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1// SPDX-License-Identifier: GPL-2.0-or-later2/*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_EXTABLE16#define ex_to_insn(x) ((x)->insn)17#else18static inline unsigned long ex_to_insn(const struct exception_table_entry *x)19{20 return (unsigned long)&x->insn + x->insn;21}22#endif23 24#ifndef ARCH_HAS_RELATIVE_EXTABLE25#define swap_ex NULL26#else27static 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_fixup37 swap_ex_entry_fixup(x, y, tmp, delta);38#else39 x->fixup = y->fixup + delta;40 y->fixup = tmp.fixup - delta;41#endif42}43#endif /* ARCH_HAS_RELATIVE_EXTABLE */44 45/*46 * The exception table needs to be sorted so that the binary47 * search that we use to find entries in it works properly.48 * This is used both for the kernel exception table and for49 * the exception tables of modules that get loaded.50 */51static 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 63void 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_MODULES71/*72 * If the exception table is sorted, any referring to the module init73 * will be at the beginning or the end.74 */75void 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 91static 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 the106 * 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 is109 * already sorted.110 */111const struct exception_table_entry *112search_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