linux/arch/x86/mm/fault.c
<<
>>
Prefs
   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
  54static 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
  64static 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 */
  94static 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
 175static 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
 188static int bad_address(void *p)
 189{
 190        unsigned long dummy;
 191        return probe_kernel_address((unsigned long *)p, dummy);
 192}
 193#endif
 194
 195static 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));
 260ret:
 261        printk("\n");
 262        return;
 263bad:
 264        printk("BAD\n");
 265#endif
 266}
 267
 268#ifdef CONFIG_X86_32
 269static 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
 307static const char errata93_warning[] =
 308KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
 309KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n"
 310KERN_ERR "******* Please consider a BIOS update.\n"
 311KERN_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 */
 323static 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 */
 351static 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
 361static 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
 380static 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
 412static 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
 431static 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 */
 450static 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 */
 496static 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
 573int 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
 581asmlinkage
 582#endif
 583void __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
 668again:
 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 */
 715good_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 */
 768bad_area:
 769        up_read(&mm->mmap_sem);
 770
 771bad_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
 811no_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 */
 863out_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
 879do_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
 896DEFINE_SPINLOCK(pgd_lock);
 897LIST_HEAD(pgd_list);
 898
 899void 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
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.