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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_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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