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/bsearch.h>
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/sort.h>
16 #include <linux/uaccess.h>
17
18 #ifndef ARCH_HAS_RELATIVE_EXTABLE
19 #define ex_to_insn(x) ((x)->insn)
20 #else
ex_to_insn(const struct exception_table_entry * x)21 static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
22 {
23 return (unsigned long)&x->insn + x->insn;
24 }
25 #endif
26
27 #ifndef ARCH_HAS_SORT_EXTABLE
28 #ifndef ARCH_HAS_RELATIVE_EXTABLE
29 #define swap_ex NULL
30 #else
swap_ex(void * a,void * b,int size)31 static void swap_ex(void *a, void *b, int size)
32 {
33 struct exception_table_entry *x = a, *y = b, tmp;
34 int delta = b - a;
35
36 tmp = *x;
37 x->insn = y->insn + delta;
38 y->insn = tmp.insn - delta;
39
40 #ifdef swap_ex_entry_fixup
41 swap_ex_entry_fixup(x, y, tmp, delta);
42 #else
43 x->fixup = y->fixup + delta;
44 y->fixup = tmp.fixup - delta;
45 #endif
46 }
47 #endif /* ARCH_HAS_RELATIVE_EXTABLE */
48
49 /*
50 * The exception table needs to be sorted so that the binary
51 * search that we use to find entries in it works properly.
52 * This is used both for the kernel exception table and for
53 * the exception tables of modules that get loaded.
54 */
cmp_ex_sort(const void * a,const void * b)55 static int cmp_ex_sort(const void *a, const void *b)
56 {
57 const struct exception_table_entry *x = a, *y = b;
58
59 /* avoid overflow */
60 if (ex_to_insn(x) > ex_to_insn(y))
61 return 1;
62 if (ex_to_insn(x) < ex_to_insn(y))
63 return -1;
64 return 0;
65 }
66
sort_extable(struct exception_table_entry * start,struct exception_table_entry * finish)67 void sort_extable(struct exception_table_entry *start,
68 struct exception_table_entry *finish)
69 {
70 sort(start, finish - start, sizeof(struct exception_table_entry),
71 cmp_ex_sort, swap_ex);
72 }
73
74 #ifdef CONFIG_MODULES
75 /*
76 * If the exception table is sorted, any referring to the module init
77 * will be at the beginning or the end.
78 */
trim_init_extable(struct module * m)79 void trim_init_extable(struct module *m)
80 {
81 /*trim the beginning*/
82 while (m->num_exentries &&
83 within_module_init(ex_to_insn(&m->extable[0]), m)) {
84 m->extable++;
85 m->num_exentries--;
86 }
87 /*trim the end*/
88 while (m->num_exentries &&
89 within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
90 m))
91 m->num_exentries--;
92 }
93 #endif /* CONFIG_MODULES */
94 #endif /* !ARCH_HAS_SORT_EXTABLE */
95
96 #ifndef ARCH_HAS_SEARCH_EXTABLE
97
cmp_ex_search(const void * key,const void * elt)98 static int cmp_ex_search(const void *key, const void *elt)
99 {
100 const struct exception_table_entry *_elt = elt;
101 unsigned long _key = *(unsigned long *)key;
102
103 /* avoid overflow */
104 if (_key > ex_to_insn(_elt))
105 return 1;
106 if (_key < ex_to_insn(_elt))
107 return -1;
108 return 0;
109 }
110
111 /*
112 * Search one exception table for an entry corresponding to the
113 * given instruction address, and return the address of the entry,
114 * or NULL if none is found.
115 * We use a binary search, and thus we assume that the table is
116 * already sorted.
117 */
118 const struct exception_table_entry *
search_extable(const struct exception_table_entry * base,const size_t num,unsigned long value)119 search_extable(const struct exception_table_entry *base,
120 const size_t num,
121 unsigned long value)
122 {
123 return bsearch(&value, base, num,
124 sizeof(struct exception_table_entry), cmp_ex_search);
125 }
126 #endif
127