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 <asm/asm.h> 17#include <asm/asm-offsets.h> 18#include <asm/export.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 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(__copy_user) 154EXPORT_SYMBOL(__copy_user) 155 /* 156 * Note: dst & src may be unaligned, len may be 0 157 * Temps 158 */ 159 # 160 # Octeon doesn't care if the destination is unaligned. The hardware 161 # can fix it faster than we can special case the assembly. 162 # 163 pref 0, 0(src) 164 sltu t0, len, NBYTES # Check if < 1 word 165 bnez t0, copy_bytes_checklen 166 and t0, src, ADDRMASK # Check if src unaligned 167 bnez t0, src_unaligned 168 sltu t0, len, 4*NBYTES # Check if < 4 words 169 bnez t0, less_than_4units 170 sltu t0, len, 8*NBYTES # Check if < 8 words 171 bnez t0, less_than_8units 172 sltu t0, len, 16*NBYTES # Check if < 16 words 173 bnez t0, cleanup_both_aligned 174 sltu t0, len, 128+1 # Check if len < 129 175 bnez t0, 1f # Skip prefetch if len is too short 176 sltu t0, len, 256+1 # Check if len < 257 177 bnez t0, 1f # Skip prefetch if len is too short 178 pref 0, 128(src) # We must not prefetch invalid addresses 179 # 180 # This is where we loop if there is more than 128 bytes left 1812: pref 0, 256(src) # We must not prefetch invalid addresses 182 # 183 # This is where we loop if we can't prefetch anymore 1841: 185EXC( LOAD t0, UNIT(0)(src), l_exc) 186EXC( LOAD t1, UNIT(1)(src), l_exc_copy) 187EXC( LOAD t2, UNIT(2)(src), l_exc_copy) 188EXC( LOAD t3, UNIT(3)(src), l_exc_copy) 189 SUB len, len, 16*NBYTES 190EXC( STORE t0, UNIT(0)(dst), s_exc_p16u) 191EXC( STORE t1, UNIT(1)(dst), s_exc_p15u) 192EXC( STORE t2, UNIT(2)(dst), s_exc_p14u) 193EXC( STORE t3, UNIT(3)(dst), s_exc_p13u) 194EXC( LOAD t0, UNIT(4)(src), l_exc_copy) 195EXC( LOAD t1, UNIT(5)(src), l_exc_copy) 196EXC( LOAD t2, UNIT(6)(src), l_exc_copy) 197EXC( LOAD t3, UNIT(7)(src), l_exc_copy) 198EXC( STORE t0, UNIT(4)(dst), s_exc_p12u) 199EXC( STORE t1, UNIT(5)(dst), s_exc_p11u) 200EXC( STORE t2, UNIT(6)(dst), s_exc_p10u) 201 ADD src, src, 16*NBYTES 202EXC( STORE t3, UNIT(7)(dst), s_exc_p9u) 203 ADD dst, dst, 16*NBYTES 204EXC( LOAD t0, UNIT(-8)(src), l_exc_copy_rewind16) 205EXC( LOAD t1, UNIT(-7)(src), l_exc_copy_rewind16) 206EXC( LOAD t2, UNIT(-6)(src), l_exc_copy_rewind16) 207EXC( LOAD t3, UNIT(-5)(src), l_exc_copy_rewind16) 208EXC( STORE t0, UNIT(-8)(dst), s_exc_p8u) 209EXC( STORE t1, UNIT(-7)(dst), s_exc_p7u) 210EXC( STORE t2, UNIT(-6)(dst), s_exc_p6u) 211EXC( STORE t3, UNIT(-5)(dst), s_exc_p5u) 212EXC( LOAD t0, UNIT(-4)(src), l_exc_copy_rewind16) 213EXC( LOAD t1, UNIT(-3)(src), l_exc_copy_rewind16) 214EXC( LOAD t2, UNIT(-2)(src), l_exc_copy_rewind16) 215EXC( LOAD t3, UNIT(-1)(src), l_exc_copy_rewind16) 216EXC( STORE t0, UNIT(-4)(dst), s_exc_p4u) 217EXC( STORE t1, UNIT(-3)(dst), s_exc_p3u) 218EXC( STORE t2, UNIT(-2)(dst), s_exc_p2u) 219EXC( STORE t3, UNIT(-1)(dst), s_exc_p1u) 220 sltu t0, len, 256+1 # See if we can prefetch more 221 beqz t0, 2b 222 sltu t0, len, 128 # See if we can loop more time 223 beqz t0, 1b 224 nop 225 # 226 # Jump here if there are less than 16*NBYTES left. 227 # 228cleanup_both_aligned: 229 beqz len, done 230 sltu t0, len, 8*NBYTES 231 bnez t0, less_than_8units 232 nop 233EXC( LOAD t0, UNIT(0)(src), l_exc) 234EXC( LOAD t1, UNIT(1)(src), l_exc_copy) 235EXC( LOAD t2, UNIT(2)(src), l_exc_copy) 236EXC( LOAD t3, UNIT(3)(src), l_exc_copy) 237 SUB len, len, 8*NBYTES 238EXC( STORE t0, UNIT(0)(dst), s_exc_p8u) 239EXC( STORE t1, UNIT(1)(dst), s_exc_p7u) 240EXC( STORE t2, UNIT(2)(dst), s_exc_p6u) 241EXC( STORE t3, UNIT(3)(dst), s_exc_p5u) 242EXC( LOAD t0, UNIT(4)(src), l_exc_copy) 243EXC( LOAD t1, UNIT(5)(src), l_exc_copy) 244EXC( LOAD t2, UNIT(6)(src), l_exc_copy) 245EXC( LOAD t3, UNIT(7)(src), l_exc_copy) 246EXC( STORE t0, UNIT(4)(dst), s_exc_p4u) 247EXC( STORE t1, UNIT(5)(dst), s_exc_p3u) 248EXC( STORE t2, UNIT(6)(dst), s_exc_p2u) 249EXC( STORE t3, UNIT(7)(dst), s_exc_p1u) 250 ADD src, src, 8*NBYTES 251 beqz len, done 252 ADD dst, dst, 8*NBYTES 253 # 254 # Jump here if there are less than 8*NBYTES left. 255 # 256less_than_8units: 257 sltu t0, len, 4*NBYTES 258 bnez t0, less_than_4units 259 nop 260EXC( LOAD t0, UNIT(0)(src), l_exc) 261EXC( LOAD t1, UNIT(1)(src), l_exc_copy) 262EXC( LOAD t2, UNIT(2)(src), l_exc_copy) 263EXC( LOAD t3, UNIT(3)(src), l_exc_copy) 264 SUB len, len, 4*NBYTES 265EXC( STORE t0, UNIT(0)(dst), s_exc_p4u) 266EXC( STORE t1, UNIT(1)(dst), s_exc_p3u) 267EXC( STORE t2, UNIT(2)(dst), s_exc_p2u) 268EXC( STORE t3, UNIT(3)(dst), s_exc_p1u) 269 ADD src, src, 4*NBYTES 270 beqz len, done 271 ADD dst, dst, 4*NBYTES 272 # 273 # Jump here if there are less than 4*NBYTES left. This means 274 # we may need to copy up to 3 NBYTES words. 275 # 276less_than_4units: 277 sltu t0, len, 1*NBYTES 278 bnez t0, copy_bytes_checklen 279 nop 280 # 281 # 1) Copy NBYTES, then check length again 282 # 283EXC( LOAD t0, 0(src), l_exc) 284 SUB len, len, NBYTES 285 sltu t1, len, 8 286EXC( STORE t0, 0(dst), s_exc_p1u) 287 ADD src, src, NBYTES 288 bnez t1, copy_bytes_checklen 289 ADD dst, dst, NBYTES 290 # 291 # 2) Copy NBYTES, then check length again 292 # 293EXC( LOAD t0, 0(src), l_exc) 294 SUB len, len, NBYTES 295 sltu t1, len, 8 296EXC( STORE t0, 0(dst), s_exc_p1u) 297 ADD src, src, NBYTES 298 bnez t1, copy_bytes_checklen 299 ADD dst, dst, NBYTES 300 # 301 # 3) Copy NBYTES, then check length again 302 # 303EXC( LOAD t0, 0(src), l_exc) 304 SUB len, len, NBYTES 305 ADD src, src, NBYTES 306 ADD dst, dst, NBYTES 307 b copy_bytes_checklen 308EXC( STORE t0, -8(dst), s_exc_p1u) 309 310src_unaligned: 311#define rem t8 312 SRL t0, len, LOG_NBYTES+2 # +2 for 4 units/iter 313 beqz t0, cleanup_src_unaligned 314 and rem, len, (4*NBYTES-1) # rem = len % 4*NBYTES 3151: 316/* 317 * Avoid consecutive LD*'s to the same register since some mips 318 * implementations can't issue them in the same cycle. 319 * It's OK to load FIRST(N+1) before REST(N) because the two addresses 320 * are to the same unit (unless src is aligned, but it's not). 321 */ 322EXC( LDFIRST t0, FIRST(0)(src), l_exc) 323EXC( LDFIRST t1, FIRST(1)(src), l_exc_copy) 324 SUB len, len, 4*NBYTES 325EXC( LDREST t0, REST(0)(src), l_exc_copy) 326EXC( LDREST t1, REST(1)(src), l_exc_copy) 327EXC( LDFIRST t2, FIRST(2)(src), l_exc_copy) 328EXC( LDFIRST t3, FIRST(3)(src), l_exc_copy) 329EXC( LDREST t2, REST(2)(src), l_exc_copy) 330EXC( LDREST t3, REST(3)(src), l_exc_copy) 331 ADD src, src, 4*NBYTES 332EXC( STORE t0, UNIT(0)(dst), s_exc_p4u) 333EXC( STORE t1, UNIT(1)(dst), s_exc_p3u) 334EXC( STORE t2, UNIT(2)(dst), s_exc_p2u) 335EXC( STORE t3, UNIT(3)(dst), s_exc_p1u) 336 bne len, rem, 1b 337 ADD dst, dst, 4*NBYTES 338 339cleanup_src_unaligned: 340 beqz len, done 341 and rem, len, NBYTES-1 # rem = len % NBYTES 342 beq rem, len, copy_bytes 343 nop 3441: 345EXC( LDFIRST t0, FIRST(0)(src), l_exc) 346EXC( LDREST t0, REST(0)(src), l_exc_copy) 347 SUB len, len, NBYTES 348EXC( STORE t0, 0(dst), s_exc_p1u) 349 ADD src, src, NBYTES 350 bne len, rem, 1b 351 ADD dst, dst, NBYTES 352 353copy_bytes_checklen: 354 beqz len, done 355 nop 356copy_bytes: 357 /* 0 < len < NBYTES */ 358#define COPY_BYTE(N) \ 359EXC( lb t0, N(src), l_exc); \ 360 SUB len, len, 1; \ 361 beqz len, done; \ 362EXC( sb t0, N(dst), s_exc_p1) 363 364 COPY_BYTE(0) 365 COPY_BYTE(1) 366 COPY_BYTE(2) 367 COPY_BYTE(3) 368 COPY_BYTE(4) 369 COPY_BYTE(5) 370EXC( lb t0, NBYTES-2(src), l_exc) 371 SUB len, len, 1 372 jr ra 373EXC( sb t0, NBYTES-2(dst), s_exc_p1) 374done: 375 jr ra 376 nop 377 END(memcpy) 378 379l_exc_copy_rewind16: 380 /* Rewind src and dst by 16*NBYTES for l_exc_copy */ 381 SUB src, src, 16*NBYTES 382 SUB dst, dst, 16*NBYTES 383l_exc_copy: 384 /* 385 * Copy bytes from src until faulting load address (or until a 386 * lb faults) 387 * 388 * When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28) 389 * may be more than a byte beyond the last address. 390 * Hence, the lb below may get an exception. 391 * 392 * Assumes src < THREAD_BUADDR($28) 393 */ 394 LOAD t0, TI_TASK($28) 395 LOAD t0, THREAD_BUADDR(t0) 3961: 397EXC( lb t1, 0(src), l_exc) 398 ADD src, src, 1 399 sb t1, 0(dst) # can't fault -- we're copy_from_user 400 bne src, t0, 1b 401 ADD dst, dst, 1 402l_exc: 403 LOAD t0, TI_TASK($28) 404 LOAD t0, THREAD_BUADDR(t0) # t0 is just past last good address 405 SUB len, AT, t0 # len number of uncopied bytes 406 jr ra 407 nop 408 409 410#define SEXC(n) \ 411s_exc_p ## n ## u: \ 412 jr ra; \ 413 ADD len, len, n*NBYTES 414 415SEXC(16) 416SEXC(15) 417SEXC(14) 418SEXC(13) 419SEXC(12) 420SEXC(11) 421SEXC(10) 422SEXC(9) 423SEXC(8) 424SEXC(7) 425SEXC(6) 426SEXC(5) 427SEXC(4) 428SEXC(3) 429SEXC(2) 430SEXC(1) 431 432s_exc_p1: 433 jr ra 434 ADD len, len, 1 435s_exc: 436 jr ra 437 nop 438 439 .align 5 440LEAF(memmove) 441EXPORT_SYMBOL(memmove) 442 ADD t0, a0, a2 443 ADD t1, a1, a2 444 sltu t0, a1, t0 # dst + len <= src -> memcpy 445 sltu t1, a0, t1 # dst >= src + len -> memcpy 446 and t0, t1 447 beqz t0, __memcpy 448 move v0, a0 /* return value */ 449 beqz a2, r_out 450 END(memmove) 451 452 /* fall through to __rmemcpy */ 453LEAF(__rmemcpy) /* a0=dst a1=src a2=len */ 454 sltu t0, a1, a0 455 beqz t0, r_end_bytes_up # src >= dst 456 nop 457 ADD a0, a2 # dst = dst + len 458 ADD a1, a2 # src = src + len 459 460r_end_bytes: 461 lb t0, -1(a1) 462 SUB a2, a2, 0x1 463 sb t0, -1(a0) 464 SUB a1, a1, 0x1 465 bnez a2, r_end_bytes 466 SUB a0, a0, 0x1 467 468r_out: 469 jr ra 470 move a2, zero 471 472r_end_bytes_up: 473 lb t0, (a1) 474 SUB a2, a2, 0x1 475 sb t0, (a0) 476 ADD a1, a1, 0x1 477 bnez a2, r_end_bytes_up 478 ADD a0, a0, 0x1 479 480 jr ra 481 move a2, zero 482 END(__rmemcpy) 483