arch/cris/mm/fault.c

   1 /*
   2  *  linux/arch/cris/mm/fault.c
   3  *
   4  *  Copyright (C) 2000-2006  Axis Communications AB
   5  *
   6  *  Authors:  Bjorn Wesen
   7  *
   8  */
   9
  10 #include <linux/mm.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/module.h>
  13 #include <asm/uaccess.h>
  14
  15 extern int find_fixup_code(struct pt_regs *);
  16 extern void die_if_kernel(const char *, struct pt_regs *, long);
  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
  62         D(printk(KERN_DEBUG
  63                  "Page fault for %lX on %X at %lX, prot %d write %d\n",
  64                  address, smp_processor_id(), instruction_pointer(regs),
  65                  protection, writeaccess));
  66
  67         tsk = current;
  68
  69         /*
  70          * We fault-in kernel-space virtual memory on-demand. The
  71          * 'reference' page table is init_mm.pgd.
  72          *
  73          * NOTE! We MUST NOT take any locks for this case. We may
  74          * be in an interrupt or a critical region, and should
  75          * only copy the information from the master page table,
  76          * nothing more.
  77          *
  78          * NOTE2: This is done so that, when updating the vmalloc
  79          * mappings we don't have to walk all processes pgdirs and
  80          * add the high mappings all at once. Instead we do it as they
  81          * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
  82          * bit set so sometimes the TLB can use a lingering entry.
  83          *
  84          * This verifies that the fault happens in kernel space
  85          * and that the fault was not a protection error (error_code & 1).
  86          */
  87
  88         if (address >= VMALLOC_START &&
  89             !protection &&
  90             !user_mode(regs))
  91                 goto vmalloc_fault;
  92
  93         /* When stack execution is not allowed we store the signal
  94          * trampolines in the reserved cris_signal_return_page.
  95          * Handle this in the exact same way as vmalloc (we know
  96          * that the mapping is there and is valid so no need to
  97          * call handle_mm_fault).
  98          */
  99         if (cris_signal_return_page &&
 100             address == cris_signal_return_page &&
 101             !protection && user_mode(regs))
 102                 goto vmalloc_fault;
 103
 104         /* we can and should enable interrupts at this point */
 105         local_irq_enable();
 106
 107         mm = tsk->mm;
 108         info.si_code = SEGV_MAPERR;
 109
 110         /*
 111          * If we're in an interrupt or have no user
 112          * context, we must not take the fault..
 113          */
 114
 115         if (in_interrupt() || !mm)
 116                 goto no_context;
 117
 118         down_read(&mm->mmap_sem);
 119         vma = find_vma(mm, address);
 120         if (!vma)
 121                 goto bad_area;
 122         if (vma->vm_start <= address)
 123                 goto good_area;
 124         if (!(vma->vm_flags & VM_GROWSDOWN))
 125                 goto bad_area;
 126         if (user_mode(regs)) {
 127                 /*
 128                  * accessing the stack below usp is always a bug.
 129                  * we get page-aligned addresses so we can only check
 130                  * if we're within a page from usp, but that might be
 131                  * enough to catch brutal errors at least.
 132                  */
 133                 if (address + PAGE_SIZE < rdusp())
 134                         goto bad_area;
 135         }
 136         if (expand_stack(vma, address))
 137                 goto bad_area;
 138
 139         /*
 140          * Ok, we have a good vm_area for this memory access, so
 141          * we can handle it..
 142          */
 143
 144  good_area:
 145         info.si_code = SEGV_ACCERR;
 146
 147         /* first do some preliminary protection checks */
 148
 149         if (writeaccess == 2){
 150                 if (!(vma->vm_flags & VM_EXEC))
 151                         goto bad_area;
 152         } else if (writeaccess == 1) {
 153                 if (!(vma->vm_flags & VM_WRITE))
 154                         goto bad_area;
 155         } else {
 156                 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
 157                         goto bad_area;
 158         }
 159
 160         /*
 161          * If for any reason at all we couldn't handle the fault,
 162          * make sure we exit gracefully rather than endlessly redo
 163          * the fault.
 164          */
 165
 166         fault = handle_mm_fault(mm, vma, address, (writeaccess & 1) ? FAULT_FLAG_WRITE : 0);
 167         if (unlikely(fault & VM_FAULT_ERROR)) {
 168                 if (fault & VM_FAULT_OOM)
 169                         goto out_of_memory;
 170                 else if (fault & VM_FAULT_SIGBUS)
 171                         goto do_sigbus;
 172                 BUG();
 173         }
 174         if (fault & VM_FAULT_MAJOR)
 175                 tsk->maj_flt++;
 176         else
 177                 tsk->min_flt++;
 178
 179         up_read(&mm->mmap_sem);
 180         return;
 181
 182         /*
 183          * Something tried to access memory that isn't in our memory map..
 184          * Fix it, but check if it's kernel or user first..
 185          */
 186
 187  bad_area:
 188         up_read(&mm->mmap_sem);
 189
 190  bad_area_nosemaphore:
 191         DPG(show_registers(regs));
 192
 193         /* User mode accesses just cause a SIGSEGV */
 194
 195         if (user_mode(regs)) {
 196                 info.si_signo = SIGSEGV;
 197                 info.si_errno = 0;
 198                 /* info.si_code has been set above */
 199                 info.si_addr = (void *)address;
 200                 force_sig_info(SIGSEGV, &info, tsk);
 201                 printk(KERN_NOTICE "%s (pid %d) segfaults for page "
 202                        "address %08lx at pc %08lx\n",
 203                        tsk->comm, tsk->pid, address, instruction_pointer(regs));
 204                 return;
 205         }
 206
 207  no_context:
 208
 209         /* Are we prepared to handle this kernel fault?
 210          *
 211          * (The kernel has valid exception-points in the source
 212          *  when it acesses user-memory. When it fails in one
 213          *  of those points, we find it in a table and do a jump
 214          *  to some fixup code that loads an appropriate error
 215          *  code)
 216          */
 217
 218         if (find_fixup_code(regs))
 219                 return;
 220
 221         /*
 222          * Oops. The kernel tried to access some bad page. We'll have to
 223          * terminate things with extreme prejudice.
 224          */
 225
 226         if (!oops_in_progress) {
 227                 oops_in_progress = 1;
 228                 if ((unsigned long) (address) < PAGE_SIZE)
 229                         printk(KERN_ALERT "Unable to handle kernel NULL "
 230                                 "pointer dereference");
 231                 else
 232                         printk(KERN_ALERT "Unable to handle kernel access"
 233                                 " at virtual address %08lx\n", address);
 234
 235                 die_if_kernel("Oops", regs, (writeaccess << 1) | protection);
 236                 oops_in_progress = 0;
 237         }
 238
 239         do_exit(SIGKILL);
 240
 241         /*
 242          * We ran out of memory, or some other thing happened to us that made
 243          * us unable to handle the page fault gracefully.
 244          */
 245
 246  out_of_memory:
 247         up_read(&mm->mmap_sem);
 248         printk("VM: killing process %s\n", tsk->comm);
 249         if (user_mode(regs))
 250                 do_exit(SIGKILL);
 251         goto no_context;
 252
 253  do_sigbus:
 254         up_read(&mm->mmap_sem);
 255
 256         /*
 257          * Send a sigbus, regardless of whether we were in kernel
 258          * or user mode.
 259          */
 260         info.si_signo = SIGBUS;
 261         info.si_errno = 0;
 262         info.si_code = BUS_ADRERR;
 263         info.si_addr = (void *)address;
 264         force_sig_info(SIGBUS, &info, tsk);
 265
 266         /* Kernel mode? Handle exceptions or die */
 267         if (!user_mode(regs))
 268                 goto no_context;
 269         return;
 270
 271 vmalloc_fault:
 272         {
 273                 /*
 274                  * Synchronize this task's top level page-table
 275                  * with the 'reference' page table.
 276                  *
 277                  * Use current_pgd instead of tsk->active_mm->pgd
 278                  * since the latter might be unavailable if this
 279                  * code is executed in a misfortunately run irq
 280                  * (like inside schedule() between switch_mm and
 281                  *  switch_to...).
 282                  */
 283
 284                 int offset = pgd_index(address);
 285                 pgd_t *pgd, *pgd_k;
 286                 pud_t *pud, *pud_k;
 287                 pmd_t *pmd, *pmd_k;
 288                 pte_t *pte_k;
 289
 290                 pgd = (pgd_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
 291                 pgd_k = init_mm.pgd + offset;
 292
 293                 /* Since we're two-level, we don't need to do both
 294                  * set_pgd and set_pmd (they do the same thing). If
 295                  * we go three-level at some point, do the right thing
 296                  * with pgd_present and set_pgd here.
 297                  *
 298                  * Also, since the vmalloc area is global, we don't
 299                  * need to copy individual PTE's, it is enough to
 300                  * copy the pgd pointer into the pte page of the
 301                  * root task. If that is there, we'll find our pte if
 302                  * it exists.
 303                  */
 304
 305                 pud = pud_offset(pgd, address);
 306                 pud_k = pud_offset(pgd_k, address);
 307                 if (!pud_present(*pud_k))
 308                         goto no_context;
 309
 310                 pmd = pmd_offset(pud, address);
 311                 pmd_k = pmd_offset(pud_k, address);
 312
 313                 if (!pmd_present(*pmd_k))
 314                         goto bad_area_nosemaphore;
 315
 316                 set_pmd(pmd, *pmd_k);
 317
 318                 /* Make sure the actual PTE exists as well to
 319                  * catch kernel vmalloc-area accesses to non-mapped
 320                  * addresses. If we don't do this, this will just
 321                  * silently loop forever.
 322                  */
 323
 324                 pte_k = pte_offset_kernel(pmd_k, address);
 325                 if (!pte_present(*pte_k))
 326                         goto no_context;
 327
 328                 return;
 329         }
 330 }
 331
 332 /* Find fixup code. */
 333 int
 334 find_fixup_code(struct pt_regs *regs)
 335 {
 336         const struct exception_table_entry *fixup;
 337
 338         if ((fixup = search_exception_tables(instruction_pointer(regs))) != 0) {
 339                 /* Adjust the instruction pointer in the stackframe. */
 340                 instruction_pointer(regs) = fixup->fixup;
 341                 arch_fixup(regs);
 342                 return 1;
 343         }
 344
 345         return 0;
 346 }