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
  22 #include <asm/system.h>
  23 #include <asm/pgtable.h>
  24 #include <asm/tlbflush.h>
  25
  26 #include "fault.h"
  27
  28 #ifdef CONFIG_MMU
  29
  30 #ifdef CONFIG_KPROBES
  31 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
  32 {
  33         int ret = 0;
  34
  35         if (!user_mode(regs)) {
  36                 /* kprobe_running() needs smp_processor_id() */
  37                 preempt_disable();
  38                 if (kprobe_running() && kprobe_fault_handler(regs, fsr))
  39                         ret = 1;
  40                 preempt_enable();
  41         }
  42
  43         return ret;
  44 }
  45 #else
  46 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
  47 {
  48         return 0;
  49 }
  50 #endif
  51
  52 /*
  53  * This is useful to dump out the page tables associated with
  54  * 'addr' in mm 'mm'.
  55  */
  56 void show_pte(struct mm_struct *mm, unsigned long addr)
  57 {
  58         pgd_t *pgd;
  59
  60         if (!mm)
  61                 mm = &init_mm;
  62
  63         printk(KERN_ALERT "pgd = %p\n", mm->pgd);
  64         pgd = pgd_offset(mm, addr);
  65         printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
  66
  67         do {
  68                 pmd_t *pmd;
  69                 pte_t *pte;
  70
  71                 if (pgd_none(*pgd))
  72                         break;
  73
  74                 if (pgd_bad(*pgd)) {
  75                         printk("(bad)");
  76                         break;
  77                 }
  78
  79                 pmd = pmd_offset(pgd, addr);
  80                 if (PTRS_PER_PMD != 1)
  81                         printk(", *pmd=%08lx", pmd_val(*pmd));
  82
  83                 if (pmd_none(*pmd))
  84                         break;
  85
  86                 if (pmd_bad(*pmd)) {
  87                         printk("(bad)");
  88                         break;
  89                 }
  90
  91                 /* We must not map this if we have highmem enabled */
  92                 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
  93                         break;
  94
  95                 pte = pte_offset_map(pmd, addr);
  96                 printk(", *pte=%08lx", pte_val(*pte));
  97                 printk(", *ppte=%08lx", pte_val(pte[-PTRS_PER_PTE]));
  98                 pte_unmap(pte);
  99         } while(0);
 100
 101         printk("\n");
 102 }
 103 #else                                   /* CONFIG_MMU */
 104 void show_pte(struct mm_struct *mm, unsigned long addr)
 105 { }
 106 #endif                                  /* CONFIG_MMU */
 107
 108 /*
 109  * Oops.  The kernel tried to access some page that wasn't present.
 110  */
 111 static void
 112 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 113                   struct pt_regs *regs)
 114 {
 115         /*
 116          * Are we prepared to handle this kernel fault?
 117          */
 118         if (fixup_exception(regs))
 119                 return;
 120
 121         /*
 122          * No handler, we'll have to terminate things with extreme prejudice.
 123          */
 124         bust_spinlocks(1);
 125         printk(KERN_ALERT
 126                 "Unable to handle kernel %s at virtual address %08lx\n",
 127                 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
 128                 "paging request", addr);
 129
 130         show_pte(mm, addr);
 131         die("Oops", regs, fsr);
 132         bust_spinlocks(0);
 133         do_exit(SIGKILL);
 134 }
 135
 136 /*
 137  * Something tried to access memory that isn't in our memory map..
 138  * User mode accesses just cause a SIGSEGV
 139  */
 140 static void
 141 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 142                 unsigned int fsr, unsigned int sig, int code,
 143                 struct pt_regs *regs)
 144 {
 145         struct siginfo si;
 146
 147 #ifdef CONFIG_DEBUG_USER
 148         if (user_debug & UDBG_SEGV) {
 149                 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
 150                        tsk->comm, sig, addr, fsr);
 151                 show_pte(tsk->mm, addr);
 152                 show_regs(regs);
 153         }
 154 #endif
 155
 156         tsk->thread.address = addr;
 157         tsk->thread.error_code = fsr;
 158         tsk->thread.trap_no = 14;
 159         si.si_signo = sig;
 160         si.si_errno = 0;
 161         si.si_code = code;
 162         si.si_addr = (void __user *)addr;
 163         force_sig_info(sig, &si, tsk);
 164 }
 165
 166 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 167 {
 168         struct task_struct *tsk = current;
 169         struct mm_struct *mm = tsk->active_mm;
 170
 171         /*
 172          * If we are in kernel mode at this point, we
 173          * have no context to handle this fault with.
 174          */
 175         if (user_mode(regs))
 176                 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 177         else
 178                 __do_kernel_fault(mm, addr, fsr, regs);
 179 }
 180
 181 #ifdef CONFIG_MMU
 182 #define VM_FAULT_BADMAP         0x010000
 183 #define VM_FAULT_BADACCESS      0x020000
 184
 185 static int
 186 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 187                 struct task_struct *tsk)
 188 {
 189         struct vm_area_struct *vma;
 190         int fault, mask;
 191
 192         vma = find_vma(mm, addr);
 193         fault = VM_FAULT_BADMAP;
 194         if (!vma)
 195                 goto out;
 196         if (vma->vm_start > addr)
 197                 goto check_stack;
 198
 199         /*
 200          * Ok, we have a good vm_area for this
 201          * memory access, so we can handle it.
 202          */
 203 good_area:
 204         if (fsr & (1 << 11)) /* write? */
 205                 mask = VM_WRITE;
 206         else
 207                 mask = VM_READ|VM_EXEC|VM_WRITE;
 208
 209         fault = VM_FAULT_BADACCESS;
 210         if (!(vma->vm_flags & mask))
 211                 goto out;
 212
 213         /*
 214          * If for any reason at all we couldn't handle
 215          * the fault, make sure we exit gracefully rather
 216          * than endlessly redo the fault.
 217          */
 218 survive:
 219         fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, (fsr & (1 << 11)) ? FAULT_FLAG_WRITE : 0);
 220         if (unlikely(fault & VM_FAULT_ERROR)) {
 221                 if (fault & VM_FAULT_OOM)
 222                         goto out_of_memory;
 223                 else if (fault & VM_FAULT_SIGBUS)
 224                         return fault;
 225                 BUG();
 226         }
 227         if (fault & VM_FAULT_MAJOR)
 228                 tsk->maj_flt++;
 229         else
 230                 tsk->min_flt++;
 231         return fault;
 232
 233 out_of_memory:
 234         if (!is_global_init(tsk))
 235                 goto out;
 236
 237         /*
 238          * If we are out of memory for pid1, sleep for a while and retry
 239          */
 240         up_read(&mm->mmap_sem);
 241         yield();
 242         down_read(&mm->mmap_sem);
 243         goto survive;
 244
 245 check_stack:
 246         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 247                 goto good_area;
 248 out:
 249         return fault;
 250 }
 251
 252 static int __kprobes
 253 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 254 {
 255         struct task_struct *tsk;
 256         struct mm_struct *mm;
 257         int fault, sig, code;
 258
 259         if (notify_page_fault(regs, fsr))
 260                 return 0;
 261
 262         tsk = current;
 263         mm  = tsk->mm;
 264
 265         /*
 266          * If we're in an interrupt or have no user
 267          * context, we must not take the fault..
 268          */
 269         if (in_atomic() || !mm)
 270                 goto no_context;
 271
 272         /*
 273          * As per x86, we may deadlock here.  However, since the kernel only
 274          * validly references user space from well defined areas of the code,
 275          * we can bug out early if this is from code which shouldn't.
 276          */
 277         if (!down_read_trylock(&mm->mmap_sem)) {
 278                 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
 279                         goto no_context;
 280                 down_read(&mm->mmap_sem);
 281         }
 282
 283         fault = __do_page_fault(mm, addr, fsr, tsk);
 284         up_read(&mm->mmap_sem);
 285
 286         /*
 287          * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
 288          */
 289         if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
 290                 return 0;
 291
 292         /*
 293          * If we are in kernel mode at this point, we
 294          * have no context to handle this fault with.
 295          */
 296         if (!user_mode(regs))
 297                 goto no_context;
 298
 299         if (fault & VM_FAULT_OOM) {
 300                 /*
 301                  * We ran out of memory, or some other thing
 302                  * happened to us that made us unable to handle
 303                  * the page fault gracefully.
 304                  */
 305                 printk("VM: killing process %s\n", tsk->comm);
 306                 do_group_exit(SIGKILL);
 307                 return 0;
 308         }
 309         if (fault & VM_FAULT_SIGBUS) {
 310                 /*
 311                  * We had some memory, but were unable to
 312                  * successfully fix up this page fault.
 313                  */
 314                 sig = SIGBUS;
 315                 code = BUS_ADRERR;
 316         } else {
 317                 /*
 318                  * Something tried to access memory that
 319                  * isn't in our memory map..
 320                  */
 321                 sig = SIGSEGV;
 322                 code = fault == VM_FAULT_BADACCESS ?
 323                         SEGV_ACCERR : SEGV_MAPERR;
 324         }
 325
 326         __do_user_fault(tsk, addr, fsr, sig, code, regs);
 327         return 0;
 328
 329 no_context:
 330         __do_kernel_fault(mm, addr, fsr, regs);
 331         return 0;
 332 }
 333 #else                                   /* CONFIG_MMU */
 334 static int
 335 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 336 {
 337         return 0;
 338 }
 339 #endif                                  /* CONFIG_MMU */
 340
 341 /*
 342  * First Level Translation Fault Handler
 343  *
 344  * We enter here because the first level page table doesn't contain
 345  * a valid entry for the address.
 346  *
 347  * If the address is in kernel space (>= TASK_SIZE), then we are
 348  * probably faulting in the vmalloc() area.
 349  *
 350  * If the init_task's first level page tables contains the relevant
 351  * entry, we copy the it to this task.  If not, we send the process
 352  * a signal, fixup the exception, or oops the kernel.
 353  *
 354  * NOTE! We MUST NOT take any locks for this case. We may be in an
 355  * interrupt or a critical region, and should only copy the information
 356  * from the master page table, nothing more.
 357  */
 358 #ifdef CONFIG_MMU
 359 static int __kprobes
 360 do_translation_fault(unsigned long addr, unsigned int fsr,
 361                      struct pt_regs *regs)
 362 {
 363         unsigned int index;
 364         pgd_t *pgd, *pgd_k;
 365         pmd_t *pmd, *pmd_k;
 366
 367         if (addr < TASK_SIZE)
 368                 return do_page_fault(addr, fsr, regs);
 369
 370         index = pgd_index(addr);
 371
 372         /*
 373          * FIXME: CP15 C1 is write only on ARMv3 architectures.
 374          */
 375         pgd = cpu_get_pgd() + index;
 376         pgd_k = init_mm.pgd + index;
 377
 378         if (pgd_none(*pgd_k))
 379                 goto bad_area;
 380
 381         if (!pgd_present(*pgd))
 382                 set_pgd(pgd, *pgd_k);
 383
 384         pmd_k = pmd_offset(pgd_k, addr);
 385         pmd   = pmd_offset(pgd, addr);
 386
 387         if (pmd_none(*pmd_k))
 388                 goto bad_area;
 389
 390         copy_pmd(pmd, pmd_k);
 391         return 0;
 392
 393 bad_area:
 394         do_bad_area(addr, fsr, regs);
 395         return 0;
 396 }
 397 #else                                   /* CONFIG_MMU */
 398 static int
 399 do_translation_fault(unsigned long addr, unsigned int fsr,
 400                      struct pt_regs *regs)
 401 {
 402         return 0;
 403 }
 404 #endif                                  /* CONFIG_MMU */
 405
 406 /*
 407  * Some section permission faults need to be handled gracefully.
 408  * They can happen due to a __{get,put}_user during an oops.
 409  */
 410 static int
 411 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 412 {
 413         do_bad_area(addr, fsr, regs);
 414         return 0;
 415 }
 416
 417 /*
 418  * This abort handler always returns "fault".
 419  */
 420 static int
 421 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 422 {
 423         return 1;
 424 }
 425
 426 static struct fsr_info {
 427         int     (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 428         int     sig;
 429         int     code;
 430         const char *name;
 431 } fsr_info[] = {
 432         /*
 433          * The following are the standard ARMv3 and ARMv4 aborts.  ARMv5
 434          * defines these to be "precise" aborts.
 435          */
 436         { do_bad,               SIGSEGV, 0,             "vector exception"                 },
 437         { do_bad,               SIGILL,  BUS_ADRALN,    "alignment exception"              },
 438         { do_bad,               SIGKILL, 0,             "terminal exception"               },
 439         { do_bad,               SIGILL,  BUS_ADRALN,    "alignment exception"              },
 440         { do_bad,               SIGBUS,  0,             "external abort on linefetch"      },
 441         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "section translation fault"        },
 442         { do_bad,               SIGBUS,  0,             "external abort on linefetch"      },
 443         { do_page_fault,        SIGSEGV, SEGV_MAPERR,   "page translation fault"           },
 444         { do_bad,               SIGBUS,  0,             "external abort on non-linefetch"  },
 445         { do_bad,               SIGSEGV, SEGV_ACCERR,   "section domain fault"             },
 446         { do_bad,               SIGBUS,  0,             "external abort on non-linefetch"  },
 447         { do_bad,               SIGSEGV, SEGV_ACCERR,   "page domain fault"                },
 448         { do_bad,               SIGBUS,  0,             "external abort on translation"    },
 449         { do_sect_fault,        SIGSEGV, SEGV_ACCERR,   "section permission fault"         },
 450         { do_bad,               SIGBUS,  0,             "external abort on translation"    },
 451         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "page permission fault"            },
 452         /*
 453          * The following are "imprecise" aborts, which are signalled by bit
 454          * 10 of the FSR, and may not be recoverable.  These are only
 455          * supported if the CPU abort handler supports bit 10.
 456          */
 457         { do_bad,               SIGBUS,  0,             "unknown 16"                       },
 458         { do_bad,               SIGBUS,  0,             "unknown 17"                       },
 459         { do_bad,               SIGBUS,  0,             "unknown 18"                       },
 460         { do_bad,               SIGBUS,  0,             "unknown 19"                       },
 461         { do_bad,               SIGBUS,  0,             "lock abort"                       }, /* xscale */
 462         { do_bad,               SIGBUS,  0,             "unknown 21"                       },
 463         { do_bad,               SIGBUS,  BUS_OBJERR,    "imprecise external abort"         }, /* xscale */
 464         { do_bad,               SIGBUS,  0,             "unknown 23"                       },
 465         { do_bad,               SIGBUS,  0,             "dcache parity error"              }, /* xscale */
 466         { do_bad,               SIGBUS,  0,             "unknown 25"                       },
 467         { do_bad,               SIGBUS,  0,             "unknown 26"                       },
 468         { do_bad,               SIGBUS,  0,             "unknown 27"                       },
 469         { do_bad,               SIGBUS,  0,             "unknown 28"                       },
 470         { do_bad,               SIGBUS,  0,             "unknown 29"                       },
 471         { do_bad,               SIGBUS,  0,             "unknown 30"                       },
 472         { do_bad,               SIGBUS,  0,             "unknown 31"                       }
 473 };
 474
 475 void __init
 476 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 477                 int sig, const char *name)
 478 {
 479         if (nr >= 0 && nr < ARRAY_SIZE(fsr_info)) {
 480                 fsr_info[nr].fn   = fn;
 481                 fsr_info[nr].sig  = sig;
 482                 fsr_info[nr].name = name;
 483         }
 484 }
 485
 486 /*
 487  * Dispatch a data abort to the relevant handler.
 488  */
 489 asmlinkage void __exception
 490 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 491 {
 492         const struct fsr_info *inf = fsr_info + (fsr & 15) + ((fsr & (1 << 10)) >> 6);
 493         struct siginfo info;
 494
 495         if (!inf->fn(addr, fsr, regs))
 496                 return;
 497
 498         printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 499                 inf->name, fsr, addr);
 500
 501         info.si_signo = inf->sig;
 502         info.si_errno = 0;
 503         info.si_code  = inf->code;
 504         info.si_addr  = (void __user *)addr;
 505         arm_notify_die("", regs, &info, fsr, 0);
 506 }
 507
 508 asmlinkage void __exception
 509 do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
 510 {
 511         do_translation_fault(addr, 0, regs);
 512 }
 513