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

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * User address space access functions.
   4  * The non-inlined parts of asm-cris/uaccess.h are here.
   5  *
   6  * Copyright (C) 2000, Axis Communications AB.
   7  *
   8  * Written by Hans-Peter Nilsson.
   9  * Pieces used from memcpy, originally by Kenny Ranerup long time ago.
  10  */
  11
  12 #include <linux/uaccess.h>
  13
  14 /* Asm:s have been tweaked (within the domain of correctness) to give
  15    satisfactory results for "gcc version 2.96 20000427 (experimental)".
  16
  17    Check regularly...
  18
  19    Note that the PC saved at a bus-fault is the address *after* the
  20    faulting instruction, which means the branch-target for instructions in
  21    delay-slots for taken branches.  Note also that the postincrement in
  22    the instruction is performed regardless of bus-fault; the register is
  23    seen updated in fault handlers.
  24
  25    Oh, and on the code formatting issue, to whomever feels like "fixing
  26    it" to Conformity: I'm too "lazy", but why don't you go ahead and "fix"
  27    string.c too.  I just don't think too many people will hack this file
  28    for the code format to be an issue.  */
  29
  30
  31 /* Copy to userspace.  This is based on the memcpy used for
  32    kernel-to-kernel copying; see "string.c".  */
  33
  34 unsigned long __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 EXPORT_SYMBOL(__copy_user);
 191
 192 /* Copy from user to kernel.  The return-value is the number of bytes that were
 193    inaccessible.  */
 194
 195 unsigned long __copy_user_in(void *pdst, const void __user *psrc,
 196                                   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       if (retn)
 221          goto exception;
 222     }
 223
 224     if (((unsigned long) src & 2) && n >= 2)
 225     {
 226       __asm_copy_from_user_2 (dst, src, retn);
 227       n -= 2;
 228       if (retn)
 229          goto exception;
 230     }
 231   }
 232
 233   /* Decide which copying method to use. */
 234   if (n >= 44*2)                /* Break even between movem and
 235                                    move16 is at 38.7*2, but modulo 44.
 236                                    FIXME: We use move4 now.  */
 237   {
 238     /* For large copies we use 'movem' */
 239
 240     /* It is not optimal to tell the compiler about clobbering any
 241        registers; that will move the saving/restoring of those registers
 242        to the function prologue/epilogue, and make non-movem sizes
 243        suboptimal.
 244
 245        This method is not foolproof; it assumes that the "asm reg"
 246        declarations at the beginning of the function really are used
 247        here (beware: they may be moved to temporary registers).
 248        This way, we do not have to save/move the registers around into
 249        temporaries; we can safely use them straight away.
 250
 251        If you want to check that the allocation was right; then
 252        check the equalities in the first comment.  It should say
 253        "r13=r13, r11=r11, r12=r12" */
 254     __asm__ volatile ("\n\
 255         .ifnc %0%1%2%3,$r13$r11$r12$r10                                 \n\
 256         .err                                                            \n\
 257         .endif                                                          \n\
 258                                                                         \n\
 259         ;; Save the registers we'll use in the movem process            \n\
 260         ;; on the stack.                                                \n\
 261         subq    11*4,$sp                                                \n\
 262         movem   $r10,[$sp]                                              \n\
 263                                                                         \n\
 264         ;; Now we've got this:                                          \n\
 265         ;; r11 - src                                                    \n\
 266         ;; r13 - dst                                                    \n\
 267         ;; r12 - n                                                      \n\
 268                                                                         \n\
 269         ;; Update n for the first loop                                  \n\
 270         subq    44,$r12                                                 \n\
 271 0:                                                                      \n\
 272         movem   [$r11+],$r10                                            \n\
 273 1:                                                                      \n\
 274         subq   44,$r12                                                  \n\
 275         bge     0b                                                      \n\
 276         movem   $r10,[$r13+]                                            \n\
 277                                                                         \n\
 278         addq   44,$r12  ;; compensate for last loop underflowing n      \n\
 279                                                                         \n\
 280         ;; Restore registers from stack                                 \n\
 281         movem [$sp+],$r10                                               \n\
 282 4:                                                                      \n\
 283         .section .fixup,\"ax\"                                          \n\
 284                                                                         \n\
 285 ;; Do not jump back into the loop if we fail.  For some uses, we get a  \n\
 286 ;; page fault somewhere on the line.  Without checking for page limits, \n\
 287 ;; we don't know where, but we need to copy accurately and keep an      \n\
 288 ;; accurate count; not just clear the whole line.  To do that, we fall  \n\
 289 ;; down in the code below, proceeding with smaller amounts.  It should  \n\
 290 ;; be kept in mind that we have to cater to code like what at one time  \n\
 291 ;; was in fs/super.c:                                                   \n\
 292 ;;  i = size - copy_from_user((void *)page, data, size);                \n\
 293 ;; which would cause repeated faults while clearing the remainder of    \n\
 294 ;; the SIZE bytes at PAGE after the first fault.                        \n\
 295 ;; A caveat here is that we must not fall through from a failing page   \n\
 296 ;; to a valid page.                                                     \n\
 297                                                                         \n\
 298 3:                                                                      \n\
 299         movem  [$sp+],$r10                                              \n\
 300         addq    44,$r12 ;; Get back count before faulting point.        \n\
 301         subq    44,$r11 ;; Get back pointer to faulting movem-line.     \n\
 302         jump    4b      ;; Fall through, pretending the fault didn't happen.\n\
 303                                                                         \n\
 304         .previous                                                       \n\
 305         .section __ex_table,\"a\"                                       \n\
 306         .dword 1b,3b                                                    \n\
 307         .previous"
 308
 309      /* Outputs */ : "=r" (dst), "=r" (src), "=r" (n), "=r" (retn)
 310      /* Inputs */ : "0" (dst), "1" (src), "2" (n), "3" (retn));
 311
 312   }
 313
 314   /* Either we directly start copying here, using dword copying in a loop,
 315      or we copy as much as possible with 'movem' and then the last block
 316      (<44 bytes) is copied here.  This will work since 'movem' will have
 317      updated src, dst and n.  (Except with failing src.)
 318
 319      Since we want to keep src accurate, we can't use
 320      __asm_copy_from_user_N with N != (1, 2, 4); it updates dst and
 321      retn, but not src (by design; it's value is ignored elsewhere).  */
 322
 323   while (n >= 4)
 324   {
 325     __asm_copy_from_user_4 (dst, src, retn);
 326     n -= 4;
 327
 328     if (retn)
 329       goto exception;
 330   }
 331
 332   /* If we get here, there were no memory read faults.  */
 333   switch (n)
 334   {
 335     /* These copies are at least "naturally aligned" (so we don't have
 336        to check each byte), due to the src alignment code before the
 337        movem loop.  The *_3 case *will* get the correct count for retn.  */
 338     case 0:
 339       /* This case deliberately left in (if you have doubts check the
 340          generated assembly code).  */
 341       break;
 342     case 1:
 343       __asm_copy_from_user_1 (dst, src, retn);
 344       break;
 345     case 2:
 346       __asm_copy_from_user_2 (dst, src, retn);
 347       break;
 348     case 3:
 349       __asm_copy_from_user_3 (dst, src, retn);
 350       break;
 351   }
 352
 353   /* If we get here, retn correctly reflects the number of failing
 354      bytes.  */
 355   return retn;
 356
 357 exception:
 358   return retn + n;
 359 }
 360 EXPORT_SYMBOL(__copy_user_in);
 361
 362 /* Zero userspace.  */
 363 unsigned long __do_clear_user(void __user *pto, unsigned long pn)
 364 {
 365   /* We want the parameters put in special registers.
 366      Make sure the compiler is able to make something useful of this.
 367       As it is now: r10 -> r13; r11 -> r11 (nop); r12 -> r12 (nop).
 368
 369      FIXME: Comment for old gcc version.  Check.
 370      If gcc was alright, it really would need no temporaries, and no
 371      stack space to save stuff on. */
 372
 373   register char *dst __asm__ ("r13") = pto;
 374   register int n __asm__ ("r12") = pn;
 375   register int retn __asm__ ("r10") = 0;
 376
 377
 378   if (((unsigned long) dst & 3) != 0
 379      /* Don't align if we wouldn't copy more than a few bytes.  */
 380       && n >= 3)
 381   {
 382     if ((unsigned long) dst & 1)
 383     {
 384       __asm_clear_1 (dst, retn);
 385       n--;
 386     }
 387
 388     if ((unsigned long) dst & 2)
 389     {
 390       __asm_clear_2 (dst, retn);
 391       n -= 2;
 392     }
 393   }
 394
 395   /* Decide which copying method to use.
 396      FIXME: This number is from the "ordinary" kernel memset.  */
 397   if (n >= (1*48))
 398   {
 399     /* For large clears we use 'movem' */
 400
 401     /* It is not optimal to tell the compiler about clobbering any
 402        call-saved registers; that will move the saving/restoring of
 403        those registers to the function prologue/epilogue, and make
 404        non-movem sizes suboptimal.
 405
 406        This method is not foolproof; it assumes that the "asm reg"
 407        declarations at the beginning of the function really are used
 408        here (beware: they may be moved to temporary registers).
 409        This way, we do not have to save/move the registers around into
 410        temporaries; we can safely use them straight away.
 411
 412       If you want to check that the allocation was right; then
 413       check the equalities in the first comment.  It should say
 414       something like "r13=r13, r11=r11, r12=r12". */
 415     __asm__ volatile ("\n\
 416         .ifnc %0%1%2,$r13$r12$r10                                       \n\
 417         .err                                                            \n\
 418         .endif                                                          \n\
 419                                                                         \n\
 420         ;; Save the registers we'll clobber in the movem process        \n\
 421         ;; on the stack.  Don't mention them to gcc, it will only be    \n\
 422         ;; upset.                                                       \n\
 423         subq    11*4,$sp                                                \n\
 424         movem   $r10,[$sp]                                              \n\
 425                                                                         \n\
 426         clear.d $r0                                                     \n\
 427         clear.d $r1                                                     \n\
 428         clear.d $r2                                                     \n\
 429         clear.d $r3                                                     \n\
 430         clear.d $r4                                                     \n\
 431         clear.d $r5                                                     \n\
 432         clear.d $r6                                                     \n\
 433         clear.d $r7                                                     \n\
 434         clear.d $r8                                                     \n\
 435         clear.d $r9                                                     \n\
 436         clear.d $r10                                                    \n\
 437         clear.d $r11                                                    \n\
 438                                                                         \n\
 439         ;; Now we've got this:                                          \n\
 440         ;; r13 - dst                                                    \n\
 441         ;; r12 - n                                                      \n\
 442                                                                         \n\
 443         ;; Update n for the first loop                                  \n\
 444         subq    12*4,$r12                                               \n\
 445 0:                                                                      \n\
 446         subq   12*4,$r12                                                \n\
 447         bge     0b                                                      \n\
 448         movem   $r11,[$r13+]                                            \n\
 449 1:                                                                      \n\
 450         addq   12*4,$r12        ;; compensate for last loop underflowing n\n\
 451                                                                         \n\
 452         ;; Restore registers from stack                                 \n\
 453         movem [$sp+],$r10                                               \n\
 454 2:                                                                      \n\
 455         .section .fixup,\"ax\"                                          \n\
 456 3:                                                                      \n\
 457         move.d [$sp],$r10                                               \n\
 458         addq 12*4,$r10                                                  \n\
 459         move.d $r10,[$sp]                                               \n\
 460         clear.d $r10                                                    \n\
 461         jump 0b                                                         \n\
 462                                                                         \n\
 463 4:                                                                      \n\
 464         movem [$sp+],$r10                                               \n\
 465         addq 12*4,$r10                                                  \n\
 466         addq 12*4,$r12                                                  \n\
 467         jump 2b                                                         \n\
 468                                                                         \n\
 469         .previous                                                       \n\
 470         .section __ex_table,\"a\"                                       \n\
 471         .dword 0b,3b                                                    \n\
 472         .dword 1b,4b                                                    \n\
 473         .previous"
 474
 475      /* Outputs */ : "=r" (dst), "=r" (n), "=r" (retn)
 476      /* Inputs */ : "0" (dst), "1" (n), "2" (retn)
 477      /* Clobber */ : "r11");
 478   }
 479
 480   while (n >= 16)
 481   {
 482     __asm_clear_16 (dst, retn);
 483     n -= 16;
 484   }
 485
 486   /* Having a separate by-four loops cuts down on cache footprint.
 487      FIXME:  Test with and without; increasing switch to be 0..15.  */
 488   while (n >= 4)
 489   {
 490     __asm_clear_4 (dst, retn);
 491     n -= 4;
 492   }
 493
 494   switch (n)
 495   {
 496     case 0:
 497       break;
 498     case 1:
 499       __asm_clear_1 (dst, retn);
 500       break;
 501     case 2:
 502       __asm_clear_2 (dst, retn);
 503       break;
 504     case 3:
 505       __asm_clear_3 (dst, retn);
 506       break;
 507   }
 508
 509   return retn;
 510 }
 511 EXPORT_SYMBOL(__do_clear_user);