blob: 4d1ee88864e8a09da7b567896a4adc1d949605a4 [file] [log] [blame]
Heiko Carstenseb608fb2012-09-05 13:26:11 +02001#include <linux/module.h>
2#include <linux/sort.h>
3#include <asm/uaccess.h>
4
5/*
6 * Search one exception table for an entry corresponding to the
7 * given instruction address, and return the address of the entry,
8 * or NULL if none is found.
9 * We use a binary search, and thus we assume that the table is
10 * already sorted.
11 */
12const struct exception_table_entry *
13search_extable(const struct exception_table_entry *first,
14 const struct exception_table_entry *last,
15 unsigned long value)
16{
17 const struct exception_table_entry *mid;
18 unsigned long addr;
19
20 while (first <= last) {
21 mid = ((last - first) >> 1) + first;
22 addr = extable_insn(mid);
23 if (addr < value)
24 first = mid + 1;
25 else if (addr > value)
26 last = mid - 1;
27 else
28 return mid;
29 }
30 return NULL;
31}
32
33/*
34 * The exception table needs to be sorted so that the binary
35 * search that we use to find entries in it works properly.
36 * This is used both for the kernel exception table and for
37 * the exception tables of modules that get loaded.
38 *
39 */
40static int cmp_ex(const void *a, const void *b)
41{
42 const struct exception_table_entry *x = a, *y = b;
43
44 /* This compare is only valid after normalization. */
45 return x->insn - y->insn;
46}
47
48void sort_extable(struct exception_table_entry *start,
49 struct exception_table_entry *finish)
50{
51 struct exception_table_entry *p;
52 int i;
53
54 /* Normalize entries to being relative to the start of the section */
55 for (p = start, i = 0; p < finish; p++, i += 8)
56 p->insn += i;
57 sort(start, finish - start, sizeof(*start), cmp_ex, NULL);
58 /* Denormalize all entries */
59 for (p = start, i = 0; p < finish; p++, i += 8)
60 p->insn -= i;
61}
62
63#ifdef CONFIG_MODULES
64/*
65 * If the exception table is sorted, any referring to the module init
66 * will be at the beginning or the end.
67 */
68void trim_init_extable(struct module *m)
69{
70 /* Trim the beginning */
71 while (m->num_exentries &&
72 within_module_init(extable_insn(&m->extable[0]), m)) {
73 m->extable++;
74 m->num_exentries--;
75 }
76 /* Trim the end */
77 while (m->num_exentries &&
78 within_module_init(extable_insn(&m->extable[m->num_exentries-1]), m))
79 m->num_exentries--;
80}
81#endif /* CONFIG_MODULES */