1/*
2 * User memory access support for Hexagon
3 *
4 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 and
8 * only version 2 as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 * 02110-1301, USA.
19 */
20
21#ifndef _ASM_UACCESS_H
22#define _ASM_UACCESS_H
23/*
24 * User space memory access functions
25 */
26#include <linux/sched.h>
27#include <linux/mm.h>
28#include <asm/segment.h>
29#include <asm/sections.h>
30
31/*
32 * access_ok: - Checks if a user space pointer is valid
33 * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE.  Note that
34 *        %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
35 *        to write to a block, it is always safe to read from it.
36 * @addr: User space pointer to start of block to check
37 * @size: Size of block to check
38 *
39 * Context: User context only. This function may sleep if pagefaults are
40 *          enabled.
41 *
42 * Checks if a pointer to a block of memory in user space is valid.
43 *
44 * Returns true (nonzero) if the memory block *may* be valid, false (zero)
45 * if it is definitely invalid.
46 *
47 * User address space in Hexagon, like x86, goes to 0xbfffffff, so the
48 * simple MSB-based tests used by MIPS won't work.  Some further
49 * optimization is probably possible here, but for now, keep it
50 * reasonably simple and not *too* slow.  After all, we've got the
51 * MMU for backup.
52 */
53#define VERIFY_READ     0
54#define VERIFY_WRITE    1
55
56#define __access_ok(addr, size) \
57	((get_fs().seg == KERNEL_DS.seg) || \
58	(((unsigned long)addr < get_fs().seg) && \
59	  (unsigned long)size < (get_fs().seg - (unsigned long)addr)))
60
61/*
62 * When a kernel-mode page fault is taken, the faulting instruction
63 * address is checked against a table of exception_table_entries.
64 * Each entry is a tuple of the address of an instruction that may
65 * be authorized to fault, and the address at which execution should
66 * be resumed instead of the faulting instruction, so as to effect
67 * a workaround.
68 */
69
70/*  Assembly somewhat optimized copy routines  */
71unsigned long __copy_from_user_hexagon(void *to, const void __user *from,
72				     unsigned long n);
73unsigned long __copy_to_user_hexagon(void __user *to, const void *from,
74				   unsigned long n);
75
76#define __copy_from_user(to, from, n) __copy_from_user_hexagon(to, from, n)
77#define __copy_to_user(to, from, n) __copy_to_user_hexagon(to, from, n)
78
79/*
80 * XXX todo: some additonal performance gain is possible by
81 * implementing __copy_to/from_user_inatomic, which is much
82 * like __copy_to/from_user, but performs slightly less checking.
83 */
84
85__kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
86#define __clear_user(a, s) __clear_user_hexagon((a), (s))
87
88#define __strncpy_from_user(dst, src, n) hexagon_strncpy_from_user(dst, src, n)
89
90/*  get around the ifndef in asm-generic/uaccess.h  */
91#define __strnlen_user __strnlen_user
92
93extern long __strnlen_user(const char __user *src, long n);
94
95static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
96					     long n);
97
98#include <asm-generic/uaccess.h>
99
100/*  Todo:  an actual accelerated version of this.  */
101static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
102					     long n)
103{
104	long res = __strnlen_user(src, n);
105
106	/* return from strnlen can't be zero -- that would be rubbish. */
107
108	if (res > n) {
109		copy_from_user(dst, src, n);
110		return n;
111	} else {
112		copy_from_user(dst, src, res);
113		return res-1;
114	}
115}
116
117#endif
118