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 */
24 static 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
36 void 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
43 #ifdef CONFIG_MODULES
44 /*
45 * If the exception table is sorted, any referring to the module init
46 * will be at the beginning or the end.
47 */
48 void trim_init_extable(struct module *m)
49 {
50 /*trim the beginning*/
51 while (m->num_exentries && within_module_init(m->extable[0].insn, m)) {
52 m->extable++;
53 m->num_exentries--;
54 }
55 /*trim the end*/
56 while (m->num_exentries &&
57 within_module_init(m->extable[m->num_exentries-1].insn, m))
58 m->num_exentries--;
59 }
60 #endif /* CONFIG_MODULES */
61 #endif /* !ARCH_HAS_SORT_EXTABLE */
62
63 #ifndef ARCH_HAS_SEARCH_EXTABLE
64 /*
65 * Search one exception table for an entry corresponding to the
66 * given instruction address, and return the address of the entry,
67 * or NULL if none is found.
68 * We use a binary search, and thus we assume that the table is
69 * already sorted.
70 */
71 const struct exception_table_entry *
72 search_extable(const struct exception_table_entry *first,
73 const struct exception_table_entry *last,
74 unsigned long value)
75 {
76 while (first <= last) {
77 const struct exception_table_entry *mid;
78
79 mid = ((last - first) >> 1) + first;
80 /*
81 * careful, the distance between value and insn
82 * can be larger than MAX_LONG:
83 */
84 if (mid->insn < value)
85 first = mid + 1;
86 else if (mid->insn > value)
87 last = mid - 1;
88 else
89 return mid;
90 }
91 return NULL;
92 }
93 #endif
94
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