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_SORT_EXTABLE 25 #ifndef ARCH_HAS_RELATIVE_EXTABLE 26 #define swap_ex NULL 27 #else 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 */ 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 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 */ 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 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 * 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