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 39 /* 40 * Page fault error code bits 41 * bit 0 == 0 means no page found, 1 means protection fault 42 * bit 1 == 0 means read, 1 means write 43 * bit 2 == 0 means kernel, 1 means user-mode 44 * bit 3 == 1 means use of reserved bit detected 45 * bit 4 == 1 means fault was an instruction fetch 46 */ 47 #define PF_PROT (1<<0) 48 #define PF_WRITE (1<<1) 49 #define PF_USER (1<<2) 50 #define PF_RSVD (1<<3) 51 #define PF_INSTR (1<<4) 52 53 static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr) 54 { 55 #ifdef CONFIG_MMIOTRACE_HOOKS 56 if (unlikely(is_kmmio_active())) 57 if (kmmio_handler(regs, addr) == 1) 58 return -1; 59 #endif 60 return 0; 61 } 62 63 static inline int notify_page_fault(struct pt_regs *regs) 64 { 65 #ifdef CONFIG_KPROBES 66 int ret = 0; 67 68 /* kprobe_running() needs smp_processor_id() */ 69 if (!user_mode_vm(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 #else 78 return 0; 79 #endif 80 } 81 82 /* 83 * X86_32 84 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch. 85 * Check that here and ignore it. 86 * 87 * X86_64 88 * Sometimes the CPU reports invalid exceptions on prefetch. 89 * Check that here and ignore it. 90 * 91 * Opcode checker based on code by Richard Brunner 92 */ 93 static int is_prefetch(struct pt_regs *regs, unsigned long addr, 94 unsigned long error_code) 95 { 96 unsigned char *instr; 97 int scan_more = 1; 98 int prefetch = 0; 99 unsigned char *max_instr; 100 101 /* 102 * If it was a exec (instruction fetch) fault on NX page, then 103 * do not ignore the fault: 104 */ 105 if (error_code & PF_INSTR) 106 return 0; 107 108 instr = (unsigned char *)convert_ip_to_linear(current, regs); 109 max_instr = instr + 15; 110 111 if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE) 112 return 0; 113 114 while (scan_more && instr < max_instr) { 115 unsigned char opcode; 116 unsigned char instr_hi; 117 unsigned char instr_lo; 118 119 if (probe_kernel_address(instr, opcode)) 120 break; 121 122 instr_hi = opcode & 0xf0; 123 instr_lo = opcode & 0x0f; 124 instr++; 125 126 switch (instr_hi) { 127 case 0x20: 128 case 0x30: 129 /* 130 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. 131 * In X86_64 long mode, the CPU will signal invalid 132 * opcode if some of these prefixes are present so 133 * X86_64 will never get here anyway 134 */ 135 scan_more = ((instr_lo & 7) == 0x6); 136 break; 137 #ifdef CONFIG_X86_64 138 case 0x40: 139 /* 140 * In AMD64 long mode 0x40..0x4F are valid REX prefixes 141 * Need to figure out under what instruction mode the 142 * instruction was issued. Could check the LDT for lm, 143 * but for now it's good enough to assume that long 144 * mode only uses well known segments or kernel. 145 */ 146 scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS); 147 break; 148 #endif 149 case 0x60: 150 /* 0x64 thru 0x67 are valid prefixes in all modes. */ 151 scan_more = (instr_lo & 0xC) == 0x4; 152 break; 153 case 0xF0: 154 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */ 155 scan_more = !instr_lo || (instr_lo>>1) == 1; 156 break; 157 case 0x00: 158 /* Prefetch instruction is 0x0F0D or 0x0F18 */ 159 scan_more = 0; 160 161 if (probe_kernel_address(instr, opcode)) 162 break; 163 prefetch = (instr_lo == 0xF) && 164 (opcode == 0x0D || opcode == 0x18); 165 break; 166 default: 167 scan_more = 0; 168 break; 169 } 170 } 171 return prefetch; 172 } 173 174 static void force_sig_info_fault(int si_signo, int si_code, 175 unsigned long address, struct task_struct *tsk) 176 { 177 siginfo_t info; 178 179 info.si_signo = si_signo; 180 info.si_errno = 0; 181 info.si_code = si_code; 182 info.si_addr = (void __user *)address; 183 force_sig_info(si_signo, &info, tsk); 184 } 185 186 #ifdef CONFIG_X86_64 187 static int bad_address(void *p) 188 { 189 unsigned long dummy; 190 return probe_kernel_address((unsigned long *)p, dummy); 191 } 192 #endif 193 194 static void dump_pagetable(unsigned long address) 195 { 196 #ifdef CONFIG_X86_32 197 __typeof__(pte_val(__pte(0))) page; 198 199 page = read_cr3(); 200 page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT]; 201 #ifdef CONFIG_X86_PAE 202 printk("*pdpt = %016Lx ", page); 203 if ((page >> PAGE_SHIFT) < max_low_pfn 204 && page & _PAGE_PRESENT) { 205 page &= PAGE_MASK; 206 page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT) 207 & (PTRS_PER_PMD - 1)]; 208 printk(KERN_CONT "*pde = %016Lx ", page); 209 page &= ~_PAGE_NX; 210 } 211 #else 212 printk("*pde = %08lx ", page); 213 #endif 214 215 /* 216 * We must not directly access the pte in the highpte 217 * case if the page table is located in highmem. 218 * And let's rather not kmap-atomic the pte, just in case 219 * it's allocated already. 220 */ 221 if ((page >> PAGE_SHIFT) < max_low_pfn 222 && (page & _PAGE_PRESENT) 223 && !(page & _PAGE_PSE)) { 224 page &= PAGE_MASK; 225 page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT) 226 & (PTRS_PER_PTE - 1)]; 227 printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page); 228 } 229 230 printk("\n"); 231 #else /* CONFIG_X86_64 */ 232 pgd_t *pgd; 233 pud_t *pud; 234 pmd_t *pmd; 235 pte_t *pte; 236 237 pgd = (pgd_t *)read_cr3(); 238 239 pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK); 240 pgd += pgd_index(address); 241 if (bad_address(pgd)) goto bad; 242 printk("PGD %lx ", pgd_val(*pgd)); 243 if (!pgd_present(*pgd)) goto ret; 244 245 pud = pud_offset(pgd, address); 246 if (bad_address(pud)) goto bad; 247 printk("PUD %lx ", pud_val(*pud)); 248 if (!pud_present(*pud) || pud_large(*pud)) 249 goto ret; 250 251 pmd = pmd_offset(pud, address); 252 if (bad_address(pmd)) goto bad; 253 printk("PMD %lx ", pmd_val(*pmd)); 254 if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret; 255 256 pte = pte_offset_kernel(pmd, address); 257 if (bad_address(pte)) goto bad; 258 printk("PTE %lx", pte_val(*pte)); 259 ret: 260 printk("\n"); 261 return; 262 bad: 263 printk("BAD\n"); 264 #endif 265 } 266 267 #ifdef CONFIG_X86_32 268 static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address) 269 { 270 unsigned index = pgd_index(address); 271 pgd_t *pgd_k; 272 pud_t *pud, *pud_k; 273 pmd_t *pmd, *pmd_k; 274 275 pgd += index; 276 pgd_k = init_mm.pgd + index; 277 278 if (!pgd_present(*pgd_k)) 279 return NULL; 280 281 /* 282 * set_pgd(pgd, *pgd_k); here would be useless on PAE 283 * and redundant with the set_pmd() on non-PAE. As would 284 * set_pud. 285 */ 286 287 pud = pud_offset(pgd, address); 288 pud_k = pud_offset(pgd_k, address); 289 if (!pud_present(*pud_k)) 290 return NULL; 291 292 pmd = pmd_offset(pud, address); 293 pmd_k = pmd_offset(pud_k, address); 294 if (!pmd_present(*pmd_k)) 295 return NULL; 296 if (!pmd_present(*pmd)) { 297 set_pmd(pmd, *pmd_k); 298 arch_flush_lazy_mmu_mode(); 299 } else 300 BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k)); 301 return pmd_k; 302 } 303 #endif 304 305 #ifdef CONFIG_X86_64 306 static const char errata93_warning[] = 307 KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n" 308 KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n" 309 KERN_ERR "******* Please consider a BIOS update.\n" 310 KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n"; 311 #endif 312 313 /* Workaround for K8 erratum #93 & buggy BIOS. 314 BIOS SMM functions are required to use a specific workaround 315 to avoid corruption of the 64bit RIP register on C stepping K8. 316 A lot of BIOS that didn't get tested properly miss this. 317 The OS sees this as a page fault with the upper 32bits of RIP cleared. 318 Try to work around it here. 319 Note we only handle faults in kernel here. 320 Does nothing for X86_32 321 */ 322 static int is_errata93(struct pt_regs *regs, unsigned long address) 323 { 324 #ifdef CONFIG_X86_64 325 static int warned; 326 if (address != regs->ip) 327 return 0; 328 if ((address >> 32) != 0) 329 return 0; 330 address |= 0xffffffffUL << 32; 331 if ((address >= (u64)_stext && address <= (u64)_etext) || 332 (address >= MODULES_VADDR && address <= MODULES_END)) { 333 if (!warned) { 334 printk(errata93_warning); 335 warned = 1; 336 } 337 regs->ip = address; 338 return 1; 339 } 340 #endif 341 return 0; 342 } 343 344 /* 345 * Work around K8 erratum #100 K8 in compat mode occasionally jumps to illegal 346 * addresses >4GB. We catch this in the page fault handler because these 347 * addresses are not reachable. Just detect this case and return. Any code 348 * segment in LDT is compatibility mode. 349 */ 350 static int is_errata100(struct pt_regs *regs, unsigned long address) 351 { 352 #ifdef CONFIG_X86_64 353 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && 354 (address >> 32)) 355 return 1; 356 #endif 357 return 0; 358 } 359 360 void do_invalid_op(struct pt_regs *, unsigned long); 361 362 static int is_f00f_bug(struct pt_regs *regs, unsigned long address) 363 { 364 #ifdef CONFIG_X86_F00F_BUG 365 unsigned long nr; 366 /* 367 * Pentium F0 0F C7 C8 bug workaround. 368 */ 369 if (boot_cpu_data.f00f_bug) { 370 nr = (address - idt_descr.address) >> 3; 371 372 if (nr == 6) { 373 do_invalid_op(regs, 0); 374 return 1; 375 } 376 } 377 #endif 378 return 0; 379 } 380 381 static void show_fault_oops(struct pt_regs *regs, unsigned long error_code, 382 unsigned long address) 383 { 384 #ifdef CONFIG_X86_32 385 if (!oops_may_print()) 386 return; 387 #endif 388 389 #ifdef CONFIG_X86_PAE 390 if (error_code & PF_INSTR) { 391 unsigned int level; 392 pte_t *pte = lookup_address(address, &level); 393 394 if (pte && pte_present(*pte) && !pte_exec(*pte)) 395 printk(KERN_CRIT "kernel tried to execute " 396 "NX-protected page - exploit attempt? " 397 "(uid: %d)\n", current->uid); 398 } 399 #endif 400 401 printk(KERN_ALERT "BUG: unable to handle kernel "); 402 if (address < PAGE_SIZE) 403 printk(KERN_CONT "NULL pointer dereference"); 404 else 405 printk(KERN_CONT "paging request"); 406 printk(KERN_CONT " at %p\n", (void *) address); 407 printk(KERN_ALERT "IP:"); 408 printk_address(regs->ip, 1); 409 dump_pagetable(address); 410 } 411 412 #ifdef CONFIG_X86_64 413 static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs, 414 unsigned long error_code) 415 { 416 unsigned long flags = oops_begin(); 417 struct task_struct *tsk; 418 419 printk(KERN_ALERT "%s: Corrupted page table at address %lx\n", 420 current->comm, address); 421 dump_pagetable(address); 422 tsk = current; 423 tsk->thread.cr2 = address; 424 tsk->thread.trap_no = 14; 425 tsk->thread.error_code = error_code; 426 if (__die("Bad pagetable", regs, error_code)) 427 regs = NULL; 428 oops_end(flags, regs, SIGKILL); 429 } 430 #endif 431 432 static int spurious_fault_check(unsigned long error_code, pte_t *pte) 433 { 434 if ((error_code & PF_WRITE) && !pte_write(*pte)) 435 return 0; 436 if ((error_code & PF_INSTR) && !pte_exec(*pte)) 437 return 0; 438 439 return 1; 440 } 441 442 /* 443 * Handle a spurious fault caused by a stale TLB entry. This allows 444 * us to lazily refresh the TLB when increasing the permissions of a 445 * kernel page (RO -> RW or NX -> X). Doing it eagerly is very 446 * expensive since that implies doing a full cross-processor TLB 447 * flush, even if no stale TLB entries exist on other processors. 448 * There are no security implications to leaving a stale TLB when 449 * increasing the permissions on a page. 450 */ 451 static int spurious_fault(unsigned long address, 452 unsigned long error_code) 453 { 454 pgd_t *pgd; 455 pud_t *pud; 456 pmd_t *pmd; 457 pte_t *pte; 458 459 /* Reserved-bit violation or user access to kernel space? */ 460 if (error_code & (PF_USER | PF_RSVD)) 461 return 0; 462 463 pgd = init_mm.pgd + pgd_index(address); 464 if (!pgd_present(*pgd)) 465 return 0; 466 467 pud = pud_offset(pgd, address); 468 if (!pud_present(*pud)) 469 return 0; 470 471 if (pud_large(*pud)) 472 return spurious_fault_check(error_code, (pte_t *) pud); 473 474 pmd = pmd_offset(pud, address); 475 if (!pmd_present(*pmd)) 476 return 0; 477 478 if (pmd_large(*pmd)) 479 return spurious_fault_check(error_code, (pte_t *) pmd); 480 481 pte = pte_offset_kernel(pmd, address); 482 if (!pte_present(*pte)) 483 return 0; 484 485 return spurious_fault_check(error_code, pte); 486 } 487 488 /* 489 * X86_32 490 * Handle a fault on the vmalloc or module mapping area 491 * 492 * X86_64 493 * Handle a fault on the vmalloc area 494 * 495 * This assumes no large pages in there. 496 */ 497 static int vmalloc_fault(unsigned long address) 498 { 499 #ifdef CONFIG_X86_32 500 unsigned long pgd_paddr; 501 pmd_t *pmd_k; 502 pte_t *pte_k; 503 504 /* Make sure we are in vmalloc area */ 505 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 506 return -1; 507 508 /* 509 * Synchronize this task's top level page-table 510 * with the 'reference' page table. 511 * 512 * Do _not_ use "current" here. We might be inside 513 * an interrupt in the middle of a task switch.. 514 */ 515 pgd_paddr = read_cr3(); 516 pmd_k = vmalloc_sync_one(__va(pgd_paddr), address); 517 if (!pmd_k) 518 return -1; 519 pte_k = pte_offset_kernel(pmd_k, address); 520 if (!pte_present(*pte_k)) 521 return -1; 522 return 0; 523 #else 524 pgd_t *pgd, *pgd_ref; 525 pud_t *pud, *pud_ref; 526 pmd_t *pmd, *pmd_ref; 527 pte_t *pte, *pte_ref; 528 529 /* Make sure we are in vmalloc area */ 530 if (!(address >= VMALLOC_START && address < VMALLOC_END)) 531 return -1; 532 533 /* Copy kernel mappings over when needed. This can also 534 happen within a race in page table update. In the later 535 case just flush. */ 536 537 pgd = pgd_offset(current->mm ?: &init_mm, address); 538 pgd_ref = pgd_offset_k(address); 539 if (pgd_none(*pgd_ref)) 540 return -1; 541 if (pgd_none(*pgd)) 542 set_pgd(pgd, *pgd_ref); 543 else 544 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 545 546 /* Below here mismatches are bugs because these lower tables 547 are shared */ 548 549 pud = pud_offset(pgd, address); 550 pud_ref = pud_offset(pgd_ref, address); 551 if (pud_none(*pud_ref)) 552 return -1; 553 if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref)) 554 BUG(); 555 pmd = pmd_offset(pud, address); 556 pmd_ref = pmd_offset(pud_ref, address); 557 if (pmd_none(*pmd_ref)) 558 return -1; 559 if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref)) 560 BUG(); 561 pte_ref = pte_offset_kernel(pmd_ref, address); 562 if (!pte_present(*pte_ref)) 563 return -1; 564 pte = pte_offset_kernel(pmd, address); 565 /* Don't use pte_page here, because the mappings can point 566 outside mem_map, and the NUMA hash lookup cannot handle 567 that. */ 568 if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref)) 569 BUG(); 570 return 0; 571 #endif 572 } 573 574 int show_unhandled_signals = 1; 575 576 /* 577 * This routine handles page faults. It determines the address, 578 * and the problem, and then passes it off to one of the appropriate 579 * routines. 580 */ 581 #ifdef CONFIG_X86_64 582 asmlinkage 583 #endif 584 void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) 585 { 586 struct task_struct *tsk; 587 struct mm_struct *mm; 588 struct vm_area_struct *vma; 589 unsigned long address; 590 int write, si_code; 591 int fault; 592 #ifdef CONFIG_X86_64 593 unsigned long flags; 594 #endif 595 596 /* 597 * We can fault from pretty much anywhere, with unknown IRQ state. 598 */ 599 trace_hardirqs_fixup(); 600 601 tsk = current; 602 mm = tsk->mm; 603 prefetchw(&mm->mmap_sem); 604 605 /* get the address */ 606 address = read_cr2(); 607 608 si_code = SEGV_MAPERR; 609 610 if (notify_page_fault(regs)) 611 return; 612 if (unlikely(kmmio_fault(regs, address))) 613 return; 614 615 /* 616 * We fault-in kernel-space virtual memory on-demand. The 617 * 'reference' page table is init_mm.pgd. 618 * 619 * NOTE! We MUST NOT take any locks for this case. We may 620 * be in an interrupt or a critical region, and should 621 * only copy the information from the master page table, 622 * nothing more. 623 * 624 * This verifies that the fault happens in kernel space 625 * (error_code & 4) == 0, and that the fault was not a 626 * protection error (error_code & 9) == 0. 627 */ 628 #ifdef CONFIG_X86_32 629 if (unlikely(address >= TASK_SIZE)) { 630 #else 631 if (unlikely(address >= TASK_SIZE64)) { 632 #endif 633 if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) && 634 vmalloc_fault(address) >= 0) 635 return; 636 637 /* Can handle a stale RO->RW TLB */ 638 if (spurious_fault(address, error_code)) 639 return; 640 641 /* 642 * Don't take the mm semaphore here. If we fixup a prefetch 643 * fault we could otherwise deadlock. 644 */ 645 goto bad_area_nosemaphore; 646 } 647 648 649 #ifdef CONFIG_X86_32 650 /* It's safe to allow irq's after cr2 has been saved and the vmalloc 651 fault has been handled. */ 652 if (regs->flags & (X86_EFLAGS_IF | X86_VM_MASK)) 653 local_irq_enable(); 654 655 /* 656 * If we're in an interrupt, have no user context or are running in an 657 * atomic region then we must not take the fault. 658 */ 659 if (in_atomic() || !mm) 660 goto bad_area_nosemaphore; 661 #else /* CONFIG_X86_64 */ 662 if (likely(regs->flags & X86_EFLAGS_IF)) 663 local_irq_enable(); 664 665 if (unlikely(error_code & PF_RSVD)) 666 pgtable_bad(address, regs, error_code); 667 668 /* 669 * If we're in an interrupt, have no user context or are running in an 670 * atomic region then we must not take the fault. 671 */ 672 if (unlikely(in_atomic() || !mm)) 673 goto bad_area_nosemaphore; 674 675 /* 676 * User-mode registers count as a user access even for any 677 * potential system fault or CPU buglet. 678 */ 679 if (user_mode_vm(regs)) 680 error_code |= PF_USER; 681 again: 682 #endif 683 /* When running in the kernel we expect faults to occur only to 684 * addresses in user space. All other faults represent errors in the 685 * kernel and should generate an OOPS. Unfortunately, in the case of an 686 * erroneous fault occurring in a code path which already holds mmap_sem 687 * we will deadlock attempting to validate the fault against the 688 * address space. Luckily the kernel only validly references user 689 * space from well defined areas of code, which are listed in the 690 * exceptions table. 691 * 692 * As the vast majority of faults will be valid we will only perform 693 * the source reference check when there is a possibility of a deadlock. 694 * Attempt to lock the address space, if we cannot we then validate the 695 * source. If this is invalid we can skip the address space check, 696 * thus avoiding the deadlock. 697 */ 698 if (!down_read_trylock(&mm->mmap_sem)) { 699 if ((error_code & PF_USER) == 0 && 700 !search_exception_tables(regs->ip)) 701 goto bad_area_nosemaphore; 702 down_read(&mm->mmap_sem); 703 } 704 705 vma = find_vma(mm, address); 706 if (!vma) 707 goto bad_area; 708 if (vma->vm_start <= address) 709 goto good_area; 710 if (!(vma->vm_flags & VM_GROWSDOWN)) 711 goto bad_area; 712 if (error_code & PF_USER) { 713 /* 714 * Accessing the stack below %sp is always a bug. 715 * The large cushion allows instructions like enter 716 * and pusha to work. ("enter $65535,$31" pushes 717 * 32 pointers and then decrements %sp by 65535.) 718 */ 719 if (address + 65536 + 32 * sizeof(unsigned long) < regs->sp) 720 goto bad_area; 721 } 722 if (expand_stack(vma, address)) 723 goto bad_area; 724 /* 725 * Ok, we have a good vm_area for this memory access, so 726 * we can handle it.. 727 */ 728 good_area: 729 si_code = SEGV_ACCERR; 730 write = 0; 731 switch (error_code & (PF_PROT|PF_WRITE)) { 732 default: /* 3: write, present */ 733 /* fall through */ 734 case PF_WRITE: /* write, not present */ 735 if (!(vma->vm_flags & VM_WRITE)) 736 goto bad_area; 737 write++; 738 break; 739 case PF_PROT: /* read, present */ 740 goto bad_area; 741 case 0: /* read, not present */ 742 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 743 goto bad_area; 744 } 745 746 #ifdef CONFIG_X86_32 747 survive: 748 #endif 749 /* 750 * If for any reason at all we couldn't handle the fault, 751 * make sure we exit gracefully rather than endlessly redo 752 * the fault. 753 */ 754 fault = handle_mm_fault(mm, vma, address, write); 755 if (unlikely(fault & VM_FAULT_ERROR)) { 756 if (fault & VM_FAULT_OOM) 757 goto out_of_memory; 758 else if (fault & VM_FAULT_SIGBUS) 759 goto do_sigbus; 760 BUG(); 761 } 762 if (fault & VM_FAULT_MAJOR) 763 tsk->maj_flt++; 764 else 765 tsk->min_flt++; 766 767 #ifdef CONFIG_X86_32 768 /* 769 * Did it hit the DOS screen memory VA from vm86 mode? 770 */ 771 if (v8086_mode(regs)) { 772 unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT; 773 if (bit < 32) 774 tsk->thread.screen_bitmap |= 1 << bit; 775 } 776 #endif 777 up_read(&mm->mmap_sem); 778 return; 779 780 /* 781 * Something tried to access memory that isn't in our memory map.. 782 * Fix it, but check if it's kernel or user first.. 783 */ 784 bad_area: 785 up_read(&mm->mmap_sem); 786 787 bad_area_nosemaphore: 788 /* User mode accesses just cause a SIGSEGV */ 789 if (error_code & PF_USER) { 790 /* 791 * It's possible to have interrupts off here. 792 */ 793 local_irq_enable(); 794 795 /* 796 * Valid to do another page fault here because this one came 797 * from user space. 798 */ 799 if (is_prefetch(regs, address, error_code)) 800 return; 801 802 if (is_errata100(regs, address)) 803 return; 804 805 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && 806 printk_ratelimit()) { 807 printk( 808 "%s%s[%d]: segfault at %lx ip %p sp %p error %lx", 809 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 810 tsk->comm, task_pid_nr(tsk), address, 811 (void *) regs->ip, (void *) regs->sp, error_code); 812 print_vma_addr(" in ", regs->ip); 813 printk("\n"); 814 } 815 816 tsk->thread.cr2 = address; 817 /* Kernel addresses are always protection faults */ 818 tsk->thread.error_code = error_code | (address >= TASK_SIZE); 819 tsk->thread.trap_no = 14; 820 force_sig_info_fault(SIGSEGV, si_code, address, tsk); 821 return; 822 } 823 824 if (is_f00f_bug(regs, address)) 825 return; 826 827 no_context: 828 /* Are we prepared to handle this kernel fault? */ 829 if (fixup_exception(regs)) 830 return; 831 832 /* 833 * X86_32 834 * Valid to do another page fault here, because if this fault 835 * had been triggered by is_prefetch fixup_exception would have 836 * handled it. 837 * 838 * X86_64 839 * Hall of shame of CPU/BIOS bugs. 840 */ 841 if (is_prefetch(regs, address, error_code)) 842 return; 843 844 if (is_errata93(regs, address)) 845 return; 846 847 /* 848 * Oops. The kernel tried to access some bad page. We'll have to 849 * terminate things with extreme prejudice. 850 */ 851 #ifdef CONFIG_X86_32 852 bust_spinlocks(1); 853 #else 854 flags = oops_begin(); 855 #endif 856 857 show_fault_oops(regs, error_code, address); 858 859 tsk->thread.cr2 = address; 860 tsk->thread.trap_no = 14; 861 tsk->thread.error_code = error_code; 862 863 #ifdef CONFIG_X86_32 864 die("Oops", regs, error_code); 865 bust_spinlocks(0); 866 do_exit(SIGKILL); 867 #else 868 if (__die("Oops", regs, error_code)) 869 regs = NULL; 870 /* Executive summary in case the body of the oops scrolled away */ 871 printk(KERN_EMERG "CR2: %016lx\n", address); 872 oops_end(flags, regs, SIGKILL); 873 #endif 874 875 /* 876 * We ran out of memory, or some other thing happened to us that made 877 * us unable to handle the page fault gracefully. 878 */ 879 out_of_memory: 880 up_read(&mm->mmap_sem); 881 if (is_global_init(tsk)) { 882 yield(); 883 #ifdef CONFIG_X86_32 884 down_read(&mm->mmap_sem); 885 goto survive; 886 #else 887 goto again; 888 #endif 889 } 890 891 printk("VM: killing process %s\n", tsk->comm); 892 if (error_code & PF_USER) 893 do_group_exit(SIGKILL); 894 goto no_context; 895 896 do_sigbus: 897 up_read(&mm->mmap_sem); 898 899 /* Kernel mode? Handle exceptions or die */ 900 if (!(error_code & PF_USER)) 901 goto no_context; 902 #ifdef CONFIG_X86_32 903 /* User space => ok to do another page fault */ 904 if (is_prefetch(regs, address, error_code)) 905 return; 906 #endif 907 tsk->thread.cr2 = address; 908 tsk->thread.error_code = error_code; 909 tsk->thread.trap_no = 14; 910 force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk); 911 } 912 913 DEFINE_SPINLOCK(pgd_lock); 914 LIST_HEAD(pgd_list); 915 916 void vmalloc_sync_all(void) 917 { 918 #ifdef CONFIG_X86_32 919 unsigned long start = VMALLOC_START & PGDIR_MASK; 920 unsigned long address; 921 922 if (SHARED_KERNEL_PMD) 923 return; 924 925 BUILD_BUG_ON(TASK_SIZE & ~PGDIR_MASK); 926 for (address = start; address >= TASK_SIZE; address += PGDIR_SIZE) { 927 unsigned long flags; 928 struct page *page; 929 930 spin_lock_irqsave(&pgd_lock, flags); 931 list_for_each_entry(page, &pgd_list, lru) { 932 if (!vmalloc_sync_one(page_address(page), 933 address)) 934 break; 935 } 936 spin_unlock_irqrestore(&pgd_lock, flags); 937 } 938 #else /* CONFIG_X86_64 */ 939 unsigned long start = VMALLOC_START & PGDIR_MASK; 940 unsigned long address; 941 942 for (address = start; address <= VMALLOC_END; address += PGDIR_SIZE) { 943 const pgd_t *pgd_ref = pgd_offset_k(address); 944 unsigned long flags; 945 struct page *page; 946 947 if (pgd_none(*pgd_ref)) 948 continue; 949 spin_lock_irqsave(&pgd_lock, flags); 950 list_for_each_entry(page, &pgd_list, lru) { 951 pgd_t *pgd; 952 pgd = (pgd_t *)page_address(page) + pgd_index(address); 953 if (pgd_none(*pgd)) 954 set_pgd(pgd, *pgd_ref); 955 else 956 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); 957 } 958 spin_unlock_irqrestore(&pgd_lock, flags); 959 } 960 #endif 961 } 962