summaryrefslogtreecommitdiffstats
path: root/arch/x86/lib/copy_user_64.S
blob: d376e4b48f881b89170802ab7b6aa072c458ed8f (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
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
/*
 * Copyright 2008 Vitaly Mayatskikh <vmayatsk@redhat.com>
 * Copyright 2002 Andi Kleen, SuSE Labs.
 * Subject to the GNU Public License v2.
 *
 * Functions to copy from and to user space.
 */

#include <linux/linkage.h>
#include <asm/current.h>
#include <asm/asm-offsets.h>
#include <asm/thread_info.h>
#include <asm/cpufeatures.h>
#include <asm/alternative-asm.h>
#include <asm/asm.h>
#include <asm/smap.h>
#include <asm/export.h>

/* Standard copy_to_user with segment limit checking */
ENTRY(_copy_to_user)
	mov PER_CPU_VAR(current_task), %rax
	movq %rdi,%rcx
	addq %rdx,%rcx
	jc bad_to_user
	cmpq TASK_addr_limit(%rax),%rcx
	ja bad_to_user
	ALTERNATIVE_2 "jmp copy_user_generic_unrolled",		\
		      "jmp copy_user_generic_string",		\
		      X86_FEATURE_REP_GOOD,			\
		      "jmp copy_user_enhanced_fast_string",	\
		      X86_FEATURE_ERMS
ENDPROC(_copy_to_user)
EXPORT_SYMBOL(_copy_to_user)

/* Standard copy_from_user with segment limit checking */
ENTRY(_copy_from_user)
	mov PER_CPU_VAR(current_task), %rax
	movq %rsi,%rcx
	addq %rdx,%rcx
	jc bad_from_user
	cmpq TASK_addr_limit(%rax),%rcx
	ja bad_from_user
	ALTERNATIVE_2 "jmp copy_user_generic_unrolled",		\
		      "jmp copy_user_generic_string",		\
		      X86_FEATURE_REP_GOOD,			\
		      "jmp copy_user_enhanced_fast_string",	\
		      X86_FEATURE_ERMS
ENDPROC(_copy_from_user)
EXPORT_SYMBOL(_copy_from_user)


	.section .fixup,"ax"
	/* must zero dest */
ENTRY(bad_from_user)
bad_from_user:
	movl %edx,%ecx
	xorl %eax,%eax
	rep
	stosb
bad_to_user:
	movl %edx,%eax
	ret
ENDPROC(bad_from_user)
	.previous

/*
 * copy_user_generic_unrolled - memory copy with exception handling.
 * This version is for CPUs like P4 that don't have efficient micro
 * code for rep movsq
 *
 * Input:
 * rdi destination
 * rsi source
 * rdx count
 *
 * Output:
 * eax uncopied bytes or 0 if successful.
 */
ENTRY(copy_user_generic_unrolled)
	ASM_STAC
	cmpl $8,%edx
	jb 20f		/* less then 8 bytes, go to byte copy loop */
	ALIGN_DESTINATION
	movl %edx,%ecx
	andl $63,%edx
	shrl $6,%ecx
	jz 17f
1:	movq (%rsi),%r8
2:	movq 1*8(%rsi),%r9
3:	movq 2*8(%rsi),%r10
4:	movq 3*8(%rsi),%r11
5:	movq %r8,(%rdi)
6:	movq %r9,1*8(%rdi)
7:	movq %r10,2*8(%rdi)
8:	movq %r11,3*8(%rdi)
9:	movq 4*8(%rsi),%r8
10:	movq 5*8(%rsi),%r9
11:	movq 6*8(%rsi),%r10
12:	movq 7*8(%rsi),%r11
13:	movq %r8,4*8(%rdi)
14:	movq %r9,5*8(%rdi)
15:	movq %r10,6*8(%rdi)
16:	movq %r11,7*8(%rdi)
	leaq 64(%rsi),%rsi
	leaq 64(%rdi),%rdi
	decl %ecx
	jnz 1b
17:	movl %edx,%ecx
	andl $7,%edx
	shrl $3,%ecx
	jz 20f
18:	movq (%rsi),%r8
19:	movq %r8,(%rdi)
	leaq 8(%rsi),%rsi
	leaq 8(%rdi),%rdi
	decl %ecx
	jnz 18b
20:	andl %edx,%edx
	jz 23f
	movl %edx,%ecx
21:	movb (%rsi),%al
22:	movb %al,(%rdi)
	incq %rsi
	incq %rdi
	decl %ecx
	jnz 21b
23:	xor %eax,%eax
	ASM_CLAC
	ret

	.section .fixup,"ax"
30:	shll $6,%ecx
	addl %ecx,%edx
	jmp 60f
40:	leal (%rdx,%rcx,8),%edx
	jmp 60f
50:	movl %ecx,%edx
60:	jmp copy_user_handle_tail /* ecx is zerorest also */
	.previous

	_ASM_EXTABLE(1b,30b)
	_ASM_EXTABLE(2b,30b)
	_ASM_EXTABLE(3b,30b)
	_ASM_EXTABLE(4b,30b)
	_ASM_EXTABLE(5b,30b)
	_ASM_EXTABLE(6b,30b)
	_ASM_EXTABLE(7b,30b)
	_ASM_EXTABLE(8b,30b)
	_ASM_EXTABLE(9b,30b)
	_ASM_EXTABLE(10b,30b)
	_ASM_EXTABLE(11b,30b)
	_ASM_EXTABLE(12b,30b)
	_ASM_EXTABLE(13b,30b)
	_ASM_EXTABLE(14b,30b)
	_ASM_EXTABLE(15b,30b)
	_ASM_EXTABLE(16b,30b)
	_ASM_EXTABLE(18b,40b)
	_ASM_EXTABLE(19b,40b)
	_ASM_EXTABLE(21b,50b)
	_ASM_EXTABLE(22b,50b)
ENDPROC(copy_user_generic_unrolled)
EXPORT_SYMBOL(copy_user_generic_unrolled)

/* Some CPUs run faster using the string copy instructions.
 * This is also a lot simpler. Use them when possible.
 *
 * Only 4GB of copy is supported. This shouldn't be a problem
 * because the kernel normally only writes from/to page sized chunks
 * even if user space passed a longer buffer.
 * And more would be dangerous because both Intel and AMD have
 * errata with rep movsq > 4GB. If someone feels the need to fix
 * this please consider this.
 *
 * Input:
 * rdi destination
 * rsi source
 * rdx count
 *
 * Output:
 * eax uncopied bytes or 0 if successful.
 */
ENTRY(copy_user_generic_string)
	ASM_STAC
	cmpl $8,%edx
	jb 2f		/* less than 8 bytes, go to byte copy loop */
	ALIGN_DESTINATION
	movl %edx,%ecx
	shrl $3,%ecx
	andl $7,%edx
1:	rep
	movsq
2:	movl %edx,%ecx
3:	rep
	movsb
	xorl %eax,%eax
	ASM_CLAC
	ret

	.section .fixup,"ax"
11:	leal (%rdx,%rcx,8),%ecx
12:	movl %ecx,%edx		/* ecx is zerorest also */
	jmp copy_user_handle_tail
	.previous

	_ASM_EXTABLE(1b,11b)
	_ASM_EXTABLE(3b,12b)
ENDPROC(copy_user_generic_string)
EXPORT_SYMBOL(copy_user_generic_string)

/*
 * Some CPUs are adding enhanced REP MOVSB/STOSB instructions.
 * It's recommended to use enhanced REP MOVSB/STOSB if it's enabled.
 *
 * Input:
 * rdi destination
 * rsi source
 * rdx count
 *
 * Output:
 * eax uncopied bytes or 0 if successful.
 */
ENTRY(copy_user_enhanced_fast_string)
	ASM_STAC
	movl %edx,%ecx
1:	rep
	movsb
	xorl %eax,%eax
	ASM_CLAC
	ret

	.section .fixup,"ax"
12:	movl %ecx,%edx		/* ecx is zerorest also */
	jmp copy_user_handle_tail
	.previous

	_ASM_EXTABLE(1b,12b)
ENDPROC(copy_user_enhanced_fast_string)
EXPORT_SYMBOL(copy_user_enhanced_fast_string)

/*
 * copy_user_nocache - Uncached memory copy with exception handling
 * This will force destination out of cache for more performance.
 *
 * Note: Cached memory copy is used when destination or size is not
 * naturally aligned. That is:
 *  - Require 8-byte alignment when size is 8 bytes or larger.
 *  - Require 4-byte alignment when size is 4 bytes.
 */
ENTRY(__copy_user_nocache)
	ASM_STAC

	/* If size is less than 8 bytes, go to 4-byte copy */
	cmpl $8,%edx
	jb .L_4b_nocache_copy_entry

	/* If destination is not 8-byte aligned, "cache" copy to align it */
	ALIGN_DESTINATION

	/* Set 4x8-byte copy count and remainder */
	movl %edx,%ecx
	andl $63,%edx
	shrl $6,%ecx
	jz .L_8b_nocache_copy_entry	/* jump if count is 0 */

	/* Perform 4x8-byte nocache loop-copy */
.L_4x8b_nocache_copy_loop:
1:	movq (%rsi),%r8
2:	movq 1*8(%rsi),%r9
3:	movq 2*8(%rsi),%r10
4:	movq 3*8(%rsi),%r11
5:	movnti %r8,(%rdi)
6:	movnti %r9,1*8(%rdi)
7:	movnti %r10,2*8(%rdi)
8:	movnti %r11,3*8(%rdi)
9:	movq 4*8(%rsi),%r8
10:	movq 5*8(%rsi),%r9
11:	movq 6*8(%rsi),%r10
12:	movq 7*8(%rsi),%r11
13:	movnti %r8,4*8(%rdi)
14:	movnti %r9,5*8(%rdi)
15:	movnti %r10,6*8(%rdi)
16:	movnti %r11,7*8(%rdi)
	leaq 64(%rsi),%rsi
	leaq 64(%rdi),%rdi
	decl %ecx
	jnz .L_4x8b_nocache_copy_loop

	/* Set 8-byte copy count and remainder */
.L_8b_nocache_copy_entry:
	movl %edx,%ecx
	andl $7,%edx
	shrl $3,%ecx
	jz .L_4b_nocache_copy_entry	/* jump if count is 0 */

	/* Perform 8-byte nocache loop-copy */
.L_8b_nocache_copy_loop:
20:	movq (%rsi),%r8
21:	movnti %r8,(%rdi)
	leaq 8(%rsi),%rsi
	leaq 8(%rdi),%rdi
	decl %ecx
	jnz .L_8b_nocache_copy_loop

	/* If no byte left, we're done */
.L_4b_nocache_copy_entry:
	andl %edx,%edx
	jz .L_finish_copy

	/* If destination is not 4-byte aligned, go to byte copy: */
	movl %edi,%ecx
	andl $3,%ecx
	jnz .L_1b_cache_copy_entry

	/* Set 4-byte copy count (1 or 0) and remainder */
	movl %edx,%ecx
	andl $3,%edx
	shrl $2,%ecx
	jz .L_1b_cache_copy_entry	/* jump if count is 0 */

	/* Perform 4-byte nocache copy: */
30:	movl (%rsi),%r8d
31:	movnti %r8d,(%rdi)
	leaq 4(%rsi),%rsi
	leaq 4(%rdi),%rdi

	/* If no bytes left, we're done: */
	andl %edx,%edx
	jz .L_finish_copy

	/* Perform byte "cache" loop-copy for the remainder */
.L_1b_cache_copy_entry:
	movl %edx,%ecx
.L_1b_cache_copy_loop:
40:	movb (%rsi),%al
41:	movb %al,(%rdi)
	incq %rsi
	incq %rdi
	decl %ecx
	jnz .L_1b_cache_copy_loop

	/* Finished copying; fence the prior stores */
.L_finish_copy:
	xorl %eax,%eax
	ASM_CLAC
	sfence
	ret

	.section .fixup,"ax"
.L_fixup_4x8b_copy:
	shll $6,%ecx
	addl %ecx,%edx
	jmp .L_fixup_handle_tail
.L_fixup_8b_copy:
	lea (%rdx,%rcx,8),%rdx
	jmp .L_fixup_handle_tail
.L_fixup_4b_copy:
	lea (%rdx,%rcx,4),%rdx
	jmp .L_fixup_handle_tail
.L_fixup_1b_copy:
	movl %ecx,%edx
.L_fixup_handle_tail:
	sfence
	jmp copy_user_handle_tail
	.previous

	_ASM_EXTABLE(1b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(2b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(3b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(4b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(5b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(6b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(7b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(8b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(9b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(10b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(11b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(12b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(13b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(14b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(15b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(16b,.L_fixup_4x8b_copy)
	_ASM_EXTABLE(20b,.L_fixup_8b_copy)
	_ASM_EXTABLE(21b,.L_fixup_8b_copy)
	_ASM_EXTABLE(30b,.L_fixup_4b_copy)
	_ASM_EXTABLE(31b,.L_fixup_4b_copy)
	_ASM_EXTABLE(40b,.L_fixup_1b_copy)
	_ASM_EXTABLE(41b,.L_fixup_1b_copy)
ENDPROC(__copy_user_nocache)
EXPORT_SYMBOL(__copy_user_nocache)
OpenPOWER on IntegriCloud