arch/x86/mm/fault_64.c

   1 /*
   2  *  linux/arch/x86-64/mm/fault.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  *  Copyright (C) 2001,2002 Andi Kleen, SuSE Labs.
   6  */
   7
   8 #include <linux/signal.h>
   9 #include <linux/sched.h>
  10 #include <linux/kernel.h>
  11 #include <linux/errno.h>
  12 #include <linux/string.h>
  13 #include <linux/types.h>
  14 #include <linux/ptrace.h>
  15 #include <linux/mman.h>
  16 #include <linux/mm.h>
  17 #include <linux/smp.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/init.h>
  20 #include <linux/tty.h>
  21 #include <linux/vt_kern.h>              /* For unblank_screen() */
  22 #include <linux/compiler.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/module.h>
  25 #include <linux/kprobes.h>
  26 #include <linux/uaccess.h>
  27 #include <linux/kdebug.h>
  28
  29 #include <asm/system.h>
  30 #include <asm/pgalloc.h>
  31 #include <asm/smp.h>
  32 #include <asm/tlbflush.h>
  33 #include <asm/proto.h>
  34 #include <asm-generic/sections.h>
  35
  36 /* Page fault error code bits */
  37 #define PF_PROT (1<<0)          /* or no page found */
  38 #define PF_WRITE        (1<<1)
  39 #define PF_USER (1<<2)
  40 #define PF_RSVD (1<<3)
  41 #define PF_INSTR        (1<<4)
  42
  43 #ifdef CONFIG_KPROBES
  44 static inline int notify_page_fault(struct pt_regs *regs)
  45 {
  46         int ret = 0;
  47
  48         /* kprobe_running() needs smp_processor_id() */
  49         if (!user_mode(regs)) {
  50                 preempt_disable();
  51                 if (kprobe_running() && kprobe_fault_handler(regs, 14))
  52                         ret = 1;
  53                 preempt_enable();
  54         }
  55
  56         return ret;
  57 }
  58 #else
  59 static inline int notify_page_fault(struct pt_regs *regs)
  60 {
  61         return 0;
  62 }
  63 #endif
  64
  65 /* Sometimes the CPU reports invalid exceptions on prefetch.
  66    Check that here and ignore.
  67    Opcode checker based on code by Richard Brunner */
  68 static noinline int is_prefetch(struct pt_regs *regs, unsigned long addr,
  69                                 unsigned long error_code)
  70 {
  71         unsigned char *instr;
  72         int scan_more = 1;
  73         int prefetch = 0;
  74         unsigned char *max_instr;
  75
  76         /* If it was a exec fault ignore */
  77         if (error_code & PF_INSTR)
  78                 return 0;
  79
  80         instr = (unsigned char __user *)convert_rip_to_linear(current, regs);
  81         max_instr = instr + 15;
  82
  83         if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
  84                 return 0;
  85
  86         while (scan_more && instr < max_instr) {
  87                 unsigned char opcode;
  88                 unsigned char instr_hi;
  89                 unsigned char instr_lo;
  90
  91                 if (probe_kernel_address(instr, opcode))
  92                         break;
  93
  94                 instr_hi = opcode & 0xf0;
  95                 instr_lo = opcode & 0x0f;
  96                 instr++;
  97
  98                 switch (instr_hi) {
  99                 case 0x20:
 100                 case 0x30:
 101                         /* Values 0x26,0x2E,0x36,0x3E are valid x86
 102                            prefixes.  In long mode, the CPU will signal
 103                            invalid opcode if some of these prefixes are
 104                            present so we will never get here anyway */
 105                         scan_more = ((instr_lo & 7) == 0x6);
 106                         break;
 107
 108                 case 0x40:
 109                         /* In AMD64 long mode, 0x40 to 0x4F are valid REX prefixes
 110                            Need to figure out under what instruction mode the
 111                            instruction was issued ... */
 112                         /* Could check the LDT for lm, but for now it's good
 113                            enough to assume that long mode only uses well known
 114                            segments or kernel. */
 115                         scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS);
 116                         break;
 117
 118                 case 0x60:
 119                         /* 0x64 thru 0x67 are valid prefixes in all modes. */
 120                         scan_more = (instr_lo & 0xC) == 0x4;
 121                         break;
 122                 case 0xF0:
 123                         /* 0xF0, 0xF2, and 0xF3 are valid prefixes in all modes. */
 124                         scan_more = !instr_lo || (instr_lo>>1) == 1;
 125                         break;
 126                 case 0x00:
 127                         /* Prefetch instruction is 0x0F0D or 0x0F18 */
 128                         scan_more = 0;
 129                         if (probe_kernel_address(instr, opcode))
 130                                 break;
 131                         prefetch = (instr_lo == 0xF) &&
 132                                 (opcode == 0x0D || opcode == 0x18);
 133                         break;
 134                 default:
 135                         scan_more = 0;
 136                         break;
 137                 }
 138         }
 139         return prefetch;
 140 }
 141
 142 static int bad_address(void *p)
 143 {
 144         unsigned long dummy;
 145         return probe_kernel_address((unsigned long *)p, dummy);
 146 }
 147
 148 void dump_pagetable(unsigned long address)
 149 {
 150         pgd_t *pgd;
 151         pud_t *pud;
 152         pmd_t *pmd;
 153         pte_t *pte;
 154
 155         pgd = (pgd_t *)read_cr3();
 156
 157         pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK);
 158         pgd += pgd_index(address);
 159         if (bad_address(pgd)) goto bad;
 160         printk("PGD %lx ", pgd_val(*pgd));
 161         if (!pgd_present(*pgd)) goto ret;
 162
 163         pud = pud_offset(pgd, address);
 164         if (bad_address(pud)) goto bad;
 165         printk("PUD %lx ", pud_val(*pud));
 166         if (!pud_present(*pud)) goto ret;
 167
 168         pmd = pmd_offset(pud, address);
 169         if (bad_address(pmd)) goto bad;
 170         printk("PMD %lx ", pmd_val(*pmd));
 171         if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret;
 172
 173         pte = pte_offset_kernel(pmd, address);
 174         if (bad_address(pte)) goto bad;
 175         printk("PTE %lx", pte_val(*pte));
 176 ret:
 177         printk("\n");
 178         return;
 179 bad:
 180         printk("BAD\n");
 181 }
 182
 183 static const char errata93_warning[] =
 184 KERN_ERR "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
 185 KERN_ERR "******* Working around it, but it may cause SEGVs or burn power.\n"
 186 KERN_ERR "******* Please consider a BIOS update.\n"
 187 KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n";
 188
 189 /* Workaround for K8 erratum #93 & buggy BIOS.
 190    BIOS SMM functions are required to use a specific workaround
 191    to avoid corruption of the 64bit RIP register on C stepping K8.
 192    A lot of BIOS that didn't get tested properly miss this.
 193    The OS sees this as a page fault with the upper 32bits of RIP cleared.
 194    Try to work around it here.
 195    Note we only handle faults in kernel here. */
 196
 197 static int is_errata93(struct pt_regs *regs, unsigned long address)
 198 {
 199         static int warned;
 200         if (address != regs->ip)
 201                 return 0;
 202         if ((address >> 32) != 0)
 203                 return 0;
 204         address |= 0xffffffffUL << 32;
 205         if ((address >= (u64)_stext && address <= (u64)_etext) ||
 206             (address >= MODULES_VADDR && address <= MODULES_END)) {
 207                 if (!warned) {
 208                         printk(errata93_warning);
 209                         warned = 1;
 210                 }
 211                 regs->ip = address;
 212                 return 1;
 213         }
 214         return 0;
 215 }
 216
 217 static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
 218                                  unsigned long error_code)
 219 {
 220         unsigned long flags = oops_begin();
 221         struct task_struct *tsk;
 222
 223         printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
 224                current->comm, address);
 225         dump_pagetable(address);
 226         tsk = current;
 227         tsk->thread.cr2 = address;
 228         tsk->thread.trap_no = 14;
 229         tsk->thread.error_code = error_code;
 230         __die("Bad pagetable", regs, error_code);
 231         oops_end(flags);
 232         do_exit(SIGKILL);
 233 }
 234
 235 /*
 236  * Handle a fault on the vmalloc area
 237  *
 238  * This assumes no large pages in there.
 239  */
 240 static int vmalloc_fault(unsigned long address)
 241 {
 242         pgd_t *pgd, *pgd_ref;
 243         pud_t *pud, *pud_ref;
 244         pmd_t *pmd, *pmd_ref;
 245         pte_t *pte, *pte_ref;
 246
 247         /* Copy kernel mappings over when needed. This can also
 248            happen within a race in page table update. In the later
 249            case just flush. */
 250
 251         pgd = pgd_offset(current->mm ?: &init_mm, address);
 252         pgd_ref = pgd_offset_k(address);
 253         if (pgd_none(*pgd_ref))
 254                 return -1;
 255         if (pgd_none(*pgd))
 256                 set_pgd(pgd, *pgd_ref);
 257         else
 258                 BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
 259
 260         /* Below here mismatches are bugs because these lower tables
 261            are shared */
 262
 263         pud = pud_offset(pgd, address);
 264         pud_ref = pud_offset(pgd_ref, address);
 265         if (pud_none(*pud_ref))
 266                 return -1;
 267         if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
 268                 BUG();
 269         pmd = pmd_offset(pud, address);
 270         pmd_ref = pmd_offset(pud_ref, address);
 271         if (pmd_none(*pmd_ref))
 272                 return -1;
 273         if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
 274                 BUG();
 275         pte_ref = pte_offset_kernel(pmd_ref, address);
 276         if (!pte_present(*pte_ref))
 277                 return -1;
 278         pte = pte_offset_kernel(pmd, address);
 279         /* Don't use pte_page here, because the mappings can point
 280            outside mem_map, and the NUMA hash lookup cannot handle
 281            that. */
 282         if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
 283                 BUG();
 284         return 0;
 285 }
 286
 287 int show_unhandled_signals = 1;
 288
 289 /*
 290  * This routine handles page faults.  It determines the address,
 291  * and the problem, and then passes it off to one of the appropriate
 292  * routines.
 293  */
 294 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 295                                         unsigned long error_code)
 296 {
 297         struct task_struct *tsk;
 298         struct mm_struct *mm;
 299         struct vm_area_struct * vma;
 300         unsigned long address;
 301         const struct exception_table_entry *fixup;
 302         int write, fault;
 303         unsigned long flags;
 304         siginfo_t info;
 305
 306         /*
 307          * We can fault from pretty much anywhere, with unknown IRQ state.
 308          */
 309         trace_hardirqs_fixup();
 310
 311         tsk = current;
 312         mm = tsk->mm;
 313         prefetchw(&mm->mmap_sem);
 314
 315         /* get the address */
 316         address = read_cr2();
 317
 318         info.si_code = SEGV_MAPERR;
 319
 320
 321         /*
 322          * We fault-in kernel-space virtual memory on-demand. The
 323          * 'reference' page table is init_mm.pgd.
 324          *
 325          * NOTE! We MUST NOT take any locks for this case. We may
 326          * be in an interrupt or a critical region, and should
 327          * only copy the information from the master page table,
 328          * nothing more.
 329          *
 330          * This verifies that the fault happens in kernel space
 331          * (error_code & 4) == 0, and that the fault was not a
 332          * protection error (error_code & 9) == 0.
 333          */
 334         if (unlikely(address >= TASK_SIZE64)) {
 335                 /*
 336                  * Don't check for the module range here: its PML4
 337                  * is always initialized because it's shared with the main
 338                  * kernel text. Only vmalloc may need PML4 syncups.
 339                  */
 340                 if (!(error_code & (PF_RSVD|PF_USER|PF_PROT)) &&
 341                       ((address >= VMALLOC_START && address < VMALLOC_END))) {
 342                         if (vmalloc_fault(address) >= 0)
 343                                 return;
 344                 }
 345                 if (notify_page_fault(regs))
 346                         return;
 347                 /*
 348                  * Don't take the mm semaphore here. If we fixup a prefetch
 349                  * fault we could otherwise deadlock.
 350                  */
 351                 goto bad_area_nosemaphore;
 352         }
 353
 354         if (notify_page_fault(regs))
 355                 return;
 356
 357         if (likely(regs->flags & X86_EFLAGS_IF))
 358                 local_irq_enable();
 359
 360         if (unlikely(error_code & PF_RSVD))
 361                 pgtable_bad(address, regs, error_code);
 362
 363         /*
 364          * If we're in an interrupt or have no user
 365          * context, we must not take the fault..
 366          */
 367         if (unlikely(in_atomic() || !mm))
 368                 goto bad_area_nosemaphore;
 369
 370         /*
 371          * User-mode registers count as a user access even for any
 372          * potential system fault or CPU buglet.
 373          */
 374         if (user_mode_vm(regs))
 375                 error_code |= PF_USER;
 376
 377  again:
 378         /* When running in the kernel we expect faults to occur only to
 379          * addresses in user space.  All other faults represent errors in the
 380          * kernel and should generate an OOPS.  Unfortunately, in the case of an
 381          * erroneous fault occurring in a code path which already holds mmap_sem
 382          * we will deadlock attempting to validate the fault against the
 383          * address space.  Luckily the kernel only validly references user
 384          * space from well defined areas of code, which are listed in the
 385          * exceptions table.
 386          *
 387          * As the vast majority of faults will be valid we will only perform
 388          * the source reference check when there is a possibility of a deadlock.
 389          * Attempt to lock the address space, if we cannot we then validate the
 390          * source.  If this is invalid we can skip the address space check,
 391          * thus avoiding the deadlock.
 392          */
 393         if (!down_read_trylock(&mm->mmap_sem)) {
 394                 if ((error_code & PF_USER) == 0 &&
 395                     !search_exception_tables(regs->ip))
 396                         goto bad_area_nosemaphore;
 397                 down_read(&mm->mmap_sem);
 398         }
 399
 400         vma = find_vma(mm, address);
 401         if (!vma)
 402                 goto bad_area;
 403         if (likely(vma->vm_start <= address))
 404                 goto good_area;
 405         if (!(vma->vm_flags & VM_GROWSDOWN))
 406                 goto bad_area;
 407         if (error_code & 4) {
 408                 /* Allow userspace just enough access below the stack pointer
 409                  * to let the 'enter' instruction work.
 410                  */
 411                 if (address + 65536 + 32 * sizeof(unsigned long) < regs->sp)
 412                         goto bad_area;
 413         }
 414         if (expand_stack(vma, address))
 415                 goto bad_area;
 416 /*
 417  * Ok, we have a good vm_area for this memory access, so
 418  * we can handle it..
 419  */
 420 good_area:
 421         info.si_code = SEGV_ACCERR;
 422         write = 0;
 423         switch (error_code & (PF_PROT|PF_WRITE)) {
 424                 default:        /* 3: write, present */
 425                         /* fall through */
 426                 case PF_WRITE:          /* write, not present */
 427                         if (!(vma->vm_flags & VM_WRITE))
 428                                 goto bad_area;
 429                         write++;
 430                         break;
 431                 case PF_PROT:           /* read, present */
 432                         goto bad_area;
 433                 case 0:                 /* read, not present */
 434                         if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
 435                                 goto bad_area;
 436         }
 437
 438         /*
 439          * If for any reason at all we couldn't handle the fault,
 440          * make sure we exit gracefully rather than endlessly redo
 441          * the fault.
 442          */
 443         fault = handle_mm_fault(mm, vma, address, write);
 444         if (unlikely(fault & VM_FAULT_ERROR)) {
 445                 if (fault & VM_FAULT_OOM)
 446                         goto out_of_memory;
 447                 else if (fault & VM_FAULT_SIGBUS)
 448                         goto do_sigbus;
 449                 BUG();
 450         }
 451         if (fault & VM_FAULT_MAJOR)
 452                 tsk->maj_flt++;
 453         else
 454                 tsk->min_flt++;
 455         up_read(&mm->mmap_sem);
 456         return;
 457
 458 /*
 459  * Something tried to access memory that isn't in our memory map..
 460  * Fix it, but check if it's kernel or user first..
 461  */
 462 bad_area:
 463         up_read(&mm->mmap_sem);
 464
 465 bad_area_nosemaphore:
 466         /* User mode accesses just cause a SIGSEGV */
 467         if (error_code & PF_USER) {
 468
 469                 /*
 470                  * It's possible to have interrupts off here.
 471                  */
 472                 local_irq_enable();
 473
 474                 if (is_prefetch(regs, address, error_code))
 475                         return;
 476
 477                 /* Work around K8 erratum #100 K8 in compat mode
 478                    occasionally jumps to illegal addresses >4GB.  We
 479                    catch this here in the page fault handler because
 480                    these addresses are not reachable. Just detect this
 481                    case and return.  Any code segment in LDT is
 482                    compatibility mode. */
 483                 if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) &&
 484                     (address >> 32))
 485                         return;
 486
 487                 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 488                     printk_ratelimit()) {
 489                         printk(
 490                        "%s%s[%d]: segfault at %lx ip %lx sp %lx error %lx\n",
 491                                         tsk->pid > 1 ? KERN_INFO : KERN_EMERG,
 492                                         tsk->comm, tsk->pid, address, regs->ip,
 493                                         regs->sp, error_code);
 494                 }
 495
 496                 tsk->thread.cr2 = address;
 497                 /* Kernel addresses are always protection faults */
 498                 tsk->thread.error_code = error_code | (address >= TASK_SIZE);
 499                 tsk->thread.trap_no = 14;
 500                 info.si_signo = SIGSEGV;
 501                 info.si_errno = 0;
 502                 /* info.si_code has been set above */
 503                 info.si_addr = (void __user *)address;
 504                 force_sig_info(SIGSEGV, &info, tsk);
 505                 return;
 506         }
 507
 508 no_context:
 509
 510         /* Are we prepared to handle this kernel fault?  */
 511         fixup = search_exception_tables(regs->ip);
 512         if (fixup) {
 513                 regs->ip = fixup->fixup;
 514                 return;
 515         }
 516
 517         /*
 518          * Hall of shame of CPU/BIOS bugs.
 519          */
 520
 521         if (is_prefetch(regs, address, error_code))
 522                 return;
 523
 524         if (is_errata93(regs, address))
 525                 return;
 526
 527 /*
 528  * Oops. The kernel tried to access some bad page. We'll have to
 529  * terminate things with extreme prejudice.
 530  */
 531
 532         flags = oops_begin();
 533
 534         if (address < PAGE_SIZE)
 535                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
 536         else
 537                 printk(KERN_ALERT "Unable to handle kernel paging request");
 538         printk(" at %016lx RIP: \n" KERN_ALERT,address);
 539         printk_address(regs->ip);
 540         dump_pagetable(address);
 541         tsk->thread.cr2 = address;
 542         tsk->thread.trap_no = 14;
 543         tsk->thread.error_code = error_code;
 544         __die("Oops", regs, error_code);
 545         /* Executive summary in case the body of the oops scrolled away */
 546         printk(KERN_EMERG "CR2: %016lx\n", address);
 547         oops_end(flags);
 548         do_exit(SIGKILL);
 549
 550 /*
 551  * We ran out of memory, or some other thing happened to us that made
 552  * us unable to handle the page fault gracefully.
 553  */
 554 out_of_memory:
 555         up_read(&mm->mmap_sem);
 556         if (is_global_init(current)) {
 557                 yield();
 558                 goto again;
 559         }
 560         printk("VM: killing process %s\n", tsk->comm);
 561         if (error_code & 4)
 562                 do_group_exit(SIGKILL);
 563         goto no_context;
 564
 565 do_sigbus:
 566         up_read(&mm->mmap_sem);
 567
 568         /* Kernel mode? Handle exceptions or die */
 569         if (!(error_code & PF_USER))
 570                 goto no_context;
 571
 572         tsk->thread.cr2 = address;
 573         tsk->thread.error_code = error_code;
 574         tsk->thread.trap_no = 14;
 575         info.si_signo = SIGBUS;
 576         info.si_errno = 0;
 577         info.si_code = BUS_ADRERR;
 578         info.si_addr = (void __user *)address;
 579         force_sig_info(SIGBUS, &info, tsk);
 580         return;
 581 }
 582
 583 DEFINE_SPINLOCK(pgd_lock);
 584 LIST_HEAD(pgd_list);
 585
 586 void vmalloc_sync_all(void)
 587 {
 588         /* Note that races in the updates of insync and start aren't
 589            problematic:
 590            insync can only get set bits added, and updates to start are only
 591            improving performance (without affecting correctness if undone). */
 592         static DECLARE_BITMAP(insync, PTRS_PER_PGD);
 593         static unsigned long start = VMALLOC_START & PGDIR_MASK;
 594         unsigned long address;
 595
 596         for (address = start; address <= VMALLOC_END; address += PGDIR_SIZE) {
 597                 if (!test_bit(pgd_index(address), insync)) {
 598                         const pgd_t *pgd_ref = pgd_offset_k(address);
 599                         struct page *page;
 600
 601                         if (pgd_none(*pgd_ref))
 602                                 continue;
 603                         spin_lock(&pgd_lock);
 604                         list_for_each_entry(page, &pgd_list, lru) {
 605                                 pgd_t *pgd;
 606                                 pgd = (pgd_t *)page_address(page) + pgd_index(address);
 607                                 if (pgd_none(*pgd))
 608                                         set_pgd(pgd, *pgd_ref);
 609                                 else
 610                                         BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
 611                         }
 612                         spin_unlock(&pgd_lock);
 613                         set_bit(pgd_index(address), insync);
 614                 }
 615                 if (address == start)
 616                         start = address + PGDIR_SIZE;
 617         }
 618         /* Check that there is no need to do the same for the modules area. */
 619         BUILD_BUG_ON(!(MODULES_VADDR > __START_KERNEL));
 620         BUILD_BUG_ON(!(((MODULES_END - 1) & PGDIR_MASK) ==
 621                                 (__START_KERNEL & PGDIR_MASK)));
 622 }