1 /* 2 * Derived from arch/ppc/mm/extable.c and arch/i386/mm/extable.c. 3 * 4 * Copyright (C) 2004 Paul Mackerras, IBM Corp. 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 12 #include <linux/module.h> 13 #include <linux/init.h> 14 #include <linux/sort.h> 15 #include <linux/uaccess.h> 16 17 #ifndef ARCH_HAS_RELATIVE_EXTABLE 18 #define ex_to_insn(x) ((x)->insn) 19 #else 20 static inline unsigned long ex_to_insn(const struct exception_table_entry *x) 21 { 22 return (unsigned long)&x->insn + x->insn; 23 } 24 #endif 25 26 #ifndef ARCH_HAS_SORT_EXTABLE 27 #ifndef ARCH_HAS_RELATIVE_EXTABLE 28 #define swap_ex NULL 29 #else 30 static void swap_ex(void *a, void *b, int size) 31 { 32 struct exception_table_entry *x = a, *y = b, tmp; 33 int delta = b - a; 34 35 tmp = *x; 36 x->insn = y->insn + delta; 37 y->insn = tmp.insn - delta; 38 39 #ifdef swap_ex_entry_fixup 40 swap_ex_entry_fixup(x, y, tmp, delta); 41 #else 42 x->fixup = y->fixup + delta; 43 y->fixup = tmp.fixup - delta; 44 #endif 45 } 46 #endif /* ARCH_HAS_RELATIVE_EXTABLE */ 47 48 /* 49 * The exception table needs to be sorted so that the binary 50 * search that we use to find entries in it works properly. 51 * This is used both for the kernel exception table and for 52 * the exception tables of modules that get loaded. 53 */ 54 static int cmp_ex(const void *a, const void *b) 55 { 56 const struct exception_table_entry *x = a, *y = b; 57 58 /* avoid overflow */ 59 if (ex_to_insn(x) > ex_to_insn(y)) 60 return 1; 61 if (ex_to_insn(x) < ex_to_insn(y)) 62 return -1; 63 return 0; 64 } 65 66 void sort_extable(struct exception_table_entry *start, 67 struct exception_table_entry *finish) 68 { 69 sort(start, finish - start, sizeof(struct exception_table_entry), 70 cmp_ex, swap_ex); 71 } 72 73 #ifdef CONFIG_MODULES 74 /* 75 * If the exception table is sorted, any referring to the module init 76 * will be at the beginning or the end. 77 */ 78 void trim_init_extable(struct module *m) 79 { 80 /*trim the beginning*/ 81 while (m->num_exentries && 82 within_module_init(ex_to_insn(&m->extable[0]), m)) { 83 m->extable++; 84 m->num_exentries--; 85 } 86 /*trim the end*/ 87 while (m->num_exentries && 88 within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]), 89 m)) 90 m->num_exentries--; 91 } 92 #endif /* CONFIG_MODULES */ 93 #endif /* !ARCH_HAS_SORT_EXTABLE */ 94 95 #ifndef ARCH_HAS_SEARCH_EXTABLE 96 /* 97 * Search one exception table for an entry corresponding to the 98 * given instruction address, and return the address of the entry, 99 * or NULL if none is found. 100 * We use a binary search, and thus we assume that the table is 101 * already sorted. 102 */ 103 const struct exception_table_entry * 104 search_extable(const struct exception_table_entry *first, 105 const struct exception_table_entry *last, 106 unsigned long value) 107 { 108 while (first <= last) { 109 const struct exception_table_entry *mid; 110 111 mid = ((last - first) >> 1) + first; 112 /* 113 * careful, the distance between value and insn 114 * can be larger than MAX_LONG: 115 */ 116 if (ex_to_insn(mid) < value) 117 first = mid + 1; 118 else if (ex_to_insn(mid) > value) 119 last = mid - 1; 120 else 121 return mid; 122 } 123 return NULL; 124 } 125 #endif 126