xref: /openbmc/linux/arch/xtensa/lib/usercopy.S (revision 9fb29c73) 
1/*
2 *  arch/xtensa/lib/usercopy.S
3 *
4 *  Copy to/from user space (derived from arch/xtensa/lib/hal/memcopy.S)
5 *
6 *  DO NOT COMBINE this function with <arch/xtensa/lib/hal/memcopy.S>.
7 *  It needs to remain separate and distinct.  The hal files are part
8 *  of the Xtensa link-time HAL, and those files may differ per
9 *  processor configuration.  Patching the kernel for another
10 *  processor configuration includes replacing the hal files, and we
11 *  could lose the special functionality for accessing user-space
12 *  memory during such a patch.  We sacrifice a little code space here
13 *  in favor to simplify code maintenance.
14 *
15 *  This file is subject to the terms and conditions of the GNU General
16 *  Public License.  See the file "COPYING" in the main directory of
17 *  this archive for more details.
18 *
19 *  Copyright (C) 2002 Tensilica Inc.
20 */
21
22
23/*
24 * size_t __xtensa_copy_user (void *dst, const void *src, size_t len);
25 *
26 * The returned value is the number of bytes not copied.  Implies zero
27 * is success.
28 *
29 * The general case algorithm is as follows:
30 *   If the destination and source are both aligned,
31 *     do 16B chunks with a loop, and then finish up with
32 *     8B, 4B, 2B, and 1B copies conditional on the length.
33 *   If destination is aligned and source unaligned,
34 *     do the same, but use SRC to align the source data.
35 *   If destination is unaligned, align it by conditionally
36 *     copying 1B and 2B and then retest.
37 *   This code tries to use fall-through braches for the common
38 *     case of aligned destinations (except for the branches to
39 *     the alignment label).
40 *
41 * Register use:
42 *	a0/ return address
43 *	a1/ stack pointer
44 *	a2/ return value
45 *	a3/ src
46 *	a4/ length
47 *	a5/ dst
48 *	a6/ tmp
49 *	a7/ tmp
50 *	a8/ tmp
51 *	a9/ tmp
52 *	a10/ tmp
53 *	a11/ original length
54 */
55
56#include <linux/linkage.h>
57#include <variant/core.h>
58#include <asm/asmmacro.h>
59
60	.text
61ENTRY(__xtensa_copy_user)
62
63	entry	sp, 16		# minimal stack frame
64	# a2/ dst, a3/ src, a4/ len
65	mov	a5, a2		# copy dst so that a2 is return value
66	mov	a11, a4		# preserve original len for error case
67.Lcommon:
68	bbsi.l	a2, 0, .Ldst1mod2 # if dst is 1 mod 2
69	bbsi.l	a2, 1, .Ldst2mod4 # if dst is 2 mod 4
70.Ldstaligned:	# return here from .Ldstunaligned when dst is aligned
71	srli	a7, a4, 4	# number of loop iterations with 16B
72				# per iteration
73	movi	a8, 3		  # if source is also aligned,
74	bnone	a3, a8, .Laligned # then use word copy
75	__ssa8	a3		# set shift amount from byte offset
76	bnez	a4, .Lsrcunaligned
77	movi	a2, 0		# return success for len==0
78	retw
79
80/*
81 * Destination is unaligned
82 */
83
84.Ldst1mod2:	# dst is only byte aligned
85	bltui	a4, 7, .Lbytecopy	# do short copies byte by byte
86
87	# copy 1 byte
88EX(10f)	l8ui	a6, a3, 0
89	addi	a3, a3,  1
90EX(10f)	s8i	a6, a5,  0
91	addi	a5, a5,  1
92	addi	a4, a4, -1
93	bbci.l	a5, 1, .Ldstaligned	# if dst is now aligned, then
94					# return to main algorithm
95.Ldst2mod4:	# dst 16-bit aligned
96	# copy 2 bytes
97	bltui	a4, 6, .Lbytecopy	# do short copies byte by byte
98EX(10f)	l8ui	a6, a3, 0
99EX(10f)	l8ui	a7, a3, 1
100	addi	a3, a3,  2
101EX(10f)	s8i	a6, a5,  0
102EX(10f)	s8i	a7, a5,  1
103	addi	a5, a5,  2
104	addi	a4, a4, -2
105	j	.Ldstaligned	# dst is now aligned, return to main algorithm
106
107/*
108 * Byte by byte copy
109 */
110	.align	4
111	.byte	0		# 1 mod 4 alignment for LOOPNEZ
112				# (0 mod 4 alignment for LBEG)
113.Lbytecopy:
114#if XCHAL_HAVE_LOOPS
115	loopnez	a4, .Lbytecopydone
116#else /* !XCHAL_HAVE_LOOPS */
117	beqz	a4, .Lbytecopydone
118	add	a7, a3, a4	# a7 = end address for source
119#endif /* !XCHAL_HAVE_LOOPS */
120.Lnextbyte:
121EX(10f)	l8ui	a6, a3, 0
122	addi	a3, a3, 1
123EX(10f)	s8i	a6, a5, 0
124	addi	a5, a5, 1
125#if !XCHAL_HAVE_LOOPS
126	blt	a3, a7, .Lnextbyte
127#endif /* !XCHAL_HAVE_LOOPS */
128.Lbytecopydone:
129	movi	a2, 0		# return success for len bytes copied
130	retw
131
132/*
133 * Destination and source are word-aligned.
134 */
135	# copy 16 bytes per iteration for word-aligned dst and word-aligned src
136	.align	4		# 1 mod 4 alignment for LOOPNEZ
137	.byte	0		# (0 mod 4 alignment for LBEG)
138.Laligned:
139#if XCHAL_HAVE_LOOPS
140	loopnez	a7, .Loop1done
141#else /* !XCHAL_HAVE_LOOPS */
142	beqz	a7, .Loop1done
143	slli	a8, a7, 4
144	add	a8, a8, a3	# a8 = end of last 16B source chunk
145#endif /* !XCHAL_HAVE_LOOPS */
146.Loop1:
147EX(10f)	l32i	a6, a3,  0
148EX(10f)	l32i	a7, a3,  4
149EX(10f)	s32i	a6, a5,  0
150EX(10f)	l32i	a6, a3,  8
151EX(10f)	s32i	a7, a5,  4
152EX(10f)	l32i	a7, a3, 12
153EX(10f)	s32i	a6, a5,  8
154	addi	a3, a3, 16
155EX(10f)	s32i	a7, a5, 12
156	addi	a5, a5, 16
157#if !XCHAL_HAVE_LOOPS
158	blt	a3, a8, .Loop1
159#endif /* !XCHAL_HAVE_LOOPS */
160.Loop1done:
161	bbci.l	a4, 3, .L2
162	# copy 8 bytes
163EX(10f)	l32i	a6, a3,  0
164EX(10f)	l32i	a7, a3,  4
165	addi	a3, a3,  8
166EX(10f)	s32i	a6, a5,  0
167EX(10f)	s32i	a7, a5,  4
168	addi	a5, a5,  8
169.L2:
170	bbci.l	a4, 2, .L3
171	# copy 4 bytes
172EX(10f)	l32i	a6, a3,  0
173	addi	a3, a3,  4
174EX(10f)	s32i	a6, a5,  0
175	addi	a5, a5,  4
176.L3:
177	bbci.l	a4, 1, .L4
178	# copy 2 bytes
179EX(10f)	l16ui	a6, a3,  0
180	addi	a3, a3,  2
181EX(10f)	s16i	a6, a5,  0
182	addi	a5, a5,  2
183.L4:
184	bbci.l	a4, 0, .L5
185	# copy 1 byte
186EX(10f)	l8ui	a6, a3,  0
187EX(10f)	s8i	a6, a5,  0
188.L5:
189	movi	a2, 0		# return success for len bytes copied
190	retw
191
192/*
193 * Destination is aligned, Source is unaligned
194 */
195
196	.align	4
197	.byte	0		# 1 mod 4 alignement for LOOPNEZ
198				# (0 mod 4 alignment for LBEG)
199.Lsrcunaligned:
200	# copy 16 bytes per iteration for word-aligned dst and unaligned src
201	and	a10, a3, a8	# save unalignment offset for below
202	sub	a3, a3, a10	# align a3 (to avoid sim warnings only; not needed for hardware)
203EX(10f)	l32i	a6, a3, 0	# load first word
204#if XCHAL_HAVE_LOOPS
205	loopnez	a7, .Loop2done
206#else /* !XCHAL_HAVE_LOOPS */
207	beqz	a7, .Loop2done
208	slli	a12, a7, 4
209	add	a12, a12, a3	# a12 = end of last 16B source chunk
210#endif /* !XCHAL_HAVE_LOOPS */
211.Loop2:
212EX(10f)	l32i	a7, a3,  4
213EX(10f)	l32i	a8, a3,  8
214	__src_b	a6, a6, a7
215EX(10f)	s32i	a6, a5,  0
216EX(10f)	l32i	a9, a3, 12
217	__src_b	a7, a7, a8
218EX(10f)	s32i	a7, a5,  4
219EX(10f)	l32i	a6, a3, 16
220	__src_b	a8, a8, a9
221EX(10f)	s32i	a8, a5,  8
222	addi	a3, a3, 16
223	__src_b	a9, a9, a6
224EX(10f)	s32i	a9, a5, 12
225	addi	a5, a5, 16
226#if !XCHAL_HAVE_LOOPS
227	blt	a3, a12, .Loop2
228#endif /* !XCHAL_HAVE_LOOPS */
229.Loop2done:
230	bbci.l	a4, 3, .L12
231	# copy 8 bytes
232EX(10f)	l32i	a7, a3,  4
233EX(10f)	l32i	a8, a3,  8
234	__src_b	a6, a6, a7
235EX(10f)	s32i	a6, a5,  0
236	addi	a3, a3,  8
237	__src_b	a7, a7, a8
238EX(10f)	s32i	a7, a5,  4
239	addi	a5, a5,  8
240	mov	a6, a8
241.L12:
242	bbci.l	a4, 2, .L13
243	# copy 4 bytes
244EX(10f)	l32i	a7, a3,  4
245	addi	a3, a3,  4
246	__src_b	a6, a6, a7
247EX(10f)	s32i	a6, a5,  0
248	addi	a5, a5,  4
249	mov	a6, a7
250.L13:
251	add	a3, a3, a10	# readjust a3 with correct misalignment
252	bbci.l	a4, 1, .L14
253	# copy 2 bytes
254EX(10f)	l8ui	a6, a3,  0
255EX(10f)	l8ui	a7, a3,  1
256	addi	a3, a3,  2
257EX(10f)	s8i	a6, a5,  0
258EX(10f)	s8i	a7, a5,  1
259	addi	a5, a5,  2
260.L14:
261	bbci.l	a4, 0, .L15
262	# copy 1 byte
263EX(10f)	l8ui	a6, a3,  0
264EX(10f)	s8i	a6, a5,  0
265.L15:
266	movi	a2, 0		# return success for len bytes copied
267	retw
268
269ENDPROC(__xtensa_copy_user)
270
271	.section .fixup, "ax"
272	.align	4
273
274/* a2 = original dst; a5 = current dst; a11= original len
275 * bytes_copied = a5 - a2
276 * retval = bytes_not_copied = original len - bytes_copied
277 * retval = a11 - (a5 - a2)
278 */
279
280
28110:
282	sub	a2, a5, a2	/* a2 <-- bytes copied */
283	sub	a2, a11, a2	/* a2 <-- bytes not copied */
284	retw
285