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  */
check_exception_ranges(unsigned long addr)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 *
search_extable(const struct exception_table_entry * first,const struct exception_table_entry * last,unsigned long value)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 
fixup_exception(struct pt_regs * regs)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 }
83