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 */
12 const struct exception_table_entry *
search_extable(const struct exception_table_entry * first,const struct exception_table_entry * last,unsigned long value)13 search_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 */
cmp_ex(const void * a,const void * b)40 static 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
sort_extable(struct exception_table_entry * start,struct exception_table_entry * finish)48 void 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 p->fixup += i + 4;
58 }
59 sort(start, finish - start, sizeof(*start), cmp_ex, NULL);
60 /* Denormalize all entries */
61 for (p = start, i = 0; p < finish; p++, i += 8) {
62 p->insn -= i;
63 p->fixup -= i + 4;
64 }
65 }
66
67 #ifdef CONFIG_MODULES
68 /*
69 * If the exception table is sorted, any referring to the module init
70 * will be at the beginning or the end.
71 */
trim_init_extable(struct module * m)72 void trim_init_extable(struct module *m)
73 {
74 /* Trim the beginning */
75 while (m->num_exentries &&
76 within_module_init(extable_insn(&m->extable[0]), m)) {
77 m->extable++;
78 m->num_exentries--;
79 }
80 /* Trim the end */
81 while (m->num_exentries &&
82 within_module_init(extable_insn(&m->extable[m->num_exentries-1]), m))
83 m->num_exentries--;
84 }
85 #endif /* CONFIG_MODULES */
86