arch/sh/mm/extable_64.c

   1 /*
   2  * arch/sh/mm/extable_64.c
   3  *
   4  * Copyright (C) 2003 Richard Curnow
   5  * Copyright (C) 2003, 2004  Paul Mundt
   6  *
   7  * Cloned from the 2.5 SH version..
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file "COPYING" in the main directory of this archive
  11  * for more details.
  12  */
  13 #include <linux/rwsem.h>
  14 #include <linux/module.h>
  15 #include <asm/uaccess.h>
  16
  17 extern unsigned long copy_user_memcpy, copy_user_memcpy_end;
  18 extern void __copy_user_fixup(void);
  19
  20 static const struct exception_table_entry __copy_user_fixup_ex = {
  21         .fixup = (unsigned long)&__copy_user_fixup,
  22 };
  23
  24 /*
  25  * Some functions that may trap due to a bad user-mode address have too
  26  * many loads and stores in them to make it at all practical to label
  27  * each one and put them all in the main exception table.
  28  *
  29  * In particular, the fast memcpy routine is like this.  It's fix-up is
  30  * just to fall back to a slow byte-at-a-time copy, which is handled the
  31  * conventional way.  So it's functionally OK to just handle any trap
  32  * occurring in the fast memcpy with that fixup.
  33  */
  34 static const struct exception_table_entry *check_exception_ranges(unsigned long addr)
  35 {
  36         if ((addr >= (unsigned long)&copy_user_memcpy) &&
  37             (addr <= (unsigned long)&copy_user_memcpy_end))
  38                 return &__copy_user_fixup_ex;
  39
  40         return NULL;
  41 }
  42
  43 /* Simple binary search */
  44 const struct exception_table_entry *
  45 search_extable(const struct exception_table_entry *first,
  46                  const struct exception_table_entry *last,
  47                  unsigned long value)
  48 {
  49         const struct exception_table_entry *mid;
  50
  51         mid = check_exception_ranges(value);
  52         if (mid)
  53                 return mid;
  54
  55         while (first <= last) {
  56                 long diff;
  57
  58                 mid = (last - first) / 2 + first;
  59                 diff = mid->insn - value;
  60                 if (diff == 0)
  61                         return mid;
  62                 else if (diff < 0)
  63                         first = mid+1;
  64                 else
  65                         last = mid-1;
  66         }
  67
  68         return NULL;
  69 }
  70
  71 int fixup_exception(struct pt_regs *regs)
  72 {
  73         const struct exception_table_entry *fixup;
  74
  75         fixup = search_exception_tables(regs->pc);
  76         if (fixup) {
  77                 regs->pc = fixup->fixup;
  78                 return 1;
  79         }
  80
  81         return 0;
  82 }