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