xref: /openbmc/linux/lib/extable.c (revision 87c2ce3b)
1 /*
2  * lib/extable.c
3  * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
4  *
5  * Copyright (C) 2004 Paul Mackerras, IBM Corp.
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version
10  * 2 of the License, or (at your option) any later version.
11  */
12 
13 #include <linux/config.h>
14 #include <linux/module.h>
15 #include <linux/init.h>
16 #include <linux/sort.h>
17 #include <asm/uaccess.h>
18 
19 #ifndef ARCH_HAS_SORT_EXTABLE
20 /*
21  * The exception table needs to be sorted so that the binary
22  * search that we use to find entries in it works properly.
23  * This is used both for the kernel exception table and for
24  * the exception tables of modules that get loaded.
25  */
26 static int cmp_ex(const void *a, const void *b)
27 {
28 	const struct exception_table_entry *x = a, *y = b;
29 
30 	/* avoid overflow */
31 	if (x->insn > y->insn)
32 		return 1;
33 	if (x->insn < y->insn)
34 		return -1;
35 	return 0;
36 }
37 
38 void sort_extable(struct exception_table_entry *start,
39 		  struct exception_table_entry *finish)
40 {
41 	sort(start, finish - start, sizeof(struct exception_table_entry),
42 	     cmp_ex, NULL);
43 }
44 #endif
45 
46 #ifndef ARCH_HAS_SEARCH_EXTABLE
47 /*
48  * Search one exception table for an entry corresponding to the
49  * given instruction address, and return the address of the entry,
50  * or NULL if none is found.
51  * We use a binary search, and thus we assume that the table is
52  * already sorted.
53  */
54 const struct exception_table_entry *
55 search_extable(const struct exception_table_entry *first,
56 	       const struct exception_table_entry *last,
57 	       unsigned long value)
58 {
59 	while (first <= last) {
60 		const struct exception_table_entry *mid;
61 
62 		mid = (last - first) / 2 + first;
63 		/*
64 		 * careful, the distance between entries can be
65 		 * larger than 2GB:
66 		 */
67 		if (mid->insn < value)
68 			first = mid + 1;
69 		else if (mid->insn > value)
70 			last = mid - 1;
71 		else
72 			return mid;
73         }
74         return NULL;
75 }
76 #endif
77