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#include <linux/config.h> 16 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 31#include <asm/asm.h> 32#include <asm/asm-offsets.h> 33#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 */ 97#ifdef CONFIG_64BIT 98#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 3 118 119/* 120 * 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 $15 136 137#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) 524