LXR linux/lib/extable.c

   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/bsearch.h>
  13#include <linux/module.h>
  14#include <linux/init.h>
  15#include <linux/sort.h>
  16#include <linux/uaccess.h>
  17
  18#ifndef ARCH_HAS_RELATIVE_EXTABLE
  19#define ex_to_insn(x)   ((x)->insn)
  20#else
  21static inline unsigned long ex_to_insn(const struct exception_table_entry *x)
  22{
  23        return (unsigned long)&x->insn + x->insn;
  24}
  25#endif
  26
  27#ifndef ARCH_HAS_SORT_EXTABLE
  28#ifndef ARCH_HAS_RELATIVE_EXTABLE
  29#define swap_ex         NULL
  30#else
  31static void swap_ex(void *a, void *b, int size)
  32{
  33        struct exception_table_entry *x = a, *y = b, tmp;
  34        int delta = b - a;
  35
  36        tmp = *x;
  37        x->insn = y->insn + delta;
  38        y->insn = tmp.insn - delta;
  39
  40#ifdef swap_ex_entry_fixup
  41        swap_ex_entry_fixup(x, y, tmp, delta);
  42#else
  43        x->fixup = y->fixup + delta;
  44        y->fixup = tmp.fixup - delta;
  45#endif
  46}
  47#endif /* ARCH_HAS_RELATIVE_EXTABLE */
  48
  49/*
  50 * The exception table needs to be sorted so that the binary
  51 * search that we use to find entries in it works properly.
  52 * This is used both for the kernel exception table and for
  53 * the exception tables of modules that get loaded.
  54 */
  55static int cmp_ex_sort(const void *a, const void *b)
  56{
  57        const struct exception_table_entry *x = a, *y = b;
  58
  59        /* avoid overflow */
  60        if (ex_to_insn(x) > ex_to_insn(y))
  61                return 1;
  62        if (ex_to_insn(x) < ex_to_insn(y))
  63                return -1;
  64        return 0;
  65}
  66
  67void sort_extable(struct exception_table_entry *start,
  68                  struct exception_table_entry *finish)
  69{
  70        sort(start, finish - start, sizeof(struct exception_table_entry),
  71             cmp_ex_sort, swap_ex);
  72}
  73
  74#ifdef CONFIG_MODULES
  75/*
  76 * If the exception table is sorted, any referring to the module init
  77 * will be at the beginning or the end.
  78 */
  79void trim_init_extable(struct module *m)
  80{
  81        /*trim the beginning*/
  82        while (m->num_exentries &&
  83               within_module_init(ex_to_insn(&m->extable[0]), m)) {
  84                m->extable++;
  85                m->num_exentries--;
  86        }
  87        /*trim the end*/
  88        while (m->num_exentries &&
  89               within_module_init(ex_to_insn(&m->extable[m->num_exentries - 1]),
  90                                  m))
  91                m->num_exentries--;
  92}
  93#endif /* CONFIG_MODULES */
  94#endif /* !ARCH_HAS_SORT_EXTABLE */
  95
  96#ifndef ARCH_HAS_SEARCH_EXTABLE
  97
  98static int cmp_ex_search(const void *key, const void *elt)
  99{
 100        const struct exception_table_entry *_elt = elt;
 101        unsigned long _key = *(unsigned long *)key;
 102
 103        /* avoid overflow */
 104        if (_key > ex_to_insn(_elt))
 105                return 1;
 106        if (_key < ex_to_insn(_elt))
 107                return -1;
 108        return 0;
 109}
 110
 111/*
 112 * Search one exception table for an entry corresponding to the
 113 * given instruction address, and return the address of the entry,
 114 * or NULL if none is found.
 115 * We use a binary search, and thus we assume that the table is
 116 * already sorted.
 117 */
 118const struct exception_table_entry *
 119search_extable(const struct exception_table_entry *base,
 120               const size_t num,
 121               unsigned long value)
 122{
 123        return bsearch(&value, base, num,
 124                       sizeof(struct exception_table_entry), cmp_ex_search);
 125}
 126#endif
 127