LXR linux/lib/extable.c

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