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