LXR linux/arch/sh/mm/extable

   1/*
   2 * arch/sh/mm/extable_64.c
   3 *
   4 * Copyright (C) 2003 Richard Curnow
   5 * Copyright (C) 2003, 2004  Paul Mundt
   6 *
   7 * Cloned from the 2.5 SH version..
   8 *
   9 * This file is subject to the terms and conditions of the GNU General Public
  10 * License.  See the file "COPYING" in the main directory of this archive
  11 * for more details.
  12 */
  13#include <linux/rwsem.h>
  14#include <linux/module.h>
  15#include <asm/uaccess.h>
  16
  17extern unsigned long copy_user_memcpy, copy_user_memcpy_end;
  18extern void __copy_user_fixup(void);
  19
  20static const struct exception_table_entry __copy_user_fixup_ex = {
  21        .fixup = (unsigned long)&__copy_user_fixup,
  22};
  23
  24/*
  25 * Some functions that may trap due to a bad user-mode address have too
  26 * many loads and stores in them to make it at all practical to label
  27 * each one and put them all in the main exception table.
  28 *
  29 * In particular, the fast memcpy routine is like this.  It's fix-up is
  30 * just to fall back to a slow byte-at-a-time copy, which is handled the
  31 * conventional way.  So it's functionally OK to just handle any trap
  32 * occurring in the fast memcpy with that fixup.
  33 */
  34static const struct exception_table_entry *check_exception_ranges(unsigned long addr)
  35{
  36        if ((addr >= (unsigned long)&copy_user_memcpy) &&
  37            (addr <= (unsigned long)&copy_user_memcpy_end))
  38                return &__copy_user_fixup_ex;
  39
  40        return NULL;
  41}
  42
  43/* Simple binary search */
  44const struct exception_table_entry *
  45search_extable(const struct exception_table_entry *first,
  46                 const struct exception_table_entry *last,
  47                 unsigned long value)
  48{
  49        const struct exception_table_entry *mid;
  50
  51        mid = check_exception_ranges(value);
  52        if (mid)
  53                return mid;
  54
  55        while (first <= last) {
  56                long diff;
  57
  58                mid = (last - first) / 2 + first;
  59                diff = mid->insn - value;
  60                if (diff == 0)
  61                        return mid;
  62                else if (diff < 0)
  63                        first = mid+1;
  64                else
  65                        last = mid-1;
  66        }
  67
  68        return NULL;
  69}
  70
  71int fixup_exception(struct pt_regs *regs)
  72{
  73        const struct exception_table_entry *fixup;
  74
  75        fixup = search_exception_tables(regs->pc);
  76        if (fixup) {
  77                regs->pc = fixup->fixup;
  78                return 1;
  79        }
  80
  81        return 0;
  82}
  83