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