1#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 */