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fault.c

/* $Id: fault.c,v 1.5 2000/01/26 16:20:29 jsm Exp $
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 *
 * Copyright (C) 1995, 1996, 1997, 1998 by Ralf Baechle
 * Copyright 1999 SuSE GmbH (Philipp Rumpf, prumpf@tux.org)
 * Copyright 1999 Hewlett Packard Co.
 *
 */

#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/module.h>

#include <asm/uaccess.h>
#include <asm/traps.h>

#define PRINT_USER_FAULTS /* (turn this on if you want user faults to be */
                   /*  dumped to the console via printk)          */


/* Various important other fields */
#define bit22set(x)           (x & 0x00000200)
#define bits23_25set(x)       (x & 0x000001c0)
#define isGraphicsFlushRead(x)      ((x & 0xfc003fdf) == 0x04001a80)
                        /* extended opcode is 0x6a */

#define BITSSET         0x1c0 /* for identifying LDCW */


DEFINE_PER_CPU(struct exception_data, exception_data);

/*
 * parisc_acctyp(unsigned int inst) --
 *    Given a PA-RISC memory access instruction, determine if the
 *    the instruction would perform a memory read or memory write
 *    operation.
 *
 *    This function assumes that the given instruction is a memory access
 *    instruction (i.e. you should really only call it if you know that
 *    the instruction has generated some sort of a memory access fault).
 *
 * Returns:
 *   VM_READ  if read operation
 *   VM_WRITE if write operation
 *   VM_EXEC  if execute operation
 */
static unsigned long
parisc_acctyp(unsigned long code, unsigned int inst)
{
      if (code == 6 || code == 16)
          return VM_EXEC;

      switch (inst & 0xf0000000) {
      case 0x40000000: /* load */
      case 0x50000000: /* new load */
            return VM_READ;

      case 0x60000000: /* store */
      case 0x70000000: /* new store */
            return VM_WRITE;

      case 0x20000000: /* coproc */
      case 0x30000000: /* coproc2 */
            if (bit22set(inst))
                  return VM_WRITE;

      case 0x0: /* indexed/memory management */
            if (bit22set(inst)) {
                  /*
                   * Check for the 'Graphics Flush Read' instruction.
                   * It resembles an FDC instruction, except for bits
                   * 20 and 21. Any combination other than zero will
                   * utilize the block mover functionality on some
                   * older PA-RISC platforms.  The case where a block
                   * move is performed from VM to graphics IO space
                   * should be treated as a READ.
                   *
                   * The significance of bits 20,21 in the FDC
                   * instruction is:
                   *
                   *   00  Flush data cache (normal instruction behavior)
                   *   01  Graphics flush write  (IO space -> VM)
                   *   10  Graphics flush read   (VM -> IO space)
                   *   11  Graphics flush read/write (VM <-> IO space)
                   */
                  if (isGraphicsFlushRead(inst))
                        return VM_READ;
                  return VM_WRITE;
            } else {
                  /*
                   * Check for LDCWX and LDCWS (semaphore instructions).
                   * If bits 23 through 25 are all 1's it is one of
                   * the above two instructions and is a write.
                   *
                   * Note: With the limited bits we are looking at,
                   * this will also catch PROBEW and PROBEWI. However,
                   * these should never get in here because they don't
                   * generate exceptions of the type:
                   *   Data TLB miss fault/data page fault
                   *   Data memory protection trap
                   */
                  if (bits23_25set(inst) == BITSSET)
                        return VM_WRITE;
            }
            return VM_READ; /* Default */
      }
      return VM_READ; /* Default */
}

#undef bit22set
#undef bits23_25set
#undef isGraphicsFlushRead
#undef BITSSET


#if 0
/* This is the treewalk to find a vma which is the highest that has
 * a start < addr.  We're using find_vma_prev instead right now, but
 * we might want to use this at some point in the future.  Probably
 * not, but I want it committed to CVS so I don't lose it :-)
 */
                  while (tree != vm_avl_empty) {
                        if (tree->vm_start > addr) {
                              tree = tree->vm_avl_left;
                        } else {
                              prev = tree;
                              if (prev->vm_next == NULL)
                                    break;
                              if (prev->vm_next->vm_start > addr)
                                    break;
                              tree = tree->vm_avl_right;
                        }
                  }
#endif

void do_page_fault(struct pt_regs *regs, unsigned long code,
                        unsigned long address)
{
      struct vm_area_struct *vma, *prev_vma;
      struct task_struct *tsk = current;
      struct mm_struct *mm = tsk->mm;
      const struct exception_table_entry *fix;
      unsigned long acc_type;
      int fault;

      if (in_atomic() || !mm)
            goto no_context;

      down_read(&mm->mmap_sem);
      vma = find_vma_prev(mm, address, &prev_vma);
      if (!vma || address < vma->vm_start)
            goto check_expansion;
/*
 * Ok, we have a good vm_area for this memory access. We still need to
 * check the access permissions.
 */

good_area:

      acc_type = parisc_acctyp(code,regs->iir);

      if ((vma->vm_flags & acc_type) != acc_type)
            goto bad_area;

      /*
       * If for any reason at all we couldn't handle the fault, make
       * sure we exit gracefully rather than endlessly redo the
       * fault.
       */

      fault = handle_mm_fault(mm, vma, address, (acc_type & VM_WRITE) != 0);
      if (unlikely(fault & VM_FAULT_ERROR)) {
            /*
             * We hit a shared mapping outside of the file, or some
             * other thing happened to us that made us unable to
             * handle the page fault gracefully.
             */
            if (fault & VM_FAULT_OOM)
                  goto out_of_memory;
            else if (fault & VM_FAULT_SIGBUS)
                  goto bad_area;
            BUG();
      }
      if (fault & VM_FAULT_MAJOR)
            current->maj_flt++;
      else
            current->min_flt++;
      up_read(&mm->mmap_sem);
      return;

check_expansion:
      vma = prev_vma;
      if (vma && (expand_stack(vma, address) == 0))
            goto good_area;

/*
 * Something tried to access memory that isn't in our memory map..
 */
bad_area:
      up_read(&mm->mmap_sem);

      if (user_mode(regs)) {
            struct siginfo si;

#ifdef PRINT_USER_FAULTS
            printk(KERN_DEBUG "\n");
            printk(KERN_DEBUG "do_page_fault() pid=%d command='%s' type=%lu address=0x%08lx\n",
                task_pid_nr(tsk), tsk->comm, code, address);
            if (vma) {
                  printk(KERN_DEBUG "vm_start = 0x%08lx, vm_end = 0x%08lx\n",
                              vma->vm_start, vma->vm_end);
            }
            show_regs(regs);
#endif
            /* FIXME: actually we need to get the signo and code correct */
            si.si_signo = SIGSEGV;
            si.si_errno = 0;
            si.si_code = SEGV_MAPERR;
            si.si_addr = (void __user *) address;
            force_sig_info(SIGSEGV, &si, current);
            return;
      }

no_context:

      if (!user_mode(regs)) {
            fix = search_exception_tables(regs->iaoq[0]);

            if (fix) {
                  struct exception_data *d;

                  d = &__get_cpu_var(exception_data);
                  d->fault_ip = regs->iaoq[0];
                  d->fault_space = regs->isr;
                  d->fault_addr = regs->ior;

                  regs->iaoq[0] = ((fix->fixup) & ~3);

                  /*
                   * NOTE: In some cases the faulting instruction
                   * may be in the delay slot of a branch. We
                   * don't want to take the branch, so we don't
                   * increment iaoq[1], instead we set it to be
                   * iaoq[0]+4, and clear the B bit in the PSW
                   */

                  regs->iaoq[1] = regs->iaoq[0] + 4;
                  regs->gr[0] &= ~PSW_B; /* IPSW in gr[0] */

                  return;
            }
      }

      parisc_terminate("Bad Address (null pointer deref?)", regs, code, address);

  out_of_memory:
      up_read(&mm->mmap_sem);
      printk(KERN_CRIT "VM: killing process %s\n", current->comm);
      if (user_mode(regs))
            do_group_exit(SIGKILL);
      goto no_context;
}

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