1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
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
8 #include <linux/bsearch.h>
9 #include <linux/module.h>
10 #include <linux/init.h>
11 #include <linux/sort.h>
12 #include <linux/uaccess.h>
13 #include <linux/extable.h>
14
15 #ifndef ARCH_HAS_RELATIVE_EXTABLE
16 #define ex_to_insn(x) ((x)->insn)
17 #else
ex_to_insn(const struct exception_table_entry * x)18 static 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
24 #ifndef ARCH_HAS_SORT_EXTABLE
25 #ifndef ARCH_HAS_RELATIVE_EXTABLE
26 #define swap_ex NULL
27 #else
swap_ex(void * a,void * b,int size)28 static 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
46 /*
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 */
cmp_ex_sort(const void * a,const void * b)52 static int cmp_ex_sort(const void *a, const void *b)
53 {
54 const struct exception_table_entry *x = a, *y = b;
55
56 /* avoid overflow */
57 if (ex_to_insn(x) > ex_to_insn(y))
58 return 1;
59 if (ex_to_insn(x) < ex_to_insn(y))
60 return -1;
61 return 0;
62 }
63
sort_extable(struct exception_table_entry * start,struct exception_table_entry * finish)64 void sort_extable(struct exception_table_entry *start,
65 struct exception_table_entry *finish)
66 {
67 sort(start, finish - start, sizeof(struct exception_table_entry),
68 cmp_ex_sort, swap_ex);
69 }
70
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 */
trim_init_extable(struct module * m)76 void trim_init_extable(struct module *m)
77 {
78 /*trim the beginning*/
79 while (m->num_exentries &&
80 within_module_init(ex_to_insn(&m->extable[0]), m)) {
81 m->extable++;
82 m->num_exentries--;
83 }
84 /*trim the end*/
85 while (m->num_exentries &&
86 within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
87 m))
88 m->num_exentries--;
89 }
90 #endif /* CONFIG_MODULES */
91 #endif /* !ARCH_HAS_SORT_EXTABLE */
92
93 #ifndef ARCH_HAS_SEARCH_EXTABLE
94
cmp_ex_search(const void * key,const void * elt)95 static 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
108 /*
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 */
115 const struct exception_table_entry *
search_extable(const struct exception_table_entry * base,const size_t num,unsigned long value)116 search_extable(const struct exception_table_entry *base,
117 const size_t num,
118 unsigned long value)
119 {
120 return bsearch(&value, base, num,
121 sizeof(struct exception_table_entry), cmp_ex_search);
122 }
123 #endif
124