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 <asm/uaccess.h> 16 17 #ifndef ARCH_HAS_SORT_EXTABLE 18 /* 19 * The exception table needs to be sorted so that the binary 20 * search that we use to find entries in it works properly. 21 * This is used both for the kernel exception table and for 22 * the exception tables of modules that get loaded. 23 */ 24 static int cmp_ex(const void *a, const void *b) 25 { 26 const struct exception_table_entry *x = a, *y = b; 27 28 /* avoid overflow */ 29 if (x->insn > y->insn) 30 return 1; 31 if (x->insn < y->insn) 32 return -1; 33 return 0; 34 } 35 36 void sort_extable(struct exception_table_entry *start, 37 struct exception_table_entry *finish) 38 { 39 sort(start, finish - start, sizeof(struct exception_table_entry), 40 cmp_ex, NULL); 41 } 42 43 #ifdef CONFIG_MODULES 44 /* 45 * If the exception table is sorted, any referring to the module init 46 * will be at the beginning or the end. 47 */ 48 void trim_init_extable(struct module *m) 49 { 50 /*trim the beginning*/ 51 while (m->num_exentries && within_module_init(m->extable[0].insn, m)) { 52 m->extable++; 53 m->num_exentries--; 54 } 55 /*trim the end*/ 56 while (m->num_exentries && 57 within_module_init(m->extable[m->num_exentries-1].insn, m)) 58 m->num_exentries--; 59 } 60 #endif /* CONFIG_MODULES */ 61 #endif /* !ARCH_HAS_SORT_EXTABLE */ 62 63 #ifndef ARCH_HAS_SEARCH_EXTABLE 64 /* 65 * Search one exception table for an entry corresponding to the 66 * given instruction address, and return the address of the entry, 67 * or NULL if none is found. 68 * We use a binary search, and thus we assume that the table is 69 * already sorted. 70 */ 71 const struct exception_table_entry * 72 search_extable(const struct exception_table_entry *first, 73 const struct exception_table_entry *last, 74 unsigned long value) 75 { 76 while (first <= last) { 77 const struct exception_table_entry *mid; 78 79 mid = ((last - first) >> 1) + first; 80 /* 81 * careful, the distance between value and insn 82 * can be larger than MAX_LONG: 83 */ 84 if (mid->insn < value) 85 first = mid + 1; 86 else if (mid->insn > value) 87 last = mid - 1; 88 else 89 return mid; 90 } 91 return NULL; 92 } 93 #endif 94