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/config.h>
  12 #include <linux/module.h>
  13 #include <linux/signal.h>
  14 #include <linux/ptrace.h>
  15 #include <linux/mm.h>
  16 #include <linux/init.h>
  17
  18 #include <asm/system.h>
  19 #include <asm/pgtable.h>
  20 #include <asm/tlbflush.h>
  21 #include <asm/uaccess.h>
  22
  23 #include "fault.h"
  24
  25 /*
  26  * This is useful to dump out the page tables associated with
  27  * 'addr' in mm 'mm'.
  28  */
  29 void show_pte(struct mm_struct *mm, unsigned long addr)
  30 {
  31         pgd_t *pgd;
  32
  33         if (!mm)
  34                 mm = &init_mm;
  35
  36         printk(KERN_ALERT "pgd = %p\n", mm->pgd);
  37         pgd = pgd_offset(mm, addr);
  38         printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
  39
  40         do {
  41                 pmd_t *pmd;
  42                 pte_t *pte;
  43
  44                 if (pgd_none(*pgd))
  45                         break;
  46
  47                 if (pgd_bad(*pgd)) {
  48                         printk("(bad)");
  49                         break;
  50                 }
  51
  52                 pmd = pmd_offset(pgd, addr);
  53 #if PTRS_PER_PMD != 1
  54                 printk(", *pmd=%08lx", pmd_val(*pmd));
  55 #endif
  56
  57                 if (pmd_none(*pmd))
  58                         break;
  59
  60                 if (pmd_bad(*pmd)) {
  61                         printk("(bad)");
  62                         break;
  63                 }
  64
  65 #ifndef CONFIG_HIGHMEM
  66                 /* We must not map this if we have highmem enabled */
  67                 pte = pte_offset_map(pmd, addr);
  68                 printk(", *pte=%08lx", pte_val(*pte));
  69                 printk(", *ppte=%08lx", pte_val(pte[-PTRS_PER_PTE]));
  70                 pte_unmap(pte);
  71 #endif
  72         } while(0);
  73
  74         printk("\n");
  75 }
  76
  77 /*
  78  * Oops.  The kernel tried to access some page that wasn't present.
  79  */
  80 static void
  81 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
  82                   struct pt_regs *regs)
  83 {
  84         /*
  85          * Are we prepared to handle this kernel fault?
  86          */
  87         if (fixup_exception(regs))
  88                 return;
  89
  90         /*
  91          * No handler, we'll have to terminate things with extreme prejudice.
  92          */
  93         bust_spinlocks(1);
  94         printk(KERN_ALERT
  95                 "Unable to handle kernel %s at virtual address %08lx\n",
  96                 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
  97                 "paging request", addr);
  98
  99         show_pte(mm, addr);
 100         die("Oops", regs, fsr);
 101         bust_spinlocks(0);
 102         do_exit(SIGKILL);
 103 }
 104
 105 /*
 106  * Something tried to access memory that isn't in our memory map..
 107  * User mode accesses just cause a SIGSEGV
 108  */
 109 static void
 110 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 111                 unsigned int fsr, unsigned int sig, int code,
 112                 struct pt_regs *regs)
 113 {
 114         struct siginfo si;
 115
 116 #ifdef CONFIG_DEBUG_USER
 117         if (user_debug & UDBG_SEGV) {
 118                 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
 119                        tsk->comm, sig, addr, fsr);
 120                 show_pte(tsk->mm, addr);
 121                 show_regs(regs);
 122         }
 123 #endif
 124
 125         tsk->thread.address = addr;
 126         tsk->thread.error_code = fsr;
 127         tsk->thread.trap_no = 14;
 128         si.si_signo = sig;
 129         si.si_errno = 0;
 130         si.si_code = code;
 131         si.si_addr = (void __user *)addr;
 132         force_sig_info(sig, &si, tsk);
 133 }
 134
 135 void
 136 do_bad_area(struct task_struct *tsk, struct mm_struct *mm, unsigned long addr,
 137             unsigned int fsr, struct pt_regs *regs)
 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;
 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 (tsk->pid != 1)
 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_interrupt() || !mm)
 234                 goto no_context;
 235
 236         down_read(&mm->mmap_sem);
 237         fault = __do_page_fault(mm, addr, fsr, tsk);
 238         up_read(&mm->mmap_sem);
 239
 240         /*
 241          * Handle the "normal" case first
 242          */
 243         if (fault > 0)
 244                 return 0;
 245
 246         /*
 247          * If we are in kernel mode at this point, we
 248          * have no context to handle this fault with.
 249          */
 250         if (!user_mode(regs))
 251                 goto no_context;
 252
 253         switch (fault) {
 254         case VM_FAULT_OOM:
 255                 /*
 256                  * We ran out of memory, or some other thing
 257                  * happened to us that made us unable to handle
 258                  * the page fault gracefully.
 259                  */
 260                 printk("VM: killing process %s\n", tsk->comm);
 261                 do_exit(SIGKILL);
 262                 return 0;
 263
 264         case 0:
 265                 /*
 266                  * We had some memory, but were unable to
 267                  * successfully fix up this page fault.
 268                  */
 269                 sig = SIGBUS;
 270                 code = BUS_ADRERR;
 271                 break;
 272
 273         default:
 274                 /*
 275                  * Something tried to access memory that
 276                  * isn't in our memory map..
 277                  */
 278                 sig = SIGSEGV;
 279                 code = fault == VM_FAULT_BADACCESS ?
 280                         SEGV_ACCERR : SEGV_MAPERR;
 281                 break;
 282         }
 283
 284         __do_user_fault(tsk, addr, fsr, sig, code, regs);
 285         return 0;
 286
 287 no_context:
 288         __do_kernel_fault(mm, addr, fsr, regs);
 289         return 0;
 290 }
 291
 292 /*
 293  * First Level Translation Fault Handler
 294  *
 295  * We enter here because the first level page table doesn't contain
 296  * a valid entry for the address.
 297  *
 298  * If the address is in kernel space (>= TASK_SIZE), then we are
 299  * probably faulting in the vmalloc() area.
 300  *
 301  * If the init_task's first level page tables contains the relevant
 302  * entry, we copy the it to this task.  If not, we send the process
 303  * a signal, fixup the exception, or oops the kernel.
 304  *
 305  * NOTE! We MUST NOT take any locks for this case. We may be in an
 306  * interrupt or a critical region, and should only copy the information
 307  * from the master page table, nothing more.
 308  */
 309 static int
 310 do_translation_fault(unsigned long addr, unsigned int fsr,
 311                      struct pt_regs *regs)
 312 {
 313         struct task_struct *tsk;
 314         unsigned int index;
 315         pgd_t *pgd, *pgd_k;
 316         pmd_t *pmd, *pmd_k;
 317
 318         if (addr < TASK_SIZE)
 319                 return do_page_fault(addr, fsr, regs);
 320
 321         index = pgd_index(addr);
 322
 323         /*
 324          * FIXME: CP15 C1 is write only on ARMv3 architectures.
 325          */
 326         pgd = cpu_get_pgd() + index;
 327         pgd_k = init_mm.pgd + index;
 328
 329         if (pgd_none(*pgd_k))
 330                 goto bad_area;
 331
 332         if (!pgd_present(*pgd))
 333                 set_pgd(pgd, *pgd_k);
 334
 335         pmd_k = pmd_offset(pgd_k, addr);
 336         pmd   = pmd_offset(pgd, addr);
 337
 338         if (pmd_none(*pmd_k))
 339                 goto bad_area;
 340
 341         copy_pmd(pmd, pmd_k);
 342         return 0;
 343
 344 bad_area:
 345         tsk = current;
 346
 347         do_bad_area(tsk, tsk->active_mm, addr, fsr, regs);
 348         return 0;
 349 }
 350
 351 /*
 352  * Some section permission faults need to be handled gracefully.
 353  * They can happen due to a __{get,put}_user during an oops.
 354  */
 355 static int
 356 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 357 {
 358         struct task_struct *tsk = current;
 359         do_bad_area(tsk, tsk->active_mm, addr, fsr, regs);
 360         return 0;
 361 }
 362
 363 /*
 364  * This abort handler always returns "fault".
 365  */
 366 static int
 367 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 368 {
 369         return 1;
 370 }
 371
 372 static struct fsr_info {
 373         int     (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 374         int     sig;
 375         const char *name;
 376 } fsr_info[] = {
 377         /*
 378          * The following are the standard ARMv3 and ARMv4 aborts.  ARMv5
 379          * defines these to be "precise" aborts.
 380          */
 381         { do_bad,               SIGSEGV, "vector exception"                },
 382         { do_bad,               SIGILL,  "alignment exception"             },
 383         { do_bad,               SIGKILL, "terminal exception"              },
 384         { do_bad,               SIGILL,  "alignment exception"             },
 385         { do_bad,               SIGBUS,  "external abort on linefetch"     },
 386         { do_translation_fault, SIGSEGV, "section translation fault"       },
 387         { do_bad,               SIGBUS,  "external abort on linefetch"     },
 388         { do_page_fault,        SIGSEGV, "page translation fault"          },
 389         { do_bad,               SIGBUS,  "external abort on non-linefetch" },
 390         { do_bad,               SIGSEGV, "section domain fault"            },
 391         { do_bad,               SIGBUS,  "external abort on non-linefetch" },
 392         { do_bad,               SIGSEGV, "page domain fault"               },
 393         { do_bad,               SIGBUS,  "external abort on translation"   },
 394         { do_sect_fault,        SIGSEGV, "section permission fault"        },
 395         { do_bad,               SIGBUS,  "external abort on translation"   },
 396         { do_page_fault,        SIGSEGV, "page permission fault"           },
 397         /*
 398          * The following are "imprecise" aborts, which are signalled by bit
 399          * 10 of the FSR, and may not be recoverable.  These are only
 400          * supported if the CPU abort handler supports bit 10.
 401          */
 402         { do_bad,               SIGBUS,  "unknown 16"                      },
 403         { do_bad,               SIGBUS,  "unknown 17"                      },
 404         { do_bad,               SIGBUS,  "unknown 18"                      },
 405         { do_bad,               SIGBUS,  "unknown 19"                      },
 406         { do_bad,               SIGBUS,  "lock abort"                      }, /* xscale */
 407         { do_bad,               SIGBUS,  "unknown 21"                      },
 408         { do_bad,               SIGBUS,  "imprecise external abort"        }, /* xscale */
 409         { do_bad,               SIGBUS,  "unknown 23"                      },
 410         { do_bad,               SIGBUS,  "dcache parity error"             }, /* xscale */
 411         { do_bad,               SIGBUS,  "unknown 25"                      },
 412         { do_bad,               SIGBUS,  "unknown 26"                      },
 413         { do_bad,               SIGBUS,  "unknown 27"                      },
 414         { do_bad,               SIGBUS,  "unknown 28"                      },
 415         { do_bad,               SIGBUS,  "unknown 29"                      },
 416         { do_bad,               SIGBUS,  "unknown 30"                      },
 417         { do_bad,               SIGBUS,  "unknown 31"                      }
 418 };
 419
 420 void __init
 421 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 422                 int sig, const char *name)
 423 {
 424         if (nr >= 0 && nr < ARRAY_SIZE(fsr_info)) {
 425                 fsr_info[nr].fn   = fn;
 426                 fsr_info[nr].sig  = sig;
 427                 fsr_info[nr].name = name;
 428         }
 429 }
 430
 431 /*
 432  * Dispatch a data abort to the relevant handler.
 433  */
 434 asmlinkage void
 435 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 436 {
 437         const struct fsr_info *inf = fsr_info + (fsr & 15) + ((fsr & (1 << 10)) >> 6);
 438
 439         if (!inf->fn(addr, fsr, regs))
 440                 return;
 441
 442         printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 443                 inf->name, fsr, addr);
 444         force_sig(inf->sig, current);
 445         show_pte(current->mm, addr);
 446         die_if_kernel("Oops", regs, 0);
 447 }
 448
 449 asmlinkage void
 450 do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
 451 {
 452         do_translation_fault(addr, 0, regs);
 453 }
 454