blob: 0be02ad561e9e346c01a65434873f9960472047a
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 |
126 |