code)) 625 sig = 0; 626 627 oops_end(flags, regs, sig); 628 } 629 630 static noinline void 631 no_context(struct pt_regs *regs, unsigned long error_code, 632 unsigned long address, int signal, int si_code) 633 { 634 struct task_struct *tsk = current; 635 unsigned long *stackend; 636 unsigned long flags; 637 int sig; 638 639 /* Are we prepared to handle this kernel fault? */ 640 if (fixup_exception(regs)) { 641 if (current_thread_info()->sig_on_uaccess_error && signal) { 642 tsk->thread.trap_nr = X86_TRAP_PF; 643 tsk->thread.error_code = error_code | PF_USER; 644 tsk->thread.cr2 = address; 645 646 /* XXX: hwpoison faults will set the wrong code. */ 647 force_sig_info_fault(signal, si_code, address, tsk, 0); 648 } 649 return; 650 } 651 652 /* 653 * 32-bit: 654 * 655 * Valid to do another page fault here, because if this fault 656 * had been triggered by is_prefetch fixup_exception would have 657 * handled it. 658 * 659 * 64-bit: 660 * 661 * Hall of shame of CPU/BIOS bugs. 662 */ 663 if (is_prefetch(regs, error_code, address)) 664 return; 665 666 if (is_errata93(regs, address)) 667 return; 668 669 /* 670 * Oops. The kernel tried to access some bad page. We'll have to 671 * terminate things with extreme prejudice: 672 */ 673 flags = oops_begin(); 674 675 show_fault_oops(regs, error_code, address); 676 677 stackend = end_of_stack(tsk); 678 if (tsk != &init_task && *stackend != STACK_END_MAGIC) 679 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); 680 681 tsk->thread.cr2 = address; 682 tsk->thread.trap_nr = X86_TRAP_PF; 683 tsk->thread.error_code = error_code; 684 685 sig = SIGKILL; 686 if (__die("Oops", regs, error_code)) 687 sig = 0; 688 689 /* Executive summary in case the body of the oops scrolled away */ 690 printk(KERN_DEFAULT "CR2: %016lx\n", address); 691 692 oops_end(flags, regs, sig); 693 } 694 695 /* 696 * Print out info about fatal segfaults, if the show_unhandled_signals 697 * sysctl is set: 698 */ 699 static inline void 700 show_signal_msg(struct pt_regs *regs, unsigned long error_code, 701 unsigned long address, struct task_struct *tsk) 702 { 703 if (!unhandled_signal(tsk, SIGSEGV)) 704 return; 705 706 if (!printk_ratelimit()) 707 return; 708 709 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx", 710 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 711 tsk->comm, task_pid_nr(tsk), address, 712 (void *)regs->ip, (void *)regs->sp, error_code); 713 714 print_vma_addr(KERN_CONT " in ", regs->ip); 715 716 printk(KERN_CONT "\n"); 717 } 718 719 static void 720 __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 721 unsigned long address, int si_code) 722 { 723 struct task_struct *tsk = current; 724 725 /* User mode accesses just cause a SIGSEGV */ 726 if (error_code & PF_USER) { 727 /* 728 * It's possible to have interrupts off here: 729 */ 730 local_irq_enable(); 731 732 /* 733 * Valid to do another page fault here because this one came 734 * from user space: 735 */ 736 if (is_prefetch(regs, error_code, address)) 737 return; 738 739 if (is_errata100(regs, address)) 740 return; 741 742 #ifdef CONFIG_X86_64 743 /* 744 * Instruction fetch faults in the vsyscall page might need 745 * emulation. 746 */ 747 if (unlikely((error_code & PF_INSTR) && 748 ((address & ~0xfff) == VSYSCALL_START))) { 749 if (emulate_vsyscall(regs, address)) 750 return; 751 } 752 #endif 753 /* Kernel addresses are always protection faults: */ 754 if (address >= TASK_SIZE) 755 error_code |= PF_PROT; 756 757 if (likely(show_unhandled_signals)) 758 show_signal_msg(regs, error_code, address, tsk); 759 760 tsk->thread.cr2 = address; 761 tsk->thread.error_code = error_code; 762 tsk->thread.trap_nr = X86_TRAP_PF; 763 764 force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0); 765 766 return; 767 } 768 769 if (is_f00f_bug(regs, address)) 770 return; 771 772 no_context(regs, error_code, address, SIGSEGV, si_code); 773 } 774 775 static noinline void 776 bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, 777 unsigned long address) 778 { 779 __bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR); 780 } 781 782 static void 783 __bad_area(struct pt_regs *regs, unsigned long error_code, 784 unsigned long address, int si_code) 785 { 786 struct mm_struct *mm = current->mm; 787 788 /* 789 * Something tried to access memory that isn't in our memory map.. 790 * Fix it, but check if it's kernel or user first.. 791 */ 792 up_read(&mm->mmap_sem); 793 794 __bad_area_nosemaphore(regs, error_code, address, si_code); 795 } 796 797 static noinline void 798 bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address) 799 { 800 __bad_area(regs, error_code, address, SEGV_MAPERR); 801 } 802 803 static noinline void 804 bad_area_access_error(struct pt_regs *regs, unsigned long error_code, 805 unsigned long address) 806 { 807 __bad_area(regs, error_code, address, SEGV_ACCERR); 808 } 809 810 static void 811 do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address, 812 unsigned int fault) 813 { 814 struct task_struct *tsk = current; 815 struct mm_struct *mm = tsk->mm; 816 int code = BUS_ADRERR; 817 818 up_read(&mm->mmap_sem); 819 820 /* Kernel mode? Handle exceptions or die: */ 821 if (!(error_code & PF_USER)) { 822 no_context(regs, error_code, address, SIGBUS, BUS_ADRERR); 823 return; 824 } 825 826 /* User-space => ok to do another page fault: */ 827 if (is_prefetch(regs, error_code, address)) 828 return; 829 830 tsk->thread.cr2 = address; 831 tsk->thread.error_code = error_code; 832 tsk->thread.trap_nr = X86_TRAP_PF; 833 834 #ifdef CONFIG_MEMORY_FAILURE 835 if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) { 836 printk(KERN_ERR 837 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n", 838 tsk->comm, tsk->pid, address); 839 code = BUS_MCEERR_AR; 840 } 841 #endif 842 force_sig_info_fault(SIGBUS, code, address, tsk, fault); 843 } 844 845 static noinline int 846 mm_fault_error(struct pt_regs *regs, unsigned long error_code, 847 unsigned long address, unsigned int fault) 848 { 849 /* 850 * Pagefault was interrupted by SIGKILL. We have no reason to 851 * continue pagefault. 852 */ 853 if (fatal_signal_pending(current)) { 854 if (!(fault & VM_FAULT_RETRY)) 855 up_read(¤t->mm->mmap_sem); 856 if (!(error_code & PF_USER)) 857 no_context(regs, error_code, address, 0, 0); 858 return 1; 859 } 860 if (!(fault & VM_FAULT_ERROR)) 861 return 0; 862 863 if (fault & VM_FAULT_OOM) { 864 /* Kernel mode? Handle exceptions or die: */ 865 if (!(error_code & PF_USER)) { 866 up_read(¤t->mm->mmap_sem); 867 no_context(regs, error_code, address, 868 SIGSEGV, SEGV_MAPERR); 869 return 1; 870 } 871 872 up_read(¤t->mm->mmap_sem); 873 874 /* 875 * We ran out of memory, call the OOM killer, and return the 876 * userspace (which will retry the fault, or kill us if we got 877 * oom-killed): 878 */ 879 pagefault_out_of_memory(); 880 } else { 881 if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON| 882 VM_FAULT_HWPOISON_LARGE)) 883 do_sigbus(regs, error_code, address, fault); 884 else 885 BUG(); 886 } 887 return 1; 888 } 889 890 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 891 { 892 if ((error_code & PF_WRITE) && !pte_write(*pte)) 893 return 0; 894 895 if ((error_code & PF_INSTR) && !pte_exec(*pte)) 896 return 0; 897 898 return 1; 899 } 900 901 /* 902 * Handle a spurious fault caused by a stale TLB entry. 903 * 904 * This allows us to lazily refresh the TLB when increasing the 905 * permissions of a kernel page (RO -> RW or NX -> X). Doing it 906 * eagerly is very expensive since that implies doing a full 907 * cross-processor TLB flush, even if no stale TLB entries exist 908 * on other processors. 909 * 910 * There are no security implications to leaving a stale TLB when 911 * increasing the permissions on a page. 912 */ 913 static noinline __kprobes int 914 spurious_fault(unsigned long error_code, unsigned long address) 915 { 916 pgd_t *pgd; 917 pud_t *pud; 918 pmd_t *pmd; 919 pte_t *pte; 920 int ret; 921 922 /* Reserved-bit violation or user access to kernel space? */ 923 if (error_code & (PF_USER | PF_RSVD)) 924 return 0; 925 926 pgd = init_mm.pgd + pgd_index(address); 927 if (!pgd_present(*pgd)) 928 return 0; 929 930 pud = pud_offset(pgd, address); 931 if (!pud_present(*pud)) 932 return 0; 933 934 if (pud_large(*pud)) 935 return spurious_fault_check(error_code, (pte_t *) pud); 936 937 pmd = pmd_offset(pud, address); 938 if (!pmd_present(*pmd)) 939 return 0; 940 941 if (pmd_large(*pmd)) 942 return spurious_fault_check(error_code, (pte_t *) pmd); 943 944 pte = pte_offset_kernel(pmd, address); 945 if (!pte_present(*pte)) 946 return 0; 947 948 ret = spurious_fault_check(error_code, pte); 949 if (!ret) 950 return 0; 951 952 /* 953 * Make sure we have permissions in PMD. 954 * If not, then there's a bug in the page tables: 955 */ 956 ret = spurious_fault_check(error_code, (pte_t *) pmd); 957 WARN_ONCE(!ret, "PMD has incorrect permission bits\n"); 958 959 return ret; 960 } 961 962 int show_unhandled_signals = 1; 963 964 static inline int 965 access_error(unsigned long error_code, struct vm_area_struct *vma) 966 { 967 if (error_code & PF_WRITE) { 968 /* write, present and write, not present: */ 969 if (unlikely(!(vma->vm_flags & VM_WRITE))) 970 return 1; 971 return 0; 972 } 973 974 /* read, present: */ 975 if (unlikely(error_code & PF_PROT)) 976 return 1; 977 978 /* read, not present: */ 979 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))) 980 return 1; 981 982 return 0; 983 } 984 985 static int fault_in_kernel_space(unsigned long address) 986 { 987 return address >= TASK_SIZE_MAX; 988 } 989 990 static inline bool smap_violation(int error_code, struct pt_regs *regs) 991 { 992 if (error_code & PF_USER) 993 return false; 994 995 if (!user_mode_vm(regs) && (regs->flags & X86_EFLAGS_AC)) 996 return false; 997 998 return true; 999 } 1000 1001 /* 1002 * This routine handles page faults. It determines the address, 1003 * and the problem, and then passes it off to one of the appropriate 1004 * routines. 1005 */ 1006 static void __kprobes 1007 __do_page_fault(struct pt_regs *regs, unsigned long error_code) 1008 { 1009 struct vm_area_struct *vma; 1010 struct task_struct *tsk; 1011 unsigned long address; 1012 struct mm_struct *mm; 1013 int fault; 1014 int write = error_code & PF_WRITE; 1015 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | 1016 (write ? FAULT_FLAG_WRITE : 0); 1017 1018 tsk = current; 1019 mm = tsk->mm; 1020 1021 /* Get the faulting address: */ 1022 address = read_cr2(); 1023 1024 /* 1025 * Detect and handle instructions that would cause a page fault for 1026 * both a tracked kernel page and a userspace page. 1027 */ 1028 if (kmemcheck_active(regs)) 1029 kmemcheck_hide(regs); 1030 prefetchw(&mm->mmap_sem); 1031 1032 if (unlikely(kmmio_fault(regs, address))) 1033 return; 1034 1035 /* 1036 * We fault-in kernel-space virtual memory on-demand. The 1037 * 'reference' page table is init_mm.pgd. 1038 * 1039 * NOTE! We MUST NOT take any locks for this case. We may 1040 * be in an interrupt or a critical region, and should 1041 * only copy the information from the master page table, 1042 * nothing more. 1043 * 1044 * This verifies that the fault happens in kernel space 1045 * (error_code & 4) == 0, and that the fault was not a 1046 * protection error (error_code & 9) == 0. 1047 */ 1048 if (unlikely(fault_in_kernel_space(address))) { 1049 if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) { 1050 if (vmalloc_fault(address) >= 0) 1051 return; 1052 1053 if (kmemcheck_fault(regs, address, error_code)) 1054 return; 1055 } 1056 1057 /* Can handle a stale RO->RW TLB: */ 1058 if (spurious_fault(error_code, address)) 1059 return; 1060 1061 /* kprobes don't want to hook the spurious faults: */ 1062 if (notify_page_fault(regs)) 1063 return; 1064 /* 1065 * Don't take the mm semaphore here. If we fixup a prefetch 1066 * fault we could otherwise deadlock: 1067 */ 1068 bad_area_nosemaphore(regs, error_code, address); 1069 1070 return; 1071 } 1072 1073 /* kprobes don't want to hook the spurious faults: */ 1074 if (unlikely(notify_page_fault(regs))) 1075 return; 1076 /* 1077 * It's safe to allow irq's after cr2 has been saved and the 1078 * vmalloc fault has been handled. 1079 * 1080 * User-mode registers count as a user access even for any 1081 * potential system fault or CPU buglet: 1082 */ 1083 if (user_mode_vm(regs)) { 1084 local_irq_enable(); 1085 error_code |= PF_USER; 1086 } else { 1087 if (regs->flags & X86_EFLAGS_IF) 1088 local_irq_enable(); 1089 } 1090 1091 if (unlikely(error_code & PF_RSVD)) 1092 pgtable_bad(regs, error_code, address); 1093 1094 if (static_cpu_has(X86_FEATURE_SMAP)) { 1095 if (unlikely(smap_violation(error_code, regs))) { 1096 bad_area_nosemaphore(regs, error_code, address); 1097 return; 1098 } 1099 } 1100 1101 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 1102 1103 /* 1104 * If we're in an interrupt, have no user context or are running 1105 * in an atomic region then we must not take the fault: 1106 */ 1107 if (unlikely(in_atomic() || !mm)) { 1108 bad_area_nosemaphore(regs, error_code, address); 1109 return; 1110 } 1111 1112 /* 1113 * When running in the kernel we expect faults to occur only to 1114 * addresses in user space. All other faults represent errors in 1115 * the kernel and should generate an OOPS. Unfortunately, in the 1116 * case of an erroneous fault occurring in a code path which already 1117 * holds mmap_sem we will deadlock attempting to validate the fault 1118 * against the address space. Luckily the kernel only validly 1119 * references user space from well defined areas of code, which are 1120 * listed in the exceptions table. 1121 * 1122 * As the vast majority of faults will be valid we will only perform 1123 * the source reference check when there is a possibility of a 1124 * deadlock. Attempt to lock the address space, if we cannot we then 1125 * validate the source. If this is invalid we can skip the address 1126 * space check, thus avoiding the deadlock: 1127 */ 1128 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 1129 if ((error_code & PF_USER) == 0 && 1130 !search_exception_tables(regs->ip)) { 1131 bad_area_nosemaphore(regs, error_code, address); 1132 return; 1133 } 1134 retry: 1135 down_read(&mm->mmap_sem); 1136 } else { 1137 /* 1138 * The above down_read_trylock() might have succeeded in 1139 * which case we'll have missed the might_sleep() from 1140 * down_read(): 1141 */ 1142 might_sleep(); 1143 } 1144 1145 vma = find_vma(mm, address); 1146 if (unlikely(!vma)) { 1147 bad_area(regs, error_code, address); 1148 return; 1149 } 1150 if (likely(vma->vm_start <= address)) 1151 goto good_area; 1152 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 1153 bad_area(regs, error_code, address); 1154 return; 1155 } 1156 if (error_code & PF_USER) { 1157 /* 1158 * Accessing the stack below %sp is always a bug. 1159 * The large cushion allows instructions like enter 1160 * and pusha to work. ("enter $65535, $31" pushes 1161 * 32 pointers and then decrements %sp by 65535.) 1162 */ 1163 if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) { 1164 bad_area(regs, error_code, address); 1165 return; 1166 } 1167 } 1168 if (unlikely(expand_stack(vma, address))) { 1169 bad_area(regs, error_code, address); 1170 return; 1171 } 1172 1173 /* 1174 * Ok, we have a good vm_area for this memory access, so 1175 * we can handle it.. 1176 */ 1177 good_area: 1178 if (unlikely(access_error(error_code, vma))) { 1179 bad_area_access_error(regs, error_code, address); 1180 return; 1181 } 1182 1183 /* 1184 * If for any reason at all we couldn't handle the fault, 1185 * make sure we exit gracefully rather than endlessly redo 1186 * the fault: 1187 */ 1188 fault = handle_mm_fault(mm, vma, address, flags); 1189 1190 if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) { 1191 if (mm_fault_error(regs, error_code, address, fault)) 1192 return; 1193 } 1194 1195 /* 1196 * Major/minor page fault accounting is only done on the 1197 * initial attempt. If we go through a retry, it is extremely 1198 * likely that the page will be found in page cache at that point. 1199 */ 1200 if (flags & FAULT_FLAG_ALLOW_RETRY) { 1201 if (fault & VM_FAULT_MAJOR) { 1202 tsk->maj_flt++; 1203 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 1204 regs, address); 1205 } else { 1206 tsk->min_flt++; 1207 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 1208 regs, address); 1209 } 1210 if (fault & VM_FAULT_RETRY) { 1211 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 1212 * of starvation. */ 1213 flags &= ~FAULT_FLAG_ALLOW_RETRY; 1214 flags |= FAULT_FLAG_TRIED; 1215 goto retry; 1216 } 1217 } 1218 1219 check_v8086_mode(regs, address, tsk); 1220 1221 up_read(&mm->mmap_sem); 1222 } 1223 1224 dotraplinkage void __kprobes 1225 do_page_fault(struct pt_regs *regs, unsigned long error_code) 1226 { 1227 enum ctx_state prev_state; 1228 1229 prev_state = exception_enter(); 1230 __do_page_fault(regs, error_code); 1231 exception_exit(prev_state); 1232 } 1233