summaryrefslogtreecommitdiffstats
path: root/arch/riscv/lib/uaccess.S
blob: 3ab438f30d1328707862134f819e8a74598c6dce (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
#include <linux/linkage.h>
#include <asm-generic/export.h>
#include <asm/asm.h>
#include <asm/asm-extable.h>
#include <asm/csr.h>

	.macro fixup op reg addr lbl
100:
	\op \reg, \addr
	_asm_extable	100b, \lbl
	.endm

SYM_FUNC_START(__asm_copy_to_user)

	/* Enable access to user memory */
	li t6, SR_SUM
	csrs CSR_STATUS, t6

	/*
	 * Save the terminal address which will be used to compute the number
	 * of bytes copied in case of a fixup exception.
	 */
	add	t5, a0, a2

	/*
	 * Register allocation for code below:
	 * a0 - start of uncopied dst
	 * a1 - start of uncopied src
	 * a2 - size
	 * t0 - end of uncopied dst
	 */
	add	t0, a0, a2

	/*
	 * Use byte copy only if too small.
	 * SZREG holds 4 for RV32 and 8 for RV64
	 */
	li	a3, 9*SZREG /* size must be larger than size in word_copy */
	bltu	a2, a3, .Lbyte_copy_tail

	/*
	 * Copy first bytes until dst is aligned to word boundary.
	 * a0 - start of dst
	 * t1 - start of aligned dst
	 */
	addi	t1, a0, SZREG-1
	andi	t1, t1, ~(SZREG-1)
	/* dst is already aligned, skip */
	beq	a0, t1, .Lskip_align_dst
1:
	/* a5 - one byte for copying data */
	fixup lb      a5, 0(a1), 10f
	addi	a1, a1, 1	/* src */
	fixup sb      a5, 0(a0), 10f
	addi	a0, a0, 1	/* dst */
	bltu	a0, t1, 1b	/* t1 - start of aligned dst */

.Lskip_align_dst:
	/*
	 * Now dst is aligned.
	 * Use shift-copy if src is misaligned.
	 * Use word-copy if both src and dst are aligned because
	 * can not use shift-copy which do not require shifting
	 */
	/* a1 - start of src */
	andi	a3, a1, SZREG-1
	bnez	a3, .Lshift_copy

.Lword_copy:
        /*
	 * Both src and dst are aligned, unrolled word copy
	 *
	 * a0 - start of aligned dst
	 * a1 - start of aligned src
	 * t0 - end of aligned dst
	 */
	addi	t0, t0, -(8*SZREG) /* not to over run */
2:
	fixup REG_L   a4,        0(a1), 10f
	fixup REG_L   a5,    SZREG(a1), 10f
	fixup REG_L   a6,  2*SZREG(a1), 10f
	fixup REG_L   a7,  3*SZREG(a1), 10f
	fixup REG_L   t1,  4*SZREG(a1), 10f
	fixup REG_L   t2,  5*SZREG(a1), 10f
	fixup REG_L   t3,  6*SZREG(a1), 10f
	fixup REG_L   t4,  7*SZREG(a1), 10f
	fixup REG_S   a4,        0(a0), 10f
	fixup REG_S   a5,    SZREG(a0), 10f
	fixup REG_S   a6,  2*SZREG(a0), 10f
	fixup REG_S   a7,  3*SZREG(a0), 10f
	fixup REG_S   t1,  4*SZREG(a0), 10f
	fixup REG_S   t2,  5*SZREG(a0), 10f
	fixup REG_S   t3,  6*SZREG(a0), 10f
	fixup REG_S   t4,  7*SZREG(a0), 10f
	addi	a0, a0, 8*SZREG
	addi	a1, a1, 8*SZREG
	bltu	a0, t0, 2b

	addi	t0, t0, 8*SZREG /* revert to original value */
	j	.Lbyte_copy_tail

.Lshift_copy:

	/*
	 * Word copy with shifting.
	 * For misaligned copy we still perform aligned word copy, but
	 * we need to use the value fetched from the previous iteration and
	 * do some shifts.
	 * This is safe because reading is less than a word size.
	 *
	 * a0 - start of aligned dst
	 * a1 - start of src
	 * a3 - a1 & mask:(SZREG-1)
	 * t0 - end of uncopied dst
	 * t1 - end of aligned dst
	 */
	/* calculating aligned word boundary for dst */
	andi	t1, t0, ~(SZREG-1)
	/* Converting unaligned src to aligned src */
	andi	a1, a1, ~(SZREG-1)

	/*
	 * Calculate shifts
	 * t3 - prev shift
	 * t4 - current shift
	 */
	slli	t3, a3, 3 /* converting bytes in a3 to bits */
	li	a5, SZREG*8
	sub	t4, a5, t3

	/* Load the first word to combine with second word */
	fixup REG_L   a5, 0(a1), 10f

3:
	/* Main shifting copy
	 *
	 * a0 - start of aligned dst
	 * a1 - start of aligned src
	 * t1 - end of aligned dst
	 */

	/* At least one iteration will be executed */
	srl	a4, a5, t3
	fixup REG_L   a5, SZREG(a1), 10f
	addi	a1, a1, SZREG
	sll	a2, a5, t4
	or	a2, a2, a4
	fixup REG_S   a2, 0(a0), 10f
	addi	a0, a0, SZREG
	bltu	a0, t1, 3b

	/* Revert src to original unaligned value  */
	add	a1, a1, a3

.Lbyte_copy_tail:
	/*
	 * Byte copy anything left.
	 *
	 * a0 - start of remaining dst
	 * a1 - start of remaining src
	 * t0 - end of remaining dst
	 */
	bgeu	a0, t0, .Lout_copy_user  /* check if end of copy */
4:
	fixup lb      a5, 0(a1), 10f
	addi	a1, a1, 1	/* src */
	fixup sb      a5, 0(a0), 10f
	addi	a0, a0, 1	/* dst */
	bltu	a0, t0, 4b	/* t0 - end of dst */

.Lout_copy_user:
	/* Disable access to user memory */
	csrc CSR_STATUS, t6
	li	a0, 0
	ret

	/* Exception fixup code */
10:
	/* Disable access to user memory */
	csrc CSR_STATUS, t6
	sub a0, t5, a0
	ret
SYM_FUNC_END(__asm_copy_to_user)
EXPORT_SYMBOL(__asm_copy_to_user)
SYM_FUNC_ALIAS(__asm_copy_from_user, __asm_copy_to_user)
EXPORT_SYMBOL(__asm_copy_from_user)


SYM_FUNC_START(__clear_user)

	/* Enable access to user memory */
	li t6, SR_SUM
	csrs CSR_STATUS, t6

	add a3, a0, a1
	addi t0, a0, SZREG-1
	andi t1, a3, ~(SZREG-1)
	andi t0, t0, ~(SZREG-1)
	/*
	 * a3: terminal address of target region
	 * t0: lowest doubleword-aligned address in target region
	 * t1: highest doubleword-aligned address in target region
	 */
	bgeu t0, t1, 2f
	bltu a0, t0, 4f
1:
	fixup REG_S, zero, (a0), 11f
	addi a0, a0, SZREG
	bltu a0, t1, 1b
2:
	bltu a0, a3, 5f

3:
	/* Disable access to user memory */
	csrc CSR_STATUS, t6
	li a0, 0
	ret
4: /* Edge case: unalignment */
	fixup sb, zero, (a0), 11f
	addi a0, a0, 1
	bltu a0, t0, 4b
	j 1b
5: /* Edge case: remainder */
	fixup sb, zero, (a0), 11f
	addi a0, a0, 1
	bltu a0, a3, 5b
	j 3b

	/* Exception fixup code */
11:
	/* Disable access to user memory */
	csrc CSR_STATUS, t6
	sub a0, a3, a0
	ret
SYM_FUNC_END(__clear_user)
EXPORT_SYMBOL(__clear_user)