lib/extable.c

   1 /*
   2  * lib/extable.c
   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  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the License, or (at your option) any later version.
  11  */
  12
  13 #include <linux/config.h>
  14 #include <linux/module.h>
  15 #include <linux/init.h>
  16 #include <linux/sort.h>
  17 #include <asm/uaccess.h>
  18
  19 extern struct exception_table_entry __start___ex_table[];
  20 extern struct exception_table_entry __stop___ex_table[];
  21
  22 #ifndef ARCH_HAS_SORT_EXTABLE
  23 /*
  24  * The exception table needs to be sorted so that the binary
  25  * search that we use to find entries in it works properly.
  26  * This is used both for the kernel exception table and for
  27  * the exception tables of modules that get loaded.
  28  */
  29 static int cmp_ex(const void *a, const void *b)
  30 {
  31         const struct exception_table_entry *x = a, *y = b;
  32
  33         /* avoid overflow */
  34         if (x->insn > y->insn)
  35                 return 1;
  36         if (x->insn < y->insn)
  37                 return -1;
  38         return 0;
  39 }
  40
  41 void sort_extable(struct exception_table_entry *start,
  42                   struct exception_table_entry *finish)
  43 {
  44         sort(start, finish - start, sizeof(struct exception_table_entry),
  45              cmp_ex, NULL);
  46 }
  47 #endif
  48
  49 #ifndef ARCH_HAS_SEARCH_EXTABLE
  50 /*
  51  * Search one exception table for an entry corresponding to the
  52  * given instruction address, and return the address of the entry,
  53  * or NULL if none is found.
  54  * We use a binary search, and thus we assume that the table is
  55  * already sorted.
  56  */
  57 const struct exception_table_entry *
  58 search_extable(const struct exception_table_entry *first,
  59                const struct exception_table_entry *last,
  60                unsigned long value)
  61 {
  62         while (first <= last) {
  63                 const struct exception_table_entry *mid;
  64
  65                 mid = (last - first) / 2 + first;
  66                 /*
  67                  * careful, the distance between entries can be
  68                  * larger than 2GB:
  69                  */
  70                 if (mid->insn < value)
  71                         first = mid + 1;
  72                 else if (mid->insn > value)
  73                         last = mid - 1;
  74                 else
  75                         return mid;
  76         }
  77         return NULL;
  78 }
  79 #endif