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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
20 static 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
30 static 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 */
54 static 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
66 void 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 */
78 void 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 */
103 const struct exception_table_entry *
104 search_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