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