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Thomas Gleixner2874c5f2019-05-27 08:55:01 +02001// SPDX-License-Identifier: GPL-2.0-or-later
Linus Torvalds1da177e2005-04-16 15:20:36 -07002/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07003 * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c.
4 *
5 * Copyright (C) 2004 Paul Mackerras, IBM Corp.
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 */
7
Thomas Meyera94c33d2017-07-10 15:51:58 -07008#include <linux/bsearch.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07009#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/sort.h>
Linus Torvalds7c0f6ba2016-12-24 11:46:01 -080012#include <linux/uaccess.h>
Valdis Kletnieks8e72a7a2019-09-25 16:46:26 -070013#include <linux/extable.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070014
Ard Biesheuvela2728582016-01-01 12:39:09 +010015#ifndef ARCH_HAS_RELATIVE_EXTABLE
16#define ex_to_insn(x) ((x)->insn)
17#else
18static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
19{
20 return (unsigned long)&x->insn + x->insn;
21}
22#endif
23
Linus Torvalds1da177e2005-04-16 15:20:36 -070024#ifndef ARCH_HAS_SORT_EXTABLE
Ard Biesheuvela2728582016-01-01 12:39:09 +010025#ifndef ARCH_HAS_RELATIVE_EXTABLE
26#define swap_ex NULL
27#else
28static void swap_ex(void *a, void *b, int size)
29{
30 struct exception_table_entry *x = a, *y = b, tmp;
31 int delta = b - a;
32
33 tmp = *x;
34 x->insn = y->insn + delta;
35 y->insn = tmp.insn - delta;
36
37#ifdef swap_ex_entry_fixup
38 swap_ex_entry_fixup(x, y, tmp, delta);
39#else
40 x->fixup = y->fixup + delta;
41 y->fixup = tmp.fixup - delta;
42#endif
43}
44#endif /* ARCH_HAS_RELATIVE_EXTABLE */
45
Linus Torvalds1da177e2005-04-16 15:20:36 -070046/*
47 * The exception table needs to be sorted so that the binary
48 * search that we use to find entries in it works properly.
49 * This is used both for the kernel exception table and for
50 * the exception tables of modules that get loaded.
51 */
Thomas Meyera94c33d2017-07-10 15:51:58 -070052static int cmp_ex_sort(const void *a, const void *b)
Linus Torvalds1da177e2005-04-16 15:20:36 -070053{
54 const struct exception_table_entry *x = a, *y = b;
55
56 /* avoid overflow */
Ard Biesheuvela2728582016-01-01 12:39:09 +010057 if (ex_to_insn(x) > ex_to_insn(y))
Linus Torvalds1da177e2005-04-16 15:20:36 -070058 return 1;
Ard Biesheuvela2728582016-01-01 12:39:09 +010059 if (ex_to_insn(x) < ex_to_insn(y))
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 return -1;
61 return 0;
62}
63
64void sort_extable(struct exception_table_entry *start,
65 struct exception_table_entry *finish)
66{
67 sort(start, finish - start, sizeof(struct exception_table_entry),
Thomas Meyera94c33d2017-07-10 15:51:58 -070068 cmp_ex_sort, swap_ex);
Linus Torvalds1da177e2005-04-16 15:20:36 -070069}
Rusty Russellad6561d2009-06-12 21:47:03 -060070
71#ifdef CONFIG_MODULES
72/*
73 * If the exception table is sorted, any referring to the module init
74 * will be at the beginning or the end.
75 */
76void trim_init_extable(struct module *m)
77{
78 /*trim the beginning*/
Ard Biesheuvela2728582016-01-01 12:39:09 +010079 while (m->num_exentries &&
80 within_module_init(ex_to_insn(&m->extable[0]), m)) {
Rusty Russellad6561d2009-06-12 21:47:03 -060081 m->extable++;
82 m->num_exentries--;
83 }
84 /*trim the end*/
85 while (m->num_exentries &&
Ard Biesheuvela2728582016-01-01 12:39:09 +010086 within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
87 m))
Rusty Russellad6561d2009-06-12 21:47:03 -060088 m->num_exentries--;
89}
90#endif /* CONFIG_MODULES */
91#endif /* !ARCH_HAS_SORT_EXTABLE */
Linus Torvalds1da177e2005-04-16 15:20:36 -070092
93#ifndef ARCH_HAS_SEARCH_EXTABLE
Thomas Meyera94c33d2017-07-10 15:51:58 -070094
95static int cmp_ex_search(const void *key, const void *elt)
96{
97 const struct exception_table_entry *_elt = elt;
98 unsigned long _key = *(unsigned long *)key;
99
100 /* avoid overflow */
101 if (_key > ex_to_insn(_elt))
102 return 1;
103 if (_key < ex_to_insn(_elt))
104 return -1;
105 return 0;
106}
107
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108/*
109 * Search one exception table for an entry corresponding to the
110 * given instruction address, and return the address of the entry,
111 * or NULL if none is found.
112 * We use a binary search, and thus we assume that the table is
113 * already sorted.
114 */
115const struct exception_table_entry *
Thomas Meyera94c33d2017-07-10 15:51:58 -0700116search_extable(const struct exception_table_entry *base,
117 const size_t num,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 unsigned long value)
119{
Thomas Meyera94c33d2017-07-10 15:51:58 -0700120 return bsearch(&value, base, num,
121 sizeof(struct exception_table_entry), cmp_ex_search);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122}
123#endif