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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 | |
4b3f686d | 8 | * of the Xtensa link-time HAL, and those files may differ per |
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9 | * processor configuration. Patching the kernel for another |
10 | * processor configuration includes replacing the hal files, and we | |
4b3f686d | 11 | * could lose the special functionality for accessing user-space |
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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 | ||
367b8112 | 56 | #include <variant/core.h> |
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57 | |
58 | #ifdef __XTENSA_EB__ | |
59 | #define ALIGN(R, W0, W1) src R, W0, W1 | |
60 | #define SSA8(R) ssa8b R | |
61 | #else | |
62 | #define ALIGN(R, W0, W1) src R, W1, W0 | |
63 | #define SSA8(R) ssa8l R | |
64 | #endif | |
65 | ||
66 | /* Load or store instructions that may cause exceptions use the EX macro. */ | |
67 | ||
68 | #define EX(insn,reg1,reg2,offset,handler) \ | |
69 | 9: insn reg1, reg2, offset; \ | |
70 | .section __ex_table, "a"; \ | |
71 | .word 9b, handler; \ | |
72 | .previous | |
73 | ||
74 | ||
75 | .text | |
76 | .align 4 | |
77 | .global __xtensa_copy_user | |
78 | .type __xtensa_copy_user,@function | |
79 | __xtensa_copy_user: | |
80 | entry sp, 16 # minimal stack frame | |
81 | # a2/ dst, a3/ src, a4/ len | |
82 | mov a5, a2 # copy dst so that a2 is return value | |
83 | mov a11, a4 # preserve original len for error case | |
84 | .Lcommon: | |
85 | bbsi.l a2, 0, .Ldst1mod2 # if dst is 1 mod 2 | |
86 | bbsi.l a2, 1, .Ldst2mod4 # if dst is 2 mod 4 | |
87 | .Ldstaligned: # return here from .Ldstunaligned when dst is aligned | |
88 | srli a7, a4, 4 # number of loop iterations with 16B | |
89 | # per iteration | |
90 | movi a8, 3 # if source is also aligned, | |
91 | bnone a3, a8, .Laligned # then use word copy | |
92 | SSA8( a3) # set shift amount from byte offset | |
93 | bnez a4, .Lsrcunaligned | |
94 | movi a2, 0 # return success for len==0 | |
95 | retw | |
96 | ||
97 | /* | |
98 | * Destination is unaligned | |
99 | */ | |
100 | ||
101 | .Ldst1mod2: # dst is only byte aligned | |
102 | bltui a4, 7, .Lbytecopy # do short copies byte by byte | |
103 | ||
104 | # copy 1 byte | |
105 | EX(l8ui, a6, a3, 0, l_fixup) | |
106 | addi a3, a3, 1 | |
107 | EX(s8i, a6, a5, 0, s_fixup) | |
108 | addi a5, a5, 1 | |
109 | addi a4, a4, -1 | |
110 | bbci.l a5, 1, .Ldstaligned # if dst is now aligned, then | |
111 | # return to main algorithm | |
112 | .Ldst2mod4: # dst 16-bit aligned | |
113 | # copy 2 bytes | |
114 | bltui a4, 6, .Lbytecopy # do short copies byte by byte | |
115 | EX(l8ui, a6, a3, 0, l_fixup) | |
116 | EX(l8ui, a7, a3, 1, l_fixup) | |
117 | addi a3, a3, 2 | |
118 | EX(s8i, a6, a5, 0, s_fixup) | |
119 | EX(s8i, a7, a5, 1, s_fixup) | |
120 | addi a5, a5, 2 | |
121 | addi a4, a4, -2 | |
122 | j .Ldstaligned # dst is now aligned, return to main algorithm | |
123 | ||
124 | /* | |
125 | * Byte by byte copy | |
126 | */ | |
127 | .align 4 | |
128 | .byte 0 # 1 mod 4 alignment for LOOPNEZ | |
129 | # (0 mod 4 alignment for LBEG) | |
130 | .Lbytecopy: | |
131 | #if XCHAL_HAVE_LOOPS | |
132 | loopnez a4, .Lbytecopydone | |
133 | #else /* !XCHAL_HAVE_LOOPS */ | |
134 | beqz a4, .Lbytecopydone | |
135 | add a7, a3, a4 # a7 = end address for source | |
136 | #endif /* !XCHAL_HAVE_LOOPS */ | |
137 | .Lnextbyte: | |
138 | EX(l8ui, a6, a3, 0, l_fixup) | |
139 | addi a3, a3, 1 | |
140 | EX(s8i, a6, a5, 0, s_fixup) | |
141 | addi a5, a5, 1 | |
142 | #if !XCHAL_HAVE_LOOPS | |
143 | blt a3, a7, .Lnextbyte | |
144 | #endif /* !XCHAL_HAVE_LOOPS */ | |
145 | .Lbytecopydone: | |
146 | movi a2, 0 # return success for len bytes copied | |
147 | retw | |
148 | ||
149 | /* | |
150 | * Destination and source are word-aligned. | |
151 | */ | |
152 | # copy 16 bytes per iteration for word-aligned dst and word-aligned src | |
153 | .align 4 # 1 mod 4 alignment for LOOPNEZ | |
154 | .byte 0 # (0 mod 4 alignment for LBEG) | |
155 | .Laligned: | |
156 | #if XCHAL_HAVE_LOOPS | |
157 | loopnez a7, .Loop1done | |
158 | #else /* !XCHAL_HAVE_LOOPS */ | |
159 | beqz a7, .Loop1done | |
160 | slli a8, a7, 4 | |
161 | add a8, a8, a3 # a8 = end of last 16B source chunk | |
162 | #endif /* !XCHAL_HAVE_LOOPS */ | |
163 | .Loop1: | |
164 | EX(l32i, a6, a3, 0, l_fixup) | |
165 | EX(l32i, a7, a3, 4, l_fixup) | |
166 | EX(s32i, a6, a5, 0, s_fixup) | |
167 | EX(l32i, a6, a3, 8, l_fixup) | |
168 | EX(s32i, a7, a5, 4, s_fixup) | |
169 | EX(l32i, a7, a3, 12, l_fixup) | |
170 | EX(s32i, a6, a5, 8, s_fixup) | |
171 | addi a3, a3, 16 | |
172 | EX(s32i, a7, a5, 12, s_fixup) | |
173 | addi a5, a5, 16 | |
174 | #if !XCHAL_HAVE_LOOPS | |
175 | blt a3, a8, .Loop1 | |
176 | #endif /* !XCHAL_HAVE_LOOPS */ | |
177 | .Loop1done: | |
178 | bbci.l a4, 3, .L2 | |
179 | # copy 8 bytes | |
180 | EX(l32i, a6, a3, 0, l_fixup) | |
181 | EX(l32i, a7, a3, 4, l_fixup) | |
182 | addi a3, a3, 8 | |
183 | EX(s32i, a6, a5, 0, s_fixup) | |
184 | EX(s32i, a7, a5, 4, s_fixup) | |
185 | addi a5, a5, 8 | |
186 | .L2: | |
187 | bbci.l a4, 2, .L3 | |
188 | # copy 4 bytes | |
189 | EX(l32i, a6, a3, 0, l_fixup) | |
190 | addi a3, a3, 4 | |
191 | EX(s32i, a6, a5, 0, s_fixup) | |
192 | addi a5, a5, 4 | |
193 | .L3: | |
194 | bbci.l a4, 1, .L4 | |
195 | # copy 2 bytes | |
196 | EX(l16ui, a6, a3, 0, l_fixup) | |
197 | addi a3, a3, 2 | |
198 | EX(s16i, a6, a5, 0, s_fixup) | |
199 | addi a5, a5, 2 | |
200 | .L4: | |
201 | bbci.l a4, 0, .L5 | |
202 | # copy 1 byte | |
203 | EX(l8ui, a6, a3, 0, l_fixup) | |
204 | EX(s8i, a6, a5, 0, s_fixup) | |
205 | .L5: | |
206 | movi a2, 0 # return success for len bytes copied | |
207 | retw | |
208 | ||
209 | /* | |
210 | * Destination is aligned, Source is unaligned | |
211 | */ | |
212 | ||
213 | .align 4 | |
214 | .byte 0 # 1 mod 4 alignement for LOOPNEZ | |
215 | # (0 mod 4 alignment for LBEG) | |
216 | .Lsrcunaligned: | |
217 | # copy 16 bytes per iteration for word-aligned dst and unaligned src | |
218 | and a10, a3, a8 # save unalignment offset for below | |
219 | sub a3, a3, a10 # align a3 (to avoid sim warnings only; not needed for hardware) | |
220 | EX(l32i, a6, a3, 0, l_fixup) # load first word | |
221 | #if XCHAL_HAVE_LOOPS | |
222 | loopnez a7, .Loop2done | |
223 | #else /* !XCHAL_HAVE_LOOPS */ | |
224 | beqz a7, .Loop2done | |
225 | slli a10, a7, 4 | |
226 | add a10, a10, a3 # a10 = end of last 16B source chunk | |
227 | #endif /* !XCHAL_HAVE_LOOPS */ | |
228 | .Loop2: | |
229 | EX(l32i, a7, a3, 4, l_fixup) | |
230 | EX(l32i, a8, a3, 8, l_fixup) | |
231 | ALIGN( a6, a6, a7) | |
232 | EX(s32i, a6, a5, 0, s_fixup) | |
233 | EX(l32i, a9, a3, 12, l_fixup) | |
234 | ALIGN( a7, a7, a8) | |
235 | EX(s32i, a7, a5, 4, s_fixup) | |
236 | EX(l32i, a6, a3, 16, l_fixup) | |
237 | ALIGN( a8, a8, a9) | |
238 | EX(s32i, a8, a5, 8, s_fixup) | |
239 | addi a3, a3, 16 | |
240 | ALIGN( a9, a9, a6) | |
241 | EX(s32i, a9, a5, 12, s_fixup) | |
242 | addi a5, a5, 16 | |
243 | #if !XCHAL_HAVE_LOOPS | |
244 | blt a3, a10, .Loop2 | |
245 | #endif /* !XCHAL_HAVE_LOOPS */ | |
246 | .Loop2done: | |
247 | bbci.l a4, 3, .L12 | |
248 | # copy 8 bytes | |
249 | EX(l32i, a7, a3, 4, l_fixup) | |
250 | EX(l32i, a8, a3, 8, l_fixup) | |
251 | ALIGN( a6, a6, a7) | |
252 | EX(s32i, a6, a5, 0, s_fixup) | |
253 | addi a3, a3, 8 | |
254 | ALIGN( a7, a7, a8) | |
255 | EX(s32i, a7, a5, 4, s_fixup) | |
256 | addi a5, a5, 8 | |
257 | mov a6, a8 | |
258 | .L12: | |
259 | bbci.l a4, 2, .L13 | |
260 | # copy 4 bytes | |
261 | EX(l32i, a7, a3, 4, l_fixup) | |
262 | addi a3, a3, 4 | |
263 | ALIGN( a6, a6, a7) | |
264 | EX(s32i, a6, a5, 0, s_fixup) | |
265 | addi a5, a5, 4 | |
266 | mov a6, a7 | |
267 | .L13: | |
268 | add a3, a3, a10 # readjust a3 with correct misalignment | |
269 | bbci.l a4, 1, .L14 | |
270 | # copy 2 bytes | |
271 | EX(l8ui, a6, a3, 0, l_fixup) | |
272 | EX(l8ui, a7, a3, 1, l_fixup) | |
273 | addi a3, a3, 2 | |
274 | EX(s8i, a6, a5, 0, s_fixup) | |
275 | EX(s8i, a7, a5, 1, s_fixup) | |
276 | addi a5, a5, 2 | |
277 | .L14: | |
278 | bbci.l a4, 0, .L15 | |
279 | # copy 1 byte | |
280 | EX(l8ui, a6, a3, 0, l_fixup) | |
281 | EX(s8i, a6, a5, 0, s_fixup) | |
282 | .L15: | |
283 | movi a2, 0 # return success for len bytes copied | |
284 | retw | |
285 | ||
286 | ||
287 | .section .fixup, "ax" | |
288 | .align 4 | |
289 | ||
290 | /* a2 = original dst; a5 = current dst; a11= original len | |
291 | * bytes_copied = a5 - a2 | |
292 | * retval = bytes_not_copied = original len - bytes_copied | |
293 | * retval = a11 - (a5 - a2) | |
294 | * | |
295 | * Clearing the remaining pieces of kernel memory plugs security | |
296 | * holes. This functionality is the equivalent of the *_zeroing | |
297 | * functions that some architectures provide. | |
298 | */ | |
299 | ||
300 | .Lmemset: | |
301 | .word memset | |
302 | ||
303 | s_fixup: | |
304 | sub a2, a5, a2 /* a2 <-- bytes copied */ | |
305 | sub a2, a11, a2 /* a2 <-- bytes not copied */ | |
306 | retw | |
307 | ||
308 | l_fixup: | |
309 | sub a2, a5, a2 /* a2 <-- bytes copied */ | |
310 | sub a2, a11, a2 /* a2 <-- bytes not copied == return value */ | |
311 | ||
312 | /* void *memset(void *s, int c, size_t n); */ | |
313 | mov a6, a5 /* s */ | |
314 | movi a7, 0 /* c */ | |
315 | mov a8, a2 /* n */ | |
316 | l32r a4, .Lmemset | |
317 | callx4 a4 | |
318 | /* Ignore memset return value in a6. */ | |
319 | /* a2 still contains bytes not copied. */ | |
320 | retw | |
321 |