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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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 <linux/sort.h>
17#include <asm/uaccess.h>
18
19extern struct exception_table_entry __start___ex_table[];
20extern struct exception_table_entry __stop___ex_table[];
21
22#ifndef ARCH_HAS_SORT_EXTABLE
23/*
24 * The exception table needs to be sorted so that the binary
25 * search that we use to find entries in it works properly.
26 * This is used both for the kernel exception table and for
27 * the exception tables of modules that get loaded.
28 */
29static int cmp_ex(const void *a, const void *b)
30{
31 const struct exception_table_entry *x = a, *y = b;
32
33 /* avoid overflow */
34 if (x->insn > y->insn)
35 return 1;
36 if (x->insn < y->insn)
37 return -1;
38 return 0;
39}
40
41void sort_extable(struct exception_table_entry *start,
42 struct exception_table_entry *finish)
43{
44 sort(start, finish - start, sizeof(struct exception_table_entry),
45 cmp_ex, NULL);
46}
47#endif
48
49#ifndef ARCH_HAS_SEARCH_EXTABLE
50/*
51 * Search one exception table for an entry corresponding to the
52 * given instruction address, and return the address of the entry,
53 * or NULL if none is found.
54 * We use a binary search, and thus we assume that the table is
55 * already sorted.
56 */
57const struct exception_table_entry *
58search_extable(const struct exception_table_entry *first,
59 const struct exception_table_entry *last,
60 unsigned long value)
61{
62 while (first <= last) {
63 const struct exception_table_entry *mid;
64
65 mid = (last - first) / 2 + first;
66 /*
67 * careful, the distance between entries can be
68 * larger than 2GB:
69 */
70 if (mid->insn < value)
71 first = mid + 1;
72 else if (mid->insn > value)
73 last = mid - 1;
74 else
75 return mid;
76 }
77 return NULL;
78}
79#endif