LXR linux/lib/extable.c

   1/*
   2 * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
   3 *
   4 * Copyright (C) 2004 Paul Mackerras, IBM Corp.
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public License
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the License, or (at your option) any later version.
  10 */
  11
  12#include <linux/module.h>
  13#include <linux/init.h>
  14#include <linux/sort.h>
  15#include <asm/uaccess.h>
  16
  17#ifndef ARCH_HAS_SORT_EXTABLE
  18/*
  19 * The exception table needs to be sorted so that the binary
  20 * search that we use to find entries in it works properly.
  21 * This is used both for the kernel exception table and for
  22 * the exception tables of modules that get loaded.
  23 */
  24static int cmp_ex(const void *a, const void *b)
  25{
  26        const struct exception_table_entry *x = a, *y = b;
  27
  28        /* avoid overflow */
  29        if (x->insn > y->insn)
  30                return 1;
  31        if (x->insn < y->insn)
  32                return -1;
  33        return 0;
  34}
  35
  36void sort_extable(struct exception_table_entry *start,
  37                  struct exception_table_entry *finish)
  38{
  39        sort(start, finish - start, sizeof(struct exception_table_entry),
  40             cmp_ex, NULL);
  41}
  42#endif
  43
  44#ifndef ARCH_HAS_SEARCH_EXTABLE
  45/*
  46 * Search one exception table for an entry corresponding to the
  47 * given instruction address, and return the address of the entry,
  48 * or NULL if none is found.
  49 * We use a binary search, and thus we assume that the table is
  50 * already sorted.
  51 */
  52const struct exception_table_entry *
  53search_extable(const struct exception_table_entry *first,
  54               const struct exception_table_entry *last,
  55               unsigned long value)
  56{
  57        while (first <= last) {
  58                const struct exception_table_entry *mid;
  59
  60                mid = (last - first) / 2 + first;
  61                /*
  62                 * careful, the distance between entries can be
  63                 * larger than 2GB:
  64                 */
  65                if (mid->insn < value)
  66                        first = mid + 1;
  67                else if (mid->insn > value)
  68                        last = mid - 1;
  69                else
  70                        return mid;
  71        }
  72        return NULL;
  73}
  74#endif
  75