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(y)) 57 return 1; 58 if (ex_to_insn(x) < ex_to_insn(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(start, finish - start, sizeof(struct exception_table_entry), 67 cmp_ex_sort, 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(ex_to_insn(&m->extable[0]), m)) { 80 m->extable++; 81 m->num_exentries--; 82 } 83 /*trim the end*/ 84 while (m->num_exentries && 85 within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]), 86 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(_elt)) 98 return 1; 99 if (_key < ex_to_insn(_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(&value, base, num, 117 sizeof(struct exception_table_entry), cmp_ex_search); 118 } 119