aboutsummaryrefslogtreecommitdiff
path: root/arch/mips/lib/memcpy.S
blob: a78865f76547848d3cc1a1b495e6a6360dfc79ff (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Unified implementation of memcpy, memmove and the __copy_user backend.
 *
 * Copyright (C) 1998, 99, 2000, 01, 2002 Ralf Baechle (ralf@gnu.org)
 * Copyright (C) 1999, 2000, 01, 2002 Silicon Graphics, Inc.
 * Copyright (C) 2002 Broadcom, Inc.
 *   memcpy/copy_user author: Mark Vandevoorde
 *
 * Mnemonic names for arguments to memcpy/__copy_user
 */
#include <linux/config.h>
#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/regdef.h>

#define dst a0
#define src a1
#define len a2

/*
 * Spec
 *
 * memcpy copies len bytes from src to dst and sets v0 to dst.
 * It assumes that
 *   - src and dst don't overlap
 *   - src is readable
 *   - dst is writable
 * memcpy uses the standard calling convention
 *
 * __copy_user copies up to len bytes from src to dst and sets a2 (len) to
 * the number of uncopied bytes due to an exception caused by a read or write.
 * __copy_user assumes that src and dst don't overlap, and that the call is
 * implementing one of the following:
 *   copy_to_user
 *     - src is readable  (no exceptions when reading src)
 *   copy_from_user
 *     - dst is writable  (no exceptions when writing dst)
 * __copy_user uses a non-standard calling convention; see
 * include/asm-mips/uaccess.h
 *
 * When an exception happens on a load, the handler must
 # ensure that all of the destination buffer is overwritten to prevent
 * leaking information to user mode programs.
 */

/*
 * Implementation
 */

/*
 * The exception handler for loads requires that:
 *  1- AT contain the address of the byte just past the end of the source
 *     of the copy,
 *  2- src_entry <= src < AT, and
 *  3- (dst - src) == (dst_entry - src_entry),
 * The _entry suffix denotes values when __copy_user was called.
 *
 * (1) is set up up by uaccess.h and maintained by not writing AT in copy_user
 * (2) is met by incrementing src by the number of bytes copied
 * (3) is met by not doing loads between a pair of increments of dst and src
 *
 * The exception handlers for stores adjust len (if necessary) and return.
 * These handlers do not need to overwrite any data.
 *
 * For __rmemcpy and memmove an exception is always a kernel bug, therefore
 * they're not protected.
 */

#define EXC(inst_reg,addr,handler)		\
9:	inst_reg, addr;				\
	.section __ex_table,"a";		\
	PTR	9b, handler;			\
	.previous

/*
 * Only on the 64-bit kernel we can made use of 64-bit registers.
 */
#ifdef CONFIG_64BIT
#define USE_DOUBLE
#endif

#ifdef USE_DOUBLE

#define LOAD   ld
#define LOADL  ldl
#define LOADR  ldr
#define STOREL sdl
#define STORER sdr
#define STORE  sd
#define ADD    daddu
#define SUB    dsubu
#define SRL    dsrl
#define SRA    dsra
#define SLL    dsll
#define SLLV   dsllv
#define SRLV   dsrlv
#define NBYTES 8
#define LOG_NBYTES 3

/*
 * As we are sharing code base with the mips32 tree (which use the o32 ABI
 * register definitions). We need to redefine the register definitions from
 * the n64 ABI register naming to the o32 ABI register naming.
 */
#undef t0
#undef t1
#undef t2
#undef t3
#define t0	$8
#define t1	$9
#define t2	$10
#define t3	$11
#define t4	$12
#define t5	$13
#define t6	$14
#define t7	$15

#else

#define LOAD   lw
#define LOADL  lwl
#define LOADR  lwr
#define STOREL swl
#define STORER swr
#define STORE  sw
#define ADD    addu
#define SUB    subu
#define SRL    srl
#define SLL    sll
#define SRA    sra
#define SLLV   sllv
#define SRLV   srlv
#define NBYTES 4
#define LOG_NBYTES 2

#endif /* USE_DOUBLE */

#ifdef CONFIG_CPU_LITTLE_ENDIAN
#define LDFIRST LOADR
#define LDREST  LOADL
#define STFIRST STORER
#define STREST  STOREL
#define SHIFT_DISCARD SLLV
#else
#define LDFIRST LOADL
#define LDREST  LOADR
#define STFIRST STOREL
#define STREST  STORER
#define SHIFT_DISCARD SRLV
#endif

#define FIRST(unit) ((unit)*NBYTES)
#define REST(unit)  (FIRST(unit)+NBYTES-1)
#define UNIT(unit)  FIRST(unit)

#define ADDRMASK (NBYTES-1)

	.text
	.set	noreorder
	.set	noat

/*
 * A combined memcpy/__copy_user
 * __copy_user sets len to 0 for success; else to an upper bound of
 * the number of uncopied bytes.
 * memcpy sets v0 to dst.
 */
	.align	5
LEAF(memcpy)					/* a0=dst a1=src a2=len */
	move	v0, dst				/* return value */
__memcpy:
FEXPORT(__copy_user)
	/*
	 * Note: dst & src may be unaligned, len may be 0
	 * Temps
	 */
#define rem t8

	/*
	 * The "issue break"s below are very approximate.
	 * Issue delays for dcache fills will perturb the schedule, as will
	 * load queue full replay traps, etc.
	 *
	 * If len < NBYTES use byte operations.
	 */
	PREF(	0, 0(src) )
	PREF(	1, 0(dst) )
	sltu	t2, len, NBYTES
	and	t1, dst, ADDRMASK
	PREF(	0, 1*32(src) )
	PREF(	1, 1*32(dst) )
	bnez	t2, copy_bytes_checklen
	 and	t0, src, ADDRMASK
	PREF(	0, 2*32(src) )
	PREF(	1, 2*32(dst) )
	bnez	t1, dst_unaligned
	 nop
	bnez	t0, src_unaligned_dst_aligned
	/*
	 * use delay slot for fall-through
	 * src and dst are aligned; need to compute rem
	 */
both_aligned:
	 SRL	t0, len, LOG_NBYTES+3    # +3 for 8 units/iter
	beqz	t0, cleanup_both_aligned # len < 8*NBYTES
	 and	rem, len, (8*NBYTES-1)	 # rem = len % (8*NBYTES)
	PREF(	0, 3*32(src) )
	PREF(	1, 3*32(dst) )
	.align	4
1:
EXC(	LOAD	t0, UNIT(0)(src),	l_exc)
EXC(	LOAD	t1, UNIT(1)(src),	l_exc_copy)
EXC(	LOAD	t2, UNIT(2)(src),	l_exc_copy)
EXC(	LOAD	t3, UNIT(3)(src),	l_exc_copy)
	SUB	len, len, 8*NBYTES
EXC(	LOAD	t4, UNIT(4)(src),	l_exc_copy)
EXC(	LOAD	t7, UNIT(5)(src),	l_exc_copy)
EXC(	STORE	t0, UNIT(0)(dst),	s_exc_p8u)
EXC(	STORE	t1, UNIT(1)(dst),	s_exc_p7u)
EXC(	LOAD	t0, UNIT(6)(src),	l_exc_copy)
EXC(	LOAD	t1, UNIT(7)(src),	l_exc_copy)
	ADD	src, src, 8*NBYTES
	ADD	dst, dst, 8*NBYTES
EXC(	STORE	t2, UNIT(-6)(dst),	s_exc_p6u)
EXC(	STORE	t3, UNIT(-5)(dst),	s_exc_p5u)
EXC(	STORE	t4, UNIT(-4)(dst),	s_exc_p4u)
EXC(	STORE	t7, UNIT(-3)(dst),	s_exc_p3u)
EXC(	STORE	t0, UNIT(-2)(dst),	s_exc_p2u)
EXC(	STORE	t1, UNIT(-1)(dst),	s_exc_p1u)
	PREF(	0, 8*32(src) )
	PREF(	1, 8*32(dst) )
	bne	len, rem, 1b
	 nop

	/*
	 * len == rem == the number of bytes left to copy < 8*NBYTES
	 */
cleanup_both_aligned:
	beqz	len, done
	 sltu	t0, len, 4*NBYTES
	bnez	t0, less_than_4units
	 and	rem, len, (NBYTES-1)	# rem = len % NBYTES
	/*
	 * len >= 4*NBYTES
	 */
EXC(	LOAD	t0, UNIT(0)(src),	l_exc)
EXC(	LOAD	t1, UNIT(1)(src),	l_exc_copy)
EXC(	LOAD	t2, UNIT(2)(src),	l_exc_copy)
EXC(	LOAD	t3, UNIT(3)(src),	l_exc_copy)
	SUB	len, len, 4*NBYTES
	ADD	src, src, 4*NBYTES
EXC(	STORE	t0, UNIT(0)(dst),	s_exc_p4u)
EXC(	STORE	t1, UNIT(1)(dst),	s_exc_p3u)
EXC(	STORE	t2, UNIT(2)(dst),	s_exc_p2u)
EXC(	STORE	t3, UNIT(3)(dst),	s_exc_p1u)
	beqz	len, done
	 ADD	dst, dst, 4*NBYTES
less_than_4units:
	/*
	 * rem = len % NBYTES
	 */
	beq	rem, len, copy_bytes
	 nop
1:
EXC(	LOAD	t0, 0(src),		l_exc)
	ADD	src, src, NBYTES
	SUB	len, len, NBYTES
EXC(	STORE	t0, 0(dst),		s_exc_p1u)
	bne	rem, len, 1b
	 ADD	dst, dst, NBYTES

	/*
	 * src and dst are aligned, need to copy rem bytes (rem < NBYTES)
	 * A loop would do only a byte at a time with possible branch
	 * mispredicts.  Can't do an explicit LOAD dst,mask,or,STORE
	 * because can't assume read-access to dst.  Instead, use
	 * STREST dst, which doesn't require read access to dst.
	 *
	 * This code should perform better than a simple loop on modern,
	 * wide-issue mips processors because the code has fewer branches and
	 * more instruction-level parallelism.
	 */
#define bits t2
	beqz	len, done
	 ADD	t1, dst, len	# t1 is just past last byte of dst
	li	bits, 8*NBYTES
	SLL	rem, len, 3	# rem = number of bits to keep
EXC(	LOAD	t0, 0(src),		l_exc)
	SUB	bits, bits, rem	# bits = number of bits to discard
	SHIFT_DISCARD t0, t0, bits
EXC(	STREST	t0, -1(t1),		s_exc)
	jr	ra
	 move	len, zero
dst_unaligned:
	/*
	 * dst is unaligned
	 * t0 = src & ADDRMASK
	 * t1 = dst & ADDRMASK; T1 > 0
	 * len >= NBYTES
	 *
	 * Copy enough bytes to align dst
	 * Set match = (src and dst have same alignment)
	 */
#define match rem
EXC(	LDFIRST	t3, FIRST(0)(src),	l_exc)
	ADD	t2, zero, NBYTES
EXC(	LDREST	t3, REST(0)(src),	l_exc_copy)
	SUB	t2, t2, t1	# t2 = number of bytes copied
	xor	match, t0, t1
EXC(	STFIRST t3, FIRST(0)(dst),	s_exc)
	beq	len, t2, done
	 SUB	len, len, t2
	ADD	dst, dst, t2
	beqz	match, both_aligned
	 ADD	src, src, t2

src_unaligned_dst_aligned:
	SRL	t0, len, LOG_NBYTES+2    # +2 for 4 units/iter
	PREF(	0, 3*32(src) )
	beqz	t0, cleanup_src_unaligned
	 and	rem, len, (4*NBYTES-1)   # rem = len % 4*NBYTES
	PREF(	1, 3*32(dst) )
1:
/*
 * Avoid consecutive LD*'s to the same register since some mips
 * implementations can't issue them in the same cycle.
 * It's OK to load FIRST(N+1) before REST(N) because the two addresses
 * are to the same unit (unless src is aligned, but it's not).
 */
EXC(	LDFIRST	t0, FIRST(0)(src),	l_exc)
EXC(	LDFIRST	t1, FIRST(1)(src),	l_exc_copy)
	SUB     len, len, 4*NBYTES
EXC(	LDREST	t0, REST(0)(src),	l_exc_copy)
EXC(	LDREST	t1, REST(1)(src),	l_exc_copy)
EXC(	LDFIRST	t2, FIRST(2)(src),	l_exc_copy)
EXC(	LDFIRST	t3, FIRST(3)(src),	l_exc_copy)
EXC(	LDREST	t2, REST(2)(src),	l_exc_copy)
EXC(	LDREST	t3, REST(3)(src),	l_exc_copy)
	PREF(	0, 9*32(src) )		# 0 is PREF_LOAD  (not streamed)
	ADD	src, src, 4*NBYTES
#ifdef CONFIG_CPU_SB1
	nop				# improves slotting
#endif
EXC(	STORE	t0, UNIT(0)(dst),	s_exc_p4u)
EXC(	STORE	t1, UNIT(1)(dst),	s_exc_p3u)
EXC(	STORE	t2, UNIT(2)(dst),	s_exc_p2u)
EXC(	STORE	t3, UNIT(3)(dst),	s_exc_p1u)
	PREF(	1, 9*32(dst) )     	# 1 is PREF_STORE (not streamed)
	bne	len, rem, 1b
	 ADD	dst, dst, 4*NBYTES

cleanup_src_unaligned:
	beqz	len, done
	 and	rem, len, NBYTES-1  # rem = len % NBYTES
	beq	rem, len, copy_bytes
	 nop
1:
EXC(	LDFIRST t0, FIRST(0)(src),	l_exc)
EXC(	LDREST	t0, REST(0)(src),	l_exc_copy)
	ADD	src, src, NBYTES
	SUB	len, len, NBYTES
EXC(	STORE	t0, 0(dst),		s_exc_p1u)
	bne	len, rem, 1b
	 ADD	dst, dst, NBYTES

copy_bytes_checklen:
	beqz	len, done
	 nop
copy_bytes:
	/* 0 < len < NBYTES  */
#define COPY_BYTE(N)			\
EXC(	lb	t0, N(src), l_exc);	\
	SUB	len, len, 1;		\
	beqz	len, done;		\
EXC(	 sb	t0, N(dst), s_exc_p1)

	COPY_BYTE(0)
	COPY_BYTE(1)
#ifdef USE_DOUBLE
	COPY_BYTE(2)
	COPY_BYTE(3)
	COPY_BYTE(4)
	COPY_BYTE(5)
#endif
EXC(	lb	t0, NBYTES-2(src), l_exc)
	SUB	len, len, 1
	jr	ra
EXC(	 sb	t0, NBYTES-2(dst), s_exc_p1)
done:
	jr	ra
	 nop
	END(memcpy)

l_exc_copy:
	/*
	 * Copy bytes from src until faulting load address (or until a
	 * lb faults)
	 *
	 * When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
	 * may be more than a byte beyond the last address.
	 * Hence, the lb below may get an exception.
	 *
	 * Assumes src < THREAD_BUADDR($28)
	 */
	LOAD	t0, TI_TASK($28)
	 nop
	LOAD	t0, THREAD_BUADDR(t0)
1:
EXC(	lb	t1, 0(src),	l_exc)
	ADD	src, src, 1
	sb	t1, 0(dst)	# can't fault -- we're copy_from_user
	bne	src, t0, 1b
	 ADD	dst, dst, 1
l_exc:
	LOAD	t0, TI_TASK($28)
	 nop
	LOAD	t0, THREAD_BUADDR(t0)	# t0 is just past last good address
	 nop
	SUB	len, AT, t0		# len number of uncopied bytes
	/*
	 * Here's where we rely on src and dst being incremented in tandem,
	 *   See (3) above.
	 * dst += (fault addr - src) to put dst at first byte to clear
	 */
	ADD	dst, t0			# compute start address in a1
	SUB	dst, src
	/*
	 * Clear len bytes starting at dst.  Can't call __bzero because it
	 * might modify len.  An inefficient loop for these rare times...
	 */
	beqz	len, done
	 SUB	src, len, 1
1:	sb	zero, 0(dst)
	ADD	dst, dst, 1
	bnez	src, 1b
	 SUB	src, src, 1
	jr	ra
	 nop


#define SEXC(n)				\
s_exc_p ## n ## u:			\
	jr	ra;			\
	 ADD	len, len, n*NBYTES

SEXC(8)
SEXC(7)
SEXC(6)
SEXC(5)
SEXC(4)
SEXC(3)
SEXC(2)
SEXC(1)

s_exc_p1:
	jr	ra
	 ADD	len, len, 1
s_exc:
	jr	ra
	 nop

	.align	5
LEAF(memmove)
	ADD	t0, a0, a2
	ADD	t1, a1, a2
	sltu	t0, a1, t0			# dst + len <= src -> memcpy
	sltu	t1, a0, t1			# dst >= src + len -> memcpy
	and	t0, t1
	beqz	t0, __memcpy
	 move	v0, a0				/* return value */
	beqz	a2, r_out
	END(memmove)

	/* fall through to __rmemcpy */
LEAF(__rmemcpy)					/* a0=dst a1=src a2=len */
	 sltu	t0, a1, a0
	beqz	t0, r_end_bytes_up		# src >= dst
	 nop
	ADD	a0, a2				# dst = dst + len
	ADD	a1, a2				# src = src + len

r_end_bytes:
	lb	t0, -1(a1)
	SUB	a2, a2, 0x1
	sb	t0, -1(a0)
	SUB	a1, a1, 0x1
	bnez	a2, r_end_bytes
	 SUB	a0, a0, 0x1

r_out:
	jr	ra
	 move	a2, zero

r_end_bytes_up:
	lb	t0, (a1)
	SUB	a2, a2, 0x1
	sb	t0, (a0)
	ADD	a1, a1, 0x1
	bnez	a2, r_end_bytes_up
	 ADD	a0, a0, 0x1

	jr	ra
	 move	a2, zero
	END(__rmemcpy)