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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 <asm/asmmacro.h>
58#include <asm/core.h>
59
60 .text
61ENTRY(__xtensa_copy_user)
62
63#if !XCHAL_HAVE_LOOPS && defined(__XTENSA_CALL0_ABI__)
64#define STACK_SIZE 4
65#else
66#define STACK_SIZE 0
67#endif
68 abi_entry(STACK_SIZE)
69 # a2/ dst, a3/ src, a4/ len
70 mov a5, a2 # copy dst so that a2 is return value
71 mov a11, a4 # preserve original len for error case
72.Lcommon:
73 bbsi.l a2, 0, .Ldst1mod2 # if dst is 1 mod 2
74 bbsi.l a2, 1, .Ldst2mod4 # if dst is 2 mod 4
75.Ldstaligned: # return here from .Ldstunaligned when dst is aligned
76 srli a7, a4, 4 # number of loop iterations with 16B
77 # per iteration
78 movi a8, 3 # if source is also aligned,
79 bnone a3, a8, .Laligned # then use word copy
80 __ssa8 a3 # set shift amount from byte offset
81 bnez a4, .Lsrcunaligned
82 movi a2, 0 # return success for len==0
83 abi_ret(STACK_SIZE)
84
85/*
86 * Destination is unaligned
87 */
88
89.Ldst1mod2: # dst is only byte aligned
90 bltui a4, 7, .Lbytecopy # do short copies byte by byte
91
92 # copy 1 byte
93EX(10f) l8ui a6, a3, 0
94 addi a3, a3, 1
95EX(10f) s8i a6, a5, 0
96 addi a5, a5, 1
97 addi a4, a4, -1
98 bbci.l a5, 1, .Ldstaligned # if dst is now aligned, then
99 # return to main algorithm
100.Ldst2mod4: # dst 16-bit aligned
101 # copy 2 bytes
102 bltui a4, 6, .Lbytecopy # do short copies byte by byte
103EX(10f) l8ui a6, a3, 0
104EX(10f) l8ui a7, a3, 1
105 addi a3, a3, 2
106EX(10f) s8i a6, a5, 0
107EX(10f) s8i a7, a5, 1
108 addi a5, a5, 2
109 addi a4, a4, -2
110 j .Ldstaligned # dst is now aligned, return to main algorithm
111
112/*
113 * Byte by byte copy
114 */
115 .align 4
116 .byte 0 # 1 mod 4 alignment for LOOPNEZ
117 # (0 mod 4 alignment for LBEG)
118.Lbytecopy:
119#if XCHAL_HAVE_LOOPS
120 loopnez a4, .Lbytecopydone
121#else /* !XCHAL_HAVE_LOOPS */
122 beqz a4, .Lbytecopydone
123 add a7, a3, a4 # a7 = end address for source
124#endif /* !XCHAL_HAVE_LOOPS */
125.Lnextbyte:
126EX(10f) l8ui a6, a3, 0
127 addi a3, a3, 1
128EX(10f) s8i a6, a5, 0
129 addi a5, a5, 1
130#if !XCHAL_HAVE_LOOPS
131 blt a3, a7, .Lnextbyte
132#endif /* !XCHAL_HAVE_LOOPS */
133.Lbytecopydone:
134 movi a2, 0 # return success for len bytes copied
135 abi_ret(STACK_SIZE)
136
137/*
138 * Destination and source are word-aligned.
139 */
140 # copy 16 bytes per iteration for word-aligned dst and word-aligned src
141 .align 4 # 1 mod 4 alignment for LOOPNEZ
142 .byte 0 # (0 mod 4 alignment for LBEG)
143.Laligned:
144#if XCHAL_HAVE_LOOPS
145 loopnez a7, .Loop1done
146#else /* !XCHAL_HAVE_LOOPS */
147 beqz a7, .Loop1done
148 slli a8, a7, 4
149 add a8, a8, a3 # a8 = end of last 16B source chunk
150#endif /* !XCHAL_HAVE_LOOPS */
151.Loop1:
152EX(10f) l32i a6, a3, 0
153EX(10f) l32i a7, a3, 4
154EX(10f) s32i a6, a5, 0
155EX(10f) l32i a6, a3, 8
156EX(10f) s32i a7, a5, 4
157EX(10f) l32i a7, a3, 12
158EX(10f) s32i a6, a5, 8
159 addi a3, a3, 16
160EX(10f) s32i a7, a5, 12
161 addi a5, a5, 16
162#if !XCHAL_HAVE_LOOPS
163 blt a3, a8, .Loop1
164#endif /* !XCHAL_HAVE_LOOPS */
165.Loop1done:
166 bbci.l a4, 3, .L2
167 # copy 8 bytes
168EX(10f) l32i a6, a3, 0
169EX(10f) l32i a7, a3, 4
170 addi a3, a3, 8
171EX(10f) s32i a6, a5, 0
172EX(10f) s32i a7, a5, 4
173 addi a5, a5, 8
174.L2:
175 bbci.l a4, 2, .L3
176 # copy 4 bytes
177EX(10f) l32i a6, a3, 0
178 addi a3, a3, 4
179EX(10f) s32i a6, a5, 0
180 addi a5, a5, 4
181.L3:
182 bbci.l a4, 1, .L4
183 # copy 2 bytes
184EX(10f) l16ui a6, a3, 0
185 addi a3, a3, 2
186EX(10f) s16i a6, a5, 0
187 addi a5, a5, 2
188.L4:
189 bbci.l a4, 0, .L5
190 # copy 1 byte
191EX(10f) l8ui a6, a3, 0
192EX(10f) s8i a6, a5, 0
193.L5:
194 movi a2, 0 # return success for len bytes copied
195 abi_ret(STACK_SIZE)
196
197/*
198 * Destination is aligned, Source is unaligned
199 */
200
201 .align 4
202 .byte 0 # 1 mod 4 alignement for LOOPNEZ
203 # (0 mod 4 alignment for LBEG)
204.Lsrcunaligned:
205 # copy 16 bytes per iteration for word-aligned dst and unaligned src
206 and a10, a3, a8 # save unalignment offset for below
207 sub a3, a3, a10 # align a3 (to avoid sim warnings only; not needed for hardware)
208EX(10f) l32i a6, a3, 0 # load first word
209#if XCHAL_HAVE_LOOPS
210 loopnez a7, .Loop2done
211#else /* !XCHAL_HAVE_LOOPS */
212 beqz a7, .Loop2done
213#if defined(__XTENSA_CALL0_ABI__)
214 s32i a10, a1, 0
215 slli a10, a7, 4
216 add a10, a10, a3 # a10 = end of last 16B source chunk
217#else
218 slli a12, a7, 4
219 add a12, a12, a3 # a12 = end of last 16B source chunk
220#endif
221#endif /* !XCHAL_HAVE_LOOPS */
222.Loop2:
223EX(10f) l32i a7, a3, 4
224EX(10f) l32i a8, a3, 8
225 __src_b a6, a6, a7
226EX(10f) s32i a6, a5, 0
227EX(10f) l32i a9, a3, 12
228 __src_b a7, a7, a8
229EX(10f) s32i a7, a5, 4
230EX(10f) l32i a6, a3, 16
231 __src_b a8, a8, a9
232EX(10f) s32i a8, a5, 8
233 addi a3, a3, 16
234 __src_b a9, a9, a6
235EX(10f) s32i a9, a5, 12
236 addi a5, a5, 16
237#if !XCHAL_HAVE_LOOPS
238#if defined(__XTENSA_CALL0_ABI__)
239 blt a3, a10, .Loop2
240 l32i a10, a1, 0
241#else
242 blt a3, a12, .Loop2
243#endif
244#endif /* !XCHAL_HAVE_LOOPS */
245.Loop2done:
246 bbci.l a4, 3, .L12
247 # copy 8 bytes
248EX(10f) l32i a7, a3, 4
249EX(10f) l32i a8, a3, 8
250 __src_b a6, a6, a7
251EX(10f) s32i a6, a5, 0
252 addi a3, a3, 8
253 __src_b a7, a7, a8
254EX(10f) s32i a7, a5, 4
255 addi a5, a5, 8
256 mov a6, a8
257.L12:
258 bbci.l a4, 2, .L13
259 # copy 4 bytes
260EX(10f) l32i a7, a3, 4
261 addi a3, a3, 4
262 __src_b a6, a6, a7
263EX(10f) s32i a6, a5, 0
264 addi a5, a5, 4
265 mov a6, a7
266.L13:
267 add a3, a3, a10 # readjust a3 with correct misalignment
268 bbci.l a4, 1, .L14
269 # copy 2 bytes
270EX(10f) l8ui a6, a3, 0
271EX(10f) l8ui a7, a3, 1
272 addi a3, a3, 2
273EX(10f) s8i a6, a5, 0
274EX(10f) s8i a7, a5, 1
275 addi a5, a5, 2
276.L14:
277 bbci.l a4, 0, .L15
278 # copy 1 byte
279EX(10f) l8ui a6, a3, 0
280EX(10f) s8i a6, a5, 0
281.L15:
282 movi a2, 0 # return success for len bytes copied
283 abi_ret(STACK_SIZE)
284
285ENDPROC(__xtensa_copy_user)
286EXPORT_SYMBOL(__xtensa_copy_user)
287
288 .section .fixup, "ax"
289 .align 4
290
291/* a2 = original dst; a5 = current dst; a11= original len
292 * bytes_copied = a5 - a2
293 * retval = bytes_not_copied = original len - bytes_copied
294 * retval = a11 - (a5 - a2)
295 */
296
297
29810:
299 sub a2, a5, a2 /* a2 <-- bytes copied */
300 sub a2, a11, a2 /* a2 <-- bytes not copied */
301 abi_ret(STACK_SIZE)