arch/cris/mm/fault.c

   1 /*
   2  *  arch/cris/mm/fault.c
   3  *
   4  *  Copyright (C) 2000-2010  Axis Communications AB
   5  */
   6
   7 #include <linux/mm.h>
   8 #include <linux/interrupt.h>
   9 #include <linux/module.h>
  10 #include <linux/wait.h>
  11 #include <linux/uaccess.h>
  12 #include <arch/system.h>
  13
  14 extern int find_fixup_code(struct pt_regs *);
  15 extern void die_if_kernel(const char *, struct pt_regs *, long);
  16 extern void show_registers(struct pt_regs *regs);
  17
  18 /* debug of low-level TLB reload */
  19 #undef DEBUG
  20
  21 #ifdef DEBUG
  22 #define D(x) x
  23 #else
  24 #define D(x)
  25 #endif
  26
  27 /* debug of higher-level faults */
  28 #define DPG(x)
  29
  30 /* current active page directory */
  31
  32 DEFINE_PER_CPU(pgd_t *, current_pgd);
  33 unsigned long cris_signal_return_page;
  34
  35 /*
  36  * This routine handles page faults.  It determines the address,
  37  * and the problem, and then passes it off to one of the appropriate
  38  * routines.
  39  *
  40  * Notice that the address we're given is aligned to the page the fault
  41  * occurred in, since we only get the PFN in R_MMU_CAUSE not the complete
  42  * address.
  43  *
  44  * error_code:
  45  *      bit 0 == 0 means no page found, 1 means protection fault
  46  *      bit 1 == 0 means read, 1 means write
  47  *
  48  * If this routine detects a bad access, it returns 1, otherwise it
  49  * returns 0.
  50  */
  51
  52 asmlinkage void
  53 do_page_fault(unsigned long address, struct pt_regs *regs,
  54               int protection, int writeaccess)
  55 {
  56         struct task_struct *tsk;
  57         struct mm_struct *mm;
  58         struct vm_area_struct * vma;
  59         siginfo_t info;
  60         int fault;
  61         unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  62
  63         D(printk(KERN_DEBUG
  64                  "Page fault for %lX on %X at %lX, prot %d write %d\n",
  65                  address, smp_processor_id(), instruction_pointer(regs),
  66                  protection, writeaccess));
  67
  68         tsk = current;
  69
  70         /*
  71          * We fault-in kernel-space virtual memory on-demand. The
  72          * 'reference' page table is init_mm.pgd.
  73          *
  74          * NOTE! We MUST NOT take any locks for this case. We may
  75          * be in an interrupt or a critical region, and should
  76          * only copy the information from the master page table,
  77          * nothing more.
  78          *
  79          * NOTE2: This is done so that, when updating the vmalloc
  80          * mappings we don't have to walk all processes pgdirs and
  81          * add the high mappings all at once. Instead we do it as they
  82          * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
  83          * bit set so sometimes the TLB can use a lingering entry.
  84          *
  85          * This verifies that the fault happens in kernel space
  86          * and that the fault was not a protection error (error_code & 1).
  87          */
  88
  89         if (address >= VMALLOC_START &&
  90             !protection &&
  91             !user_mode(regs))
  92                 goto vmalloc_fault;
  93
  94         /* When stack execution is not allowed we store the signal
  95          * trampolines in the reserved cris_signal_return_page.
  96          * Handle this in the exact same way as vmalloc (we know
  97          * that the mapping is there and is valid so no need to
  98          * call handle_mm_fault).
  99          */
 100         if (cris_signal_return_page &&
 101             address == cris_signal_return_page &&
 102             !protection && user_mode(regs))
 103                 goto vmalloc_fault;
 104
 105         /* we can and should enable interrupts at this point */
 106         local_irq_enable();
 107
 108         mm = tsk->mm;
 109         info.si_code = SEGV_MAPERR;
 110
 111         /*
 112          * If we're in an interrupt, have pagefaults disabled or have no
 113          * user context, we must not take the fault.
 114          */
 115
 116         if (faulthandler_disabled() || !mm)
 117                 goto no_context;
 118
 119         if (user_mode(regs))
 120                 flags |= FAULT_FLAG_USER;
 121 retry:
 122         down_read(&mm->mmap_sem);
 123         vma = find_vma(mm, address);
 124         if (!vma)
 125                 goto bad_area;
 126         if (vma->vm_start <= address)
 127                 goto good_area;
 128         if (!(vma->vm_flags & VM_GROWSDOWN))
 129                 goto bad_area;
 130         if (user_mode(regs)) {
 131                 /*
 132                  * accessing the stack below usp is always a bug.
 133                  * we get page-aligned addresses so we can only check
 134                  * if we're within a page from usp, but that might be
 135                  * enough to catch brutal errors at least.
 136                  */
 137                 if (address + PAGE_SIZE < rdusp())
 138                         goto bad_area;
 139         }
 140         if (expand_stack(vma, address))
 141                 goto bad_area;
 142
 143         /*
 144          * Ok, we have a good vm_area for this memory access, so
 145          * we can handle it..
 146          */
 147
 148  good_area:
 149         info.si_code = SEGV_ACCERR;
 150
 151         /* first do some preliminary protection checks */
 152
 153         if (writeaccess == 2){
 154                 if (!(vma->vm_flags & VM_EXEC))
 155                         goto bad_area;
 156         } else if (writeaccess == 1) {
 157                 if (!(vma->vm_flags & VM_WRITE))
 158                         goto bad_area;
 159                 flags |= FAULT_FLAG_WRITE;
 160         } else {
 161                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 162                         goto bad_area;
 163         }
 164
 165         /*
 166          * If for any reason at all we couldn't handle the fault,
 167          * make sure we exit gracefully rather than endlessly redo
 168          * the fault.
 169          */
 170
 171         fault = handle_mm_fault(mm, vma, address, flags);
 172
 173         if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
 174                 return;
 175
 176         if (unlikely(fault & VM_FAULT_ERROR)) {
 177                 if (fault & VM_FAULT_OOM)
 178                         goto out_of_memory;
 179                 else if (fault & VM_FAULT_SIGSEGV)
 180                         goto bad_area;
 181                 else if (fault & VM_FAULT_SIGBUS)
 182                         goto do_sigbus;
 183                 BUG();
 184         }
 185
 186         if (flags & FAULT_FLAG_ALLOW_RETRY) {
 187                 if (fault & VM_FAULT_MAJOR)
 188                         tsk->maj_flt++;
 189                 else
 190                         tsk->min_flt++;
 191                 if (fault & VM_FAULT_RETRY) {
 192                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
 193                         flags |= FAULT_FLAG_TRIED;
 194
 195                         /*
 196                          * No need to up_read(&mm->mmap_sem) as we would
 197                          * have already released it in __lock_page_or_retry
 198                          * in mm/filemap.c.
 199                          */
 200
 201                         goto retry;
 202                 }
 203         }
 204
 205         up_read(&mm->mmap_sem);
 206         return;
 207
 208         /*
 209          * Something tried to access memory that isn't in our memory map..
 210          * Fix it, but check if it's kernel or user first..
 211          */
 212
 213  bad_area:
 214         up_read(&mm->mmap_sem);
 215
 216  bad_area_nosemaphore:
 217         DPG(show_registers(regs));
 218
 219         /* User mode accesses just cause a SIGSEGV */
 220
 221         if (user_mode(regs)) {
 222 #ifdef CONFIG_NO_SEGFAULT_TERMINATION
 223                 DECLARE_WAIT_QUEUE_HEAD(wq);
 224 #endif
 225                 printk(KERN_NOTICE "%s (pid %d) segfaults for page "
 226                         "address %08lx at pc %08lx\n",
 227                         tsk->comm, tsk->pid,
 228                         address, instruction_pointer(regs));
 229
 230                 /* With DPG on, we've already dumped registers above.  */
 231                 DPG(if (0))
 232                         show_registers(regs);
 233
 234 #ifdef CONFIG_NO_SEGFAULT_TERMINATION
 235                 wait_event_interruptible(wq, 0 == 1);
 236 #else
 237                 info.si_signo = SIGSEGV;
 238                 info.si_errno = 0;
 239                 /* info.si_code has been set above */
 240                 info.si_addr = (void *)address;
 241                 force_sig_info(SIGSEGV, &info, tsk);
 242 #endif
 243                 return;
 244         }
 245
 246  no_context:
 247
 248         /* Are we prepared to handle this kernel fault?
 249          *
 250          * (The kernel has valid exception-points in the source
 251          *  when it accesses user-memory. When it fails in one
 252          *  of those points, we find it in a table and do a jump
 253          *  to some fixup code that loads an appropriate error
 254          *  code)
 255          */
 256
 257         if (find_fixup_code(regs))
 258                 return;
 259
 260         /*
 261          * Oops. The kernel tried to access some bad page. We'll have to
 262          * terminate things with extreme prejudice.
 263          */
 264
 265         if (!oops_in_progress) {
 266                 oops_in_progress = 1;
 267                 if ((unsigned long) (address) < PAGE_SIZE)
 268                         printk(KERN_ALERT "Unable to handle kernel NULL "
 269                                 "pointer dereference");
 270                 else
 271                         printk(KERN_ALERT "Unable to handle kernel access"
 272                                 " at virtual address %08lx\n", address);
 273
 274                 die_if_kernel("Oops", regs, (writeaccess << 1) | protection);
 275                 oops_in_progress = 0;
 276         }
 277
 278         do_exit(SIGKILL);
 279
 280         /*
 281          * We ran out of memory, or some other thing happened to us that made
 282          * us unable to handle the page fault gracefully.
 283          */
 284
 285  out_of_memory:
 286         up_read(&mm->mmap_sem);
 287         if (!user_mode(regs))
 288                 goto no_context;
 289         pagefault_out_of_memory();
 290         return;
 291
 292  do_sigbus:
 293         up_read(&mm->mmap_sem);
 294
 295         /*
 296          * Send a sigbus, regardless of whether we were in kernel
 297          * or user mode.
 298          */
 299         info.si_signo = SIGBUS;
 300         info.si_errno = 0;
 301         info.si_code = BUS_ADRERR;
 302         info.si_addr = (void *)address;
 303         force_sig_info(SIGBUS, &info, tsk);
 304
 305         /* Kernel mode? Handle exceptions or die */
 306         if (!user_mode(regs))
 307                 goto no_context;
 308         return;
 309
 310 vmalloc_fault:
 311         {
 312                 /*
 313                  * Synchronize this task's top level page-table
 314                  * with the 'reference' page table.
 315                  *
 316                  * Use current_pgd instead of tsk->active_mm->pgd
 317                  * since the latter might be unavailable if this
 318                  * code is executed in a misfortunately run irq
 319                  * (like inside schedule() between switch_mm and
 320                  *  switch_to...).
 321                  */
 322
 323                 int offset = pgd_index(address);
 324                 pgd_t *pgd, *pgd_k;
 325                 pud_t *pud, *pud_k;
 326                 pmd_t *pmd, *pmd_k;
 327                 pte_t *pte_k;
 328
 329                 pgd = (pgd_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
 330                 pgd_k = init_mm.pgd + offset;
 331
 332                 /* Since we're two-level, we don't need to do both
 333                  * set_pgd and set_pmd (they do the same thing). If
 334                  * we go three-level at some point, do the right thing
 335                  * with pgd_present and set_pgd here.
 336                  *
 337                  * Also, since the vmalloc area is global, we don't
 338                  * need to copy individual PTE's, it is enough to
 339                  * copy the pgd pointer into the pte page of the
 340                  * root task. If that is there, we'll find our pte if
 341                  * it exists.
 342                  */
 343
 344                 pud = pud_offset(pgd, address);
 345                 pud_k = pud_offset(pgd_k, address);
 346                 if (!pud_present(*pud_k))
 347                         goto no_context;
 348
 349                 pmd = pmd_offset(pud, address);
 350                 pmd_k = pmd_offset(pud_k, address);
 351
 352                 if (!pmd_present(*pmd_k))
 353                         goto bad_area_nosemaphore;
 354
 355                 set_pmd(pmd, *pmd_k);
 356
 357                 /* Make sure the actual PTE exists as well to
 358                  * catch kernel vmalloc-area accesses to non-mapped
 359                  * addresses. If we don't do this, this will just
 360                  * silently loop forever.
 361                  */
 362
 363                 pte_k = pte_offset_kernel(pmd_k, address);
 364                 if (!pte_present(*pte_k))
 365                         goto no_context;
 366
 367                 return;
 368         }
 369 }
 370
 371 /* Find fixup code. */
 372 int
 373 find_fixup_code(struct pt_regs *regs)
 374 {
 375         const struct exception_table_entry *fixup;
 376         /* in case of delay slot fault (v32) */
 377         unsigned long ip = (instruction_pointer(regs) & ~0x1);
 378
 379         fixup = search_exception_tables(ip);
 380         if (fixup != 0) {
 381                 /* Adjust the instruction pointer in the stackframe. */
 382                 instruction_pointer(regs) = fixup->fixup;
 383                 arch_fixup(regs);
 384                 return 1;
 385         }
 386
 387         return 0;
 388 }