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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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#include <linux/config.h>
Ralf Baechlee5adb872005-10-20 22:55:26 +010016
17/*
18 * Hack to resolve longstanding prefetch issue
19 *
20 * Prefetching may be fatal on some systems if we're prefetching beyond the
21 * end of memory on some systems. It's also a seriously bad idea on non
22 * dma-coherent systems.
23 */
24#if !defined(CONFIG_DMA_COHERENT) || !defined(CONFIG_DMA_IP27)
25#undef CONFIG_CPU_HAS_PREFETCH
26#endif
27#ifdef CONFIG_MIPS_MALTA
28#undef CONFIG_CPU_HAS_PREFETCH
29#endif
30
Linus Torvalds1da177e2005-04-16 15:20:36 -070031#include <asm/asm.h>
Sam Ravnborg048eb582005-09-09 22:32:31 +020032#include <asm/asm-offsets.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070033#include <asm/regdef.h>
34
35#define dst a0
36#define src a1
37#define len a2
38
39/*
40 * Spec
41 *
42 * memcpy copies len bytes from src to dst and sets v0 to dst.
43 * It assumes that
44 * - src and dst don't overlap
45 * - src is readable
46 * - dst is writable
47 * memcpy uses the standard calling convention
48 *
49 * __copy_user copies up to len bytes from src to dst and sets a2 (len) to
50 * the number of uncopied bytes due to an exception caused by a read or write.
51 * __copy_user assumes that src and dst don't overlap, and that the call is
52 * implementing one of the following:
53 * copy_to_user
54 * - src is readable (no exceptions when reading src)
55 * copy_from_user
56 * - dst is writable (no exceptions when writing dst)
57 * __copy_user uses a non-standard calling convention; see
58 * include/asm-mips/uaccess.h
59 *
60 * When an exception happens on a load, the handler must
61 # ensure that all of the destination buffer is overwritten to prevent
62 * leaking information to user mode programs.
63 */
64
65/*
66 * Implementation
67 */
68
69/*
70 * The exception handler for loads requires that:
71 * 1- AT contain the address of the byte just past the end of the source
72 * of the copy,
73 * 2- src_entry <= src < AT, and
74 * 3- (dst - src) == (dst_entry - src_entry),
75 * The _entry suffix denotes values when __copy_user was called.
76 *
77 * (1) is set up up by uaccess.h and maintained by not writing AT in copy_user
78 * (2) is met by incrementing src by the number of bytes copied
79 * (3) is met by not doing loads between a pair of increments of dst and src
80 *
81 * The exception handlers for stores adjust len (if necessary) and return.
82 * These handlers do not need to overwrite any data.
83 *
84 * For __rmemcpy and memmove an exception is always a kernel bug, therefore
85 * they're not protected.
86 */
87
88#define EXC(inst_reg,addr,handler) \
899: inst_reg, addr; \
90 .section __ex_table,"a"; \
91 PTR 9b, handler; \
92 .previous
93
94/*
95 * Only on the 64-bit kernel we can made use of 64-bit registers.
96 */
Ralf Baechle875d43e2005-09-03 15:56:16 -070097#ifdef CONFIG_64BIT
Linus Torvalds1da177e2005-04-16 15:20:36 -070098#define USE_DOUBLE
99#endif
100
101#ifdef USE_DOUBLE
102
103#define LOAD ld
104#define LOADL ldl
105#define LOADR ldr
106#define STOREL sdl
107#define STORER sdr
108#define STORE sd
109#define ADD daddu
110#define SUB dsubu
111#define SRL dsrl
112#define SRA dsra
113#define SLL dsll
114#define SLLV dsllv
115#define SRLV dsrlv
116#define NBYTES 8
117#define LOG_NBYTES 3
118
Ralf Baechle42a3b4f2005-09-03 15:56:17 -0700119/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 * As we are sharing code base with the mips32 tree (which use the o32 ABI
121 * register definitions). We need to redefine the register definitions from
122 * the n64 ABI register naming to the o32 ABI register naming.
123 */
124#undef t0
125#undef t1
126#undef t2
127#undef t3
128#define t0 $8
129#define t1 $9
130#define t2 $10
131#define t3 $11
132#define t4 $12
133#define t5 $13
134#define t6 $14
135#define t7 $15
Ralf Baechle42a3b4f2005-09-03 15:56:17 -0700136
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137#else
138
139#define LOAD lw
140#define LOADL lwl
141#define LOADR lwr
142#define STOREL swl
143#define STORER swr
144#define STORE sw
145#define ADD addu
146#define SUB subu
147#define SRL srl
148#define SLL sll
149#define SRA sra
150#define SLLV sllv
151#define SRLV srlv
152#define NBYTES 4
153#define LOG_NBYTES 2
154
155#endif /* USE_DOUBLE */
156
157#ifdef CONFIG_CPU_LITTLE_ENDIAN
158#define LDFIRST LOADR
159#define LDREST LOADL
160#define STFIRST STORER
161#define STREST STOREL
162#define SHIFT_DISCARD SLLV
163#else
164#define LDFIRST LOADL
165#define LDREST LOADR
166#define STFIRST STOREL
167#define STREST STORER
168#define SHIFT_DISCARD SRLV
169#endif
170
171#define FIRST(unit) ((unit)*NBYTES)
172#define REST(unit) (FIRST(unit)+NBYTES-1)
173#define UNIT(unit) FIRST(unit)
174
175#define ADDRMASK (NBYTES-1)
176
177 .text
178 .set noreorder
179 .set noat
180
181/*
182 * A combined memcpy/__copy_user
183 * __copy_user sets len to 0 for success; else to an upper bound of
184 * the number of uncopied bytes.
185 * memcpy sets v0 to dst.
186 */
187 .align 5
188LEAF(memcpy) /* a0=dst a1=src a2=len */
189 move v0, dst /* return value */
190__memcpy:
191FEXPORT(__copy_user)
192 /*
193 * Note: dst & src may be unaligned, len may be 0
194 * Temps
195 */
196#define rem t8
197
198 /*
199 * The "issue break"s below are very approximate.
200 * Issue delays for dcache fills will perturb the schedule, as will
201 * load queue full replay traps, etc.
202 *
203 * If len < NBYTES use byte operations.
204 */
205 PREF( 0, 0(src) )
206 PREF( 1, 0(dst) )
207 sltu t2, len, NBYTES
208 and t1, dst, ADDRMASK
209 PREF( 0, 1*32(src) )
210 PREF( 1, 1*32(dst) )
211 bnez t2, copy_bytes_checklen
212 and t0, src, ADDRMASK
213 PREF( 0, 2*32(src) )
214 PREF( 1, 2*32(dst) )
215 bnez t1, dst_unaligned
216 nop
217 bnez t0, src_unaligned_dst_aligned
218 /*
219 * use delay slot for fall-through
220 * src and dst are aligned; need to compute rem
221 */
222both_aligned:
223 SRL t0, len, LOG_NBYTES+3 # +3 for 8 units/iter
224 beqz t0, cleanup_both_aligned # len < 8*NBYTES
225 and rem, len, (8*NBYTES-1) # rem = len % (8*NBYTES)
226 PREF( 0, 3*32(src) )
227 PREF( 1, 3*32(dst) )
228 .align 4
2291:
230EXC( LOAD t0, UNIT(0)(src), l_exc)
231EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
232EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
233EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
234 SUB len, len, 8*NBYTES
235EXC( LOAD t4, UNIT(4)(src), l_exc_copy)
236EXC( LOAD t7, UNIT(5)(src), l_exc_copy)
237EXC( STORE t0, UNIT(0)(dst), s_exc_p8u)
238EXC( STORE t1, UNIT(1)(dst), s_exc_p7u)
239EXC( LOAD t0, UNIT(6)(src), l_exc_copy)
240EXC( LOAD t1, UNIT(7)(src), l_exc_copy)
241 ADD src, src, 8*NBYTES
242 ADD dst, dst, 8*NBYTES
243EXC( STORE t2, UNIT(-6)(dst), s_exc_p6u)
244EXC( STORE t3, UNIT(-5)(dst), s_exc_p5u)
245EXC( STORE t4, UNIT(-4)(dst), s_exc_p4u)
246EXC( STORE t7, UNIT(-3)(dst), s_exc_p3u)
247EXC( STORE t0, UNIT(-2)(dst), s_exc_p2u)
248EXC( STORE t1, UNIT(-1)(dst), s_exc_p1u)
249 PREF( 0, 8*32(src) )
250 PREF( 1, 8*32(dst) )
251 bne len, rem, 1b
252 nop
253
254 /*
255 * len == rem == the number of bytes left to copy < 8*NBYTES
256 */
257cleanup_both_aligned:
258 beqz len, done
259 sltu t0, len, 4*NBYTES
260 bnez t0, less_than_4units
261 and rem, len, (NBYTES-1) # rem = len % NBYTES
262 /*
263 * len >= 4*NBYTES
264 */
265EXC( LOAD t0, UNIT(0)(src), l_exc)
266EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
267EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
268EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
269 SUB len, len, 4*NBYTES
270 ADD src, src, 4*NBYTES
271EXC( STORE t0, UNIT(0)(dst), s_exc_p4u)
272EXC( STORE t1, UNIT(1)(dst), s_exc_p3u)
273EXC( STORE t2, UNIT(2)(dst), s_exc_p2u)
274EXC( STORE t3, UNIT(3)(dst), s_exc_p1u)
275 beqz len, done
276 ADD dst, dst, 4*NBYTES
277less_than_4units:
278 /*
279 * rem = len % NBYTES
280 */
281 beq rem, len, copy_bytes
282 nop
2831:
284EXC( LOAD t0, 0(src), l_exc)
285 ADD src, src, NBYTES
286 SUB len, len, NBYTES
287EXC( STORE t0, 0(dst), s_exc_p1u)
288 bne rem, len, 1b
289 ADD dst, dst, NBYTES
290
291 /*
292 * src and dst are aligned, need to copy rem bytes (rem < NBYTES)
293 * A loop would do only a byte at a time with possible branch
294 * mispredicts. Can't do an explicit LOAD dst,mask,or,STORE
295 * because can't assume read-access to dst. Instead, use
296 * STREST dst, which doesn't require read access to dst.
297 *
298 * This code should perform better than a simple loop on modern,
299 * wide-issue mips processors because the code has fewer branches and
300 * more instruction-level parallelism.
301 */
302#define bits t2
303 beqz len, done
304 ADD t1, dst, len # t1 is just past last byte of dst
305 li bits, 8*NBYTES
306 SLL rem, len, 3 # rem = number of bits to keep
307EXC( LOAD t0, 0(src), l_exc)
308 SUB bits, bits, rem # bits = number of bits to discard
309 SHIFT_DISCARD t0, t0, bits
310EXC( STREST t0, -1(t1), s_exc)
311 jr ra
312 move len, zero
313dst_unaligned:
314 /*
315 * dst is unaligned
316 * t0 = src & ADDRMASK
317 * t1 = dst & ADDRMASK; T1 > 0
318 * len >= NBYTES
319 *
320 * Copy enough bytes to align dst
321 * Set match = (src and dst have same alignment)
322 */
323#define match rem
324EXC( LDFIRST t3, FIRST(0)(src), l_exc)
325 ADD t2, zero, NBYTES
326EXC( LDREST t3, REST(0)(src), l_exc_copy)
327 SUB t2, t2, t1 # t2 = number of bytes copied
328 xor match, t0, t1
329EXC( STFIRST t3, FIRST(0)(dst), s_exc)
330 beq len, t2, done
331 SUB len, len, t2
332 ADD dst, dst, t2
333 beqz match, both_aligned
334 ADD src, src, t2
335
336src_unaligned_dst_aligned:
337 SRL t0, len, LOG_NBYTES+2 # +2 for 4 units/iter
338 PREF( 0, 3*32(src) )
339 beqz t0, cleanup_src_unaligned
340 and rem, len, (4*NBYTES-1) # rem = len % 4*NBYTES
341 PREF( 1, 3*32(dst) )
3421:
343/*
344 * Avoid consecutive LD*'s to the same register since some mips
345 * implementations can't issue them in the same cycle.
346 * It's OK to load FIRST(N+1) before REST(N) because the two addresses
347 * are to the same unit (unless src is aligned, but it's not).
348 */
349EXC( LDFIRST t0, FIRST(0)(src), l_exc)
350EXC( LDFIRST t1, FIRST(1)(src), l_exc_copy)
351 SUB len, len, 4*NBYTES
352EXC( LDREST t0, REST(0)(src), l_exc_copy)
353EXC( LDREST t1, REST(1)(src), l_exc_copy)
354EXC( LDFIRST t2, FIRST(2)(src), l_exc_copy)
355EXC( LDFIRST t3, FIRST(3)(src), l_exc_copy)
356EXC( LDREST t2, REST(2)(src), l_exc_copy)
357EXC( LDREST t3, REST(3)(src), l_exc_copy)
358 PREF( 0, 9*32(src) ) # 0 is PREF_LOAD (not streamed)
359 ADD src, src, 4*NBYTES
360#ifdef CONFIG_CPU_SB1
361 nop # improves slotting
362#endif
363EXC( STORE t0, UNIT(0)(dst), s_exc_p4u)
364EXC( STORE t1, UNIT(1)(dst), s_exc_p3u)
365EXC( STORE t2, UNIT(2)(dst), s_exc_p2u)
366EXC( STORE t3, UNIT(3)(dst), s_exc_p1u)
367 PREF( 1, 9*32(dst) ) # 1 is PREF_STORE (not streamed)
368 bne len, rem, 1b
369 ADD dst, dst, 4*NBYTES
370
371cleanup_src_unaligned:
372 beqz len, done
373 and rem, len, NBYTES-1 # rem = len % NBYTES
374 beq rem, len, copy_bytes
375 nop
3761:
377EXC( LDFIRST t0, FIRST(0)(src), l_exc)
378EXC( LDREST t0, REST(0)(src), l_exc_copy)
379 ADD src, src, NBYTES
380 SUB len, len, NBYTES
381EXC( STORE t0, 0(dst), s_exc_p1u)
382 bne len, rem, 1b
383 ADD dst, dst, NBYTES
384
385copy_bytes_checklen:
386 beqz len, done
387 nop
388copy_bytes:
389 /* 0 < len < NBYTES */
390#define COPY_BYTE(N) \
391EXC( lb t0, N(src), l_exc); \
392 SUB len, len, 1; \
393 beqz len, done; \
394EXC( sb t0, N(dst), s_exc_p1)
395
396 COPY_BYTE(0)
397 COPY_BYTE(1)
398#ifdef USE_DOUBLE
399 COPY_BYTE(2)
400 COPY_BYTE(3)
401 COPY_BYTE(4)
402 COPY_BYTE(5)
403#endif
404EXC( lb t0, NBYTES-2(src), l_exc)
405 SUB len, len, 1
406 jr ra
407EXC( sb t0, NBYTES-2(dst), s_exc_p1)
408done:
409 jr ra
410 nop
411 END(memcpy)
412
413l_exc_copy:
414 /*
415 * Copy bytes from src until faulting load address (or until a
416 * lb faults)
417 *
418 * When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
419 * may be more than a byte beyond the last address.
420 * Hence, the lb below may get an exception.
421 *
422 * Assumes src < THREAD_BUADDR($28)
423 */
424 LOAD t0, TI_TASK($28)
425 nop
426 LOAD t0, THREAD_BUADDR(t0)
4271:
428EXC( lb t1, 0(src), l_exc)
429 ADD src, src, 1
430 sb t1, 0(dst) # can't fault -- we're copy_from_user
431 bne src, t0, 1b
432 ADD dst, dst, 1
433l_exc:
434 LOAD t0, TI_TASK($28)
435 nop
436 LOAD t0, THREAD_BUADDR(t0) # t0 is just past last good address
437 nop
438 SUB len, AT, t0 # len number of uncopied bytes
439 /*
440 * Here's where we rely on src and dst being incremented in tandem,
441 * See (3) above.
442 * dst += (fault addr - src) to put dst at first byte to clear
443 */
444 ADD dst, t0 # compute start address in a1
445 SUB dst, src
446 /*
447 * Clear len bytes starting at dst. Can't call __bzero because it
448 * might modify len. An inefficient loop for these rare times...
449 */
450 beqz len, done
451 SUB src, len, 1
4521: sb zero, 0(dst)
453 ADD dst, dst, 1
454 bnez src, 1b
455 SUB src, src, 1
456 jr ra
457 nop
458
459
460#define SEXC(n) \
461s_exc_p ## n ## u: \
462 jr ra; \
463 ADD len, len, n*NBYTES
464
465SEXC(8)
466SEXC(7)
467SEXC(6)
468SEXC(5)
469SEXC(4)
470SEXC(3)
471SEXC(2)
472SEXC(1)
473
474s_exc_p1:
475 jr ra
476 ADD len, len, 1
477s_exc:
478 jr ra
479 nop
480
481 .align 5
482LEAF(memmove)
483 ADD t0, a0, a2
484 ADD t1, a1, a2
485 sltu t0, a1, t0 # dst + len <= src -> memcpy
486 sltu t1, a0, t1 # dst >= src + len -> memcpy
487 and t0, t1
488 beqz t0, __memcpy
489 move v0, a0 /* return value */
490 beqz a2, r_out
491 END(memmove)
492
493 /* fall through to __rmemcpy */
494LEAF(__rmemcpy) /* a0=dst a1=src a2=len */
495 sltu t0, a1, a0
496 beqz t0, r_end_bytes_up # src >= dst
497 nop
498 ADD a0, a2 # dst = dst + len
499 ADD a1, a2 # src = src + len
500
501r_end_bytes:
502 lb t0, -1(a1)
503 SUB a2, a2, 0x1
504 sb t0, -1(a0)
505 SUB a1, a1, 0x1
506 bnez a2, r_end_bytes
507 SUB a0, a0, 0x1
508
509r_out:
510 jr ra
511 move a2, zero
512
513r_end_bytes_up:
514 lb t0, (a1)
515 SUB a2, a2, 0x1
516 sb t0, (a0)
517 ADD a1, a1, 0x1
518 bnez a2, r_end_bytes_up
519 ADD a0, a0, 0x1
520
521 jr ra
522 move a2, zero
523 END(__rmemcpy)