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/bsearch.h>
  14#include <linux/rwsem.h>
  15#include <linux/extable.h>
  16#include <linux/uaccess.h>
  17
  18extern unsigned long copy_user_memcpy, copy_user_memcpy_end;
  19extern void __copy_user_fixup(void);
  20
  21static const struct exception_table_entry __copy_user_fixup_ex = {
  22        .fixup = (unsigned long)&__copy_user_fixup,
  23};
  24
  25/*
  26 * Some functions that may trap due to a bad user-mode address have too
  27 * many loads and stores in them to make it at all practical to label
  28 * each one and put them all in the main exception table.
  29 *
  30 * In particular, the fast memcpy routine is like this.  It's fix-up is
  31 * just to fall back to a slow byte-at-a-time copy, which is handled the
  32 * conventional way.  So it's functionally OK to just handle any trap
  33 * occurring in the fast memcpy with that fixup.
  34 */
  35static const struct exception_table_entry *check_exception_ranges(unsigned long addr)
  36{
  37        if ((addr >= (unsigned long)&copy_user_memcpy) &&
  38            (addr <= (unsigned long)&copy_user_memcpy_end))
  39                return &__copy_user_fixup_ex;
  40
  41        return NULL;
  42}
  43
  44static int cmp_ex_search(const void *key, const void *elt)
  45{
  46        const struct exception_table_entry *_elt = elt;
  47        unsigned long _key = *(unsigned long *)key;
  48
  49        /* avoid overflow */
  50        if (_key > _elt->insn)
  51                return 1;
  52        if (_key < _elt->insn)
  53                return -1;
  54        return 0;
  55}
  56
  57/* Simple binary search */
  58const struct exception_table_entry *
  59search_extable(const struct exception_table_entry *base,
  60                 const size_t num,
  61                 unsigned long value)
  62{
  63        const struct exception_table_entry *mid;
  64
  65        mid = check_exception_ranges(value);
  66        if (mid)
  67                return mid;
  68
  69        return bsearch(&value, base, num,
  70                       sizeof(struct exception_table_entry), cmp_ex_search);
  71}
  72
  73int fixup_exception(struct pt_regs *regs)
  74{
  75        const struct exception_table_entry *fixup;
  76
  77        fixup = search_exception_tables(regs->pc);
  78        if (fixup) {
  79                regs->pc = fixup->fixup;
  80                return 1;
  81        }
  82
  83        return 0;
  84}
  85