arch/arm/mm/fault.c

   1 /*
   2  *  linux/arch/arm/mm/fault.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  *  Modifications for ARM processor (c) 1995-2004 Russell King
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/extable.h>
  12 #include <linux/signal.h>
  13 #include <linux/mm.h>
  14 #include <linux/hardirq.h>
  15 #include <linux/init.h>
  16 #include <linux/kprobes.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/page-flags.h>
  19 #include <linux/sched.h>
  20 #include <linux/highmem.h>
  21 #include <linux/perf_event.h>
  22
  23 #include <asm/exception.h>
  24 #include <asm/pgtable.h>
  25 #include <asm/system_misc.h>
  26 #include <asm/system_info.h>
  27 #include <asm/tlbflush.h>
  28
  29 #include "fault.h"
  30
  31 #ifdef CONFIG_MMU
  32
  33 #ifdef CONFIG_KPROBES
  34 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
  35 {
  36         int ret = 0;
  37
  38         if (!user_mode(regs)) {
  39                 /* kprobe_running() needs smp_processor_id() */
  40                 preempt_disable();
  41                 if (kprobe_running() && kprobe_fault_handler(regs, fsr))
  42                         ret = 1;
  43                 preempt_enable();
  44         }
  45
  46         return ret;
  47 }
  48 #else
  49 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
  50 {
  51         return 0;
  52 }
  53 #endif
  54
  55 /*
  56  * This is useful to dump out the page tables associated with
  57  * 'addr' in mm 'mm'.
  58  */
  59 void show_pte(struct mm_struct *mm, unsigned long addr)
  60 {
  61         pgd_t *pgd;
  62
  63         if (!mm)
  64                 mm = &init_mm;
  65
  66         pr_alert("pgd = %p\n", mm->pgd);
  67         pgd = pgd_offset(mm, addr);
  68         pr_alert("[%08lx] *pgd=%08llx",
  69                         addr, (long long)pgd_val(*pgd));
  70
  71         do {
  72                 pud_t *pud;
  73                 pmd_t *pmd;
  74                 pte_t *pte;
  75
  76                 if (pgd_none(*pgd))
  77                         break;
  78
  79                 if (pgd_bad(*pgd)) {
  80                         pr_cont("(bad)");
  81                         break;
  82                 }
  83
  84                 pud = pud_offset(pgd, addr);
  85                 if (PTRS_PER_PUD != 1)
  86                         pr_cont(", *pud=%08llx", (long long)pud_val(*pud));
  87
  88                 if (pud_none(*pud))
  89                         break;
  90
  91                 if (pud_bad(*pud)) {
  92                         pr_cont("(bad)");
  93                         break;
  94                 }
  95
  96                 pmd = pmd_offset(pud, addr);
  97                 if (PTRS_PER_PMD != 1)
  98                         pr_cont(", *pmd=%08llx", (long long)pmd_val(*pmd));
  99
 100                 if (pmd_none(*pmd))
 101                         break;
 102
 103                 if (pmd_bad(*pmd)) {
 104                         pr_cont("(bad)");
 105                         break;
 106                 }
 107
 108                 /* We must not map this if we have highmem enabled */
 109                 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
 110                         break;
 111
 112                 pte = pte_offset_map(pmd, addr);
 113                 pr_cont(", *pte=%08llx", (long long)pte_val(*pte));
 114 #ifndef CONFIG_ARM_LPAE
 115                 pr_cont(", *ppte=%08llx",
 116                        (long long)pte_val(pte[PTE_HWTABLE_PTRS]));
 117 #endif
 118                 pte_unmap(pte);
 119         } while(0);
 120
 121         pr_cont("\n");
 122 }
 123 #else                                   /* CONFIG_MMU */
 124 void show_pte(struct mm_struct *mm, unsigned long addr)
 125 { }
 126 #endif                                  /* CONFIG_MMU */
 127
 128 /*
 129  * Oops.  The kernel tried to access some page that wasn't present.
 130  */
 131 static void
 132 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 133                   struct pt_regs *regs)
 134 {
 135         /*
 136          * Are we prepared to handle this kernel fault?
 137          */
 138         if (fixup_exception(regs))
 139                 return;
 140
 141         /*
 142          * No handler, we'll have to terminate things with extreme prejudice.
 143          */
 144         bust_spinlocks(1);
 145         pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
 146                  (addr < PAGE_SIZE) ? "NULL pointer dereference" :
 147                  "paging request", addr);
 148
 149         show_pte(mm, addr);
 150         die("Oops", regs, fsr);
 151         bust_spinlocks(0);
 152         do_exit(SIGKILL);
 153 }
 154
 155 /*
 156  * Something tried to access memory that isn't in our memory map..
 157  * User mode accesses just cause a SIGSEGV
 158  */
 159 static void
 160 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 161                 unsigned int fsr, unsigned int sig, int code,
 162                 struct pt_regs *regs)
 163 {
 164         struct siginfo si;
 165
 166 #ifdef CONFIG_DEBUG_USER
 167         if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
 168             ((user_debug & UDBG_BUS)  && (sig == SIGBUS))) {
 169                 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
 170                        tsk->comm, sig, addr, fsr);
 171                 show_pte(tsk->mm, addr);
 172                 show_regs(regs);
 173         }
 174 #endif
 175
 176         tsk->thread.address = addr;
 177         tsk->thread.error_code = fsr;
 178         tsk->thread.trap_no = 14;
 179         si.si_signo = sig;
 180         si.si_errno = 0;
 181         si.si_code = code;
 182         si.si_addr = (void __user *)addr;
 183         force_sig_info(sig, &si, tsk);
 184 }
 185
 186 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 187 {
 188         struct task_struct *tsk = current;
 189         struct mm_struct *mm = tsk->active_mm;
 190
 191         /*
 192          * If we are in kernel mode at this point, we
 193          * have no context to handle this fault with.
 194          */
 195         if (user_mode(regs))
 196                 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 197         else
 198                 __do_kernel_fault(mm, addr, fsr, regs);
 199 }
 200
 201 #ifdef CONFIG_MMU
 202 #define VM_FAULT_BADMAP         0x010000
 203 #define VM_FAULT_BADACCESS      0x020000
 204
 205 /*
 206  * Check that the permissions on the VMA allow for the fault which occurred.
 207  * If we encountered a write fault, we must have write permission, otherwise
 208  * we allow any permission.
 209  */
 210 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 211 {
 212         unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
 213
 214         if (fsr & FSR_WRITE)
 215                 mask = VM_WRITE;
 216         if (fsr & FSR_LNX_PF)
 217                 mask = VM_EXEC;
 218
 219         return vma->vm_flags & mask ? false : true;
 220 }
 221
 222 static int __kprobes
 223 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 224                 unsigned int flags, struct task_struct *tsk)
 225 {
 226         struct vm_area_struct *vma;
 227         int fault;
 228
 229         vma = find_vma(mm, addr);
 230         fault = VM_FAULT_BADMAP;
 231         if (unlikely(!vma))
 232                 goto out;
 233         if (unlikely(vma->vm_start > addr))
 234                 goto check_stack;
 235
 236         /*
 237          * Ok, we have a good vm_area for this
 238          * memory access, so we can handle it.
 239          */
 240 good_area:
 241         if (access_error(fsr, vma)) {
 242                 fault = VM_FAULT_BADACCESS;
 243                 goto out;
 244         }
 245
 246         return handle_mm_fault(vma, addr & PAGE_MASK, flags);
 247
 248 check_stack:
 249         /* Don't allow expansion below FIRST_USER_ADDRESS */
 250         if (vma->vm_flags & VM_GROWSDOWN &&
 251             addr >= FIRST_USER_ADDRESS && !expand_stack(vma, addr))
 252                 goto good_area;
 253 out:
 254         return fault;
 255 }
 256
 257 static int __kprobes
 258 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 259 {
 260         struct task_struct *tsk;
 261         struct mm_struct *mm;
 262         int fault, sig, code;
 263         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 264
 265         if (notify_page_fault(regs, fsr))
 266                 return 0;
 267
 268         tsk = current;
 269         mm  = tsk->mm;
 270
 271         /* Enable interrupts if they were enabled in the parent context. */
 272         if (interrupts_enabled(regs))
 273                 local_irq_enable();
 274
 275         /*
 276          * If we're in an interrupt or have no user
 277          * context, we must not take the fault..
 278          */
 279         if (faulthandler_disabled() || !mm)
 280                 goto no_context;
 281
 282         if (user_mode(regs))
 283                 flags |= FAULT_FLAG_USER;
 284         if (fsr & FSR_WRITE)
 285                 flags |= FAULT_FLAG_WRITE;
 286
 287         /*
 288          * As per x86, we may deadlock here.  However, since the kernel only
 289          * validly references user space from well defined areas of the code,
 290          * we can bug out early if this is from code which shouldn't.
 291          */
 292         if (!down_read_trylock(&mm->mmap_sem)) {
 293                 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
 294                         goto no_context;
 295 retry:
 296                 down_read(&mm->mmap_sem);
 297         } else {
 298                 /*
 299                  * The above down_read_trylock() might have succeeded in
 300                  * which case, we'll have missed the might_sleep() from
 301                  * down_read()
 302                  */
 303                 might_sleep();
 304 #ifdef CONFIG_DEBUG_VM
 305                 if (!user_mode(regs) &&
 306                     !search_exception_tables(regs->ARM_pc))
 307                         goto no_context;
 308 #endif
 309         }
 310
 311         fault = __do_page_fault(mm, addr, fsr, flags, tsk);
 312
 313         /* If we need to retry but a fatal signal is pending, handle the
 314          * signal first. We do not need to release the mmap_sem because
 315          * it would already be released in __lock_page_or_retry in
 316          * mm/filemap.c. */
 317         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 318                 return 0;
 319
 320         /*
 321          * Major/minor page fault accounting is only done on the
 322          * initial attempt. If we go through a retry, it is extremely
 323          * likely that the page will be found in page cache at that point.
 324          */
 325
 326         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
 327         if (!(fault & VM_FAULT_ERROR) && flags & FAULT_FLAG_ALLOW_RETRY) {
 328                 if (fault & VM_FAULT_MAJOR) {
 329                         tsk->maj_flt++;
 330                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
 331                                         regs, addr);
 332                 } else {
 333                         tsk->min_flt++;
 334                         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
 335                                         regs, addr);
 336                 }
 337                 if (fault & VM_FAULT_RETRY) {
 338                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
 339                         * of starvation. */
 340                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 341                         flags |= FAULT_FLAG_TRIED;
 342                         goto retry;
 343                 }
 344         }
 345
 346         up_read(&mm->mmap_sem);
 347
 348         /*
 349          * Handle the "normal" case first - VM_FAULT_MAJOR
 350          */
 351         if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
 352                 return 0;
 353
 354         /*
 355          * If we are in kernel mode at this point, we
 356          * have no context to handle this fault with.
 357          */
 358         if (!user_mode(regs))
 359                 goto no_context;
 360
 361         if (fault & VM_FAULT_OOM) {
 362                 /*
 363                  * We ran out of memory, call the OOM killer, and return to
 364                  * userspace (which will retry the fault, or kill us if we
 365                  * got oom-killed)
 366                  */
 367                 pagefault_out_of_memory();
 368                 return 0;
 369         }
 370
 371         if (fault & VM_FAULT_SIGBUS) {
 372                 /*
 373                  * We had some memory, but were unable to
 374                  * successfully fix up this page fault.
 375                  */
 376                 sig = SIGBUS;
 377                 code = BUS_ADRERR;
 378         } else {
 379                 /*
 380                  * Something tried to access memory that
 381                  * isn't in our memory map..
 382                  */
 383                 sig = SIGSEGV;
 384                 code = fault == VM_FAULT_BADACCESS ?
 385                         SEGV_ACCERR : SEGV_MAPERR;
 386         }
 387
 388         __do_user_fault(tsk, addr, fsr, sig, code, regs);
 389         return 0;
 390
 391 no_context:
 392         __do_kernel_fault(mm, addr, fsr, regs);
 393         return 0;
 394 }
 395 #else                                   /* CONFIG_MMU */
 396 static int
 397 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 398 {
 399         return 0;
 400 }
 401 #endif                                  /* CONFIG_MMU */
 402
 403 /*
 404  * First Level Translation Fault Handler
 405  *
 406  * We enter here because the first level page table doesn't contain
 407  * a valid entry for the address.
 408  *
 409  * If the address is in kernel space (>= TASK_SIZE), then we are
 410  * probably faulting in the vmalloc() area.
 411  *
 412  * If the init_task's first level page tables contains the relevant
 413  * entry, we copy the it to this task.  If not, we send the process
 414  * a signal, fixup the exception, or oops the kernel.
 415  *
 416  * NOTE! We MUST NOT take any locks for this case. We may be in an
 417  * interrupt or a critical region, and should only copy the information
 418  * from the master page table, nothing more.
 419  */
 420 #ifdef CONFIG_MMU
 421 static int __kprobes
 422 do_translation_fault(unsigned long addr, unsigned int fsr,
 423                      struct pt_regs *regs)
 424 {
 425         unsigned int index;
 426         pgd_t *pgd, *pgd_k;
 427         pud_t *pud, *pud_k;
 428         pmd_t *pmd, *pmd_k;
 429
 430         if (addr < TASK_SIZE)
 431                 return do_page_fault(addr, fsr, regs);
 432
 433         if (user_mode(regs))
 434                 goto bad_area;
 435
 436         index = pgd_index(addr);
 437
 438         pgd = cpu_get_pgd() + index;
 439         pgd_k = init_mm.pgd + index;
 440
 441         if (pgd_none(*pgd_k))
 442                 goto bad_area;
 443         if (!pgd_present(*pgd))
 444                 set_pgd(pgd, *pgd_k);
 445
 446         pud = pud_offset(pgd, addr);
 447         pud_k = pud_offset(pgd_k, addr);
 448
 449         if (pud_none(*pud_k))
 450                 goto bad_area;
 451         if (!pud_present(*pud))
 452                 set_pud(pud, *pud_k);
 453
 454         pmd = pmd_offset(pud, addr);
 455         pmd_k = pmd_offset(pud_k, addr);
 456
 457 #ifdef CONFIG_ARM_LPAE
 458         /*
 459          * Only one hardware entry per PMD with LPAE.
 460          */
 461         index = 0;
 462 #else
 463         /*
 464          * On ARM one Linux PGD entry contains two hardware entries (see page
 465          * tables layout in pgtable.h). We normally guarantee that we always
 466          * fill both L1 entries. But create_mapping() doesn't follow the rule.
 467          * It can create inidividual L1 entries, so here we have to call
 468          * pmd_none() check for the entry really corresponded to address, not
 469          * for the first of pair.
 470          */
 471         index = (addr >> SECTION_SHIFT) & 1;
 472 #endif
 473         if (pmd_none(pmd_k[index]))
 474                 goto bad_area;
 475
 476         copy_pmd(pmd, pmd_k);
 477         return 0;
 478
 479 bad_area:
 480         do_bad_area(addr, fsr, regs);
 481         return 0;
 482 }
 483 #else                                   /* CONFIG_MMU */
 484 static int
 485 do_translation_fault(unsigned long addr, unsigned int fsr,
 486                      struct pt_regs *regs)
 487 {
 488         return 0;
 489 }
 490 #endif                                  /* CONFIG_MMU */
 491
 492 /*
 493  * Some section permission faults need to be handled gracefully.
 494  * They can happen due to a __{get,put}_user during an oops.
 495  */
 496 #ifndef CONFIG_ARM_LPAE
 497 static int
 498 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 499 {
 500         do_bad_area(addr, fsr, regs);
 501         return 0;
 502 }
 503 #endif /* CONFIG_ARM_LPAE */
 504
 505 /*
 506  * This abort handler always returns "fault".
 507  */
 508 static int
 509 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 510 {
 511         return 1;
 512 }
 513
 514 struct fsr_info {
 515         int     (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 516         int     sig;
 517         int     code;
 518         const char *name;
 519 };
 520
 521 /* FSR definition */
 522 #ifdef CONFIG_ARM_LPAE
 523 #include "fsr-3level.c"
 524 #else
 525 #include "fsr-2level.c"
 526 #endif
 527
 528 void __init
 529 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 530                 int sig, int code, const char *name)
 531 {
 532         if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
 533                 BUG();
 534
 535         fsr_info[nr].fn   = fn;
 536         fsr_info[nr].sig  = sig;
 537         fsr_info[nr].code = code;
 538         fsr_info[nr].name = name;
 539 }
 540
 541 /*
 542  * Dispatch a data abort to the relevant handler.
 543  */
 544 asmlinkage void __exception
 545 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 546 {
 547         const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
 548         struct siginfo info;
 549
 550         if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
 551                 return;
 552
 553         pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 554                 inf->name, fsr, addr);
 555         show_pte(current->mm, addr);
 556
 557         info.si_signo = inf->sig;
 558         info.si_errno = 0;
 559         info.si_code  = inf->code;
 560         info.si_addr  = (void __user *)addr;
 561         arm_notify_die("", regs, &info, fsr, 0);
 562 }
 563
 564 void __init
 565 hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 566                  int sig, int code, const char *name)
 567 {
 568         if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
 569                 BUG();
 570
 571         ifsr_info[nr].fn   = fn;
 572         ifsr_info[nr].sig  = sig;
 573         ifsr_info[nr].code = code;
 574         ifsr_info[nr].name = name;
 575 }
 576
 577 asmlinkage void __exception
 578 do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
 579 {
 580         const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
 581         struct siginfo info;
 582
 583         if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
 584                 return;
 585
 586         pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
 587                 inf->name, ifsr, addr);
 588
 589         info.si_signo = inf->sig;
 590         info.si_errno = 0;
 591         info.si_code  = inf->code;
 592         info.si_addr  = (void __user *)addr;
 593         arm_notify_die("", regs, &info, ifsr, 0);
 594 }
 595
 596 /*
 597  * Abort handler to be used only during first unmasking of asynchronous aborts
 598  * on the boot CPU. This makes sure that the machine will not die if the
 599  * firmware/bootloader left an imprecise abort pending for us to trip over.
 600  */
 601 static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
 602                                       struct pt_regs *regs)
 603 {
 604         pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
 605                 "first unmask, this is most likely caused by a "
 606                 "firmware/bootloader bug.\n", fsr);
 607
 608         return 0;
 609 }
 610
 611 void __init early_abt_enable(void)
 612 {
 613         fsr_info[FSR_FS_AEA].fn = early_abort_handler;
 614         local_abt_enable();
 615         fsr_info[FSR_FS_AEA].fn = do_bad;
 616 }
 617
 618 #ifndef CONFIG_ARM_LPAE
 619 static int __init exceptions_init(void)
 620 {
 621         if (cpu_architecture() >= CPU_ARCH_ARMv6) {
 622                 hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
 623                                 "I-cache maintenance fault");
 624         }
 625
 626         if (cpu_architecture() >= CPU_ARCH_ARMv7) {
 627                 /*
 628                  * TODO: Access flag faults introduced in ARMv6K.
 629                  * Runtime check for 'K' extension is needed
 630                  */
 631                 hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
 632                                 "section access flag fault");
 633                 hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
 634                                 "section access flag fault");
 635         }
 636
 637         return 0;
 638 }
 639
 640 arch_initcall(exceptions_init);
 641 #endif