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, int code, 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 at 0x%08lx, code 0x%03x\n",
 118                        tsk->comm, 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 = SIGSEGV;
 128         si.si_errno = 0;
 129         si.si_code = code;
 130         si.si_addr = (void __user *)addr;
 131         force_sig_info(SIGSEGV, &si, tsk);
 132 }
 133
 134 void
 135 do_bad_area(struct task_struct *tsk, struct mm_struct *mm, unsigned long addr,
 136             unsigned int fsr, struct pt_regs *regs)
 137 {
 138         /*
 139          * If we are in kernel mode at this point, we
 140          * have no context to handle this fault with.
 141          */
 142         if (user_mode(regs))
 143                 __do_user_fault(tsk, addr, fsr, SEGV_MAPERR, regs);
 144         else
 145                 __do_kernel_fault(mm, addr, fsr, regs);
 146 }
 147
 148 #define VM_FAULT_BADMAP         (-20)
 149 #define VM_FAULT_BADACCESS      (-21)
 150
 151 static int
 152 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 153                 struct task_struct *tsk)
 154 {
 155         struct vm_area_struct *vma;
 156         int fault, mask;
 157
 158         vma = find_vma(mm, addr);
 159         fault = VM_FAULT_BADMAP;
 160         if (!vma)
 161                 goto out;
 162         if (vma->vm_start > addr)
 163                 goto check_stack;
 164
 165         /*
 166          * Ok, we have a good vm_area for this
 167          * memory access, so we can handle it.
 168          */
 169 good_area:
 170         if (fsr & (1 << 11)) /* write? */
 171                 mask = VM_WRITE;
 172         else
 173                 mask = VM_READ|VM_EXEC;
 174
 175         fault = VM_FAULT_BADACCESS;
 176         if (!(vma->vm_flags & mask))
 177                 goto out;
 178
 179         /*
 180          * If for any reason at all we couldn't handle
 181          * the fault, make sure we exit gracefully rather
 182          * than endlessly redo the fault.
 183          */
 184 survive:
 185         fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, fsr & (1 << 11));
 186
 187         /*
 188          * Handle the "normal" cases first - successful and sigbus
 189          */
 190         switch (fault) {
 191         case VM_FAULT_MAJOR:
 192                 tsk->maj_flt++;
 193                 return fault;
 194         case VM_FAULT_MINOR:
 195                 tsk->min_flt++;
 196         case VM_FAULT_SIGBUS:
 197                 return fault;
 198         }
 199
 200         if (tsk->pid != 1)
 201                 goto out;
 202
 203         /*
 204          * If we are out of memory for pid1,
 205          * sleep for a while and retry
 206          */
 207         yield();
 208         goto survive;
 209
 210 check_stack:
 211         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 212                 goto good_area;
 213 out:
 214         return fault;
 215 }
 216
 217 static int
 218 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 219 {
 220         struct task_struct *tsk;
 221         struct mm_struct *mm;
 222         int fault;
 223
 224         tsk = current;
 225         mm  = tsk->mm;
 226
 227         /*
 228          * If we're in an interrupt or have no user
 229          * context, we must not take the fault..
 230          */
 231         if (in_interrupt() || !mm)
 232                 goto no_context;
 233
 234         down_read(&mm->mmap_sem);
 235         fault = __do_page_fault(mm, addr, fsr, tsk);
 236         up_read(&mm->mmap_sem);
 237
 238         /*
 239          * Handle the "normal" case first
 240          */
 241         if (fault > 0)
 242                 return 0;
 243
 244         /*
 245          * We had some memory, but were unable to
 246          * successfully fix up this page fault.
 247          */
 248         if (fault == 0)
 249                 goto do_sigbus;
 250
 251         /*
 252          * If we are in kernel mode at this point, we
 253          * have no context to handle this fault with.
 254          */
 255         if (!user_mode(regs))
 256                 goto no_context;
 257
 258         if (fault == VM_FAULT_OOM) {
 259                 /*
 260                  * We ran out of memory, or some other thing happened to
 261                  * us that made us unable to handle the page fault gracefully.
 262                  */
 263                 printk("VM: killing process %s\n", tsk->comm);
 264                 do_exit(SIGKILL);
 265         } else
 266                 __do_user_fault(tsk, addr, fsr, fault == VM_FAULT_BADACCESS ?
 267                                 SEGV_ACCERR : SEGV_MAPERR, regs);
 268         return 0;
 269
 270
 271 /*
 272  * We ran out of memory, or some other thing happened to us that made
 273  * us unable to handle the page fault gracefully.
 274  */
 275 do_sigbus:
 276         /*
 277          * Send a sigbus, regardless of whether we were in kernel
 278          * or user mode.
 279          */
 280         tsk->thread.address = addr;
 281         tsk->thread.error_code = fsr;
 282         tsk->thread.trap_no = 14;
 283         force_sig(SIGBUS, tsk);
 284 #ifdef CONFIG_DEBUG_USER
 285         if (user_debug & UDBG_BUS) {
 286                 printk(KERN_DEBUG "%s: sigbus at 0x%08lx, pc=0x%08lx\n",
 287                         current->comm, addr, instruction_pointer(regs));
 288         }
 289 #endif
 290
 291         /* Kernel mode? Handle exceptions or die */
 292         if (user_mode(regs))
 293                 return 0;
 294
 295 no_context:
 296         __do_kernel_fault(mm, addr, fsr, regs);
 297         return 0;
 298 }
 299
 300 /*
 301  * First Level Translation Fault Handler
 302  *
 303  * We enter here because the first level page table doesn't contain
 304  * a valid entry for the address.
 305  *
 306  * If the address is in kernel space (>= TASK_SIZE), then we are
 307  * probably faulting in the vmalloc() area.
 308  *
 309  * If the init_task's first level page tables contains the relevant
 310  * entry, we copy the it to this task.  If not, we send the process
 311  * a signal, fixup the exception, or oops the kernel.
 312  *
 313  * NOTE! We MUST NOT take any locks for this case. We may be in an
 314  * interrupt or a critical region, and should only copy the information
 315  * from the master page table, nothing more.
 316  */
 317 static int
 318 do_translation_fault(unsigned long addr, unsigned int fsr,
 319                      struct pt_regs *regs)
 320 {
 321         struct task_struct *tsk;
 322         unsigned int index;
 323         pgd_t *pgd, *pgd_k;
 324         pmd_t *pmd, *pmd_k;
 325
 326         if (addr < TASK_SIZE)
 327                 return do_page_fault(addr, fsr, regs);
 328
 329         index = pgd_index(addr);
 330
 331         /*
 332          * FIXME: CP15 C1 is write only on ARMv3 architectures.
 333          */
 334         pgd = cpu_get_pgd() + index;
 335         pgd_k = init_mm.pgd + index;
 336
 337         if (pgd_none(*pgd_k))
 338                 goto bad_area;
 339
 340         if (!pgd_present(*pgd))
 341                 set_pgd(pgd, *pgd_k);
 342
 343         pmd_k = pmd_offset(pgd_k, addr);
 344         pmd   = pmd_offset(pgd, addr);
 345
 346         if (pmd_none(*pmd_k))
 347                 goto bad_area;
 348
 349         copy_pmd(pmd, pmd_k);
 350         return 0;
 351
 352 bad_area:
 353         tsk = current;
 354
 355         do_bad_area(tsk, tsk->active_mm, addr, fsr, regs);
 356         return 0;
 357 }
 358
 359 /*
 360  * Some section permission faults need to be handled gracefully.
 361  * They can happen due to a __{get,put}_user during an oops.
 362  */
 363 static int
 364 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 365 {
 366         struct task_struct *tsk = current;
 367         do_bad_area(tsk, tsk->active_mm, addr, fsr, regs);
 368         return 0;
 369 }
 370
 371 /*
 372  * This abort handler always returns "fault".
 373  */
 374 static int
 375 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 376 {
 377         return 1;
 378 }
 379
 380 static struct fsr_info {
 381         int     (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 382         int     sig;
 383         const char *name;
 384 } fsr_info[] = {
 385         /*
 386          * The following are the standard ARMv3 and ARMv4 aborts.  ARMv5
 387          * defines these to be "precise" aborts.
 388          */
 389         { do_bad,               SIGSEGV, "vector exception"                },
 390         { do_bad,               SIGILL,  "alignment exception"             },
 391         { do_bad,               SIGKILL, "terminal exception"              },
 392         { do_bad,               SIGILL,  "alignment exception"             },
 393         { do_bad,               SIGBUS,  "external abort on linefetch"     },
 394         { do_translation_fault, SIGSEGV, "section translation fault"       },
 395         { do_bad,               SIGBUS,  "external abort on linefetch"     },
 396         { do_page_fault,        SIGSEGV, "page translation fault"          },
 397         { do_bad,               SIGBUS,  "external abort on non-linefetch" },
 398         { do_bad,               SIGSEGV, "section domain fault"            },
 399         { do_bad,               SIGBUS,  "external abort on non-linefetch" },
 400         { do_bad,               SIGSEGV, "page domain fault"               },
 401         { do_bad,               SIGBUS,  "external abort on translation"   },
 402         { do_sect_fault,        SIGSEGV, "section permission fault"        },
 403         { do_bad,               SIGBUS,  "external abort on translation"   },
 404         { do_page_fault,        SIGSEGV, "page permission fault"           },
 405         /*
 406          * The following are "imprecise" aborts, which are signalled by bit
 407          * 10 of the FSR, and may not be recoverable.  These are only
 408          * supported if the CPU abort handler supports bit 10.
 409          */
 410         { do_bad,               SIGBUS,  "unknown 16"                      },
 411         { do_bad,               SIGBUS,  "unknown 17"                      },
 412         { do_bad,               SIGBUS,  "unknown 18"                      },
 413         { do_bad,               SIGBUS,  "unknown 19"                      },
 414         { do_bad,               SIGBUS,  "lock abort"                      }, /* xscale */
 415         { do_bad,               SIGBUS,  "unknown 21"                      },
 416         { do_bad,               SIGBUS,  "imprecise external abort"        }, /* xscale */
 417         { do_bad,               SIGBUS,  "unknown 23"                      },
 418         { do_bad,               SIGBUS,  "dcache parity error"             }, /* xscale */
 419         { do_bad,               SIGBUS,  "unknown 25"                      },
 420         { do_bad,               SIGBUS,  "unknown 26"                      },
 421         { do_bad,               SIGBUS,  "unknown 27"                      },
 422         { do_bad,               SIGBUS,  "unknown 28"                      },
 423         { do_bad,               SIGBUS,  "unknown 29"                      },
 424         { do_bad,               SIGBUS,  "unknown 30"                      },
 425         { do_bad,               SIGBUS,  "unknown 31"                      }
 426 };
 427
 428 void __init
 429 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 430                 int sig, const char *name)
 431 {
 432         if (nr >= 0 && nr < ARRAY_SIZE(fsr_info)) {
 433                 fsr_info[nr].fn   = fn;
 434                 fsr_info[nr].sig  = sig;
 435                 fsr_info[nr].name = name;
 436         }
 437 }
 438
 439 /*
 440  * Dispatch a data abort to the relevant handler.
 441  */
 442 asmlinkage void
 443 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 444 {
 445         const struct fsr_info *inf = fsr_info + (fsr & 15) + ((fsr & (1 << 10)) >> 6);
 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         force_sig(inf->sig, current);
 453         show_pte(current->mm, addr);
 454         die_if_kernel("Oops", regs, 0);
 455 }
 456
 457 asmlinkage void
 458 do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
 459 {
 460         do_translation_fault(addr, 0, regs);
 461 }
 462