1/*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Unified implementation of memcpy, memmove and the __copy_user backend.
7 *
8 * Copyright (C) 1998, 99, 2000, 01, 2002 Ralf Baechle (ralf@gnu.org)
9 * Copyright (C) 1999, 2000, 01, 2002 Silicon Graphics, Inc.
10 * Copyright (C) 2002 Broadcom, Inc.
11 * memcpy/copy_user author: Mark Vandevoorde
12 *
13 * Mnemonic names for arguments to memcpy/__copy_user
14 */
15
16#include <linux/export.h>
17#include <asm/asm.h>
18#include <asm/asm-offsets.h>
19#include <asm/regdef.h>
20
21#define dst a0
22#define src a1
23#define len a2
24
25/*
26 * Spec
27 *
28 * memcpy copies len bytes from src to dst and sets v0 to dst.
29 * It assumes that
30 * - src and dst don't overlap
31 * - src is readable
32 * - dst is writable
33 * memcpy uses the standard calling convention
34 *
35 * __copy_user copies up to len bytes from src to dst and sets a2 (len) to
36 * the number of uncopied bytes due to an exception caused by a read or write.
37 * __copy_user assumes that src and dst don't overlap, and that the call is
38 * implementing one of the following:
39 * copy_to_user
40 * - src is readable (no exceptions when reading src)
41 * copy_from_user
42 * - dst is writable (no exceptions when writing dst)
43 * __copy_user uses a non-standard calling convention; see
44 * arch/mips/include/asm/uaccess.h
45 *
46 * When an exception happens on a load, the handler must
47 # ensure that all of the destination buffer is overwritten to prevent
48 * leaking information to user mode programs.
49 */
50
51/*
52 * Implementation
53 */
54
55/*
56 * The exception handler for loads requires that:
57 * 1- AT contain the address of the byte just past the end of the source
58 * of the copy,
59 * 2- src_entry <= src < AT, and
60 * 3- (dst - src) == (dst_entry - src_entry),
61 * The _entry suffix denotes values when __copy_user was called.
62 *
63 * (1) is set up up by uaccess.h and maintained by not writing AT in copy_user
64 * (2) is met by incrementing src by the number of bytes copied
65 * (3) is met by not doing loads between a pair of increments of dst and src
66 *
67 * The exception handlers for stores adjust len (if necessary) and return.
68 * These handlers do not need to overwrite any data.
69 *
70 * For __rmemcpy and memmove an exception is always a kernel bug, therefore
71 * they're not protected.
72 */
73
74#define EXC(inst_reg,addr,handler) \
759: inst_reg, addr; \
76 .section __ex_table,"a"; \
77 PTR_WD 9b, handler; \
78 .previous
79
80/*
81 * Only on the 64-bit kernel we can made use of 64-bit registers.
82 */
83
84#define LOAD ld
85#define LOADL ldl
86#define LOADR ldr
87#define STOREL sdl
88#define STORER sdr
89#define STORE sd
90#define ADD daddu
91#define SUB dsubu
92#define SRL dsrl
93#define SRA dsra
94#define SLL dsll
95#define SLLV dsllv
96#define SRLV dsrlv
97#define NBYTES 8
98#define LOG_NBYTES 3
99
100/*
101 * As we are sharing code base with the mips32 tree (which use the o32 ABI
102 * register definitions). We need to redefine the register definitions from
103 * the n64 ABI register naming to the o32 ABI register naming.
104 */
105#undef t0
106#undef t1
107#undef t2
108#undef t3
109#define t0 $8
110#define t1 $9
111#define t2 $10
112#define t3 $11
113#define t4 $12
114#define t5 $13
115#define t6 $14
116#define t7 $15
117
118#ifdef CONFIG_CPU_LITTLE_ENDIAN
119#define LDFIRST LOADR
120#define LDREST LOADL
121#define STFIRST STORER
122#define STREST STOREL
123#define SHIFT_DISCARD SLLV
124#else
125#define LDFIRST LOADL
126#define LDREST LOADR
127#define STFIRST STOREL
128#define STREST STORER
129#define SHIFT_DISCARD SRLV
130#endif
131
132#define FIRST(unit) ((unit)*NBYTES)
133#define REST(unit) (FIRST(unit)+NBYTES-1)
134#define UNIT(unit) FIRST(unit)
135
136#define ADDRMASK (NBYTES-1)
137
138 .text
139 .set noreorder
140 .set noat
141
142/*
143 * A combined memcpy/__copy_user
144 * __copy_user sets len to 0 for success; else to an upper bound of
145 * the number of uncopied bytes.
146 * memcpy sets v0 to dst.
147 */
148 .align 5
149LEAF(memcpy) /* a0=dst a1=src a2=len */
150EXPORT_SYMBOL(memcpy)
151 move v0, dst /* return value */
152__memcpy:
153FEXPORT(__raw_copy_from_user)
154EXPORT_SYMBOL(__raw_copy_from_user)
155FEXPORT(__raw_copy_to_user)
156EXPORT_SYMBOL(__raw_copy_to_user)
157 /*
158 * Note: dst & src may be unaligned, len may be 0
159 * Temps
160 */
161 #
162 # Octeon doesn't care if the destination is unaligned. The hardware
163 # can fix it faster than we can special case the assembly.
164 #
165 pref 0, 0(src)
166 sltu t0, len, NBYTES # Check if < 1 word
167 bnez t0, copy_bytes_checklen
168 and t0, src, ADDRMASK # Check if src unaligned
169 bnez t0, src_unaligned
170 sltu t0, len, 4*NBYTES # Check if < 4 words
171 bnez t0, less_than_4units
172 sltu t0, len, 8*NBYTES # Check if < 8 words
173 bnez t0, less_than_8units
174 sltu t0, len, 16*NBYTES # Check if < 16 words
175 bnez t0, cleanup_both_aligned
176 sltu t0, len, 128+1 # Check if len < 129
177 bnez t0, 1f # Skip prefetch if len is too short
178 sltu t0, len, 256+1 # Check if len < 257
179 bnez t0, 1f # Skip prefetch if len is too short
180 pref 0, 128(src) # We must not prefetch invalid addresses
181 #
182 # This is where we loop if there is more than 128 bytes left
1832: pref 0, 256(src) # We must not prefetch invalid addresses
184 #
185 # This is where we loop if we can't prefetch anymore
1861:
187EXC( LOAD t0, UNIT(0)(src), l_exc)
188EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
189EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
190EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
191 SUB len, len, 16*NBYTES
192EXC( STORE t0, UNIT(0)(dst), s_exc_p16u)
193EXC( STORE t1, UNIT(1)(dst), s_exc_p15u)
194EXC( STORE t2, UNIT(2)(dst), s_exc_p14u)
195EXC( STORE t3, UNIT(3)(dst), s_exc_p13u)
196EXC( LOAD t0, UNIT(4)(src), l_exc_copy)
197EXC( LOAD t1, UNIT(5)(src), l_exc_copy)
198EXC( LOAD t2, UNIT(6)(src), l_exc_copy)
199EXC( LOAD t3, UNIT(7)(src), l_exc_copy)
200EXC( STORE t0, UNIT(4)(dst), s_exc_p12u)
201EXC( STORE t1, UNIT(5)(dst), s_exc_p11u)
202EXC( STORE t2, UNIT(6)(dst), s_exc_p10u)
203 ADD src, src, 16*NBYTES
204EXC( STORE t3, UNIT(7)(dst), s_exc_p9u)
205 ADD dst, dst, 16*NBYTES
206EXC( LOAD t0, UNIT(-8)(src), l_exc_copy_rewind16)
207EXC( LOAD t1, UNIT(-7)(src), l_exc_copy_rewind16)
208EXC( LOAD t2, UNIT(-6)(src), l_exc_copy_rewind16)
209EXC( LOAD t3, UNIT(-5)(src), l_exc_copy_rewind16)
210EXC( STORE t0, UNIT(-8)(dst), s_exc_p8u)
211EXC( STORE t1, UNIT(-7)(dst), s_exc_p7u)
212EXC( STORE t2, UNIT(-6)(dst), s_exc_p6u)
213EXC( STORE t3, UNIT(-5)(dst), s_exc_p5u)
214EXC( LOAD t0, UNIT(-4)(src), l_exc_copy_rewind16)
215EXC( LOAD t1, UNIT(-3)(src), l_exc_copy_rewind16)
216EXC( LOAD t2, UNIT(-2)(src), l_exc_copy_rewind16)
217EXC( LOAD t3, UNIT(-1)(src), l_exc_copy_rewind16)
218EXC( STORE t0, UNIT(-4)(dst), s_exc_p4u)
219EXC( STORE t1, UNIT(-3)(dst), s_exc_p3u)
220EXC( STORE t2, UNIT(-2)(dst), s_exc_p2u)
221EXC( STORE t3, UNIT(-1)(dst), s_exc_p1u)
222 sltu t0, len, 256+1 # See if we can prefetch more
223 beqz t0, 2b
224 sltu t0, len, 128 # See if we can loop more time
225 beqz t0, 1b
226 nop
227 #
228 # Jump here if there are less than 16*NBYTES left.
229 #
230cleanup_both_aligned:
231 beqz len, done
232 sltu t0, len, 8*NBYTES
233 bnez t0, less_than_8units
234 nop
235EXC( LOAD t0, UNIT(0)(src), l_exc)
236EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
237EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
238EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
239 SUB len, len, 8*NBYTES
240EXC( STORE t0, UNIT(0)(dst), s_exc_p8u)
241EXC( STORE t1, UNIT(1)(dst), s_exc_p7u)
242EXC( STORE t2, UNIT(2)(dst), s_exc_p6u)
243EXC( STORE t3, UNIT(3)(dst), s_exc_p5u)
244EXC( LOAD t0, UNIT(4)(src), l_exc_copy)
245EXC( LOAD t1, UNIT(5)(src), l_exc_copy)
246EXC( LOAD t2, UNIT(6)(src), l_exc_copy)
247EXC( LOAD t3, UNIT(7)(src), l_exc_copy)
248EXC( STORE t0, UNIT(4)(dst), s_exc_p4u)
249EXC( STORE t1, UNIT(5)(dst), s_exc_p3u)
250EXC( STORE t2, UNIT(6)(dst), s_exc_p2u)
251EXC( STORE t3, UNIT(7)(dst), s_exc_p1u)
252 ADD src, src, 8*NBYTES
253 beqz len, done
254 ADD dst, dst, 8*NBYTES
255 #
256 # Jump here if there are less than 8*NBYTES left.
257 #
258less_than_8units:
259 sltu t0, len, 4*NBYTES
260 bnez t0, less_than_4units
261 nop
262EXC( LOAD t0, UNIT(0)(src), l_exc)
263EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
264EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
265EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
266 SUB len, len, 4*NBYTES
267EXC( STORE t0, UNIT(0)(dst), s_exc_p4u)
268EXC( STORE t1, UNIT(1)(dst), s_exc_p3u)
269EXC( STORE t2, UNIT(2)(dst), s_exc_p2u)
270EXC( STORE t3, UNIT(3)(dst), s_exc_p1u)
271 ADD src, src, 4*NBYTES
272 beqz len, done
273 ADD dst, dst, 4*NBYTES
274 #
275 # Jump here if there are less than 4*NBYTES left. This means
276 # we may need to copy up to 3 NBYTES words.
277 #
278less_than_4units:
279 sltu t0, len, 1*NBYTES
280 bnez t0, copy_bytes_checklen
281 nop
282 #
283 # 1) Copy NBYTES, then check length again
284 #
285EXC( LOAD t0, 0(src), l_exc)
286 SUB len, len, NBYTES
287 sltu t1, len, 8
288EXC( STORE t0, 0(dst), s_exc_p1u)
289 ADD src, src, NBYTES
290 bnez t1, copy_bytes_checklen
291 ADD dst, dst, NBYTES
292 #
293 # 2) Copy NBYTES, then check length again
294 #
295EXC( LOAD t0, 0(src), l_exc)
296 SUB len, len, NBYTES
297 sltu t1, len, 8
298EXC( STORE t0, 0(dst), s_exc_p1u)
299 ADD src, src, NBYTES
300 bnez t1, copy_bytes_checklen
301 ADD dst, dst, NBYTES
302 #
303 # 3) Copy NBYTES, then check length again
304 #
305EXC( LOAD t0, 0(src), l_exc)
306 SUB len, len, NBYTES
307 ADD src, src, NBYTES
308 ADD dst, dst, NBYTES
309 b copy_bytes_checklen
310EXC( STORE t0, -8(dst), s_exc_p1u)
311
312src_unaligned:
313#define rem t8
314 SRL t0, len, LOG_NBYTES+2 # +2 for 4 units/iter
315 beqz t0, cleanup_src_unaligned
316 and rem, len, (4*NBYTES-1) # rem = len % 4*NBYTES
3171:
318/*
319 * Avoid consecutive LD*'s to the same register since some mips
320 * implementations can't issue them in the same cycle.
321 * It's OK to load FIRST(N+1) before REST(N) because the two addresses
322 * are to the same unit (unless src is aligned, but it's not).
323 */
324EXC( LDFIRST t0, FIRST(0)(src), l_exc)
325EXC( LDFIRST t1, FIRST(1)(src), l_exc_copy)
326 SUB len, len, 4*NBYTES
327EXC( LDREST t0, REST(0)(src), l_exc_copy)
328EXC( LDREST t1, REST(1)(src), l_exc_copy)
329EXC( LDFIRST t2, FIRST(2)(src), l_exc_copy)
330EXC( LDFIRST t3, FIRST(3)(src), l_exc_copy)
331EXC( LDREST t2, REST(2)(src), l_exc_copy)
332EXC( LDREST t3, REST(3)(src), l_exc_copy)
333 ADD src, src, 4*NBYTES
334EXC( STORE t0, UNIT(0)(dst), s_exc_p4u)
335EXC( STORE t1, UNIT(1)(dst), s_exc_p3u)
336EXC( STORE t2, UNIT(2)(dst), s_exc_p2u)
337EXC( STORE t3, UNIT(3)(dst), s_exc_p1u)
338 bne len, rem, 1b
339 ADD dst, dst, 4*NBYTES
340
341cleanup_src_unaligned:
342 beqz len, done
343 and rem, len, NBYTES-1 # rem = len % NBYTES
344 beq rem, len, copy_bytes
345 nop
3461:
347EXC( LDFIRST t0, FIRST(0)(src), l_exc)
348EXC( LDREST t0, REST(0)(src), l_exc_copy)
349 SUB len, len, NBYTES
350EXC( STORE t0, 0(dst), s_exc_p1u)
351 ADD src, src, NBYTES
352 bne len, rem, 1b
353 ADD dst, dst, NBYTES
354
355copy_bytes_checklen:
356 beqz len, done
357 nop
358copy_bytes:
359 /* 0 < len < NBYTES */
360#define COPY_BYTE(N) \
361EXC( lb t0, N(src), l_exc); \
362 SUB len, len, 1; \
363 beqz len, done; \
364EXC( sb t0, N(dst), s_exc_p1)
365
366 COPY_BYTE(0)
367 COPY_BYTE(1)
368 COPY_BYTE(2)
369 COPY_BYTE(3)
370 COPY_BYTE(4)
371 COPY_BYTE(5)
372EXC( lb t0, NBYTES-2(src), l_exc)
373 SUB len, len, 1
374 jr ra
375EXC( sb t0, NBYTES-2(dst), s_exc_p1)
376done:
377 jr ra
378 nop
379 END(memcpy)
380
381l_exc_copy_rewind16:
382 /* Rewind src and dst by 16*NBYTES for l_exc_copy */
383 SUB src, src, 16*NBYTES
384 SUB dst, dst, 16*NBYTES
385l_exc_copy:
386 /*
387 * Copy bytes from src until faulting load address (or until a
388 * lb faults)
389 *
390 * When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
391 * may be more than a byte beyond the last address.
392 * Hence, the lb below may get an exception.
393 *
394 * Assumes src < THREAD_BUADDR($28)
395 */
396 LOAD t0, TI_TASK($28)
397 LOAD t0, THREAD_BUADDR(t0)
3981:
399EXC( lb t1, 0(src), l_exc)
400 ADD src, src, 1
401 sb t1, 0(dst) # can't fault -- we're copy_from_user
402 bne src, t0, 1b
403 ADD dst, dst, 1
404l_exc:
405 LOAD t0, TI_TASK($28)
406 LOAD t0, THREAD_BUADDR(t0) # t0 is just past last good address
407 SUB len, AT, t0 # len number of uncopied bytes
408 jr ra
409 nop
410
411
412#define SEXC(n) \
413s_exc_p ## n ## u: \
414 jr ra; \
415 ADD len, len, n*NBYTES
416
417SEXC(16)
418SEXC(15)
419SEXC(14)
420SEXC(13)
421SEXC(12)
422SEXC(11)
423SEXC(10)
424SEXC(9)
425SEXC(8)
426SEXC(7)
427SEXC(6)
428SEXC(5)
429SEXC(4)
430SEXC(3)
431SEXC(2)
432SEXC(1)
433
434s_exc_p1:
435 jr ra
436 ADD len, len, 1
437s_exc:
438 jr ra
439 nop
440
441 .align 5
442LEAF(memmove)
443EXPORT_SYMBOL(memmove)
444 ADD t0, a0, a2
445 ADD t1, a1, a2
446 sltu t0, a1, t0 # dst + len <= src -> memcpy
447 sltu t1, a0, t1 # dst >= src + len -> memcpy
448 and t0, t1
449 beqz t0, __memcpy
450 move v0, a0 /* return value */
451 beqz a2, r_out
452 END(memmove)
453
454 /* fall through to __rmemcpy */
455LEAF(__rmemcpy) /* a0=dst a1=src a2=len */
456 sltu t0, a1, a0
457 beqz t0, r_end_bytes_up # src >= dst
458 nop
459 ADD a0, a2 # dst = dst + len
460 ADD a1, a2 # src = src + len
461
462r_end_bytes:
463 lb t0, -1(a1)
464 SUB a2, a2, 0x1
465 sb t0, -1(a0)
466 SUB a1, a1, 0x1
467 bnez a2, r_end_bytes
468 SUB a0, a0, 0x1
469
470r_out:
471 jr ra
472 move a2, zero
473
474r_end_bytes_up:
475 lb t0, (a1)
476 SUB a2, a2, 0x1
477 sb t0, (a0)
478 ADD a1, a1, 0x1
479 bnez a2, r_end_bytes_up
480 ADD a0, a0, 0x1
481
482 jr ra
483 move a2, zero
484 END(__rmemcpy)
485

source code of linux/arch/mips/cavium-octeon/octeon-memcpy.S