arch/cris/arch-v10/lib/usercopy.c

   1 /*
   2  * User address space access functions.
   3  * The non-inlined parts of asm-cris/uaccess.h are here.
   4  *
   5  * Copyright (C) 2000, Axis Communications AB.
   6  *
   7  * Written by Hans-Peter Nilsson.
   8  * Pieces used from memcpy, originally by Kenny Ranerup long time ago.
   9  */
  10
  11 #include <asm/uaccess.h>
  12
  13 /* Asm:s have been tweaked (within the domain of correctness) to give
  14    satisfactory results for "gcc version 2.96 20000427 (experimental)".
  15
  16    Check regularly...
  17
  18    Note that the PC saved at a bus-fault is the address *after* the
  19    faulting instruction, which means the branch-target for instructions in
  20    delay-slots for taken branches.  Note also that the postincrement in
  21    the instruction is performed regardless of bus-fault; the register is
  22    seen updated in fault handlers.
  23
  24    Oh, and on the code formatting issue, to whomever feels like "fixing
  25    it" to Conformity: I'm too "lazy", but why don't you go ahead and "fix"
  26    string.c too.  I just don't think too many people will hack this file
  27    for the code format to be an issue.  */
  28
  29
  30 /* Copy to userspace.  This is based on the memcpy used for
  31    kernel-to-kernel copying; see "string.c".  */
  32
  33 unsigned long
  34 __copy_user (void __user *pdst, const void *psrc, unsigned long pn)
  35 {
  36   /* We want the parameters put in special registers.
  37      Make sure the compiler is able to make something useful of this.
  38      As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
  39
  40      FIXME: Comment for old gcc version.  Check.
  41      If gcc was alright, it really would need no temporaries, and no
  42      stack space to save stuff on. */
  43
  44   register char *dst __asm__ ("r13") = pdst;
  45   register const char *src __asm__ ("r11") = psrc;
  46   register int n __asm__ ("r12") = pn;
  47   register int retn __asm__ ("r10") = 0;
  48
  49
  50   /* When src is aligned but not dst, this makes a few extra needless
  51      cycles.  I believe it would take as many to check that the
  52      re-alignment was unnecessary.  */
  53   if (((unsigned long) dst & 3) != 0
  54       /* Don't align if we wouldn't copy more than a few bytes; so we
  55          don't have to check further for overflows.  */
  56       && n >= 3)
  57   {
  58     if ((unsigned long) dst & 1)
  59     {
  60       __asm_copy_to_user_1 (dst, src, retn);
  61       n--;
  62     }
  63
  64     if ((unsigned long) dst & 2)
  65     {
  66       __asm_copy_to_user_2 (dst, src, retn);
  67       n -= 2;
  68     }
  69   }
  70
  71   /* Decide which copying method to use. */
  72   if (n >= 44*2)                /* Break even between movem and
  73                                    move16 is at 38.7*2, but modulo 44. */
  74   {
  75     /* For large copies we use 'movem'.  */
  76
  77     /* It is not optimal to tell the compiler about clobbering any
  78        registers; that will move the saving/restoring of those registers
  79        to the function prologue/epilogue, and make non-movem sizes
  80        suboptimal.
  81
  82        This method is not foolproof; it assumes that the "asm reg"
  83        declarations at the beginning of the function really are used
  84        here (beware: they may be moved to temporary registers).
  85        This way, we do not have to save/move the registers around into
  86        temporaries; we can safely use them straight away.
  87
  88        If you want to check that the allocation was right; then
  89        check the equalities in the first comment.  It should say
  90        "r13=r13, r11=r11, r12=r12".  */
  91     __asm__ volatile ("\
  92         .ifnc %0%1%2%3,$r13$r11$r12$r10                                 \n\
  93         .err                                                            \n\
  94         .endif                                                          \n\
  95                                                                         \n\
  96         ;; Save the registers we'll use in the movem process            \n\
  97         ;; on the stack.                                                \n\
  98         subq    11*4,$sp                                                \n\
  99         movem   $r10,[$sp]                                              \n\
 100                                                                         \n\
 101         ;; Now we've got this:                                          \n\
 102         ;; r11 - src                                                    \n\
 103         ;; r13 - dst                                                    \n\
 104         ;; r12 - n                                                      \n\
 105                                                                         \n\
 106         ;; Update n for the first loop                                  \n\
 107         subq    44,$r12                                                 \n\
 108                                                                         \n\
 109 ; Since the noted PC of a faulting instruction in a delay-slot of a taken \n\
 110 ; branch, is that of the branch target, we actually point at the from-movem \n\
 111 ; for this case.  There is no ambiguity here; if there was a fault in that \n\
 112 ; instruction (meaning a kernel oops), the faulted PC would be the address \n\
 113 ; after *that* movem.                                                   \n\
 114                                                                         \n\
 115 0:                                                                      \n\
 116         movem   [$r11+],$r10                                            \n\
 117         subq   44,$r12                                                  \n\
 118         bge     0b                                                      \n\
 119         movem   $r10,[$r13+]                                            \n\
 120 1:                                                                      \n\
 121         addq   44,$r12  ;; compensate for last loop underflowing n      \n\
 122                                                                         \n\
 123         ;; Restore registers from stack                                 \n\
 124         movem [$sp+],$r10                                               \n\
 125 2:                                                                      \n\
 126         .section .fixup,\"ax\"                                          \n\
 127                                                                         \n\
 128 ; To provide a correct count in r10 of bytes that failed to be copied,  \n\
 129 ; we jump back into the loop if the loop-branch was taken.  There is no \n\
 130 ; performance penalty for sany use; the program will segfault soon enough.\n\
 131                                                                         \n\
 132 3:                                                                      \n\
 133         move.d [$sp],$r10                                               \n\
 134         addq 44,$r10                                                    \n\
 135         move.d $r10,[$sp]                                               \n\
 136         jump 0b                                                         \n\
 137 4:                                                                      \n\
 138         movem [$sp+],$r10                                               \n\
 139         addq 44,$r10                                                    \n\
 140         addq 44,$r12                                                    \n\
 141         jump 2b                                                         \n\
 142                                                                         \n\
 143         .previous                                                       \n\
 144         .section __ex_table,\"a\"                                       \n\
 145         .dword 0b,3b                                                    \n\
 146         .dword 1b,4b                                                    \n\
 147         .previous"
 148
 149      /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
 150      /* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
 151
 152   }
 153
 154   /* Either we directly start copying, using dword copying in a loop, or
 155      we copy as much as possible with 'movem' and then the last block (<44
 156      bytes) is copied here.  This will work since 'movem' will have
 157      updated SRC, DST and N.  */
 158
 159   while (n >= 16)
 160   {
 161     __asm_copy_to_user_16 (dst, src, retn);
 162     n -= 16;
 163   }
 164
 165   /* Having a separate by-four loops cuts down on cache footprint.
 166      FIXME:  Test with and without; increasing switch to be 0..15.  */
 167   while (n >= 4)
 168   {
 169     __asm_copy_to_user_4 (dst, src, retn);
 170     n -= 4;
 171   }
 172
 173   switch (n)
 174   {
 175     case 0:
 176       break;
 177     case 1:
 178       __asm_copy_to_user_1 (dst, src, retn);
 179       break;
 180     case 2:
 181       __asm_copy_to_user_2 (dst, src, retn);
 182       break;
 183     case 3:
 184       __asm_copy_to_user_3 (dst, src, retn);
 185       break;
 186   }
 187
 188   return retn;
 189 }
 190
 191 /* Copy from user to kernel, zeroing the bytes that were inaccessible in
 192    userland.  The return-value is the number of bytes that were
 193    inaccessible.  */
 194
 195 unsigned long
 196 __copy_user_zeroing(void *pdst, const void __user *psrc, unsigned long pn)
 197 {
 198   /* We want the parameters put in special registers.
 199      Make sure the compiler is able to make something useful of this.
 200      As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
 201
 202      FIXME: Comment for old gcc version.  Check.
 203      If gcc was alright, it really would need no temporaries, and no
 204      stack space to save stuff on.  */
 205
 206   register char *dst __asm__ ("r13") = pdst;
 207   register const char *src __asm__ ("r11") = psrc;
 208   register int n __asm__ ("r12") = pn;
 209   register int retn __asm__ ("r10") = 0;
 210
 211   /* The best reason to align src is that we then know that a read-fault
 212      was for aligned bytes; there's no 1..3 remaining good bytes to
 213      pickle.  */
 214   if (((unsigned long) src & 3) != 0)
 215   {
 216     if (((unsigned long) src & 1) && n != 0)
 217     {
 218       __asm_copy_from_user_1 (dst, src, retn);
 219       n--;
 220     }
 221
 222     if (((unsigned long) src & 2) && n >= 2)
 223     {
 224       __asm_copy_from_user_2 (dst, src, retn);
 225       n -= 2;
 226     }
 227
 228     /* We only need one check after the unalignment-adjustments, because
 229        if both adjustments were done, either both or neither reference
 230        had an exception.  */
 231     if (retn != 0)
 232       goto copy_exception_bytes;
 233   }
 234
 235   /* Decide which copying method to use. */
 236   if (n >= 44*2)                /* Break even between movem and
 237                                    move16 is at 38.7*2, but modulo 44.
 238                                    FIXME: We use move4 now.  */
 239   {
 240     /* For large copies we use 'movem' */
 241
 242     /* It is not optimal to tell the compiler about clobbering any
 243        registers; that will move the saving/restoring of those registers
 244        to the function prologue/epilogue, and make non-movem sizes
 245        suboptimal.
 246
 247        This method is not foolproof; it assumes that the "asm reg"
 248        declarations at the beginning of the function really are used
 249        here (beware: they may be moved to temporary registers).
 250        This way, we do not have to save/move the registers around into
 251        temporaries; we can safely use them straight away.
 252
 253        If you want to check that the allocation was right; then
 254        check the equalities in the first comment.  It should say
 255        "r13=r13, r11=r11, r12=r12" */
 256     __asm__ volatile ("\n\
 257         .ifnc %0%1%2%3,$r13$r11$r12$r10                                 \n\
 258         .err                                                            \n\
 259         .endif                                                          \n\
 260                                                                         \n\
 261         ;; Save the registers we'll use in the movem process            \n\
 262         ;; on the stack.                                                \n\
 263         subq    11*4,$sp                                                \n\
 264         movem   $r10,[$sp]                                              \n\
 265                                                                         \n\
 266         ;; Now we've got this:                                          \n\
 267         ;; r11 - src                                                    \n\
 268         ;; r13 - dst                                                    \n\
 269         ;; r12 - n                                                      \n\
 270                                                                         \n\
 271         ;; Update n for the first loop                                  \n\
 272         subq    44,$r12                                                 \n\
 273 0:                                                                      \n\
 274         movem   [$r11+],$r10                                            \n\
 275 1:                                                                      \n\
 276         subq   44,$r12                                                  \n\
 277         bge     0b                                                      \n\
 278         movem   $r10,[$r13+]                                            \n\
 279                                                                         \n\
 280         addq   44,$r12  ;; compensate for last loop underflowing n      \n\
 281                                                                         \n\
 282         ;; Restore registers from stack                                 \n\
 283         movem [$sp+],$r10                                               \n\
 284 4:                                                                      \n\
 285         .section .fixup,\"ax\"                                          \n\
 286                                                                         \n\
 287 ;; Do not jump back into the loop if we fail.  For some uses, we get a  \n\
 288 ;; page fault somewhere on the line.  Without checking for page limits, \n\
 289 ;; we don't know where, but we need to copy accurately and keep an      \n\
 290 ;; accurate count; not just clear the whole line.  To do that, we fall  \n\
 291 ;; down in the code below, proceeding with smaller amounts.  It should  \n\
 292 ;; be kept in mind that we have to cater to code like what at one time  \n\
 293 ;; was in fs/super.c:                                                   \n\
 294 ;;  i = size - copy_from_user((void *)page, data, size);                \n\
 295 ;; which would cause repeated faults while clearing the remainder of    \n\
 296 ;; the SIZE bytes at PAGE after the first fault.                        \n\
 297 ;; A caveat here is that we must not fall through from a failing page   \n\
 298 ;; to a valid page.                                                     \n\
 299                                                                         \n\
 300 3:                                                                      \n\
 301         movem  [$sp+],$r10                                              \n\
 302         addq    44,$r12 ;; Get back count before faulting point.        \n\
 303         subq    44,$r11 ;; Get back pointer to faulting movem-line.     \n\
 304         jump    4b      ;; Fall through, pretending the fault didn't happen.\n\
 305                                                                         \n\
 306         .previous                                                       \n\
 307         .section __ex_table,\"a\"                                       \n\
 308         .dword 1b,3b                                                    \n\
 309         .previous"
 310
 311      /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
 312      /* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
 313
 314   }
 315
 316   /* Either we directly start copying here, using dword copying in a loop,
 317      or we copy as much as possible with 'movem' and then the last block
 318      (<44 bytes) is copied here.  This will work since 'movem' will have
 319      updated src, dst and n.  (Except with failing src.)
 320
 321      Since we want to keep src accurate, we can't use
 322      __asm_copy_from_user_N with N != (1, 2, 4); it updates dst and
 323      retn, but not src (by design; it's value is ignored elsewhere).  */
 324
 325   while (n >= 4)
 326   {
 327     __asm_copy_from_user_4 (dst, src, retn);
 328     n -= 4;
 329
 330     if (retn)
 331       goto copy_exception_bytes;
 332   }
 333
 334   /* If we get here, there were no memory read faults.  */
 335   switch (n)
 336   {
 337     /* These copies are at least "naturally aligned" (so we don't have
 338        to check each byte), due to the src alignment code before the
 339        movem loop.  The *_3 case *will* get the correct count for retn.  */
 340     case 0:
 341       /* This case deliberately left in (if you have doubts check the
 342          generated assembly code).  */
 343       break;
 344     case 1:
 345       __asm_copy_from_user_1 (dst, src, retn);
 346       break;
 347     case 2:
 348       __asm_copy_from_user_2 (dst, src, retn);
 349       break;
 350     case 3:
 351       __asm_copy_from_user_3 (dst, src, retn);
 352       break;
 353   }
 354
 355   /* If we get here, retn correctly reflects the number of failing
 356      bytes.  */
 357   return retn;
 358
 359 copy_exception_bytes:
 360   /* We already have "retn" bytes cleared, and need to clear the
 361      remaining "n" bytes.  A non-optimized simple byte-for-byte in-line
 362      memset is preferred here, since this isn't speed-critical code and
 363      we'd rather have this a leaf-function than calling memset.  */
 364   {
 365     char *endp;
 366     for (endp = dst + n; dst < endp; dst++)
 367       *dst = 0;
 368   }
 369
 370   return retn + n;
 371 }
 372
 373 /* Zero userspace.  */
 374
 375 unsigned long
 376 __do_clear_user (void __user *pto, unsigned long pn)
 377 {
 378   /* We want the parameters put in special registers.
 379      Make sure the compiler is able to make something useful of this.
 380       As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
 381
 382      FIXME: Comment for old gcc version.  Check.
 383      If gcc was alright, it really would need no temporaries, and no
 384      stack space to save stuff on. */
 385
 386   register char *dst __asm__ ("r13") = pto;
 387   register int n __asm__ ("r12") = pn;
 388   register int retn __asm__ ("r10") = 0;
 389
 390
 391   if (((unsigned long) dst & 3) != 0
 392      /* Don't align if we wouldn't copy more than a few bytes.  */
 393       && n >= 3)
 394   {
 395     if ((unsigned long) dst & 1)
 396     {
 397       __asm_clear_1 (dst, retn);
 398       n--;
 399     }
 400
 401     if ((unsigned long) dst & 2)
 402     {
 403       __asm_clear_2 (dst, retn);
 404       n -= 2;
 405     }
 406   }
 407
 408   /* Decide which copying method to use.
 409      FIXME: This number is from the "ordinary" kernel memset.  */
 410   if (n >= (1*48))
 411   {
 412     /* For large clears we use 'movem' */
 413
 414     /* It is not optimal to tell the compiler about clobbering any
 415        call-saved registers; that will move the saving/restoring of
 416        those registers to the function prologue/epilogue, and make
 417        non-movem sizes suboptimal.
 418
 419        This method is not foolproof; it assumes that the "asm reg"
 420        declarations at the beginning of the function really are used
 421        here (beware: they may be moved to temporary registers).
 422        This way, we do not have to save/move the registers around into
 423        temporaries; we can safely use them straight away.
 424
 425       If you want to check that the allocation was right; then
 426       check the equalities in the first comment.  It should say
 427       something like "r13=r13, r11=r11, r12=r12". */
 428     __asm__ volatile ("\n\
 429         .ifnc %0%1%2,$r13$r12$r10                                       \n\
 430         .err                                                            \n\
 431         .endif                                                          \n\
 432                                                                         \n\
 433         ;; Save the registers we'll clobber in the movem process        \n\
 434         ;; on the stack.  Don't mention them to gcc, it will only be    \n\
 435         ;; upset.                                                       \n\
 436         subq    11*4,$sp                                                \n\
 437         movem   $r10,[$sp]                                              \n\
 438                                                                         \n\
 439         clear.d $r0                                                     \n\
 440         clear.d $r1                                                     \n\
 441         clear.d $r2                                                     \n\
 442         clear.d $r3                                                     \n\
 443         clear.d $r4                                                     \n\
 444         clear.d $r5                                                     \n\
 445         clear.d $r6                                                     \n\
 446         clear.d $r7                                                     \n\
 447         clear.d $r8                                                     \n\
 448         clear.d $r9                                                     \n\
 449         clear.d $r10                                                    \n\
 450         clear.d $r11                                                    \n\
 451                                                                         \n\
 452         ;; Now we've got this:                                          \n\
 453         ;; r13 - dst                                                    \n\
 454         ;; r12 - n                                                      \n\
 455                                                                         \n\
 456         ;; Update n for the first loop                                  \n\
 457         subq    12*4,$r12                                               \n\
 458 0:                                                                      \n\
 459         subq   12*4,$r12                                                \n\
 460         bge     0b                                                      \n\
 461         movem   $r11,[$r13+]                                            \n\
 462 1:                                                                      \n\
 463         addq   12*4,$r12        ;; compensate for last loop underflowing n\n\
 464                                                                         \n\
 465         ;; Restore registers from stack                                 \n\
 466         movem [$sp+],$r10                                               \n\
 467 2:                                                                      \n\
 468         .section .fixup,\"ax\"                                          \n\
 469 3:                                                                      \n\
 470         move.d [$sp],$r10                                               \n\
 471         addq 12*4,$r10                                                  \n\
 472         move.d $r10,[$sp]                                               \n\
 473         clear.d $r10                                                    \n\
 474         jump 0b                                                         \n\
 475                                                                         \n\
 476 4:                                                                      \n\
 477         movem [$sp+],$r10                                               \n\
 478         addq 12*4,$r10                                                  \n\
 479         addq 12*4,$r12                                                  \n\
 480         jump 2b                                                         \n\
 481                                                                         \n\
 482         .previous                                                       \n\
 483         .section __ex_table,\"a\"                                       \n\
 484         .dword 0b,3b                                                    \n\
 485         .dword 1b,4b                                                    \n\
 486         .previous"
 487
 488      /* Outputs */ : "=r" (dst), "=r" (n), "=r" (retn)
 489      /* Inputs */ : "0" (dst), "1" (n), "2" (retn)
 490      /* Clobber */ : "r11");
 491   }
 492
 493   while (n >= 16)
 494   {
 495     __asm_clear_16 (dst, retn);
 496     n -= 16;
 497   }
 498
 499   /* Having a separate by-four loops cuts down on cache footprint.
 500      FIXME:  Test with and without; increasing switch to be 0..15.  */
 501   while (n >= 4)
 502   {
 503     __asm_clear_4 (dst, retn);
 504     n -= 4;
 505   }
 506
 507   switch (n)
 508   {
 509     case 0:
 510       break;
 511     case 1:
 512       __asm_clear_1 (dst, retn);
 513       break;
 514     case 2:
 515       __asm_clear_2 (dst, retn);
 516       break;
 517     case 3:
 518       __asm_clear_3 (dst, retn);
 519       break;
 520   }
 521
 522   return retn;
 523 }