xref: /openbmc/linux/arch/x86/lib/copy_user_64.S (revision 95db3b25) 
1/*
2 * Copyright 2008 Vitaly Mayatskikh <vmayatsk@redhat.com>
3 * Copyright 2002 Andi Kleen, SuSE Labs.
4 * Subject to the GNU Public License v2.
5 *
6 * Functions to copy from and to user space.
7 */
8
9#include <linux/linkage.h>
10#include <asm/current.h>
11#include <asm/asm-offsets.h>
12#include <asm/thread_info.h>
13#include <asm/cpufeatures.h>
14#include <asm/alternative-asm.h>
15#include <asm/asm.h>
16#include <asm/smap.h>
17
18/* Standard copy_to_user with segment limit checking */
19ENTRY(_copy_to_user)
20	GET_THREAD_INFO(%rax)
21	movq %rdi,%rcx
22	addq %rdx,%rcx
23	jc bad_to_user
24	cmpq TI_addr_limit(%rax),%rcx
25	ja bad_to_user
26	ALTERNATIVE_2 "jmp copy_user_generic_unrolled",		\
27		      "jmp copy_user_generic_string",		\
28		      X86_FEATURE_REP_GOOD,			\
29		      "jmp copy_user_enhanced_fast_string",	\
30		      X86_FEATURE_ERMS
31ENDPROC(_copy_to_user)
32
33/* Standard copy_from_user with segment limit checking */
34ENTRY(_copy_from_user)
35	GET_THREAD_INFO(%rax)
36	movq %rsi,%rcx
37	addq %rdx,%rcx
38	jc bad_from_user
39	cmpq TI_addr_limit(%rax),%rcx
40	ja bad_from_user
41	ALTERNATIVE_2 "jmp copy_user_generic_unrolled",		\
42		      "jmp copy_user_generic_string",		\
43		      X86_FEATURE_REP_GOOD,			\
44		      "jmp copy_user_enhanced_fast_string",	\
45		      X86_FEATURE_ERMS
46ENDPROC(_copy_from_user)
47
48	.section .fixup,"ax"
49	/* must zero dest */
50ENTRY(bad_from_user)
51bad_from_user:
52	movl %edx,%ecx
53	xorl %eax,%eax
54	rep
55	stosb
56bad_to_user:
57	movl %edx,%eax
58	ret
59ENDPROC(bad_from_user)
60	.previous
61
62/*
63 * copy_user_generic_unrolled - memory copy with exception handling.
64 * This version is for CPUs like P4 that don't have efficient micro
65 * code for rep movsq
66 *
67 * Input:
68 * rdi destination
69 * rsi source
70 * rdx count
71 *
72 * Output:
73 * eax uncopied bytes or 0 if successful.
74 */
75ENTRY(copy_user_generic_unrolled)
76	ASM_STAC
77	cmpl $8,%edx
78	jb 20f		/* less then 8 bytes, go to byte copy loop */
79	ALIGN_DESTINATION
80	movl %edx,%ecx
81	andl $63,%edx
82	shrl $6,%ecx
83	jz 17f
841:	movq (%rsi),%r8
852:	movq 1*8(%rsi),%r9
863:	movq 2*8(%rsi),%r10
874:	movq 3*8(%rsi),%r11
885:	movq %r8,(%rdi)
896:	movq %r9,1*8(%rdi)
907:	movq %r10,2*8(%rdi)
918:	movq %r11,3*8(%rdi)
929:	movq 4*8(%rsi),%r8
9310:	movq 5*8(%rsi),%r9
9411:	movq 6*8(%rsi),%r10
9512:	movq 7*8(%rsi),%r11
9613:	movq %r8,4*8(%rdi)
9714:	movq %r9,5*8(%rdi)
9815:	movq %r10,6*8(%rdi)
9916:	movq %r11,7*8(%rdi)
100	leaq 64(%rsi),%rsi
101	leaq 64(%rdi),%rdi
102	decl %ecx
103	jnz 1b
10417:	movl %edx,%ecx
105	andl $7,%edx
106	shrl $3,%ecx
107	jz 20f
10818:	movq (%rsi),%r8
10919:	movq %r8,(%rdi)
110	leaq 8(%rsi),%rsi
111	leaq 8(%rdi),%rdi
112	decl %ecx
113	jnz 18b
11420:	andl %edx,%edx
115	jz 23f
116	movl %edx,%ecx
11721:	movb (%rsi),%al
11822:	movb %al,(%rdi)
119	incq %rsi
120	incq %rdi
121	decl %ecx
122	jnz 21b
12323:	xor %eax,%eax
124	ASM_CLAC
125	ret
126
127	.section .fixup,"ax"
12830:	shll $6,%ecx
129	addl %ecx,%edx
130	jmp 60f
13140:	leal (%rdx,%rcx,8),%edx
132	jmp 60f
13350:	movl %ecx,%edx
13460:	jmp copy_user_handle_tail /* ecx is zerorest also */
135	.previous
136
137	_ASM_EXTABLE(1b,30b)
138	_ASM_EXTABLE(2b,30b)
139	_ASM_EXTABLE(3b,30b)
140	_ASM_EXTABLE(4b,30b)
141	_ASM_EXTABLE(5b,30b)
142	_ASM_EXTABLE(6b,30b)
143	_ASM_EXTABLE(7b,30b)
144	_ASM_EXTABLE(8b,30b)
145	_ASM_EXTABLE(9b,30b)
146	_ASM_EXTABLE(10b,30b)
147	_ASM_EXTABLE(11b,30b)
148	_ASM_EXTABLE(12b,30b)
149	_ASM_EXTABLE(13b,30b)
150	_ASM_EXTABLE(14b,30b)
151	_ASM_EXTABLE(15b,30b)
152	_ASM_EXTABLE(16b,30b)
153	_ASM_EXTABLE(18b,40b)
154	_ASM_EXTABLE(19b,40b)
155	_ASM_EXTABLE(21b,50b)
156	_ASM_EXTABLE(22b,50b)
157ENDPROC(copy_user_generic_unrolled)
158
159/* Some CPUs run faster using the string copy instructions.
160 * This is also a lot simpler. Use them when possible.
161 *
162 * Only 4GB of copy is supported. This shouldn't be a problem
163 * because the kernel normally only writes from/to page sized chunks
164 * even if user space passed a longer buffer.
165 * And more would be dangerous because both Intel and AMD have
166 * errata with rep movsq > 4GB. If someone feels the need to fix
167 * this please consider this.
168 *
169 * Input:
170 * rdi destination
171 * rsi source
172 * rdx count
173 *
174 * Output:
175 * eax uncopied bytes or 0 if successful.
176 */
177ENTRY(copy_user_generic_string)
178	ASM_STAC
179	cmpl $8,%edx
180	jb 2f		/* less than 8 bytes, go to byte copy loop */
181	ALIGN_DESTINATION
182	movl %edx,%ecx
183	shrl $3,%ecx
184	andl $7,%edx
1851:	rep
186	movsq
1872:	movl %edx,%ecx
1883:	rep
189	movsb
190	xorl %eax,%eax
191	ASM_CLAC
192	ret
193
194	.section .fixup,"ax"
19511:	leal (%rdx,%rcx,8),%ecx
19612:	movl %ecx,%edx		/* ecx is zerorest also */
197	jmp copy_user_handle_tail
198	.previous
199
200	_ASM_EXTABLE(1b,11b)
201	_ASM_EXTABLE(3b,12b)
202ENDPROC(copy_user_generic_string)
203
204/*
205 * Some CPUs are adding enhanced REP MOVSB/STOSB instructions.
206 * It's recommended to use enhanced REP MOVSB/STOSB if it's enabled.
207 *
208 * Input:
209 * rdi destination
210 * rsi source
211 * rdx count
212 *
213 * Output:
214 * eax uncopied bytes or 0 if successful.
215 */
216ENTRY(copy_user_enhanced_fast_string)
217	ASM_STAC
218	movl %edx,%ecx
2191:	rep
220	movsb
221	xorl %eax,%eax
222	ASM_CLAC
223	ret
224
225	.section .fixup,"ax"
22612:	movl %ecx,%edx		/* ecx is zerorest also */
227	jmp copy_user_handle_tail
228	.previous
229
230	_ASM_EXTABLE(1b,12b)
231ENDPROC(copy_user_enhanced_fast_string)
232
233/*
234 * copy_user_nocache - Uncached memory copy with exception handling
235 * This will force destination out of cache for more performance.
236 *
237 * Note: Cached memory copy is used when destination or size is not
238 * naturally aligned. That is:
239 *  - Require 8-byte alignment when size is 8 bytes or larger.
240 *  - Require 4-byte alignment when size is 4 bytes.
241 */
242ENTRY(__copy_user_nocache)
243	ASM_STAC
244
245	/* If size is less than 8 bytes, go to 4-byte copy */
246	cmpl $8,%edx
247	jb .L_4b_nocache_copy_entry
248
249	/* If destination is not 8-byte aligned, "cache" copy to align it */
250	ALIGN_DESTINATION
251
252	/* Set 4x8-byte copy count and remainder */
253	movl %edx,%ecx
254	andl $63,%edx
255	shrl $6,%ecx
256	jz .L_8b_nocache_copy_entry	/* jump if count is 0 */
257
258	/* Perform 4x8-byte nocache loop-copy */
259.L_4x8b_nocache_copy_loop:
2601:	movq (%rsi),%r8
2612:	movq 1*8(%rsi),%r9
2623:	movq 2*8(%rsi),%r10
2634:	movq 3*8(%rsi),%r11
2645:	movnti %r8,(%rdi)
2656:	movnti %r9,1*8(%rdi)
2667:	movnti %r10,2*8(%rdi)
2678:	movnti %r11,3*8(%rdi)
2689:	movq 4*8(%rsi),%r8
26910:	movq 5*8(%rsi),%r9
27011:	movq 6*8(%rsi),%r10
27112:	movq 7*8(%rsi),%r11
27213:	movnti %r8,4*8(%rdi)
27314:	movnti %r9,5*8(%rdi)
27415:	movnti %r10,6*8(%rdi)
27516:	movnti %r11,7*8(%rdi)
276	leaq 64(%rsi),%rsi
277	leaq 64(%rdi),%rdi
278	decl %ecx
279	jnz .L_4x8b_nocache_copy_loop
280
281	/* Set 8-byte copy count and remainder */
282.L_8b_nocache_copy_entry:
283	movl %edx,%ecx
284	andl $7,%edx
285	shrl $3,%ecx
286	jz .L_4b_nocache_copy_entry	/* jump if count is 0 */
287
288	/* Perform 8-byte nocache loop-copy */
289.L_8b_nocache_copy_loop:
29020:	movq (%rsi),%r8
29121:	movnti %r8,(%rdi)
292	leaq 8(%rsi),%rsi
293	leaq 8(%rdi),%rdi
294	decl %ecx
295	jnz .L_8b_nocache_copy_loop
296
297	/* If no byte left, we're done */
298.L_4b_nocache_copy_entry:
299	andl %edx,%edx
300	jz .L_finish_copy
301
302	/* If destination is not 4-byte aligned, go to byte copy: */
303	movl %edi,%ecx
304	andl $3,%ecx
305	jnz .L_1b_cache_copy_entry
306
307	/* Set 4-byte copy count (1 or 0) and remainder */
308	movl %edx,%ecx
309	andl $3,%edx
310	shrl $2,%ecx
311	jz .L_1b_cache_copy_entry	/* jump if count is 0 */
312
313	/* Perform 4-byte nocache copy: */
31430:	movl (%rsi),%r8d
31531:	movnti %r8d,(%rdi)
316	leaq 4(%rsi),%rsi
317	leaq 4(%rdi),%rdi
318
319	/* If no bytes left, we're done: */
320	andl %edx,%edx
321	jz .L_finish_copy
322
323	/* Perform byte "cache" loop-copy for the remainder */
324.L_1b_cache_copy_entry:
325	movl %edx,%ecx
326.L_1b_cache_copy_loop:
32740:	movb (%rsi),%al
32841:	movb %al,(%rdi)
329	incq %rsi
330	incq %rdi
331	decl %ecx
332	jnz .L_1b_cache_copy_loop
333
334	/* Finished copying; fence the prior stores */
335.L_finish_copy:
336	xorl %eax,%eax
337	ASM_CLAC
338	sfence
339	ret
340
341	.section .fixup,"ax"
342.L_fixup_4x8b_copy:
343	shll $6,%ecx
344	addl %ecx,%edx
345	jmp .L_fixup_handle_tail
346.L_fixup_8b_copy:
347	lea (%rdx,%rcx,8),%rdx
348	jmp .L_fixup_handle_tail
349.L_fixup_4b_copy:
350	lea (%rdx,%rcx,4),%rdx
351	jmp .L_fixup_handle_tail
352.L_fixup_1b_copy:
353	movl %ecx,%edx
354.L_fixup_handle_tail:
355	sfence
356	jmp copy_user_handle_tail
357	.previous
358
359	_ASM_EXTABLE(1b,.L_fixup_4x8b_copy)
360	_ASM_EXTABLE(2b,.L_fixup_4x8b_copy)
361	_ASM_EXTABLE(3b,.L_fixup_4x8b_copy)
362	_ASM_EXTABLE(4b,.L_fixup_4x8b_copy)
363	_ASM_EXTABLE(5b,.L_fixup_4x8b_copy)
364	_ASM_EXTABLE(6b,.L_fixup_4x8b_copy)
365	_ASM_EXTABLE(7b,.L_fixup_4x8b_copy)
366	_ASM_EXTABLE(8b,.L_fixup_4x8b_copy)
367	_ASM_EXTABLE(9b,.L_fixup_4x8b_copy)
368	_ASM_EXTABLE(10b,.L_fixup_4x8b_copy)
369	_ASM_EXTABLE(11b,.L_fixup_4x8b_copy)
370	_ASM_EXTABLE(12b,.L_fixup_4x8b_copy)
371	_ASM_EXTABLE(13b,.L_fixup_4x8b_copy)
372	_ASM_EXTABLE(14b,.L_fixup_4x8b_copy)
373	_ASM_EXTABLE(15b,.L_fixup_4x8b_copy)
374	_ASM_EXTABLE(16b,.L_fixup_4x8b_copy)
375	_ASM_EXTABLE(20b,.L_fixup_8b_copy)
376	_ASM_EXTABLE(21b,.L_fixup_8b_copy)
377	_ASM_EXTABLE(30b,.L_fixup_4b_copy)
378	_ASM_EXTABLE(31b,.L_fixup_4b_copy)
379	_ASM_EXTABLE(40b,.L_fixup_1b_copy)
380	_ASM_EXTABLE(41b,.L_fixup_1b_copy)
381ENDPROC(__copy_user_nocache)
382