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uaccess.h
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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.
40  *
41  * Checks if a pointer to a block of memory in user space is valid.
42  *
43  * Returns true (nonzero) if the memory block *may* be valid, false (zero)
44  * if it is definitely invalid.
45  *
46  * User address space in Hexagon, like x86, goes to 0xbfffffff, so the
47  * simple MSB-based tests used by MIPS won't work. Some further
48  * optimization is probably possible here, but for now, keep it
49  * reasonably simple and not *too* slow. After all, we've got the
50  * MMU for backup.
51  */
52 #define VERIFY_READ 0
53 #define VERIFY_WRITE 1
54 
55 #define __access_ok(addr, size) \
56  ((get_fs().seg == KERNEL_DS.seg) || \
57  (((unsigned long)addr < get_fs().seg) && \
58  (unsigned long)size < (get_fs().seg - (unsigned long)addr)))
59 
60 /*
61  * When a kernel-mode page fault is taken, the faulting instruction
62  * address is checked against a table of exception_table_entries.
63  * Each entry is a tuple of the address of an instruction that may
64  * be authorized to fault, and the address at which execution should
65  * be resumed instead of the faulting instruction, so as to effect
66  * a workaround.
67  */
68 
69 /* Assembly somewhat optimized copy routines */
70 unsigned long __copy_from_user_hexagon(void *to, const void __user *from,
71  unsigned long n);
72 unsigned long __copy_to_user_hexagon(void __user *to, const void *from,
73  unsigned long n);
74 
75 #define __copy_from_user(to, from, n) __copy_from_user_hexagon(to, from, n)
76 #define __copy_to_user(to, from, n) __copy_to_user_hexagon(to, from, n)
77 
78 /*
79  * XXX todo: some additonal performance gain is possible by
80  * implementing __copy_to/from_user_inatomic, which is much
81  * like __copy_to/from_user, but performs slightly less checking.
82  */
83 
84 __kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
85 #define __clear_user(a, s) __clear_user_hexagon((a), (s))
86 
87 #define __strncpy_from_user(dst, src, n) hexagon_strncpy_from_user(dst, src, n)
88 
89 /* get around the ifndef in asm-generic/uaccess.h */
90 #define __strnlen_user __strnlen_user
91 
92 extern long __strnlen_user(const char __user *src, long n);
93 
94 static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
95  long n);
96 
97 #include <asm-generic/uaccess.h>
98 
99 /* Todo: an actual accelerated version of this. */
100 static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
101  long n)
102 {
103  long res = __strnlen_user(src, n);
104 
105  /* return from strnlen can't be zero -- that would be rubbish. */
106 
107  if (res > n) {
108  copy_from_user(dst, src, n);
109  return n;
110  } else {
111  copy_from_user(dst, src, res);
112  return res-1;
113  }
114 }
115 
116 #endif