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