arch/parisc/lib/memcpy.c

   1 /*
   2  *    Optimized memory copy routines.
   3  *
   4  *    Copyright (C) 2004 Randolph Chung <tausq@debian.org>
   5  *
   6  *    This program is free software; you can redistribute it and/or modify
   7  *    it under the terms of the GNU General Public License as published by
   8  *    the Free Software Foundation; either version 2, or (at your option)
   9  *    any later version.
  10  *
  11  *    This program is distributed in the hope that it will be useful,
  12  *    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *    GNU General Public License for more details.
  15  *
  16  *    You should have received a copy of the GNU General Public License
  17  *    along with this program; if not, write to the Free Software
  18  *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  *
  20  *    Portions derived from the GNU C Library
  21  *    Copyright (C) 1991, 1997, 2003 Free Software Foundation, Inc.
  22  *
  23  * Several strategies are tried to try to get the best performance for various
  24  * conditions. In the optimal case, we copy 64-bytes in an unrolled loop using
  25  * fp regs. This is followed by loops that copy 32- or 16-bytes at a time using
  26  * general registers.  Unaligned copies are handled either by aligning the
  27  * destination and then using shift-and-write method, or in a few cases by
  28  * falling back to a byte-at-a-time copy.
  29  *
  30  * I chose to implement this in C because it is easier to maintain and debug,
  31  * and in my experiments it appears that the C code generated by gcc (3.3/3.4
  32  * at the time of writing) is fairly optimal. Unfortunately some of the
  33  * semantics of the copy routine (exception handling) is difficult to express
  34  * in C, so we have to play some tricks to get it to work.
  35  *
  36  * All the loads and stores are done via explicit asm() code in order to use
  37  * the right space registers.
  38  *
  39  * Testing with various alignments and buffer sizes shows that this code is
  40  * often >10x faster than a simple byte-at-a-time copy, even for strangely
  41  * aligned operands. It is interesting to note that the glibc version
  42  * of memcpy (written in C) is actually quite fast already. This routine is
  43  * able to beat it by 30-40% for aligned copies because of the loop unrolling,
  44  * but in some cases the glibc version is still slightly faster. This lends
  45  * more credibility that gcc can generate very good code as long as we are
  46  * careful.
  47  *
  48  * TODO:
  49  * - cache prefetching needs more experimentation to get optimal settings
  50  * - try not to use the post-increment address modifiers; they create additional
  51  *   interlocks
  52  * - replace byte-copy loops with stybs sequences
  53  */
  54
  55 #ifdef __KERNEL__
  56 #include <linux/config.h>
  57 #include <linux/module.h>
  58 #include <linux/compiler.h>
  59 #include <asm/uaccess.h>
  60 #define s_space "%%sr1"
  61 #define d_space "%%sr2"
  62 #else
  63 #include "memcpy.h"
  64 #define s_space "%%sr0"
  65 #define d_space "%%sr0"
  66 #define pa_memcpy new2_copy
  67 #endif
  68
  69 DECLARE_PER_CPU(struct exception_data, exception_data);
  70
  71 #define preserve_branch(label)  do {                                    \
  72         volatile int dummy;                                             \
  73         /* The following branch is never taken, it's just here to  */   \
  74         /* prevent gcc from optimizing away our exception code. */      \
  75         if (unlikely(dummy != dummy))                                   \
  76                 goto label;                                             \
  77 } while (0)
  78
  79 #define get_user_space() (segment_eq(get_fs(), KERNEL_DS) ? 0 : mfsp(3))
  80 #define get_kernel_space() (0)
  81
  82 #define MERGE(w0, sh_1, w1, sh_2)  ({                                   \
  83         unsigned int _r;                                                \
  84         asm volatile (                                                  \
  85         "mtsar %3\n"                                                    \
  86         "shrpw %1, %2, %%sar, %0\n"                                     \
  87         : "=r"(_r)                                                      \
  88         : "r"(w0), "r"(w1), "r"(sh_2)                                   \
  89         );                                                              \
  90         _r;                                                             \
  91 })
  92 #define THRESHOLD       16
  93
  94 #ifdef DEBUG_MEMCPY
  95 #define DPRINTF(fmt, args...) do { printk(KERN_DEBUG "%s:%d:%s ", __FILE__, __LINE__, __FUNCTION__ ); printk(KERN_DEBUG fmt, ##args ); } while (0)
  96 #else
  97 #define DPRINTF(fmt, args...)
  98 #endif
  99
 100 #ifndef __LP64__
 101 #define EXC_WORD ".word"
 102 #else
 103 #define EXC_WORD ".dword"
 104 #endif
 105
 106 #define def_load_ai_insn(_insn,_sz,_tt,_s,_a,_t,_e)     \
 107         __asm__ __volatile__ (                          \
 108         "1:\t" #_insn ",ma " #_sz "(" _s ",%1), %0\n"   \
 109         "\t.section __ex_table,\"aw\"\n"                \
 110         "\t" EXC_WORD "\t1b\n"                          \
 111         "\t" EXC_WORD "\t" #_e "\n"                     \
 112         "\t.previous\n"                                 \
 113         : _tt(_t), "+r"(_a)                             \
 114         :                                               \
 115         : "r8")
 116
 117 #define def_store_ai_insn(_insn,_sz,_tt,_s,_a,_t,_e)    \
 118         __asm__ __volatile__ (                          \
 119         "1:\t" #_insn ",ma %1, " #_sz "(" _s ",%0)\n"   \
 120         "\t.section __ex_table,\"aw\"\n"                \
 121         "\t" EXC_WORD "\t1b\n"                          \
 122         "\t" EXC_WORD "\t" #_e "\n"                     \
 123         "\t.previous\n"                                 \
 124         : "+r"(_a)                                      \
 125         : _tt(_t)                                       \
 126         : "r8")
 127
 128 #define ldbma(_s, _a, _t, _e) def_load_ai_insn(ldbs,1,"=r",_s,_a,_t,_e)
 129 #define stbma(_s, _t, _a, _e) def_store_ai_insn(stbs,1,"r",_s,_a,_t,_e)
 130 #define ldwma(_s, _a, _t, _e) def_load_ai_insn(ldw,4,"=r",_s,_a,_t,_e)
 131 #define stwma(_s, _t, _a, _e) def_store_ai_insn(stw,4,"r",_s,_a,_t,_e)
 132 #define flddma(_s, _a, _t, _e) def_load_ai_insn(fldd,8,"=f",_s,_a,_t,_e)
 133 #define fstdma(_s, _t, _a, _e) def_store_ai_insn(fstd,8,"f",_s,_a,_t,_e)
 134
 135 #define def_load_insn(_insn,_tt,_s,_o,_a,_t,_e)         \
 136         __asm__ __volatile__ (                          \
 137         "1:\t" #_insn " " #_o "(" _s ",%1), %0\n"       \
 138         "\t.section __ex_table,\"aw\"\n"                \
 139         "\t" EXC_WORD "\t1b\n"                          \
 140         "\t" EXC_WORD "\t" #_e "\n"                     \
 141         "\t.previous\n"                                 \
 142         : _tt(_t)                                       \
 143         : "r"(_a)                                       \
 144         : "r8")
 145
 146 #define def_store_insn(_insn,_tt,_s,_t,_o,_a,_e)        \
 147         __asm__ __volatile__ (                          \
 148         "1:\t" #_insn " %0, " #_o "(" _s ",%1)\n"       \
 149         "\t.section __ex_table,\"aw\"\n"                \
 150         "\t" EXC_WORD "\t1b\n"                          \
 151         "\t" EXC_WORD "\t" #_e "\n"                     \
 152         "\t.previous\n"                                 \
 153         :                                               \
 154         : _tt(_t), "r"(_a)                              \
 155         : "r8")
 156
 157 #define ldw(_s,_o,_a,_t,_e)     def_load_insn(ldw,"=r",_s,_o,_a,_t,_e)
 158 #define stw(_s,_t,_o,_a,_e)     def_store_insn(stw,"r",_s,_t,_o,_a,_e)
 159
 160 #ifdef  CONFIG_PREFETCH
 161 extern inline void prefetch_src(const void *addr)
 162 {
 163         __asm__("ldw 0(" s_space ",%0), %%r0" : : "r" (addr));
 164 }
 165
 166 extern inline void prefetch_dst(const void *addr)
 167 {
 168         __asm__("ldd 0(" d_space ",%0), %%r0" : : "r" (addr));
 169 }
 170 #else
 171 #define prefetch_src(addr)
 172 #define prefetch_dst(addr)
 173 #endif
 174
 175 /* Copy from a not-aligned src to an aligned dst, using shifts. Handles 4 words
 176  * per loop.  This code is derived from glibc.
 177  */
 178 static inline unsigned long copy_dstaligned(unsigned long dst, unsigned long src, unsigned long len, unsigned long o_dst, unsigned long o_src, unsigned long o_len)
 179 {
 180         /* gcc complains that a2 and a3 may be uninitialized, but actually
 181          * they cannot be.  Initialize a2/a3 to shut gcc up.
 182          */
 183         register unsigned int a0, a1, a2 = 0, a3 = 0;
 184         int sh_1, sh_2;
 185         struct exception_data *d;
 186
 187         /* prefetch_src((const void *)src); */
 188
 189         /* Calculate how to shift a word read at the memory operation
 190            aligned srcp to make it aligned for copy.  */
 191         sh_1 = 8 * (src % sizeof(unsigned int));
 192         sh_2 = 8 * sizeof(unsigned int) - sh_1;
 193
 194         /* Make src aligned by rounding it down.  */
 195         src &= -sizeof(unsigned int);
 196
 197         switch (len % 4)
 198         {
 199                 case 2:
 200                         /* a1 = ((unsigned int *) src)[0];
 201                            a2 = ((unsigned int *) src)[1]; */
 202                         ldw(s_space, 0, src, a1, cda_ldw_exc);
 203                         ldw(s_space, 4, src, a2, cda_ldw_exc);
 204                         src -= 1 * sizeof(unsigned int);
 205                         dst -= 3 * sizeof(unsigned int);
 206                         len += 2;
 207                         goto do1;
 208                 case 3:
 209                         /* a0 = ((unsigned int *) src)[0];
 210                            a1 = ((unsigned int *) src)[1]; */
 211                         ldw(s_space, 0, src, a0, cda_ldw_exc);
 212                         ldw(s_space, 4, src, a1, cda_ldw_exc);
 213                         src -= 0 * sizeof(unsigned int);
 214                         dst -= 2 * sizeof(unsigned int);
 215                         len += 1;
 216                         goto do2;
 217                 case 0:
 218                         if (len == 0)
 219                                 return 0;
 220                         /* a3 = ((unsigned int *) src)[0];
 221                            a0 = ((unsigned int *) src)[1]; */
 222                         ldw(s_space, 0, src, a3, cda_ldw_exc);
 223                         ldw(s_space, 4, src, a0, cda_ldw_exc);
 224                         src -=-1 * sizeof(unsigned int);
 225                         dst -= 1 * sizeof(unsigned int);
 226                         len += 0;
 227                         goto do3;
 228                 case 1:
 229                         /* a2 = ((unsigned int *) src)[0];
 230                            a3 = ((unsigned int *) src)[1]; */
 231                         ldw(s_space, 0, src, a2, cda_ldw_exc);
 232                         ldw(s_space, 4, src, a3, cda_ldw_exc);
 233                         src -=-2 * sizeof(unsigned int);
 234                         dst -= 0 * sizeof(unsigned int);
 235                         len -= 1;
 236                         if (len == 0)
 237                                 goto do0;
 238                         goto do4;                       /* No-op.  */
 239         }
 240
 241         do
 242         {
 243                 /* prefetch_src((const void *)(src + 4 * sizeof(unsigned int))); */
 244 do4:
 245                 /* a0 = ((unsigned int *) src)[0]; */
 246                 ldw(s_space, 0, src, a0, cda_ldw_exc);
 247                 /* ((unsigned int *) dst)[0] = MERGE (a2, sh_1, a3, sh_2); */
 248                 stw(d_space, MERGE (a2, sh_1, a3, sh_2), 0, dst, cda_stw_exc);
 249 do3:
 250                 /* a1 = ((unsigned int *) src)[1]; */
 251                 ldw(s_space, 4, src, a1, cda_ldw_exc);
 252                 /* ((unsigned int *) dst)[1] = MERGE (a3, sh_1, a0, sh_2); */
 253                 stw(d_space, MERGE (a3, sh_1, a0, sh_2), 4, dst, cda_stw_exc);
 254 do2:
 255                 /* a2 = ((unsigned int *) src)[2]; */
 256                 ldw(s_space, 8, src, a2, cda_ldw_exc);
 257                 /* ((unsigned int *) dst)[2] = MERGE (a0, sh_1, a1, sh_2); */
 258                 stw(d_space, MERGE (a0, sh_1, a1, sh_2), 8, dst, cda_stw_exc);
 259 do1:
 260                 /* a3 = ((unsigned int *) src)[3]; */
 261                 ldw(s_space, 12, src, a3, cda_ldw_exc);
 262                 /* ((unsigned int *) dst)[3] = MERGE (a1, sh_1, a2, sh_2); */
 263                 stw(d_space, MERGE (a1, sh_1, a2, sh_2), 12, dst, cda_stw_exc);
 264
 265                 src += 4 * sizeof(unsigned int);
 266                 dst += 4 * sizeof(unsigned int);
 267                 len -= 4;
 268         }
 269         while (len != 0);
 270
 271 do0:
 272         /* ((unsigned int *) dst)[0] = MERGE (a2, sh_1, a3, sh_2); */
 273         stw(d_space, MERGE (a2, sh_1, a3, sh_2), 0, dst, cda_stw_exc);
 274
 275         preserve_branch(handle_load_error);
 276         preserve_branch(handle_store_error);
 277
 278         return 0;
 279
 280 handle_load_error:
 281         __asm__ __volatile__ ("cda_ldw_exc:\n");
 282         d = &__get_cpu_var(exception_data);
 283         DPRINTF("cda_ldw_exc: o_len=%lu fault_addr=%lu o_src=%lu ret=%lu\n",
 284                 o_len, d->fault_addr, o_src, o_len - d->fault_addr + o_src);
 285         return o_len * 4 - d->fault_addr + o_src;
 286
 287 handle_store_error:
 288         __asm__ __volatile__ ("cda_stw_exc:\n");
 289         d = &__get_cpu_var(exception_data);
 290         DPRINTF("cda_stw_exc: o_len=%lu fault_addr=%lu o_dst=%lu ret=%lu\n",
 291                 o_len, d->fault_addr, o_dst, o_len - d->fault_addr + o_dst);
 292         return o_len * 4 - d->fault_addr + o_dst;
 293 }
 294
 295
 296 /* Returns 0 for success, otherwise, returns number of bytes not transferred. */
 297 unsigned long pa_memcpy(void *dstp, const void *srcp, unsigned long len)
 298 {
 299         register unsigned long src, dst, t1, t2, t3;
 300         register unsigned char *pcs, *pcd;
 301         register unsigned int *pws, *pwd;
 302         register double *pds, *pdd;
 303         unsigned long ret = 0;
 304         unsigned long o_dst, o_src, o_len;
 305         struct exception_data *d;
 306
 307         src = (unsigned long)srcp;
 308         dst = (unsigned long)dstp;
 309         pcs = (unsigned char *)srcp;
 310         pcd = (unsigned char *)dstp;
 311
 312         o_dst = dst; o_src = src; o_len = len;
 313
 314         /* prefetch_src((const void *)srcp); */
 315
 316         if (len < THRESHOLD)
 317                 goto byte_copy;
 318
 319         /* Check alignment */
 320         t1 = (src ^ dst);
 321         if (unlikely(t1 & (sizeof(double)-1)))
 322                 goto unaligned_copy;
 323
 324         /* src and dst have same alignment. */
 325
 326         /* Copy bytes till we are double-aligned. */
 327         t2 = src & (sizeof(double) - 1);
 328         if (unlikely(t2 != 0)) {
 329                 t2 = sizeof(double) - t2;
 330                 while (t2 && len) {
 331                         /* *pcd++ = *pcs++; */
 332                         ldbma(s_space, pcs, t3, pmc_load_exc);
 333                         len--;
 334                         stbma(d_space, t3, pcd, pmc_store_exc);
 335                         t2--;
 336                 }
 337         }
 338
 339         pds = (double *)pcs;
 340         pdd = (double *)pcd;
 341
 342         /* Copy 8 doubles at a time */
 343         while (len >= 8*sizeof(double)) {
 344                 register double r1, r2, r3, r4, r5, r6, r7, r8;
 345                 /* prefetch_src((char *)pds + L1_CACHE_BYTES); */
 346                 flddma(s_space, pds, r1, pmc_load_exc);
 347                 flddma(s_space, pds, r2, pmc_load_exc);
 348                 flddma(s_space, pds, r3, pmc_load_exc);
 349                 flddma(s_space, pds, r4, pmc_load_exc);
 350                 fstdma(d_space, r1, pdd, pmc_store_exc);
 351                 fstdma(d_space, r2, pdd, pmc_store_exc);
 352                 fstdma(d_space, r3, pdd, pmc_store_exc);
 353                 fstdma(d_space, r4, pdd, pmc_store_exc);
 354
 355 #if 0
 356                 if (L1_CACHE_BYTES <= 32)
 357                         prefetch_src((char *)pds + L1_CACHE_BYTES);
 358 #endif
 359                 flddma(s_space, pds, r5, pmc_load_exc);
 360                 flddma(s_space, pds, r6, pmc_load_exc);
 361                 flddma(s_space, pds, r7, pmc_load_exc);
 362                 flddma(s_space, pds, r8, pmc_load_exc);
 363                 fstdma(d_space, r5, pdd, pmc_store_exc);
 364                 fstdma(d_space, r6, pdd, pmc_store_exc);
 365                 fstdma(d_space, r7, pdd, pmc_store_exc);
 366                 fstdma(d_space, r8, pdd, pmc_store_exc);
 367                 len -= 8*sizeof(double);
 368         }
 369
 370         pws = (unsigned int *)pds;
 371         pwd = (unsigned int *)pdd;
 372
 373 word_copy:
 374         while (len >= 8*sizeof(unsigned int)) {
 375                 register unsigned int r1,r2,r3,r4,r5,r6,r7,r8;
 376                 /* prefetch_src((char *)pws + L1_CACHE_BYTES); */
 377                 ldwma(s_space, pws, r1, pmc_load_exc);
 378                 ldwma(s_space, pws, r2, pmc_load_exc);
 379                 ldwma(s_space, pws, r3, pmc_load_exc);
 380                 ldwma(s_space, pws, r4, pmc_load_exc);
 381                 stwma(d_space, r1, pwd, pmc_store_exc);
 382                 stwma(d_space, r2, pwd, pmc_store_exc);
 383                 stwma(d_space, r3, pwd, pmc_store_exc);
 384                 stwma(d_space, r4, pwd, pmc_store_exc);
 385
 386                 ldwma(s_space, pws, r5, pmc_load_exc);
 387                 ldwma(s_space, pws, r6, pmc_load_exc);
 388                 ldwma(s_space, pws, r7, pmc_load_exc);
 389                 ldwma(s_space, pws, r8, pmc_load_exc);
 390                 stwma(d_space, r5, pwd, pmc_store_exc);
 391                 stwma(d_space, r6, pwd, pmc_store_exc);
 392                 stwma(d_space, r7, pwd, pmc_store_exc);
 393                 stwma(d_space, r8, pwd, pmc_store_exc);
 394                 len -= 8*sizeof(unsigned int);
 395         }
 396
 397         while (len >= 4*sizeof(unsigned int)) {
 398                 register unsigned int r1,r2,r3,r4;
 399                 ldwma(s_space, pws, r1, pmc_load_exc);
 400                 ldwma(s_space, pws, r2, pmc_load_exc);
 401                 ldwma(s_space, pws, r3, pmc_load_exc);
 402                 ldwma(s_space, pws, r4, pmc_load_exc);
 403                 stwma(d_space, r1, pwd, pmc_store_exc);
 404                 stwma(d_space, r2, pwd, pmc_store_exc);
 405                 stwma(d_space, r3, pwd, pmc_store_exc);
 406                 stwma(d_space, r4, pwd, pmc_store_exc);
 407                 len -= 4*sizeof(unsigned int);
 408         }
 409
 410         pcs = (unsigned char *)pws;
 411         pcd = (unsigned char *)pwd;
 412
 413 byte_copy:
 414         while (len) {
 415                 /* *pcd++ = *pcs++; */
 416                 ldbma(s_space, pcs, t3, pmc_load_exc);
 417                 stbma(d_space, t3, pcd, pmc_store_exc);
 418                 len--;
 419         }
 420
 421         return 0;
 422
 423 unaligned_copy:
 424         /* possibly we are aligned on a word, but not on a double... */
 425         if (likely(t1 & (sizeof(unsigned int)-1)) == 0) {
 426                 t2 = src & (sizeof(unsigned int) - 1);
 427
 428                 if (unlikely(t2 != 0)) {
 429                         t2 = sizeof(unsigned int) - t2;
 430                         while (t2) {
 431                                 /* *pcd++ = *pcs++; */
 432                                 ldbma(s_space, pcs, t3, pmc_load_exc);
 433                                 stbma(d_space, t3, pcd, pmc_store_exc);
 434                                 len--;
 435                                 t2--;
 436                         }
 437                 }
 438
 439                 pws = (unsigned int *)pcs;
 440                 pwd = (unsigned int *)pcd;
 441                 goto word_copy;
 442         }
 443
 444         /* Align the destination.  */
 445         if (unlikely((dst & (sizeof(unsigned int) - 1)) != 0)) {
 446                 t2 = sizeof(unsigned int) - (dst & (sizeof(unsigned int) - 1));
 447                 while (t2) {
 448                         /* *pcd++ = *pcs++; */
 449                         ldbma(s_space, pcs, t3, pmc_load_exc);
 450                         stbma(d_space, t3, pcd, pmc_store_exc);
 451                         len--;
 452                         t2--;
 453                 }
 454                 dst = (unsigned long)pcd;
 455                 src = (unsigned long)pcs;
 456         }
 457
 458         ret = copy_dstaligned(dst, src, len / sizeof(unsigned int),
 459                 o_dst, o_src, o_len);
 460         if (ret)
 461                 return ret;
 462
 463         pcs += (len & -sizeof(unsigned int));
 464         pcd += (len & -sizeof(unsigned int));
 465         len %= sizeof(unsigned int);
 466
 467         preserve_branch(handle_load_error);
 468         preserve_branch(handle_store_error);
 469
 470         goto byte_copy;
 471
 472 handle_load_error:
 473         __asm__ __volatile__ ("pmc_load_exc:\n");
 474         d = &__get_cpu_var(exception_data);
 475         DPRINTF("pmc_load_exc: o_len=%lu fault_addr=%lu o_src=%lu ret=%lu\n",
 476                 o_len, d->fault_addr, o_src, o_len - d->fault_addr + o_src);
 477         return o_len - d->fault_addr + o_src;
 478
 479 handle_store_error:
 480         __asm__ __volatile__ ("pmc_store_exc:\n");
 481         d = &__get_cpu_var(exception_data);
 482         DPRINTF("pmc_store_exc: o_len=%lu fault_addr=%lu o_dst=%lu ret=%lu\n",
 483                 o_len, d->fault_addr, o_dst, o_len - d->fault_addr + o_dst);
 484         return o_len - d->fault_addr + o_dst;
 485 }
 486
 487 #ifdef __KERNEL__
 488 unsigned long copy_to_user(void __user *dst, const void *src, unsigned long len)
 489 {
 490         mtsp(get_kernel_space(), 1);
 491         mtsp(get_user_space(), 2);
 492         return pa_memcpy((void __force *)dst, src, len);
 493 }
 494
 495 unsigned long copy_from_user(void *dst, const void __user *src, unsigned long len)
 496 {
 497         mtsp(get_user_space(), 1);
 498         mtsp(get_kernel_space(), 2);
 499         return pa_memcpy(dst, (void __force *)src, len);
 500 }
 501
 502 unsigned long copy_in_user(void __user *dst, const void __user *src, unsigned long len)
 503 {
 504         mtsp(get_user_space(), 1);
 505         mtsp(get_user_space(), 2);
 506         return pa_memcpy((void __force *)dst, (void __force *)src, len);
 507 }
 508
 509
 510 void * memcpy(void * dst,const void *src, size_t count)
 511 {
 512         mtsp(get_kernel_space(), 1);
 513         mtsp(get_kernel_space(), 2);
 514         pa_memcpy(dst, src, count);
 515         return dst;
 516 }
 517
 518 EXPORT_SYMBOL(copy_to_user);
 519 EXPORT_SYMBOL(copy_from_user);
 520 EXPORT_SYMBOL(copy_in_user);
 521 EXPORT_SYMBOL(memcpy);
 522 #endif