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 /*
  29  * Fault status register encodings.  We steal bit 31 for our own purposes.
  30  */
  31 #define FSR_LNX_PF              (1 << 31)
  32 #define FSR_WRITE               (1 << 11)
  33 #define FSR_FS4                 (1 << 10)
  34 #define FSR_FS3_0               (15)
  35
  36 static inline int fsr_fs(unsigned int fsr)
  37 {
  38         return (fsr & FSR_FS3_0) | (fsr & FSR_FS4) >> 6;
  39 }
  40
  41 #ifdef CONFIG_MMU
  42
  43 #ifdef CONFIG_KPROBES
  44 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
  45 {
  46         int ret = 0;
  47
  48         if (!user_mode(regs)) {
  49                 /* kprobe_running() needs smp_processor_id() */
  50                 preempt_disable();
  51                 if (kprobe_running() && kprobe_fault_handler(regs, fsr))
  52                         ret = 1;
  53                 preempt_enable();
  54         }
  55
  56         return ret;
  57 }
  58 #else
  59 static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
  60 {
  61         return 0;
  62 }
  63 #endif
  64
  65 /*
  66  * This is useful to dump out the page tables associated with
  67  * 'addr' in mm 'mm'.
  68  */
  69 void show_pte(struct mm_struct *mm, unsigned long addr)
  70 {
  71         pgd_t *pgd;
  72
  73         if (!mm)
  74                 mm = &init_mm;
  75
  76         printk(KERN_ALERT "pgd = %p\n", mm->pgd);
  77         pgd = pgd_offset(mm, addr);
  78         printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
  79
  80         do {
  81                 pmd_t *pmd;
  82                 pte_t *pte;
  83
  84                 if (pgd_none(*pgd))
  85                         break;
  86
  87                 if (pgd_bad(*pgd)) {
  88                         printk("(bad)");
  89                         break;
  90                 }
  91
  92                 pmd = pmd_offset(pgd, addr);
  93                 if (PTRS_PER_PMD != 1)
  94                         printk(", *pmd=%08lx", pmd_val(*pmd));
  95
  96                 if (pmd_none(*pmd))
  97                         break;
  98
  99                 if (pmd_bad(*pmd)) {
 100                         printk("(bad)");
 101                         break;
 102                 }
 103
 104                 /* We must not map this if we have highmem enabled */
 105                 if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
 106                         break;
 107
 108                 pte = pte_offset_map(pmd, addr);
 109                 printk(", *pte=%08lx", pte_val(*pte));
 110                 printk(", *ppte=%08lx", pte_val(pte[-PTRS_PER_PTE]));
 111                 pte_unmap(pte);
 112         } while(0);
 113
 114         printk("\n");
 115 }
 116 #else                                   /* CONFIG_MMU */
 117 void show_pte(struct mm_struct *mm, unsigned long addr)
 118 { }
 119 #endif                                  /* CONFIG_MMU */
 120
 121 /*
 122  * Oops.  The kernel tried to access some page that wasn't present.
 123  */
 124 static void
 125 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 126                   struct pt_regs *regs)
 127 {
 128         /*
 129          * Are we prepared to handle this kernel fault?
 130          */
 131         if (fixup_exception(regs))
 132                 return;
 133
 134         /*
 135          * No handler, we'll have to terminate things with extreme prejudice.
 136          */
 137         bust_spinlocks(1);
 138         printk(KERN_ALERT
 139                 "Unable to handle kernel %s at virtual address %08lx\n",
 140                 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
 141                 "paging request", addr);
 142
 143         show_pte(mm, addr);
 144         die("Oops", regs, fsr);
 145         bust_spinlocks(0);
 146         do_exit(SIGKILL);
 147 }
 148
 149 /*
 150  * Something tried to access memory that isn't in our memory map..
 151  * User mode accesses just cause a SIGSEGV
 152  */
 153 static void
 154 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 155                 unsigned int fsr, unsigned int sig, int code,
 156                 struct pt_regs *regs)
 157 {
 158         struct siginfo si;
 159
 160 #ifdef CONFIG_DEBUG_USER
 161         if (user_debug & UDBG_SEGV) {
 162                 printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
 163                        tsk->comm, sig, addr, fsr);
 164                 show_pte(tsk->mm, addr);
 165                 show_regs(regs);
 166         }
 167 #endif
 168
 169         tsk->thread.address = addr;
 170         tsk->thread.error_code = fsr;
 171         tsk->thread.trap_no = 14;
 172         si.si_signo = sig;
 173         si.si_errno = 0;
 174         si.si_code = code;
 175         si.si_addr = (void __user *)addr;
 176         force_sig_info(sig, &si, tsk);
 177 }
 178
 179 void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 180 {
 181         struct task_struct *tsk = current;
 182         struct mm_struct *mm = tsk->active_mm;
 183
 184         /*
 185          * If we are in kernel mode at this point, we
 186          * have no context to handle this fault with.
 187          */
 188         if (user_mode(regs))
 189                 __do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
 190         else
 191                 __do_kernel_fault(mm, addr, fsr, regs);
 192 }
 193
 194 #ifdef CONFIG_MMU
 195 #define VM_FAULT_BADMAP         0x010000
 196 #define VM_FAULT_BADACCESS      0x020000
 197
 198 /*
 199  * Check that the permissions on the VMA allow for the fault which occurred.
 200  * If we encountered a write fault, we must have write permission, otherwise
 201  * we allow any permission.
 202  */
 203 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 204 {
 205         unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
 206
 207         if (fsr & FSR_WRITE)
 208                 mask = VM_WRITE;
 209         if (fsr & FSR_LNX_PF)
 210                 mask = VM_EXEC;
 211
 212         return vma->vm_flags & mask ? false : true;
 213 }
 214
 215 static int __kprobes
 216 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 217                 struct task_struct *tsk)
 218 {
 219         struct vm_area_struct *vma;
 220         int fault;
 221
 222         vma = find_vma(mm, addr);
 223         fault = VM_FAULT_BADMAP;
 224         if (unlikely(!vma))
 225                 goto out;
 226         if (unlikely(vma->vm_start > addr))
 227                 goto check_stack;
 228
 229         /*
 230          * Ok, we have a good vm_area for this
 231          * memory access, so we can handle it.
 232          */
 233 good_area:
 234         if (access_error(fsr, vma)) {
 235                 fault = VM_FAULT_BADACCESS;
 236                 goto out;
 237         }
 238
 239         /*
 240          * If for any reason at all we couldn't handle the fault, make
 241          * sure we exit gracefully rather than endlessly redo the fault.
 242          */
 243         fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, (fsr & FSR_WRITE) ? FAULT_FLAG_WRITE : 0);
 244         if (unlikely(fault & VM_FAULT_ERROR))
 245                 return fault;
 246         if (fault & VM_FAULT_MAJOR)
 247                 tsk->maj_flt++;
 248         else
 249                 tsk->min_flt++;
 250         return fault;
 251
 252 check_stack:
 253         if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 254                 goto good_area;
 255 out:
 256         return fault;
 257 }
 258
 259 static int __kprobes
 260 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 261 {
 262         struct task_struct *tsk;
 263         struct mm_struct *mm;
 264         int fault, sig, code;
 265
 266         if (notify_page_fault(regs, fsr))
 267                 return 0;
 268
 269         tsk = current;
 270         mm  = tsk->mm;
 271
 272         /*
 273          * If we're in an interrupt or have no user
 274          * context, we must not take the fault..
 275          */
 276         if (in_atomic() || !mm)
 277                 goto no_context;
 278
 279         /*
 280          * As per x86, we may deadlock here.  However, since the kernel only
 281          * validly references user space from well defined areas of the code,
 282          * we can bug out early if this is from code which shouldn't.
 283          */
 284         if (!down_read_trylock(&mm->mmap_sem)) {
 285                 if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
 286                         goto no_context;
 287                 down_read(&mm->mmap_sem);
 288         } else {
 289                 /*
 290                  * The above down_read_trylock() might have succeeded in
 291                  * which case, we'll have missed the might_sleep() from
 292                  * down_read()
 293                  */
 294                 might_sleep();
 295         }
 296
 297         fault = __do_page_fault(mm, addr, fsr, tsk);
 298         up_read(&mm->mmap_sem);
 299
 300         /*
 301          * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
 302          */
 303         if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
 304                 return 0;
 305
 306         if (fault & VM_FAULT_OOM) {
 307                 /*
 308                  * We ran out of memory, call the OOM killer, and return to
 309                  * userspace (which will retry the fault, or kill us if we
 310                  * got oom-killed)
 311                  */
 312                 pagefault_out_of_memory();
 313                 return 0;
 314         }
 315
 316         /*
 317          * If we are in kernel mode at this point, we
 318          * have no context to handle this fault with.
 319          */
 320         if (!user_mode(regs))
 321                 goto no_context;
 322
 323         if (fault & VM_FAULT_SIGBUS) {
 324                 /*
 325                  * We had some memory, but were unable to
 326                  * successfully fix up this page fault.
 327                  */
 328                 sig = SIGBUS;
 329                 code = BUS_ADRERR;
 330         } else {
 331                 /*
 332                  * Something tried to access memory that
 333                  * isn't in our memory map..
 334                  */
 335                 sig = SIGSEGV;
 336                 code = fault == VM_FAULT_BADACCESS ?
 337                         SEGV_ACCERR : SEGV_MAPERR;
 338         }
 339
 340         __do_user_fault(tsk, addr, fsr, sig, code, regs);
 341         return 0;
 342
 343 no_context:
 344         __do_kernel_fault(mm, addr, fsr, regs);
 345         return 0;
 346 }
 347 #else                                   /* CONFIG_MMU */
 348 static int
 349 do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 350 {
 351         return 0;
 352 }
 353 #endif                                  /* CONFIG_MMU */
 354
 355 /*
 356  * First Level Translation Fault Handler
 357  *
 358  * We enter here because the first level page table doesn't contain
 359  * a valid entry for the address.
 360  *
 361  * If the address is in kernel space (>= TASK_SIZE), then we are
 362  * probably faulting in the vmalloc() area.
 363  *
 364  * If the init_task's first level page tables contains the relevant
 365  * entry, we copy the it to this task.  If not, we send the process
 366  * a signal, fixup the exception, or oops the kernel.
 367  *
 368  * NOTE! We MUST NOT take any locks for this case. We may be in an
 369  * interrupt or a critical region, and should only copy the information
 370  * from the master page table, nothing more.
 371  */
 372 #ifdef CONFIG_MMU
 373 static int __kprobes
 374 do_translation_fault(unsigned long addr, unsigned int fsr,
 375                      struct pt_regs *regs)
 376 {
 377         unsigned int index;
 378         pgd_t *pgd, *pgd_k;
 379         pmd_t *pmd, *pmd_k;
 380
 381         if (addr < TASK_SIZE)
 382                 return do_page_fault(addr, fsr, regs);
 383
 384         index = pgd_index(addr);
 385
 386         /*
 387          * FIXME: CP15 C1 is write only on ARMv3 architectures.
 388          */
 389         pgd = cpu_get_pgd() + index;
 390         pgd_k = init_mm.pgd + index;
 391
 392         if (pgd_none(*pgd_k))
 393                 goto bad_area;
 394
 395         if (!pgd_present(*pgd))
 396                 set_pgd(pgd, *pgd_k);
 397
 398         pmd_k = pmd_offset(pgd_k, addr);
 399         pmd   = pmd_offset(pgd, addr);
 400
 401         if (pmd_none(*pmd_k))
 402                 goto bad_area;
 403
 404         copy_pmd(pmd, pmd_k);
 405         return 0;
 406
 407 bad_area:
 408         do_bad_area(addr, fsr, regs);
 409         return 0;
 410 }
 411 #else                                   /* CONFIG_MMU */
 412 static int
 413 do_translation_fault(unsigned long addr, unsigned int fsr,
 414                      struct pt_regs *regs)
 415 {
 416         return 0;
 417 }
 418 #endif                                  /* CONFIG_MMU */
 419
 420 /*
 421  * Some section permission faults need to be handled gracefully.
 422  * They can happen due to a __{get,put}_user during an oops.
 423  */
 424 static int
 425 do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 426 {
 427         do_bad_area(addr, fsr, regs);
 428         return 0;
 429 }
 430
 431 /*
 432  * This abort handler always returns "fault".
 433  */
 434 static int
 435 do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 436 {
 437         return 1;
 438 }
 439
 440 static struct fsr_info {
 441         int     (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
 442         int     sig;
 443         int     code;
 444         const char *name;
 445 } fsr_info[] = {
 446         /*
 447          * The following are the standard ARMv3 and ARMv4 aborts.  ARMv5
 448          * defines these to be "precise" aborts.
 449          */
 450         { do_bad,               SIGSEGV, 0,             "vector exception"                 },
 451         { do_bad,               SIGILL,  BUS_ADRALN,    "alignment exception"              },
 452         { do_bad,               SIGKILL, 0,             "terminal exception"               },
 453         { do_bad,               SIGILL,  BUS_ADRALN,    "alignment exception"              },
 454         { do_bad,               SIGBUS,  0,             "external abort on linefetch"      },
 455         { do_translation_fault, SIGSEGV, SEGV_MAPERR,   "section translation fault"        },
 456         { do_bad,               SIGBUS,  0,             "external abort on linefetch"      },
 457         { do_page_fault,        SIGSEGV, SEGV_MAPERR,   "page translation fault"           },
 458         { do_bad,               SIGBUS,  0,             "external abort on non-linefetch"  },
 459         { do_bad,               SIGSEGV, SEGV_ACCERR,   "section domain fault"             },
 460         { do_bad,               SIGBUS,  0,             "external abort on non-linefetch"  },
 461         { do_bad,               SIGSEGV, SEGV_ACCERR,   "page domain fault"                },
 462         { do_bad,               SIGBUS,  0,             "external abort on translation"    },
 463         { do_sect_fault,        SIGSEGV, SEGV_ACCERR,   "section permission fault"         },
 464         { do_bad,               SIGBUS,  0,             "external abort on translation"    },
 465         { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "page permission fault"            },
 466         /*
 467          * The following are "imprecise" aborts, which are signalled by bit
 468          * 10 of the FSR, and may not be recoverable.  These are only
 469          * supported if the CPU abort handler supports bit 10.
 470          */
 471         { do_bad,               SIGBUS,  0,             "unknown 16"                       },
 472         { do_bad,               SIGBUS,  0,             "unknown 17"                       },
 473         { do_bad,               SIGBUS,  0,             "unknown 18"                       },
 474         { do_bad,               SIGBUS,  0,             "unknown 19"                       },
 475         { do_bad,               SIGBUS,  0,             "lock abort"                       }, /* xscale */
 476         { do_bad,               SIGBUS,  0,             "unknown 21"                       },
 477         { do_bad,               SIGBUS,  BUS_OBJERR,    "imprecise external abort"         }, /* xscale */
 478         { do_bad,               SIGBUS,  0,             "unknown 23"                       },
 479         { do_bad,               SIGBUS,  0,             "dcache parity error"              }, /* xscale */
 480         { do_bad,               SIGBUS,  0,             "unknown 25"                       },
 481         { do_bad,               SIGBUS,  0,             "unknown 26"                       },
 482         { do_bad,               SIGBUS,  0,             "unknown 27"                       },
 483         { do_bad,               SIGBUS,  0,             "unknown 28"                       },
 484         { do_bad,               SIGBUS,  0,             "unknown 29"                       },
 485         { do_bad,               SIGBUS,  0,             "unknown 30"                       },
 486         { do_bad,               SIGBUS,  0,             "unknown 31"                       }
 487 };
 488
 489 void __init
 490 hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
 491                 int sig, const char *name)
 492 {
 493         if (nr >= 0 && nr < ARRAY_SIZE(fsr_info)) {
 494                 fsr_info[nr].fn   = fn;
 495                 fsr_info[nr].sig  = sig;
 496                 fsr_info[nr].name = name;
 497         }
 498 }
 499
 500 /*
 501  * Dispatch a data abort to the relevant handler.
 502  */
 503 asmlinkage void __exception
 504 do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 505 {
 506         const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
 507         struct siginfo info;
 508
 509         if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
 510                 return;
 511
 512         printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
 513                 inf->name, fsr, addr);
 514
 515         info.si_signo = inf->sig;
 516         info.si_errno = 0;
 517         info.si_code  = inf->code;
 518         info.si_addr  = (void __user *)addr;
 519         arm_notify_die("", regs, &info, fsr, 0);
 520 }
 521
 522 asmlinkage void __exception
 523 do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
 524 {
 525         do_translation_fault(addr, FSR_LNX_PF, regs);
 526 }
 527