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/ptrace.h>
  14 #include <linux/mm.h>
  15 #include <linux/init.h>
  16
  17 #include <asm/system.h>
  18 #include <asm/pgtable.h>
  19 #include <asm/tlbflush.h>
  20 #include <asm/uaccess.h>
  21
  22 #include "fault.h"
  23
  24 /*
  25  * This is useful to dump out the page tables associated with
  26  * 'addr' in mm 'mm'.
  27  */
  28 void show_pte(struct mm_struct *mm, unsigned long addr)
  29 {
  30         pgd_t *pgd;
  31
  32         if (!mm)
  33                 mm = &init_mm;
  34
  35         printk(KERN_ALERT "pgd = %p\n", mm->pgd);
  36         pgd = pgd_offset(mm, addr);
  37         printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
  38
  39         do {
  40                 pmd_t *pmd;
  41                 pte_t *pte;
  42
  43                 if (pgd_none(*pgd))
  44                         break;
  45
  46                 if (pgd_bad(*pgd)) {
  47                         printk("(bad)");
  48                         break;
  49                 }
  50
  51                 pmd = pmd_offset(pgd, addr);
  52 #if PTRS_PER_PMD != 1
  53                 printk(", *pmd=%08lx", pmd_val(*pmd));
  54 #endif
  55
  56                 if (pmd_none(*pmd))
  57                         break;
  58
  59                 if (pmd_bad(*pmd)) {
  60                         printk("(bad)");
  61                         break;
  62                 }
  63
  64 #ifndef CONFIG_HIGHMEM
  65                 /* We must not map this if we have highmem enabled */
  66                 pte = pte_offset_map(pmd, addr);
  67                 printk(", *pte=%08lx", pte_val(*pte));
  68                 printk(", *ppte=%08lx", pte_val(pte[-PTRS_PER_PTE]));
  69                 pte_unmap(pte);
  70 #endif
  71         } while(0);
  72
  73         printk("\n");
  74 }
  75
  76 /*
  77  * Oops.  The kernel tried to access some page that wasn't present.
  78  */
  79 static void
  80 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
  81                   struct pt_regs *regs)
  82 {
  83         /*
  84          * Are we prepared to handle this kernel fault?
  85          */
  86         if (fixup_exception(regs))
  87                 return;
  88
  89         /*
  90          * No handler, we'll have to terminate things with extreme prejudice.
  91          */
  92         bust_spinlocks(1);
  93         printk(KERN_ALERT
  94                 "Unable to handle kernel %s at virtual address %08lx\n",
  95                 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
  96                 "paging request", addr);
  97
  98         show_pte(mm, addr);
  99         die("Oops", regs, fsr);
 100         bust_spinlocks(0);
 101         do_exit(SIGKILL);
 102 }
 103
 104 /*
 105  * Something tried to access memory that isn't in our memory map..
 106  * User mode accesses just cause a SIGSEGV
 107  */
 108 static void
 109 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 110                 unsigned int fsr, unsigned int sig, int code,
 111                 struct pt_regs *regs)
 112 {
 113         struct siginfo si;
 114
 115 #ifdef CONFIG_DEBUG_USER
 116         if (user_debug & UDBG_SEGV) {
 117                 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
 118                        tsk->comm, sig, addr, fsr);
 119                 show_pte(tsk->mm, addr);
 120                 show_regs(regs);
 121         }
 122 #endif
 123
 124         tsk->thread.address = addr;
 125         tsk->thread.error_code = fsr;
 126         tsk->thread.trap_no = 14;
 127         si.si_signo = sig;
 128         si.si_errno = 0;
 129         si.si_code = code;
 130         si.si_addr = (void __user *)addr;
 131         force_sig_info(sig, &si, tsk);
 132 }
 133
 134 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 135 {
 136         struct task_struct *tsk = current;
 137         struct mm_struct *mm = tsk->active_mm;
 138
 139         /*
 140          * If we are in kernel mode at this point, we
 141          * have no context to handle this fault with.
 142          */
 143         if (user_mode(regs))
 144                 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 145         else
 146                 __do_kernel_fault(mm, addr, fsr, regs);
 147 }
 148
 149 #define VM_FAULT_BADMAP         (-20)
 150 #define VM_FAULT_BADACCESS      (-21)
 151
 152 static int
 153 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 154                 struct task_struct *tsk)
 155 {
 156         struct vm_area_struct *vma;
 157         int fault, mask;
 158
 159         vma = find_vma(mm, addr);
 160         fault = VM_FAULT_BADMAP;
 161         if (!vma)
 162                 goto out;
 163         if (vma->vm_start > addr)
 164                 goto check_stack;
 165
 166         /*
 167          * Ok, we have a good vm_area for this
 168          * memory access, so we can handle it.
 169          */
 170 good_area:
 171         if (fsr & (1 << 11)) /* write? */
 172                 mask = VM_WRITE;
 173         else
 174                 mask = VM_READ|VM_EXEC|VM_WRITE;
 175
 176         fault = VM_FAULT_BADACCESS;
 177         if (!(vma->vm_flags & mask))
 178                 goto out;
 179
 180         /*
 181          * If for any reason at all we couldn't handle
 182          * the fault, make sure we exit gracefully rather
 183          * than endlessly redo the fault.
 184          */
 185 survive:
 186         fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, fsr & (1 << 11));
 187
 188         /*
 189          * Handle the "normal" cases first - successful and sigbus
 190          */
 191         switch (fault) {
 192         case VM_FAULT_MAJOR:
 193                 tsk->maj_flt++;
 194                 return fault;
 195         case VM_FAULT_MINOR:
 196                 tsk->min_flt++;
 197         case VM_FAULT_SIGBUS:
 198                 return fault;
 199         }
 200
 201         if (!is_init(tsk))
 202                 goto out;
 203
 204         /*
 205          * If we are out of memory for pid1, sleep for a while and retry
 206          */
 207         up_read(&mm->mmap_sem);
 208         yield();
 209         down_read(&mm->mmap_sem);
 210         goto survive;
 211
 212 check_stack:
 213         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 214                 goto good_area;
 215 out:
 216         return fault;
 217 }
 218
 219 static int
 220 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 221 {
 222         struct task_struct *tsk;
 223         struct mm_struct *mm;
 224         int fault, sig, code;
 225
 226         tsk = current;
 227         mm  = tsk->mm;
 228
 229         /*
 230          * If we're in an interrupt or have no user
 231          * context, we must not take the fault..
 232          */
 233         if (in_atomic() || !mm)
 234                 goto no_context;
 235
 236         /*
 237          * As per x86, we may deadlock here.  However, since the kernel only
 238          * validly references user space from well defined areas of the code,
 239          * we can bug out early if this is from code which shouldn't.
 240          */
 241         if (!down_read_trylock(&mm->mmap_sem)) {
 242                 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
 243                         goto no_context;
 244                 down_read(&mm->mmap_sem);
 245         }
 246
 247         fault = __do_page_fault(mm, addr, fsr, tsk);
 248         up_read(&mm->mmap_sem);
 249
 250         /*
 251          * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
 252          */
 253         if (fault >= VM_FAULT_MINOR)
 254                 return 0;
 255
 256         /*
 257          * If we are in kernel mode at this point, we
 258          * have no context to handle this fault with.
 259          */
 260         if (!user_mode(regs))
 261                 goto no_context;
 262
 263         switch (fault) {
 264         case VM_FAULT_OOM:
 265                 /*
 266                  * We ran out of memory, or some other thing
 267                  * happened to us that made us unable to handle
 268                  * the page fault gracefully.
 269                  */
 270                 printk("VM: killing process %s\n", tsk->comm);
 271                 do_exit(SIGKILL);
 272                 return 0;
 273
 274         case VM_FAULT_SIGBUS:
 275                 /*
 276                  * We had some memory, but were unable to
 277                  * successfully fix up this page fault.
 278                  */
 279                 sig = SIGBUS;
 280                 code = BUS_ADRERR;
 281                 break;
 282
 283         default:
 284                 /*
 285                  * Something tried to access memory that
 286                  * isn't in our memory map..
 287                  */
 288                 sig = SIGSEGV;
 289                 code = fault == VM_FAULT_BADACCESS ?
 290                         SEGV_ACCERR : SEGV_MAPERR;
 291                 break;
 292         }
 293
 294         __do_user_fault(tsk, addr, fsr, sig, code, regs);
 295         return 0;
 296
 297 no_context:
 298         __do_kernel_fault(mm, addr, fsr, regs);
 299         return 0;
 300 }
 301
 302 /*
 303  * First Level Translation Fault Handler
 304  *
 305  * We enter here because the first level page table doesn't contain
 306  * a valid entry for the address.
 307  *
 308  * If the address is in kernel space (>= TASK_SIZE), then we are
 309  * probably faulting in the vmalloc() area.
 310  *
 311  * If the init_task's first level page tables contains the relevant
 312  * entry, we copy the it to this task.  If not, we send the process
 313  * a signal, fixup the exception, or oops the kernel.
 314  *
 315  * NOTE! We MUST NOT take any locks for this case. We may be in an
 316  * interrupt or a critical region, and should only copy the information
 317  * from the master page table, nothing more.
 318  */
 319 static int
 320 do_translation_fault(unsigned long addr, unsigned int fsr,
 321                      struct pt_regs *regs)
 322 {
 323         unsigned int index;
 324         pgd_t *pgd, *pgd_k;
 325         pmd_t *pmd, *pmd_k;
 326
 327         if (addr < TASK_SIZE)
 328                 return do_page_fault(addr, fsr, regs);
 329
 330         index = pgd_index(addr);
 331
 332         /*
 333          * FIXME: CP15 C1 is write only on ARMv3 architectures.
 334          */
 335         pgd = cpu_get_pgd() + index;
 336         pgd_k = init_mm.pgd + index;
 337
 338         if (pgd_none(*pgd_k))
 339                 goto bad_area;
 340
 341         if (!pgd_present(*pgd))
 342                 set_pgd(pgd, *pgd_k);
 343
 344         pmd_k = pmd_offset(pgd_k, addr);
 345         pmd   = pmd_offset(pgd, addr);
 346
 347         if (pmd_none(*pmd_k))
 348                 goto bad_area;
 349
 350         copy_pmd(pmd, pmd_k);
 351         return 0;
 352
 353 bad_area:
 354         do_bad_area(addr, fsr, regs);
 355         return 0;
 356 }
 357
 358 /*
 359  * Some section permission faults need to be handled gracefully.
 360  * They can happen due to a __{get,put}_user during an oops.
 361  */
 362 static int
 363 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 364 {
 365         do_bad_area(addr, fsr, regs);
 366         return 0;
 367 }
 368
 369 /*
 370  * This abort handler always returns "fault".
 371  */
 372 static int
 373 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 374 {
 375         return 1;
 376 }
 377
 378 static struct fsr_info {
 379         int     (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 380         int     sig;
 381         int     code;
 382         const char *name;
 383 } fsr_info[] = {
 384         /*
 385          * The following are the standard ARMv3 and ARMv4 aborts.  ARMv5
 386          * defines these to be "precise" aborts.
 387          */
 388         { do_bad,               SIGSEGV, 0,             "vector exception"                 },
 389         { do_bad,               SIGILL,  BUS_ADRALN,    "alignment exception"              },
 390         { do_bad,               SIGKILL, 0,             "terminal exception"               },
 391         { do_bad,               SIGILL,  BUS_ADRALN,    "alignment exception"              },
 392         { do_bad,               SIGBUS,  0,             "external abort on linefetch"      },
 393         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "section translation fault"        },
 394         { do_bad,               SIGBUS,  0,             "external abort on linefetch"      },
 395         { do_page_fault,        SIGSEGV, SEGV_MAPERR,   "page translation fault"           },
 396         { do_bad,               SIGBUS,  0,             "external abort on non-linefetch"  },
 397         { do_bad,               SIGSEGV, SEGV_ACCERR,   "section domain fault"             },
 398         { do_bad,               SIGBUS,  0,             "external abort on non-linefetch"  },
 399         { do_bad,               SIGSEGV, SEGV_ACCERR,   "page domain fault"                },
 400         { do_bad,               SIGBUS,  0,             "external abort on translation"    },
 401         { do_sect_fault,        SIGSEGV, SEGV_ACCERR,   "section permission fault"         },
 402         { do_bad,               SIGBUS,  0,             "external abort on translation"    },
 403         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "page permission fault"            },
 404         /*
 405          * The following are "imprecise" aborts, which are signalled by bit
 406          * 10 of the FSR, and may not be recoverable.  These are only
 407          * supported if the CPU abort handler supports bit 10.
 408          */
 409         { do_bad,               SIGBUS,  0,             "unknown 16"                       },
 410         { do_bad,               SIGBUS,  0,             "unknown 17"                       },
 411         { do_bad,               SIGBUS,  0,             "unknown 18"                       },
 412         { do_bad,               SIGBUS,  0,             "unknown 19"                       },
 413         { do_bad,               SIGBUS,  0,             "lock abort"                       }, /* xscale */
 414         { do_bad,               SIGBUS,  0,             "unknown 21"                       },
 415         { do_bad,               SIGBUS,  BUS_OBJERR,    "imprecise external abort"         }, /* xscale */
 416         { do_bad,               SIGBUS,  0,             "unknown 23"                       },
 417         { do_bad,               SIGBUS,  0,             "dcache parity error"              }, /* xscale */
 418         { do_bad,               SIGBUS,  0,             "unknown 25"                       },
 419         { do_bad,               SIGBUS,  0,             "unknown 26"                       },
 420         { do_bad,               SIGBUS,  0,             "unknown 27"                       },
 421         { do_bad,               SIGBUS,  0,             "unknown 28"                       },
 422         { do_bad,               SIGBUS,  0,             "unknown 29"                       },
 423         { do_bad,               SIGBUS,  0,             "unknown 30"                       },
 424         { do_bad,               SIGBUS,  0,             "unknown 31"                       }
 425 };
 426
 427 void __init
 428 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 429                 int sig, const char *name)
 430 {
 431         if (nr >= 0 && nr < ARRAY_SIZE(fsr_info)) {
 432                 fsr_info[nr].fn   = fn;
 433                 fsr_info[nr].sig  = sig;
 434                 fsr_info[nr].name = name;
 435         }
 436 }
 437
 438 /*
 439  * Dispatch a data abort to the relevant handler.
 440  */
 441 asmlinkage void
 442 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 443 {
 444         const struct fsr_info *inf = fsr_info + (fsr & 15) + ((fsr & (1 << 10)) >> 6);
 445         struct siginfo info;
 446
 447         if (!inf->fn(addr, fsr, regs))
 448                 return;
 449
 450         printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 451                 inf->name, fsr, addr);
 452
 453         info.si_signo = inf->sig;
 454         info.si_errno = 0;
 455         info.si_code  = inf->code;
 456         info.si_addr  = (void __user *)addr;
 457         notify_die("", regs, &info, fsr, 0);
 458 }
 459
 460 asmlinkage void
 461 do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
 462 {
 463         do_translation_fault(addr, 0, regs);
 464 }
 465