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/bsearch.h>
  14 #include <linux/rwsem.h>
  15 #include <linux/extable.h>
  16 #include <linux/uaccess.h>
  17
  18 extern unsigned long copy_user_memcpy, copy_user_memcpy_end;
  19 extern void __copy_user_fixup(void);
  20
  21 static const struct exception_table_entry __copy_user_fixup_ex = {
  22         .fixup = (unsigned long)&__copy_user_fixup,
  23 };
  24
  25 /*
  26  * Some functions that may trap due to a bad user-mode address have too
  27  * many loads and stores in them to make it at all practical to label
  28  * each one and put them all in the main exception table.
  29  *
  30  * In particular, the fast memcpy routine is like this.  It's fix-up is
  31  * just to fall back to a slow byte-at-a-time copy, which is handled the
  32  * conventional way.  So it's functionally OK to just handle any trap
  33  * occurring in the fast memcpy with that fixup.
  34  */
  35 static const struct exception_table_entry *check_exception_ranges(unsigned long addr)
  36 {
  37         if ((addr >= (unsigned long)&copy_user_memcpy) &&
  38             (addr <= (unsigned long)&copy_user_memcpy_end))
  39                 return &__copy_user_fixup_ex;
  40
  41         return NULL;
  42 }
  43
  44 static int cmp_ex_search(const void *key, const void *elt)
  45 {
  46         const struct exception_table_entry *_elt = elt;
  47         unsigned long _key = *(unsigned long *)key;
  48
  49         /* avoid overflow */
  50         if (_key > _elt->insn)
  51                 return 1;
  52         if (_key < _elt->insn)
  53                 return -1;
  54         return 0;
  55 }
  56
  57 /* Simple binary search */
  58 const struct exception_table_entry *
  59 search_extable(const struct exception_table_entry *base,
  60                  const size_t num,
  61                  unsigned long value)
  62 {
  63         const struct exception_table_entry *mid;
  64
  65         mid = check_exception_ranges(value);
  66         if (mid)
  67                 return mid;
  68
  69         return bsearch(&value, base, num,
  70                        sizeof(struct exception_table_entry), cmp_ex_search);
  71 }
  72
  73 int fixup_exception(struct pt_regs *regs)
  74 {
  75         const struct exception_table_entry *fixup;
  76
  77         fixup = search_exception_tables(regs->pc);
  78         if (fixup) {
  79                 regs->pc = fixup->fixup;
  80                 return 1;
  81         }
  82
  83         return 0;
  84 }