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 <asm/uaccess.h>
  17
  18 extern struct exception_table_entry __start___ex_table[];
  19 extern struct exception_table_entry __stop___ex_table[];
  20
  21 #ifndef ARCH_HAS_SORT_EXTABLE
  22 /*
  23  * The exception table needs to be sorted so that the binary
  24  * search that we use to find entries in it works properly.
  25  * This is used both for the kernel exception table and for
  26  * the exception tables of modules that get loaded.
  27  */
  28 void sort_extable(struct exception_table_entry *start,
  29                   struct exception_table_entry *finish)
  30 {
  31         struct exception_table_entry el, *p, *q;
  32
  33         /* insertion sort */
  34         for (p = start + 1; p < finish; ++p) {
  35                 /* start .. p-1 is sorted */
  36                 if (p[0].insn < p[-1].insn) {
  37                         /* move element p down to its right place */
  38                         el = *p;
  39                         q = p;
  40                         do {
  41                                 /* el comes before q[-1], move q[-1] up one */
  42                                 q[0] = q[-1];
  43                                 --q;
  44                         } while (q > start && el.insn < q[-1].insn);
  45                         *q = el;
  46                 }
  47         }
  48 }
  49 #endif
  50
  51 #ifndef ARCH_HAS_SEARCH_EXTABLE
  52 /*
  53  * Search one exception table for an entry corresponding to the
  54  * given instruction address, and return the address of the entry,
  55  * or NULL if none is found.
  56  * We use a binary search, and thus we assume that the table is
  57  * already sorted.
  58  */
  59 const struct exception_table_entry *
  60 search_extable(const struct exception_table_entry *first,
  61                const struct exception_table_entry *last,
  62                unsigned long value)
  63 {
  64         while (first <= last) {
  65                 const struct exception_table_entry *mid;
  66
  67                 mid = (last - first) / 2 + first;
  68                 /*
  69                  * careful, the distance between entries can be
  70                  * larger than 2GB:
  71                  */
  72                 if (mid->insn < value)
  73                         first = mid + 1;
  74                 else if (mid->insn > value)
  75                         last = mid - 1;
  76                 else
  77                         return mid;
  78         }
  79         return NULL;
  80 }
  81 #endif