arch/ia64/mm/fault.c

   1 /*
   2  * MMU fault handling support.
   3  *
   4  * Copyright (C) 1998-2002 Hewlett-Packard Co
   5  *      David Mosberger-Tang <davidm@hpl.hp.com>
   6  */
   7 #include <linux/sched.h>
   8 #include <linux/kernel.h>
   9 #include <linux/mm.h>
  10 #include <linux/smp_lock.h>
  11 #include <linux/interrupt.h>
  12
  13 #include <asm/pgtable.h>
  14 #include <asm/processor.h>
  15 #include <asm/system.h>
  16 #include <asm/uaccess.h>
  17
  18 extern void die (char *, struct pt_regs *, long);
  19
  20 /*
  21  * This routine is analogous to expand_stack() but instead grows the
  22  * register backing store (which grows towards higher addresses).
  23  * Since the register backing store is access sequentially, we
  24  * disallow growing the RBS by more than a page at a time.  Note that
  25  * the VM_GROWSUP flag can be set on any VM area but that's fine
  26  * because the total process size is still limited by RLIMIT_STACK and
  27  * RLIMIT_AS.
  28  */
  29 static inline long
  30 expand_backing_store (struct vm_area_struct *vma, unsigned long address)
  31 {
  32         unsigned long grow;
  33
  34         grow = PAGE_SIZE >> PAGE_SHIFT;
  35         if (address - vma->vm_start > current->signal->rlim[RLIMIT_STACK].rlim_cur
  36             || (((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) > current->signal->rlim[RLIMIT_AS].rlim_cur))
  37                 return -ENOMEM;
  38         vma->vm_end += PAGE_SIZE;
  39         vma->vm_mm->total_vm += grow;
  40         if (vma->vm_flags & VM_LOCKED)
  41                 vma->vm_mm->locked_vm += grow;
  42         __vm_stat_account(vma->vm_mm, vma->vm_flags, vma->vm_file, grow);
  43         return 0;
  44 }
  45
  46 /*
  47  * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
  48  * (inside region 5, on ia64) and that page is present.
  49  */
  50 static int
  51 mapped_kernel_page_is_present (unsigned long address)
  52 {
  53         pgd_t *pgd;
  54         pud_t *pud;
  55         pmd_t *pmd;
  56         pte_t *ptep, pte;
  57
  58         pgd = pgd_offset_k(address);
  59         if (pgd_none(*pgd) || pgd_bad(*pgd))
  60                 return 0;
  61
  62         pud = pud_offset(pgd, address);
  63         if (pud_none(*pud) || pud_bad(*pud))
  64                 return 0;
  65
  66         pmd = pmd_offset(pud, address);
  67         if (pmd_none(*pmd) || pmd_bad(*pmd))
  68                 return 0;
  69
  70         ptep = pte_offset_kernel(pmd, address);
  71         if (!ptep)
  72                 return 0;
  73
  74         pte = *ptep;
  75         return pte_present(pte);
  76 }
  77
  78 void
  79 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
  80 {
  81         int signal = SIGSEGV, code = SEGV_MAPERR;
  82         struct vm_area_struct *vma, *prev_vma;
  83         struct mm_struct *mm = current->mm;
  84         struct siginfo si;
  85         unsigned long mask;
  86
  87         /*
  88          * If we're in an interrupt or have no user context, we must not take the fault..
  89          */
  90         if (in_atomic() || !mm)
  91                 goto no_context;
  92
  93 #ifdef CONFIG_VIRTUAL_MEM_MAP
  94         /*
  95          * If fault is in region 5 and we are in the kernel, we may already
  96          * have the mmap_sem (pfn_valid macro is called during mmap). There
  97          * is no vma for region 5 addr's anyway, so skip getting the semaphore
  98          * and go directly to the exception handling code.
  99          */
 100
 101         if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
 102                 goto bad_area_no_up;
 103 #endif
 104
 105         down_read(&mm->mmap_sem);
 106
 107         vma = find_vma_prev(mm, address, &prev_vma);
 108         if (!vma)
 109                 goto bad_area;
 110
 111         /* find_vma_prev() returns vma such that address < vma->vm_end or NULL */
 112         if (address < vma->vm_start)
 113                 goto check_expansion;
 114
 115   good_area:
 116         code = SEGV_ACCERR;
 117
 118         /* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
 119
 120 #       define VM_READ_BIT      0
 121 #       define VM_WRITE_BIT     1
 122 #       define VM_EXEC_BIT      2
 123
 124 #       if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
 125             || (1 << VM_EXEC_BIT) != VM_EXEC)
 126 #               error File is out of sync with <linux/mm.h>.  Please update.
 127 #       endif
 128
 129         mask = (  (((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
 130                 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)
 131                 | (((isr >> IA64_ISR_R_BIT) & 1UL) << VM_READ_BIT));
 132
 133         if ((vma->vm_flags & mask) != mask)
 134                 goto bad_area;
 135
 136   survive:
 137         /*
 138          * If for any reason at all we couldn't handle the fault, make
 139          * sure we exit gracefully rather than endlessly redo the
 140          * fault.
 141          */
 142         switch (handle_mm_fault(mm, vma, address, (mask & VM_WRITE) != 0)) {
 143               case VM_FAULT_MINOR:
 144                 ++current->min_flt;
 145                 break;
 146               case VM_FAULT_MAJOR:
 147                 ++current->maj_flt;
 148                 break;
 149               case VM_FAULT_SIGBUS:
 150                 /*
 151                  * We ran out of memory, or some other thing happened
 152                  * to us that made us unable to handle the page fault
 153                  * gracefully.
 154                  */
 155                 signal = SIGBUS;
 156                 goto bad_area;
 157               case VM_FAULT_OOM:
 158                 goto out_of_memory;
 159               default:
 160                 BUG();
 161         }
 162         up_read(&mm->mmap_sem);
 163         return;
 164
 165   check_expansion:
 166         if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
 167                 if (!(vma->vm_flags & VM_GROWSDOWN))
 168                         goto bad_area;
 169                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 170                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 171                         goto bad_area;
 172                 if (expand_stack(vma, address))
 173                         goto bad_area;
 174         } else {
 175                 vma = prev_vma;
 176                 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
 177                     || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
 178                         goto bad_area;
 179                 if (expand_backing_store(vma, address))
 180                         goto bad_area;
 181         }
 182         goto good_area;
 183
 184   bad_area:
 185         up_read(&mm->mmap_sem);
 186 #ifdef CONFIG_VIRTUAL_MEM_MAP
 187   bad_area_no_up:
 188 #endif
 189         if ((isr & IA64_ISR_SP)
 190             || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
 191         {
 192                 /*
 193                  * This fault was due to a speculative load or lfetch.fault, set the "ed"
 194                  * bit in the psr to ensure forward progress.  (Target register will get a
 195                  * NaT for ld.s, lfetch will be canceled.)
 196                  */
 197                 ia64_psr(regs)->ed = 1;
 198                 return;
 199         }
 200         if (user_mode(regs)) {
 201                 si.si_signo = signal;
 202                 si.si_errno = 0;
 203                 si.si_code = code;
 204                 si.si_addr = (void __user *) address;
 205                 si.si_isr = isr;
 206                 si.si_flags = __ISR_VALID;
 207                 force_sig_info(signal, &si, current);
 208                 return;
 209         }
 210
 211   no_context:
 212         if (isr & IA64_ISR_SP) {
 213                 /*
 214                  * This fault was due to a speculative load set the "ed" bit in the psr to
 215                  * ensure forward progress (target register will get a NaT).
 216                  */
 217                 ia64_psr(regs)->ed = 1;
 218                 return;
 219         }
 220
 221         if (ia64_done_with_exception(regs))
 222                 return;
 223
 224         /*
 225          * Since we have no vma's for region 5, we might get here even if the address is
 226          * valid, due to the VHPT walker inserting a non present translation that becomes
 227          * stale. If that happens, the non present fault handler already purged the stale
 228          * translation, which fixed the problem. So, we check to see if the translation is
 229          * valid, and return if it is.
 230          */
 231         if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
 232                 return;
 233
 234         /*
 235          * Oops. The kernel tried to access some bad page. We'll have to terminate things
 236          * with extreme prejudice.
 237          */
 238         bust_spinlocks(1);
 239
 240         if (address < PAGE_SIZE)
 241                 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address);
 242         else
 243                 printk(KERN_ALERT "Unable to handle kernel paging request at "
 244                        "virtual address %016lx\n", address);
 245         die("Oops", regs, isr);
 246         bust_spinlocks(0);
 247         do_exit(SIGKILL);
 248         return;
 249
 250   out_of_memory:
 251         up_read(&mm->mmap_sem);
 252         if (current->pid == 1) {
 253                 yield();
 254                 down_read(&mm->mmap_sem);
 255                 goto survive;
 256         }
 257         printk(KERN_CRIT "VM: killing process %s\n", current->comm);
 258         if (user_mode(regs))
 259                 do_exit(SIGKILL);
 260         goto no_context;
 261 }