Linux kernel mirror (for testing)
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linux
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_RELATIVE_EXTABLE
18#define ex_to_insn(x) ((x)->insn)
19#else
20static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
21{
22 return (unsigned long)&x->insn + x->insn;
23}
24#endif
25
26#ifndef ARCH_HAS_SORT_EXTABLE
27#ifndef ARCH_HAS_RELATIVE_EXTABLE
28#define swap_ex NULL
29#else
30static void swap_ex(void *a, void *b, int size)
31{
32 struct exception_table_entry *x = a, *y = b, tmp;
33 int delta = b - a;
34
35 tmp = *x;
36 x->insn = y->insn + delta;
37 y->insn = tmp.insn - delta;
38
39#ifdef swap_ex_entry_fixup
40 swap_ex_entry_fixup(x, y, tmp, delta);
41#else
42 x->fixup = y->fixup + delta;
43 y->fixup = tmp.fixup - delta;
44#endif
45}
46#endif /* ARCH_HAS_RELATIVE_EXTABLE */
47
48/*
49 * The exception table needs to be sorted so that the binary
50 * search that we use to find entries in it works properly.
51 * This is used both for the kernel exception table and for
52 * the exception tables of modules that get loaded.
53 */
54static int cmp_ex(const void *a, const void *b)
55{
56 const struct exception_table_entry *x = a, *y = b;
57
58 /* avoid overflow */
59 if (ex_to_insn(x) > ex_to_insn(y))
60 return 1;
61 if (ex_to_insn(x) < ex_to_insn(y))
62 return -1;
63 return 0;
64}
65
66void sort_extable(struct exception_table_entry *start,
67 struct exception_table_entry *finish)
68{
69 sort(start, finish - start, sizeof(struct exception_table_entry),
70 cmp_ex, swap_ex);
71}
72
73#ifdef CONFIG_MODULES
74/*
75 * If the exception table is sorted, any referring to the module init
76 * will be at the beginning or the end.
77 */
78void trim_init_extable(struct module *m)
79{
80 /*trim the beginning*/
81 while (m->num_exentries &&
82 within_module_init(ex_to_insn(&m->extable[0]), m)) {
83 m->extable++;
84 m->num_exentries--;
85 }
86 /*trim the end*/
87 while (m->num_exentries &&
88 within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
89 m))
90 m->num_exentries--;
91}
92#endif /* CONFIG_MODULES */
93#endif /* !ARCH_HAS_SORT_EXTABLE */
94
95#ifndef ARCH_HAS_SEARCH_EXTABLE
96/*
97 * Search one exception table for an entry corresponding to the
98 * given instruction address, and return the address of the entry,
99 * or NULL if none is found.
100 * We use a binary search, and thus we assume that the table is
101 * already sorted.
102 */
103const struct exception_table_entry *
104search_extable(const struct exception_table_entry *first,
105 const struct exception_table_entry *last,
106 unsigned long value)
107{
108 while (first <= last) {
109 const struct exception_table_entry *mid;
110
111 mid = ((last - first) >> 1) + first;
112 /*
113 * careful, the distance between value and insn
114 * can be larger than MAX_LONG:
115 */
116 if (ex_to_insn(mid) < value)
117 first = mid + 1;
118 else if (ex_to_insn(mid) > value)
119 last = mid - 1;
120 else
121 return mid;
122 }
123 return NULL;
124}
125#endif