1 /* 2 * Copyright (C) 1995 Linus Torvalds 3 * Copyright (C) 2001,2002 Andi Kleen, SuSE Labs. 4 */ 5 6 #include <linux/signal.h> 7 #include <linux/sched.h> 8 #include <linux/kernel.h> 9 #include <linux/errno.h> 10 #include <linux/string.h> 11 #include <linux/types.h> 12 #include <linux/ptrace.h> 13 #include <linux/mmiotrace.h> 14 #include <linux/mman.h> 15 #include <linux/mm.h> 16 #include <linux/smp.h> 17 #include <linux/interrupt.h> 18 #include <linux/init.h> 19 #include <linux/tty.h> 20 #include <linux/vt_kern.h> /* For unblank_screen() */ 21 #include <linux/compiler.h> 22 #include <linux/highmem.h> 23 #include <linux/bootmem.h> /* for max_low_pfn */ 24 #include <linux/vmalloc.h> 25 #include <linux/module.h> 26 #include <linux/kprobes.h> 27 #include <linux/uaccess.h> 28 #include <linux/kdebug.h> 29 30 #include <asm/system.h> 31 #include <asm/desc.h> 32 #include <asm/segment.h> 33 #include <asm/pgalloc.h> 34 #include <asm/smp.h> 35 #include <asm/tlbflush.h> 36 #include <asm/proto.h> 37 #include <asm-generic/sections.h> 38 #include <asm/traps.h> 39 40 /* 41 * Page fault error code bits 42 * bit 0 == 0 means no page found, 1 means protection fault 43 * bit 1 == 0 means read, 1 means write 44 * bit 2 == 0 means kernel, 1 means user-mode 45 * bit 3 == 1 means use of reserved bit detected 46 * bit 4 == 1 means fault was an instruction fetch 47 */ 48 #define PF_PROT (1<<0) 49 #define PF_WRITE (1<<1) 50 #define PF_USER (1<<2) 51 #define PF_RSVD (1<<3) 52 #define PF_INSTR (1<<4) 53 54 static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr) 55 { 56 #ifdef CONFIG_MMIOTRACE_HOOKS 57 if (unlikely(is_kmmio_active())) 58 if (kmmio_handler(regs, addr) == 1) 59 return -1; 60 #endif 61 return 0; 62 } 63 64 static inline int notify_page_fault(struct pt_regs *regs) 65 { 66 #ifdef CONFIG_KPROBES 67 int ret = 0; 68 69 /* kprobe_running() needs smp_processor_id() */ 70 if (!user_mode_vm(regs)) { 71 preempt_disable(); 72 if (kprobe_running() && kprobe_fault_handler(regs, 14)) 73 ret = 1; 74 preempt_enable(); 75 } 76 77 return ret; 78 #else 79 return 0; 80 #endif 81 } 82 83 /* 84 * X86_32 85 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 86 * Check that here and ignore it. 87 * 88 * X86_64 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 int is_prefetch(struct pt_regs *regs, unsigned long addr, 95 unsigned long error_code) 96 { 97 unsigned char *instr; 98 int scan_more = 1; 99 int prefetch = 0; 100 unsigned char *max_instr; 101 102 /* 103 * If it was a exec (instruction fetch) fault on NX page, then 104 * do not ignore the fault: 105 */ 106 if (error_code & PF_INSTR) 107 return 0; 108 109 instr = (unsigned char *)convert_ip_to_linear(current, regs); 110 max_instr = instr + 15; 111 112 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE) 113 return 0; 114 115 while (scan_more && instr < max_instr) { 116 unsigned char opcode; 117 unsigned char instr_hi; 118 unsigned char instr_lo; 119 120 if (probe_kernel_address(instr, opcode)) 121 break; 122 123 instr_hi = opcode & 0xf0; 124 instr_lo = opcode & 0x0f; 125 instr++; 126 127 switch (instr_hi) { 128 case 0x20: 129 case 0x30: 130 /* 131 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 132 * In X86_64 long mode, the CPU will signal invalid 133 * opcode if some of these prefixes are present so 134 * X86_64 will never get here anyway 135 */ 136 scan_more = ((instr_lo & 7) == 0x6); 137 break; 138 #ifdef CONFIG_X86_64 139 case 0x40: 140 /* 141 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 142 * Need to figure out under what instruction mode the 143 * instruction was issued. Could check the LDT for lm, 144 * but for now it's good enough to assume that long 145 * mode only uses well known segments or kernel. 146 */ 147 scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS); 148 break; 149 #endif 150 case 0x60: 151 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 152 scan_more = (instr_lo & 0xC) == 0x4; 153 break; 154 case 0xF0: 155 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 156 scan_more = !instr_lo || (instr_lo>>1) == 1; 157 break; 158 case 0x00: 159 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 160 scan_more = 0; 161 162 if (probe_kernel_address(instr, opcode)) 163 break; 164 prefetch = (instr_lo == 0xF) && 165 (opcode == 0x0D || opcode == 0x18); 166 break; 167 default: 168 scan_more = 0; 169 break; 170 } 171 } 172 return prefetch; 173 } 174 175 static void force_sig_info_fault(int si_signo, int si_code, 176 unsigned long address, struct task_struct *tsk) 177 { 178 siginfo_t info; 179 180 info.si_signo = si_signo; 181 info.si_errno = 0; 182 info.si_code = si_code; 183 info.si_addr = (void __user *)address; 184 force_sig_info(si_signo, &info, tsk); 185 } 186 187 #ifdef CONFIG_X86_64 188 static int bad_address(void *p) 189 { 190 unsigned long dummy; 191 return probe_kernel_address((unsigned long *)p, dummy); 192 } 193 #endif 194 195 static void dump_pagetable(unsigned long address) 196 { 197 #ifdef CONFIG_X86_32 198 __typeof__(pte_val(__pte(0))) page; 199 200 page = read_cr3(); 201 page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT]; 202 #ifdef CONFIG_X86_PAE 203 printk("*pdpt = %016Lx ", page); 204 if ((page >> PAGE_SHIFT) < max_low_pfn 205 && page & _PAGE_PRESENT) { 206 page &= PAGE_MASK; 207 page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT) 208 & (PTRS_PER_PMD - 1)]; 209 printk(KERN_CONT "*pde = %016Lx ", page); 210 page &= ~_PAGE_NX; 211 } 212 #else 213 printk("*pde = %08lx ", page); 214 #endif 215 216 /* 217 * We must not directly access the pte in the highpte 218 * case if the page table is located in highmem. 219 * And let's rather not kmap-atomic the pte, just in case 220 * it's allocated already. 221 */ 222 if ((page >> PAGE_SHIFT) < max_low_pfn 223 && (page & _PAGE_PRESENT) 224 && !(page & _PAGE_PSE)) { 225 page &= PAGE_MASK; 226 page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT) 227 & (PTRS_PER_PTE - 1)]; 228 printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page); 229 } 230 231 printk("\n"); 232 #else /* CONFIG_X86_64 */ 233 pgd_t *pgd; 234 pud_t *pud; 235 pmd_t *pmd; 236 pte_t *pte; 237 238 pgd = (pgd_t *)read_cr3(); 239 240 pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK); 241 pgd += pgd_index(address); 242 if (bad_address(pgd)) goto bad; 243 printk("PGD %lx ", pgd_val(*pgd)); 244 if (!pgd_present(*pgd)) goto ret; 245 246 pud = pud_offset(pgd, address); 247 if (bad_address(pud)) goto bad; 248 printk("PUD %lx ", pud_val(*pud)); 249 if (!pud_present(*pud) || pud_large(*pud)) 250 goto ret; 251 252 pmd = pmd_offset(pud, address); 253 if (bad_address(pmd)) goto bad; 254 printk("PMD %lx ", pmd_val(*pmd)); 255 if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret; 256 257 pte = pte_offset_kernel(pmd, address); 258 if (bad_address(pte)) goto bad; 259 printk("PTE %lx", pte_val(*pte)); 260 ret: 261 printk("\n"); 262 return; 263 bad: 264 printk("BAD\n"); 265 #endif 266 } 267 268 #ifdef CONFIG_X86_32 269 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 270 { 271 unsigned index = pgd_index(address); 272 pgd_t *pgd_k; 273 pud_t *pud, *pud_k; 274 pmd_t *pmd, *pmd_k; 275 276 pgd += index; 277 pgd_k = init_mm.pgd + index; 278 279 if (!pgd_present(*pgd_k)) 280 return NULL; 281 282 /* 283 * set_pgd(pgd, *pgd_k); here would be useless on PAE 284 * and redundant with the set_pmd() on non-PAE. As would 285 * set_pud. 286 */ 287 288 pud = pud_offset(pgd, address); 289 pud_k = pud_offset(pgd_k, address); 290 if (!pud_present(*pud_k)) 291 return NULL; 292 293 pmd = pmd_offset(pud, address); 294 pmd_k = pmd_offset(pud_k, address); 295 if (!pmd_present(*pmd_k)) 296 return NULL; 297 if (!pmd_present(*pmd)) { 298 set_pmd(pmd, *pmd_k); 299 arch_flush_lazy_mmu_mode(); 300 } else 301 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 302 return pmd_k; 303 } 304 #endif 305 306 #ifdef CONFIG_X86_64 307 static const char errata93_warning[] = 308 KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 309 KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n" 310 KERN_ERR "******* Please consider a BIOS update.\n" 311 KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n"; 312 #endif 313 314 /* Workaround for K8 erratum #93 & buggy BIOS. 315 BIOS SMM functions are required to use a specific workaround 316 to avoid corruption of the 64bit RIP register on C stepping K8. 317 A lot of BIOS that didn't get tested properly miss this. 318 The OS sees this as a page fault with the upper 32bits of RIP cleared. 319 Try to work around it here. 320 Note we only handle faults in kernel here. 321 Does nothing for X86_32 322 */ 323 static int is_errata93(struct pt_regs *regs, unsigned long address) 324 { 325 #ifdef CONFIG_X86_64 326 static int warned; 327 if (address != regs->ip) 328 return 0; 329 if ((address >> 32) != 0) 330 return 0; 331 address |= 0xffffffffUL << 32; 332 if ((address >= (u64)_stext && address <= (u64)_etext) || 333 (address >= MODULES_VADDR && address <= MODULES_END)) { 334 if (!warned) { 335 printk(errata93_warning); 336 warned = 1; 337 } 338 regs->ip = address; 339 return 1; 340 } 341 #endif 342 return 0; 343 } 344 345 /* 346 * Work around K8 erratum #100 K8 in compat mode occasionally jumps to illegal 347 * addresses >4GB. We catch this in the page fault handler because these 348 * addresses are not reachable. Just detect this case and return. Any code 349 * segment in LDT is compatibility mode. 350 */ 351 static int is_errata100(struct pt_regs *regs, unsigned long address) 352 { 353 #ifdef CONFIG_X86_64 354 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && 355 (address >> 32)) 356 return 1; 357 #endif 358 return 0; 359 } 360 361 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 362 { 363 #ifdef CONFIG_X86_F00F_BUG 364 unsigned long nr; 365 /* 366 * Pentium F0 0F C7 C8 bug workaround. 367 */ 368 if (boot_cpu_data.f00f_bug) { 369 nr = (address - idt_descr.address) >> 3; 370 371 if (nr == 6) { 372 do_invalid_op(regs, 0); 373 return 1; 374 } 375 } 376 #endif 377 return 0; 378 } 379 380 static void show_fault_oops(struct pt_regs *regs, unsigned long error_code, 381 unsigned long address) 382 { 383 #ifdef CONFIG_X86_32 384 if (!oops_may_print()) 385 return; 386 #endif 387 388 #ifdef CONFIG_X86_PAE 389 if (error_code & PF_INSTR) { 390 unsigned int level; 391 pte_t *pte = lookup_address(address, &level); 392 393 if (pte && pte_present(*pte) && !pte_exec(*pte)) 394 printk(KERN_CRIT "kernel tried to execute " 395 "NX-protected page - exploit attempt? " 396 "(uid: %d)\n", current->uid); 397 } 398 #endif 399 400 printk(KERN_ALERT "BUG: unable to handle kernel "); 401 if (address < PAGE_SIZE) 402 printk(KERN_CONT "NULL pointer dereference"); 403 else 404 printk(KERN_CONT "paging request"); 405 printk(KERN_CONT " at %p\n", (void *) address); 406 printk(KERN_ALERT "IP:"); 407 printk_address(regs->ip, 1); 408 dump_pagetable(address); 409 } 410 411 #ifdef CONFIG_X86_64 412 static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs, 413 unsigned long error_code) 414 { 415 unsigned long flags = oops_begin(); 416 struct task_struct *tsk; 417 418 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 419 current->comm, address); 420 dump_pagetable(address); 421 tsk = current; 422 tsk->thread.cr2 = address; 423 tsk->thread.trap_no = 14; 424 tsk->thread.error_code = error_code; 425 if (__die("Bad pagetable", regs, error_code)) 426 regs = NULL; 427 oops_end(flags, regs, SIGKILL); 428 } 429 #endif 430 431 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 432 { 433 if ((error_code & PF_WRITE) && !pte_write(*pte)) 434 return 0; 435 if ((error_code & PF_INSTR) && !pte_exec(*pte)) 436 return 0; 437 438 return 1; 439 } 440 441 /* 442 * Handle a spurious fault caused by a stale TLB entry. This allows 443 * us to lazily refresh the TLB when increasing the permissions of a 444 * kernel page (RO -> RW or NX -> X). Doing it eagerly is very 445 * expensive since that implies doing a full cross-processor TLB 446 * flush, even if no stale TLB entries exist on other processors. 447 * There are no security implications to leaving a stale TLB when 448 * increasing the permissions on a page. 449 */ 450 static int spurious_fault(unsigned long address, 451 unsigned long error_code) 452 { 453 pgd_t *pgd; 454 pud_t *pud; 455 pmd_t *pmd; 456 pte_t *pte; 457 458 /* Reserved-bit violation or user access to kernel space? */ 459 if (error_code & (PF_USER | PF_RSVD)) 460 return 0; 461 462 pgd = init_mm.pgd + pgd_index(address); 463 if (!pgd_present(*pgd)) 464 return 0; 465 466 pud = pud_offset(pgd, address); 467 if (!pud_present(*pud)) 468 return 0; 469 470 if (pud_large(*pud)) 471 return spurious_fault_check(error_code, (pte_t *) pud); 472 473 pmd = pmd_offset(pud, address); 474 if (!pmd_present(*pmd)) 475 return 0; 476 477 if (pmd_large(*pmd)) 478 return spurious_fault_check(error_code, (pte_t *) pmd); 479 480 pte = pte_offset_kernel(pmd, address); 481 if (!pte_present(*pte)) 482 return 0; 483 484 return spurious_fault_check(error_code, pte); 485 } 486 487 /* 488 * X86_32 489 * Handle a fault on the vmalloc or module mapping area 490 * 491 * X86_64 492 * Handle a fault on the vmalloc area 493 * 494 * This assumes no large pages in there. 495 */ 496 static int vmalloc_fault(unsigned long address) 497 { 498 #ifdef CONFIG_X86_32 499 unsigned long pgd_paddr; 500 pmd_t *pmd_k; 501 pte_t *pte_k; 502 503 /* Make sure we are in vmalloc area */ 504 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 505 return -1; 506 507 /* 508 * Synchronize this task's top level page-table 509 * with the 'reference' page table. 510 * 511 * Do _not_ use "current" here. We might be inside 512 * an interrupt in the middle of a task switch.. 513 */ 514 pgd_paddr = read_cr3(); 515 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 516 if (!pmd_k) 517 return -1; 518 pte_k = pte_offset_kernel(pmd_k, address); 519 if (!pte_present(*pte_k)) 520 return -1; 521 return 0; 522 #else 523 pgd_t *pgd, *pgd_ref; 524 pud_t *pud, *pud_ref; 525 pmd_t *pmd, *pmd_ref; 526 pte_t *pte, *pte_ref; 527 528 /* Make sure we are in vmalloc area */ 529 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 530 return -1; 531 532 /* Copy kernel mappings over when needed. This can also 533 happen within a race in page table update. In the later 534 case just flush. */ 535 536 pgd = pgd_offset(current->mm ?: &init_mm, address); 537 pgd_ref = pgd_offset_k(address); 538 if (pgd_none(*pgd_ref)) 539 return -1; 540 if (pgd_none(*pgd)) 541 set_pgd(pgd, *pgd_ref); 542 else 543 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 544 545 /* Below here mismatches are bugs because these lower tables 546 are shared */ 547 548 pud = pud_offset(pgd, address); 549 pud_ref = pud_offset(pgd_ref, address); 550 if (pud_none(*pud_ref)) 551 return -1; 552 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref)) 553 BUG(); 554 pmd = pmd_offset(pud, address); 555 pmd_ref = pmd_offset(pud_ref, address); 556 if (pmd_none(*pmd_ref)) 557 return -1; 558 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref)) 559 BUG(); 560 pte_ref = pte_offset_kernel(pmd_ref, address); 561 if (!pte_present(*pte_ref)) 562 return -1; 563 pte = pte_offset_kernel(pmd, address); 564 /* Don't use pte_page here, because the mappings can point 565 outside mem_map, and the NUMA hash lookup cannot handle 566 that. */ 567 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) 568 BUG(); 569 return 0; 570 #endif 571 } 572 573 int show_unhandled_signals = 1; 574 575 /* 576 * This routine handles page faults. It determines the address, 577 * and the problem, and then passes it off to one of the appropriate 578 * routines. 579 */ 580 #ifdef CONFIG_X86_64 581 asmlinkage 582 #endif 583 void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) 584 { 585 struct task_struct *tsk; 586 struct mm_struct *mm; 587 struct vm_area_struct *vma; 588 unsigned long address; 589 int write, si_code; 590 int fault; 591 #ifdef CONFIG_X86_64 592 unsigned long flags; 593 #endif 594 595 tsk = current; 596 mm = tsk->mm; 597 prefetchw(&mm->mmap_sem); 598 599 /* get the address */ 600 address = read_cr2(); 601 602 si_code = SEGV_MAPERR; 603 604 if (notify_page_fault(regs)) 605 return; 606 if (unlikely(kmmio_fault(regs, address))) 607 return; 608 609 /* 610 * We fault-in kernel-space virtual memory on-demand. The 611 * 'reference' page table is init_mm.pgd. 612 * 613 * NOTE! We MUST NOT take any locks for this case. We may 614 * be in an interrupt or a critical region, and should 615 * only copy the information from the master page table, 616 * nothing more. 617 * 618 * This verifies that the fault happens in kernel space 619 * (error_code & 4) == 0, and that the fault was not a 620 * protection error (error_code & 9) == 0. 621 */ 622 #ifdef CONFIG_X86_32 623 if (unlikely(address >= TASK_SIZE)) { 624 #else 625 if (unlikely(address >= TASK_SIZE64)) { 626 #endif 627 if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) && 628 vmalloc_fault(address) >= 0) 629 return; 630 631 /* Can handle a stale RO->RW TLB */ 632 if (spurious_fault(address, error_code)) 633 return; 634 635 /* 636 * Don't take the mm semaphore here. If we fixup a prefetch 637 * fault we could otherwise deadlock. 638 */ 639 goto bad_area_nosemaphore; 640 } 641 642 643 /* 644 * It's safe to allow irq's after cr2 has been saved and the 645 * vmalloc fault has been handled. 646 * 647 * User-mode registers count as a user access even for any 648 * potential system fault or CPU buglet. 649 */ 650 if (user_mode_vm(regs)) { 651 local_irq_enable(); 652 error_code |= PF_USER; 653 } else if (regs->flags & X86_EFLAGS_IF) 654 local_irq_enable(); 655 656 #ifdef CONFIG_X86_64 657 if (unlikely(error_code & PF_RSVD)) 658 pgtable_bad(address, regs, error_code); 659 #endif 660 661 /* 662 * If we're in an interrupt, have no user context or are running in an 663 * atomic region then we must not take the fault. 664 */ 665 if (unlikely(in_atomic() || !mm)) 666 goto bad_area_nosemaphore; 667 668 again: 669 /* 670 * When running in the kernel we expect faults to occur only to 671 * addresses in user space. All other faults represent errors in the 672 * kernel and should generate an OOPS. Unfortunately, in the case of an 673 * erroneous fault occurring in a code path which already holds mmap_sem 674 * we will deadlock attempting to validate the fault against the 675 * address space. Luckily the kernel only validly references user 676 * space from well defined areas of code, which are listed in the 677 * exceptions table. 678 * 679 * As the vast majority of faults will be valid we will only perform 680 * the source reference check when there is a possibility of a deadlock. 681 * Attempt to lock the address space, if we cannot we then validate the 682 * source. If this is invalid we can skip the address space check, 683 * thus avoiding the deadlock. 684 */ 685 if (!down_read_trylock(&mm->mmap_sem)) { 686 if ((error_code & PF_USER) == 0 && 687 !search_exception_tables(regs->ip)) 688 goto bad_area_nosemaphore; 689 down_read(&mm->mmap_sem); 690 } 691 692 vma = find_vma(mm, address); 693 if (!vma) 694 goto bad_area; 695 if (vma->vm_start <= address) 696 goto good_area; 697 if (!(vma->vm_flags & VM_GROWSDOWN)) 698 goto bad_area; 699 if (error_code & PF_USER) { 700 /* 701 * Accessing the stack below %sp is always a bug. 702 * The large cushion allows instructions like enter 703 * and pusha to work. ("enter $65535,$31" pushes 704 * 32 pointers and then decrements %sp by 65535.) 705 */ 706 if (address + 65536 + 32 * sizeof(unsigned long) < regs->sp) 707 goto bad_area; 708 } 709 if (expand_stack(vma, address)) 710 goto bad_area; 711 /* 712 * Ok, we have a good vm_area for this memory access, so 713 * we can handle it.. 714 */ 715 good_area: 716 si_code = SEGV_ACCERR; 717 write = 0; 718 switch (error_code & (PF_PROT|PF_WRITE)) { 719 default: /* 3: write, present */ 720 /* fall through */ 721 case PF_WRITE: /* write, not present */ 722 if (!(vma->vm_flags & VM_WRITE)) 723 goto bad_area; 724 write++; 725 break; 726 case PF_PROT: /* read, present */ 727 goto bad_area; 728 case 0: /* read, not present */ 729 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 730 goto bad_area; 731 } 732 733 /* 734 * If for any reason at all we couldn't handle the fault, 735 * make sure we exit gracefully rather than endlessly redo 736 * the fault. 737 */ 738 fault = handle_mm_fault(mm, vma, address, write); 739 if (unlikely(fault & VM_FAULT_ERROR)) { 740 if (fault & VM_FAULT_OOM) 741 goto out_of_memory; 742 else if (fault & VM_FAULT_SIGBUS) 743 goto do_sigbus; 744 BUG(); 745 } 746 if (fault & VM_FAULT_MAJOR) 747 tsk->maj_flt++; 748 else 749 tsk->min_flt++; 750 751 #ifdef CONFIG_X86_32 752 /* 753 * Did it hit the DOS screen memory VA from vm86 mode? 754 */ 755 if (v8086_mode(regs)) { 756 unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT; 757 if (bit < 32) 758 tsk->thread.screen_bitmap |= 1 << bit; 759 } 760 #endif 761 up_read(&mm->mmap_sem); 762 return; 763 764 /* 765 * Something tried to access memory that isn't in our memory map.. 766 * Fix it, but check if it's kernel or user first.. 767 */ 768 bad_area: 769 up_read(&mm->mmap_sem); 770 771 bad_area_nosemaphore: 772 /* User mode accesses just cause a SIGSEGV */ 773 if (error_code & PF_USER) { 774 /* 775 * It's possible to have interrupts off here. 776 */ 777 local_irq_enable(); 778 779 /* 780 * Valid to do another page fault here because this one came 781 * from user space. 782 */ 783 if (is_prefetch(regs, address, error_code)) 784 return; 785 786 if (is_errata100(regs, address)) 787 return; 788 789 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && 790 printk_ratelimit()) { 791 printk( 792 "%s%s[%d]: segfault at %lx ip %p sp %p error %lx", 793 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 794 tsk->comm, task_pid_nr(tsk), address, 795 (void *) regs->ip, (void *) regs->sp, error_code); 796 print_vma_addr(" in ", regs->ip); 797 printk("\n"); 798 } 799 800 tsk->thread.cr2 = address; 801 /* Kernel addresses are always protection faults */ 802 tsk->thread.error_code = error_code | (address >= TASK_SIZE); 803 tsk->thread.trap_no = 14; 804 force_sig_info_fault(SIGSEGV, si_code, address, tsk); 805 return; 806 } 807 808 if (is_f00f_bug(regs, address)) 809 return; 810 811 no_context: 812 /* Are we prepared to handle this kernel fault? */ 813 if (fixup_exception(regs)) 814 return; 815 816 /* 817 * X86_32 818 * Valid to do another page fault here, because if this fault 819 * had been triggered by is_prefetch fixup_exception would have 820 * handled it. 821 * 822 * X86_64 823 * Hall of shame of CPU/BIOS bugs. 824 */ 825 if (is_prefetch(regs, address, error_code)) 826 return; 827 828 if (is_errata93(regs, address)) 829 return; 830 831 /* 832 * Oops. The kernel tried to access some bad page. We'll have to 833 * terminate things with extreme prejudice. 834 */ 835 #ifdef CONFIG_X86_32 836 bust_spinlocks(1); 837 #else 838 flags = oops_begin(); 839 #endif 840 841 show_fault_oops(regs, error_code, address); 842 843 tsk->thread.cr2 = address; 844 tsk->thread.trap_no = 14; 845 tsk->thread.error_code = error_code; 846 847 #ifdef CONFIG_X86_32 848 die("Oops", regs, error_code); 849 bust_spinlocks(0); 850 do_exit(SIGKILL); 851 #else 852 if (__die("Oops", regs, error_code)) 853 regs = NULL; 854 /* Executive summary in case the body of the oops scrolled away */ 855 printk(KERN_EMERG "CR2: %016lx\n", address); 856 oops_end(flags, regs, SIGKILL); 857 #endif 858 859 /* 860 * We ran out of memory, or some other thing happened to us that made 861 * us unable to handle the page fault gracefully. 862 */ 863 out_of_memory: 864 up_read(&mm->mmap_sem); 865 if (is_global_init(tsk)) { 866 yield(); 867 /* 868 * Re-lookup the vma - in theory the vma tree might 869 * have changed: 870 */ 871 goto again; 872 } 873 874 printk("VM: killing process %s\n", tsk->comm); 875 if (error_code & PF_USER) 876 do_group_exit(SIGKILL); 877 goto no_context; 878 879 do_sigbus: 880 up_read(&mm->mmap_sem); 881 882 /* Kernel mode? Handle exceptions or die */ 883 if (!(error_code & PF_USER)) 884 goto no_context; 885 #ifdef CONFIG_X86_32 886 /* User space => ok to do another page fault */ 887 if (is_prefetch(regs, address, error_code)) 888 return; 889 #endif 890 tsk->thread.cr2 = address; 891 tsk->thread.error_code = error_code; 892 tsk->thread.trap_no = 14; 893 force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk); 894 } 895 896 DEFINE_SPINLOCK(pgd_lock); 897 LIST_HEAD(pgd_list); 898 899 void vmalloc_sync_all(void) 900 { 901 unsigned long address; 902 903 #ifdef CONFIG_X86_32 904 if (SHARED_KERNEL_PMD) 905 return; 906 907 for (address = VMALLOC_START & PMD_MASK; 908 address >= TASK_SIZE && address < FIXADDR_TOP; 909 address += PMD_SIZE) { 910 unsigned long flags; 911 struct page *page; 912 913 spin_lock_irqsave(&pgd_lock, flags); 914 list_for_each_entry(page, &pgd_list, lru) { 915 if (!vmalloc_sync_one(page_address(page), 916 address)) 917 break; 918 } 919 spin_unlock_irqrestore(&pgd_lock, flags); 920 } 921 #else /* CONFIG_X86_64 */ 922 for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END; 923 address += PGDIR_SIZE) { 924 const pgd_t *pgd_ref = pgd_offset_k(address); 925 unsigned long flags; 926 struct page *page; 927 928 if (pgd_none(*pgd_ref)) 929 continue; 930 spin_lock_irqsave(&pgd_lock, flags); 931 list_for_each_entry(page, &pgd_list, lru) { 932 pgd_t *pgd; 933 pgd = (pgd_t *)page_address(page) + pgd_index(address); 934 if (pgd_none(*pgd)) 935 set_pgd(pgd, *pgd_ref); 936 else 937 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 938 } 939 spin_unlock_irqrestore(&pgd_lock, flags); 940 } 941 #endif 942 } 943