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