LXR linux-bk/lib/extable.c

   1/*
   2 * lib/extable.c
   3 * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
   4 *
   5 * Copyright (C) 2004 Paul Mackerras, IBM Corp.
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License
   9 * as published by the Free Software Foundation; either version
  10 * 2 of the License, or (at your option) any later version.
  11 */
  12
  13#include <linux/config.h>
  14#include <linux/module.h>
  15#include <linux/init.h>
  16#include <asm/uaccess.h>
  17
  18extern struct exception_table_entry __start___ex_table[];
  19extern struct exception_table_entry __stop___ex_table[];
  20
  21#ifndef ARCH_HAS_SORT_EXTABLE
  22/*
  23 * The exception table needs to be sorted so that the binary
  24 * search that we use to find entries in it works properly.
  25 * This is used both for the kernel exception table and for
  26 * the exception tables of modules that get loaded.
  27 */
  28void sort_extable(struct exception_table_entry *start,
  29                  struct exception_table_entry *finish)
  30{
  31        struct exception_table_entry el, *p, *q;
  32
  33        /* insertion sort */
  34        for (p = start + 1; p < finish; ++p) {
  35                /* start .. p-1 is sorted */
  36                if (p[0].insn < p[-1].insn) {
  37                        /* move element p down to its right place */
  38                        el = *p;
  39                        q = p;
  40                        do {
  41                                /* el comes before q[-1], move q[-1] up one */
  42                                q[0] = q[-1];
  43                                --q;
  44                        } while (q > start && el.insn < q[-1].insn);
  45                        *q = el;
  46                }
  47        }
  48}
  49#endif
  50
  51#ifndef ARCH_HAS_SEARCH_EXTABLE
  52/*
  53 * Search one exception table for an entry corresponding to the
  54 * given instruction address, and return the address of the entry,
  55 * or NULL if none is found.
  56 * We use a binary search, and thus we assume that the table is
  57 * already sorted.
  58 */
  59const struct exception_table_entry *
  60search_extable(const struct exception_table_entry *first,
  61               const struct exception_table_entry *last,
  62               unsigned long value)
  63{
  64        while (first <= last) {
  65                const struct exception_table_entry *mid;
  66
  67                mid = (last - first) / 2 + first;
  68                /*
  69                 * careful, the distance between entries can be
  70                 * larger than 2GB:
  71                 */
  72                if (mid->insn < value)
  73                        first = mid + 1;
  74                else if (mid->insn > value)
  75                        last = mid - 1;
  76                else
  77                        return mid;
  78        }
  79        return NULL;
  80}
  81#endif
  82