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 |
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_RELATIVE_EXTABLE |
25 | #define swap_ex NULL |
26 | #else |
27 | static void swap_ex(void *a, void *b, int size) |
28 | { |
29 | struct exception_table_entry *x = a, *y = b, tmp; |
30 | int delta = b - a; |
31 | |
32 | tmp = *x; |
33 | x->insn = y->insn + delta; |
34 | y->insn = tmp.insn - delta; |
35 | |
36 | #ifdef swap_ex_entry_fixup |
37 | swap_ex_entry_fixup(x, y, tmp, delta); |
38 | #else |
39 | x->fixup = y->fixup + delta; |
40 | y->fixup = tmp.fixup - delta; |
41 | #endif |
42 | } |
43 | #endif /* ARCH_HAS_RELATIVE_EXTABLE */ |
44 | |
45 | /* |
46 | * The exception table needs to be sorted so that the binary |
47 | * search that we use to find entries in it works properly. |
48 | * This is used both for the kernel exception table and for |
49 | * the exception tables of modules that get loaded. |
50 | */ |
51 | static int cmp_ex_sort(const void *a, const void *b) |
52 | { |
53 | const struct exception_table_entry *x = a, *y = b; |
54 | |
55 | /* avoid overflow */ |
56 | if (ex_to_insn(x) > ex_to_insn(x: y)) |
57 | return 1; |
58 | if (ex_to_insn(x) < ex_to_insn(x: y)) |
59 | return -1; |
60 | return 0; |
61 | } |
62 | |
63 | void sort_extable(struct exception_table_entry *start, |
64 | struct exception_table_entry *finish) |
65 | { |
66 | sort(base: start, num: finish - start, size: sizeof(struct exception_table_entry), |
67 | cmp_func: cmp_ex_sort, swap_func: swap_ex); |
68 | } |
69 | |
70 | #ifdef CONFIG_MODULES |
71 | /* |
72 | * If the exception table is sorted, any referring to the module init |
73 | * will be at the beginning or the end. |
74 | */ |
75 | void trim_init_extable(struct module *m) |
76 | { |
77 | /*trim the beginning*/ |
78 | while (m->num_exentries && |
79 | within_module_init(addr: ex_to_insn(x: &m->extable[0]), mod: m)) { |
80 | m->extable++; |
81 | m->num_exentries--; |
82 | } |
83 | /*trim the end*/ |
84 | while (m->num_exentries && |
85 | within_module_init(addr: ex_to_insn(x: &m->extable[m->num_exentries - 1]), |
86 | mod: m)) |
87 | m->num_exentries--; |
88 | } |
89 | #endif /* CONFIG_MODULES */ |
90 | |
91 | static int cmp_ex_search(const void *key, const void *elt) |
92 | { |
93 | const struct exception_table_entry *_elt = elt; |
94 | unsigned long _key = *(unsigned long *)key; |
95 | |
96 | /* avoid overflow */ |
97 | if (_key > ex_to_insn(x: _elt)) |
98 | return 1; |
99 | if (_key < ex_to_insn(x: _elt)) |
100 | return -1; |
101 | return 0; |
102 | } |
103 | |
104 | /* |
105 | * Search one exception table for an entry corresponding to the |
106 | * given instruction address, and return the address of the entry, |
107 | * or NULL if none is found. |
108 | * We use a binary search, and thus we assume that the table is |
109 | * already sorted. |
110 | */ |
111 | const struct exception_table_entry * |
112 | search_extable(const struct exception_table_entry *base, |
113 | const size_t num, |
114 | unsigned long value) |
115 | { |
116 | return bsearch(key: &value, base, num, |
117 | size: sizeof(struct exception_table_entry), cmp: cmp_ex_search); |
118 | } |
119 | |