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