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1/*
2 * include/asm-xtensa/uaccess.h
3 *
4 * User space memory access functions
5 *
6 * These routines provide basic accessing functions to the user memory
7 * space for the kernel. This header file provides functions such as:
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 * Copyright (C) 2001 - 2005 Tensilica Inc.
14 */
15
16#ifndef _XTENSA_ASM_UACCESS_H
17#define _XTENSA_ASM_UACCESS_H
18
19#include <linux/errno.h>
20#include <asm/types.h>
21
22#define VERIFY_READ 0
23#define VERIFY_WRITE 1
24
25#include <asm/current.h>
26#include <asm/asm-offsets.h>
27#include <asm/processor.h>
28
29/*
30 * These assembly macros mirror the C macros in asm/uaccess.h. They
31 * should always have identical functionality. See
32 * arch/xtensa/kernel/sys.S for usage.
33 */
34
35#define KERNEL_DS 0
36#define USER_DS 1
37
38#define get_ds (KERNEL_DS)
39
40/*
41 * get_fs reads current->thread.current_ds into a register.
42 * On Entry:
43 * <ad> anything
44 * <sp> stack
45 * On Exit:
46 * <ad> contains current->thread.current_ds
47 */
48 .macro get_fs ad, sp
49 GET_CURRENT(\ad,\sp)
50#if THREAD_CURRENT_DS > 1020
51 addi \ad, \ad, TASK_THREAD
52 l32i \ad, \ad, THREAD_CURRENT_DS - TASK_THREAD
53#else
54 l32i \ad, \ad, THREAD_CURRENT_DS
55#endif
56 .endm
57
58/*
59 * set_fs sets current->thread.current_ds to some value.
60 * On Entry:
61 * <at> anything (temp register)
62 * <av> value to write
63 * <sp> stack
64 * On Exit:
65 * <at> destroyed (actually, current)
66 * <av> preserved, value to write
67 */
68 .macro set_fs at, av, sp
69 GET_CURRENT(\at,\sp)
70 s32i \av, \at, THREAD_CURRENT_DS
71 .endm
72
73/*
74 * kernel_ok determines whether we should bypass addr/size checking.
75 * See the equivalent C-macro version below for clarity.
76 * On success, kernel_ok branches to a label indicated by parameter
77 * <success>. This implies that the macro falls through to the next
78 * insruction on an error.
79 *
80 * Note that while this macro can be used independently, we designed
81 * in for optimal use in the access_ok macro below (i.e., we fall
82 * through on error).
83 *
84 * On Entry:
85 * <at> anything (temp register)
86 * <success> label to branch to on success; implies
87 * fall-through macro on error
88 * <sp> stack pointer
89 * On Exit:
90 * <at> destroyed (actually, current->thread.current_ds)
91 */
92
93#if ((KERNEL_DS != 0) || (USER_DS == 0))
94# error Assembly macro kernel_ok fails
95#endif
96 .macro kernel_ok at, sp, success
97 get_fs \at, \sp
98 beqz \at, \success
99 .endm
100
101/*
102 * user_ok determines whether the access to user-space memory is allowed.
103 * See the equivalent C-macro version below for clarity.
104 *
105 * On error, user_ok branches to a label indicated by parameter
106 * <error>. This implies that the macro falls through to the next
107 * instruction on success.
108 *
109 * Note that while this macro can be used independently, we designed
110 * in for optimal use in the access_ok macro below (i.e., we fall
111 * through on success).
112 *
113 * On Entry:
114 * <aa> register containing memory address
115 * <as> register containing memory size
116 * <at> temp register
117 * <error> label to branch to on error; implies fall-through
118 * macro on success
119 * On Exit:
120 * <aa> preserved
121 * <as> preserved
122 * <at> destroyed (actually, (TASK_SIZE + 1 - size))
123 */
124 .macro user_ok aa, as, at, error
125 movi \at, __XTENSA_UL_CONST(TASK_SIZE)
126 bgeu \as, \at, \error
127 sub \at, \at, \as
128 bgeu \aa, \at, \error
129 .endm
130
131/*
132 * access_ok determines whether a memory access is allowed. See the
133 * equivalent C-macro version below for clarity.
134 *
135 * On error, access_ok branches to a label indicated by parameter
136 * <error>. This implies that the macro falls through to the next
137 * instruction on success.
138 *
139 * Note that we assume success is the common case, and we optimize the
140 * branch fall-through case on success.
141 *
142 * On Entry:
143 * <aa> register containing memory address
144 * <as> register containing memory size
145 * <at> temp register
146 * <sp>
147 * <error> label to branch to on error; implies fall-through
148 * macro on success
149 * On Exit:
150 * <aa> preserved
151 * <as> preserved
152 * <at> destroyed
153 */
154 .macro access_ok aa, as, at, sp, error
155 kernel_ok \at, \sp, .Laccess_ok_\@
156 user_ok \aa, \as, \at, \error
157.Laccess_ok_\@:
158 .endm
159
160#endif /* _XTENSA_ASM_UACCESS_H */