sys/platform/pc64/x86_64/support.s

   1 /*-
   2  * Copyright (c) 1993 The Regents of the University of California.
   3  * Copyright (c) 2003 Peter Wemm.
   4  * Copyright (c) 2008 The DragonFly Project.
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the University nor the names of its contributors
  16  *    may be used to endorse or promote products derived from this software
  17  *    without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  *
  31  * $FreeBSD: src/sys/amd64/amd64/support.S,v 1.127 2007/05/23 08:33:04 kib Exp $
  32  */
  33
  34 #include <machine/asmacros.h>
  35 #include <machine/pmap.h>
  36
  37 #include "assym.s"
  38
  39         ALIGN_DATA
  40
  41         .text
  42
  43 /*
  44  * bcopy family
  45  * void bzero(void *buf, size_t len)
  46  */
  47
  48 /* done */
  49 ENTRY(bzero)
  50         movq    %rsi,%rcx
  51         xorl    %eax,%eax
  52         shrq    $3,%rcx
  53         cld
  54         rep
  55         stosq
  56         movq    %rsi,%rcx
  57         andq    $7,%rcx
  58         rep
  59         stosb
  60         ret
  61
  62 /* Address: %rdi */
  63 ENTRY(pagezero)
  64         movq    $-PAGE_SIZE,%rdx
  65         subq    %rdx,%rdi
  66         xorl    %eax,%eax
  67 1:
  68         movq    %rax,(%rdi,%rdx)        /* movnti */
  69         movq    %rax,8(%rdi,%rdx)       /* movnti */
  70         movq    %rax,16(%rdi,%rdx)      /* movnti */
  71         movq    %rax,24(%rdi,%rdx)      /* movnti */
  72         addq    $32,%rdx
  73         jne     1b
  74         /*sfence*/
  75         ret
  76
  77 ENTRY(bcmp)
  78         movq    %rdx,%rcx
  79         shrq    $3,%rcx
  80         cld                                     /* compare forwards */
  81         repe
  82         cmpsq
  83         jne     1f
  84
  85         movq    %rdx,%rcx
  86         andq    $7,%rcx
  87         repe
  88         cmpsb
  89 1:
  90         setne   %al
  91         movsbl  %al,%eax
  92         ret
  93
  94 /*
  95  * bcopy(src, dst, cnt)
  96  *       rdi, rsi, rdx
  97  *  ws@tools.de     (Wolfgang Solfrank, TooLs GmbH) +49-228-985800
  98  */
  99 ENTRY(generic_bcopy)    /* generic_bcopy is bcopy without FPU */
 100 ENTRY(ovbcopy) /* our bcopy doesn't use the FPU, so ovbcopy is the same */
 101 ENTRY(bcopy)
 102         xchgq   %rsi,%rdi
 103         movq    %rdx,%rcx
 104
 105         movq    %rdi,%rax
 106         subq    %rsi,%rax
 107         cmpq    %rcx,%rax                       /* overlapping && src < dst? */
 108         jb      1f
 109
 110         shrq    $3,%rcx                         /* copy by 64-bit words */
 111         cld                                     /* nope, copy forwards */
 112         rep
 113         movsq
 114         movq    %rdx,%rcx
 115         andq    $7,%rcx                         /* any bytes left? */
 116         rep
 117         movsb
 118         ret
 119
 120         /* ALIGN_TEXT */
 121 1:
 122         addq    %rcx,%rdi                       /* copy backwards */
 123         addq    %rcx,%rsi
 124         decq    %rdi
 125         decq    %rsi
 126         andq    $7,%rcx                         /* any fractional bytes? */
 127         std
 128         rep
 129         movsb
 130         movq    %rdx,%rcx                       /* copy remainder by 32-bit words */
 131         shrq    $3,%rcx
 132         subq    $7,%rsi
 133         subq    $7,%rdi
 134         rep
 135         movsq
 136         cld
 137         ret
 138 ENTRY(reset_dbregs)
 139         movq    $0x200,%rax   /* the manual says that bit 10 must be set to 1 */
 140         movq    %rax,%dr7     /* disable all breapoints first */
 141         movq    $0,%rax
 142         movq    %rax,%dr0
 143         movq    %rax,%dr1
 144         movq    %rax,%dr2
 145         movq    %rax,%dr3
 146         movq    %rax,%dr6
 147         ret
 148
 149 /*
 150  * Note: memcpy does not support overlapping copies
 151  */
 152 ENTRY(memcpy)
 153         movq    %rdx,%rcx
 154         shrq    $3,%rcx                         /* copy by 64-bit words */
 155         cld                                     /* copy forwards */
 156         rep
 157         movsq
 158         movq    %rdx,%rcx
 159         andq    $7,%rcx                         /* any bytes left? */
 160         rep
 161         movsb
 162         ret
 163
 164 /*
 165  * pagecopy(%rdi=from, %rsi=to)
 166  */
 167 ENTRY(pagecopy)
 168         movq    $-PAGE_SIZE,%rax
 169         movq    %rax,%rdx
 170         subq    %rax,%rdi
 171         subq    %rax,%rsi
 172 1:
 173         /*prefetchnta (%rdi,%rax)*/
 174         /*addq  $64,%rax*/
 175         /*jne   1b*/
 176 2:
 177         movq    (%rdi,%rdx),%rax
 178         movq    %rax,(%rsi,%rdx)        /* movnti */
 179         movq    8(%rdi,%rdx),%rax
 180         movq    %rax,8(%rsi,%rdx)       /* movnti */
 181         movq    16(%rdi,%rdx),%rax
 182         movq    %rax,16(%rsi,%rdx)      /* movnti */
 183         movq    24(%rdi,%rdx),%rax
 184         movq    %rax,24(%rsi,%rdx)      /* movnti */
 185         addq    $32,%rdx
 186         jne     2b
 187         /*sfence*/
 188         ret
 189
 190 /* fillw(pat, base, cnt) */
 191 /*       %rdi,%rsi, %rdx */
 192 ENTRY(fillw)
 193         movq    %rdi,%rax
 194         movq    %rsi,%rdi
 195         movq    %rdx,%rcx
 196         cld
 197         rep
 198         stosw
 199         ret
 200
 201 /*****************************************************************************/
 202 /* copyout and fubyte family                                                 */
 203 /*****************************************************************************/
 204 /*
 205  * Access user memory from inside the kernel. These routines should be
 206  * the only places that do this.
 207  *
 208  * These routines set curpcb->onfault for the time they execute. When a
 209  * protection violation occurs inside the functions, the trap handler
 210  * returns to *curpcb->onfault instead of the function.
 211  */
 212
 213 /*
 214  * std_copyout(from_kernel, to_user, len)  - MP SAFE
 215  *         %rdi,        %rsi,    %rdx
 216  */
 217 ENTRY(std_copyout)
 218         movq    PCPU(curthread),%rax
 219         movq    TD_PCB(%rax), %rax
 220         movq    $copyout_fault,PCB_ONFAULT(%rax)
 221         movq    %rsp,PCB_ONFAULT_SP(%rax)
 222         testq   %rdx,%rdx                       /* anything to do? */
 223         jz      done_copyout
 224
 225         /*
 226          * Check explicitly for non-user addresses.  If 486 write protection
 227          * is being used, this check is essential because we are in kernel
 228          * mode so the h/w does not provide any protection against writing
 229          * kernel addresses.
 230          */
 231
 232         /*
 233          * First, prevent address wrapping.
 234          */
 235         movq    %rsi,%rax
 236         addq    %rdx,%rax
 237         jc      copyout_fault
 238 /*
 239  * XXX STOP USING VM_MAX_USER_ADDRESS.
 240  * It is an end address, not a max, so every time it is used correctly it
 241  * looks like there is an off by one error, and of course it caused an off
 242  * by one error in several places.
 243  */
 244         movq    $VM_MAX_USER_ADDRESS,%rcx
 245         cmpq    %rcx,%rax
 246         ja      copyout_fault
 247
 248         xchgq   %rdi,%rsi
 249         /* bcopy(%rsi, %rdi, %rdx) */
 250         movq    %rdx,%rcx
 251
 252         shrq    $3,%rcx
 253         cld
 254         rep
 255         movsq
 256         movb    %dl,%cl
 257         andb    $7,%cl
 258         rep
 259         movsb
 260
 261 done_copyout:
 262         xorl    %eax,%eax
 263         movq    PCPU(curthread),%rdx
 264         movq    TD_PCB(%rdx), %rdx
 265         movq    %rax,PCB_ONFAULT(%rdx)
 266         ret
 267
 268         ALIGN_TEXT
 269 copyout_fault:
 270         movq    PCPU(curthread),%rdx
 271         movq    TD_PCB(%rdx), %rdx
 272         movq    $0,PCB_ONFAULT(%rdx)
 273         movq    $EFAULT,%rax
 274         ret
 275
 276 /*
 277  * std_copyin(from_user, to_kernel, len) - MP SAFE
 278  *        %rdi,      %rsi,      %rdx
 279  */
 280 ENTRY(std_copyin)
 281         movq    PCPU(curthread),%rax
 282         movq    TD_PCB(%rax), %rax
 283         movq    $copyin_fault,PCB_ONFAULT(%rax)
 284         movq    %rsp,PCB_ONFAULT_SP(%rax)
 285         testq   %rdx,%rdx                       /* anything to do? */
 286         jz      done_copyin
 287
 288         /*
 289          * make sure address is valid
 290          */
 291         movq    %rdi,%rax
 292         addq    %rdx,%rax
 293         jc      copyin_fault
 294         movq    $VM_MAX_USER_ADDRESS,%rcx
 295         cmpq    %rcx,%rax
 296         ja      copyin_fault
 297
 298         xchgq   %rdi,%rsi
 299         movq    %rdx,%rcx
 300         movb    %cl,%al
 301         shrq    $3,%rcx                         /* copy longword-wise */
 302         cld
 303         rep
 304         movsq
 305         movb    %al,%cl
 306         andb    $7,%cl                          /* copy remaining bytes */
 307         rep
 308         movsb
 309
 310 done_copyin:
 311         xorl    %eax,%eax
 312         movq    PCPU(curthread),%rdx
 313         movq    TD_PCB(%rdx), %rdx
 314         movq    %rax,PCB_ONFAULT(%rdx)
 315         ret
 316
 317         ALIGN_TEXT
 318 copyin_fault:
 319         movq    PCPU(curthread),%rdx
 320         movq    TD_PCB(%rdx), %rdx
 321         movq    $0,PCB_ONFAULT(%rdx)
 322         movq    $EFAULT,%rax
 323         ret
 324
 325 /*
 326  * casuword32.  Compare and set user integer.  Returns -1 or the current value.
 327  *        dst = %rdi, old = %rsi, new = %rdx
 328  */
 329 ENTRY(casuword32)
 330         movq    PCPU(curthread),%rcx
 331         movq    TD_PCB(%rcx), %rcx
 332         movq    $fusufault,PCB_ONFAULT(%rcx)
 333         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 334
 335         movq    $VM_MAX_USER_ADDRESS-4,%rax
 336         cmpq    %rax,%rdi                       /* verify address is valid */
 337         ja      fusufault
 338
 339         movl    %esi,%eax                       /* old */
 340         lock
 341         cmpxchgl %edx,(%rdi)                    /* new = %edx */
 342
 343         /*
 344          * The old value is in %eax.  If the store succeeded it will be the
 345          * value we expected (old) from before the store, otherwise it will
 346          * be the current value.
 347          */
 348
 349         movq    PCPU(curthread),%rcx
 350         movq    TD_PCB(%rcx), %rcx
 351         movq    $0,PCB_ONFAULT(%rcx)
 352         ret
 353
 354 /*
 355  * casuword.  Compare and set user word.  Returns -1 or the current value.
 356  *        dst = %rdi, old = %rsi, new = %rdx
 357  */
 358 ENTRY(casuword)
 359         movq    PCPU(curthread),%rcx
 360         movq    TD_PCB(%rcx), %rcx
 361         movq    $fusufault,PCB_ONFAULT(%rcx)
 362         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 363
 364         movq    $VM_MAX_USER_ADDRESS-8,%rax
 365         cmpq    %rax,%rdi                       /* verify address is valid */
 366         ja      fusufault
 367
 368         movq    %rsi,%rax                       /* old */
 369         lock
 370         cmpxchgq %rdx,(%rdi)                    /* new = %rdx */
 371
 372         /*
 373          * The old value is in %rax.  If the store succeeded it will be the
 374          * value we expected (old) from before the store, otherwise it will
 375          * be the current value.
 376          */
 377
 378         movq    PCPU(curthread),%rcx
 379         movq    TD_PCB(%rcx), %rcx
 380         movq    $0,PCB_ONFAULT(%rcx)
 381         ret
 382
 383 /*
 384  * Fetch (load) a 64-bit word, a 32-bit word, a 16-bit word, or an 8-bit
 385  * byte from user memory.  All these functions are MPSAFE.
 386  * addr = %rdi
 387  */
 388
 389 ALTENTRY(fuword64)
 390 ENTRY(std_fuword)
 391         movq    PCPU(curthread),%rcx
 392         movq    TD_PCB(%rcx), %rcx
 393         movq    $fusufault,PCB_ONFAULT(%rcx)
 394         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 395
 396         movq    $VM_MAX_USER_ADDRESS-8,%rax
 397         cmpq    %rax,%rdi                       /* verify address is valid */
 398         ja      fusufault
 399
 400         movq    (%rdi),%rax
 401         movq    $0,PCB_ONFAULT(%rcx)
 402         ret
 403
 404 ENTRY(fuword32)
 405         movq    PCPU(curthread),%rcx
 406         movq    TD_PCB(%rcx), %rcx
 407         movq    $fusufault,PCB_ONFAULT(%rcx)
 408         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 409
 410         movq    $VM_MAX_USER_ADDRESS-4,%rax
 411         cmpq    %rax,%rdi                       /* verify address is valid */
 412         ja      fusufault
 413
 414         movl    (%rdi),%eax
 415         movq    $0,PCB_ONFAULT(%rcx)
 416         ret
 417
 418 /*
 419  * fuswintr() and suswintr() are specialized variants of fuword16() and
 420  * suword16(), respectively.  They are called from the profiling code,
 421  * potentially at interrupt time.  If they fail, that's okay; good things
 422  * will happen later.  They always fail for now, until the trap code is
 423  * able to deal with this.
 424  */
 425 ALTENTRY(suswintr)
 426 ENTRY(fuswintr)
 427         movq    $-1,%rax
 428         ret
 429
 430 ENTRY(fuword16)
 431         movq    PCPU(curthread),%rcx
 432         movq    TD_PCB(%rcx), %rcx
 433         movq    $fusufault,PCB_ONFAULT(%rcx)
 434         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 435
 436         movq    $VM_MAX_USER_ADDRESS-2,%rax
 437         cmpq    %rax,%rdi
 438         ja      fusufault
 439
 440         movzwl  (%rdi),%eax
 441         movq    $0,PCB_ONFAULT(%rcx)
 442         ret
 443
 444 ENTRY(std_fubyte)
 445         movq    PCPU(curthread),%rcx
 446         movq    TD_PCB(%rcx), %rcx
 447         movq    $fusufault,PCB_ONFAULT(%rcx)
 448         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 449
 450         movq    $VM_MAX_USER_ADDRESS-1,%rax
 451         cmpq    %rax,%rdi
 452         ja      fusufault
 453
 454         movzbl  (%rdi),%eax
 455         movq    $0,PCB_ONFAULT(%rcx)
 456         ret
 457
 458         ALIGN_TEXT
 459 fusufault:
 460         movq    PCPU(curthread),%rcx
 461         xorl    %eax,%eax
 462         movq    TD_PCB(%rcx), %rcx
 463         movq    %rax,PCB_ONFAULT(%rcx)
 464         decq    %rax
 465         ret
 466
 467 /*
 468  * Store a 64-bit word, a 32-bit word, a 16-bit word, or an 8-bit byte to
 469  * user memory.  All these functions are MPSAFE.
 470  *
 471  * addr = %rdi, value = %rsi
 472  *
 473  * Write a long
 474  */
 475 ALTENTRY(suword64)
 476 ENTRY(std_suword)
 477         movq    PCPU(curthread),%rcx
 478         movq    TD_PCB(%rcx), %rcx
 479         movq    $fusufault,PCB_ONFAULT(%rcx)
 480         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 481
 482         movq    $VM_MAX_USER_ADDRESS-8,%rax
 483         cmpq    %rax,%rdi                       /* verify address validity */
 484         ja      fusufault
 485
 486         movq    %rsi,(%rdi)
 487         xorl    %eax,%eax
 488         movq    PCPU(curthread),%rcx
 489         movq    TD_PCB(%rcx), %rcx
 490         movq    %rax,PCB_ONFAULT(%rcx)
 491         ret
 492
 493 /*
 494  * Write an int
 495  */
 496 ENTRY(std_suword32)
 497         movq    PCPU(curthread),%rcx
 498         movq    TD_PCB(%rcx), %rcx
 499         movq    $fusufault,PCB_ONFAULT(%rcx)
 500         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 501
 502         movq    $VM_MAX_USER_ADDRESS-4,%rax
 503         cmpq    %rax,%rdi                       /* verify address validity */
 504         ja      fusufault
 505
 506         movl    %esi,(%rdi)
 507         xorl    %eax,%eax
 508         movq    PCPU(curthread),%rcx
 509         movq    TD_PCB(%rcx), %rcx
 510         movq    %rax,PCB_ONFAULT(%rcx)
 511         ret
 512
 513 ENTRY(suword16)
 514         movq    PCPU(curthread),%rcx
 515         movq    TD_PCB(%rcx), %rcx
 516         movq    $fusufault,PCB_ONFAULT(%rcx)
 517         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 518
 519         movq    $VM_MAX_USER_ADDRESS-2,%rax
 520         cmpq    %rax,%rdi                       /* verify address validity */
 521         ja      fusufault
 522
 523         movw    %si,(%rdi)
 524         xorl    %eax,%eax
 525         movq    PCPU(curthread),%rcx            /* restore trashed register */
 526         movq    TD_PCB(%rcx), %rcx
 527         movq    %rax,PCB_ONFAULT(%rcx)
 528         ret
 529
 530 ENTRY(std_subyte)
 531         movq    PCPU(curthread),%rcx
 532         movq    TD_PCB(%rcx), %rcx
 533         movq    $fusufault,PCB_ONFAULT(%rcx)
 534         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 535
 536         movq    $VM_MAX_USER_ADDRESS-1,%rax
 537         cmpq    %rax,%rdi                       /* verify address validity */
 538         ja      fusufault
 539
 540         movl    %esi,%eax
 541         movb    %al,(%rdi)
 542         xorl    %eax,%eax
 543         movq    PCPU(curthread),%rcx            /* restore trashed register */
 544         movq    TD_PCB(%rcx), %rcx
 545         movq    %rax,PCB_ONFAULT(%rcx)
 546         ret
 547
 548 /*
 549  * std_copyinstr(from, to, maxlen, int *lencopied) - MP SAFE
 550  *           %rdi, %rsi, %rdx, %rcx
 551  *
 552  *      copy a string from from to to, stop when a 0 character is reached.
 553  *      return ENAMETOOLONG if string is longer than maxlen, and
 554  *      EFAULT on protection violations. If lencopied is non-zero,
 555  *      return the actual length in *lencopied.
 556  */
 557 ENTRY(std_copyinstr)
 558         movq    %rdx,%r8                        /* %r8 = maxlen */
 559         movq    %rcx,%r9                        /* %r9 = *len */
 560         xchgq   %rdi,%rsi                       /* %rdi = from, %rsi = to */
 561         movq    PCPU(curthread),%rcx
 562         movq    TD_PCB(%rcx), %rcx
 563         movq    $cpystrflt,PCB_ONFAULT(%rcx)
 564         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 565
 566         movq    $VM_MAX_USER_ADDRESS,%rax
 567
 568         /* make sure 'from' is within bounds */
 569         subq    %rsi,%rax
 570         jbe     cpystrflt
 571
 572         /* restrict maxlen to <= VM_MAX_USER_ADDRESS-from */
 573         cmpq    %rdx,%rax
 574         jae     1f
 575         movq    %rax,%rdx
 576         movq    %rax,%r8
 577 1:
 578         incq    %rdx
 579         cld
 580
 581 2:
 582         decq    %rdx
 583         jz      3f
 584
 585         lodsb
 586         stosb
 587         orb     %al,%al
 588         jnz     2b
 589
 590         /* Success -- 0 byte reached */
 591         decq    %rdx
 592         xorl    %eax,%eax
 593         jmp     cpystrflt_x
 594 3:
 595         /* rdx is zero - return ENAMETOOLONG or EFAULT */
 596         movq    $VM_MAX_USER_ADDRESS,%rax
 597         cmpq    %rax,%rsi
 598         jae     cpystrflt
 599 4:
 600         movq    $ENAMETOOLONG,%rax
 601         jmp     cpystrflt_x
 602
 603 cpystrflt:
 604         movq    $EFAULT,%rax
 605
 606 cpystrflt_x:
 607         /* set *lencopied and return %eax */
 608         movq    PCPU(curthread),%rcx
 609         movq    TD_PCB(%rcx), %rcx
 610         movq    $0,PCB_ONFAULT(%rcx)
 611
 612         testq   %r9,%r9
 613         jz      1f
 614         subq    %rdx,%r8
 615         movq    %r8,(%r9)
 616 1:
 617         ret
 618
 619
 620 /*
 621  * copystr(from, to, maxlen, int *lencopied) - MP SAFE
 622  *         %rdi, %rsi, %rdx, %rcx
 623  */
 624 ENTRY(copystr)
 625         movq    %rdx,%r8                        /* %r8 = maxlen */
 626
 627         xchgq   %rdi,%rsi
 628         incq    %rdx
 629         cld
 630 1:
 631         decq    %rdx
 632         jz      4f
 633         lodsb
 634         stosb
 635         orb     %al,%al
 636         jnz     1b
 637
 638         /* Success -- 0 byte reached */
 639         decq    %rdx
 640         xorl    %eax,%eax
 641         jmp     6f
 642 4:
 643         /* rdx is zero -- return ENAMETOOLONG */
 644         movq    $ENAMETOOLONG,%rax
 645
 646 6:
 647
 648         testq   %rcx,%rcx
 649         jz      7f
 650         /* set *lencopied and return %rax */
 651         subq    %rdx,%r8
 652         movq    %r8,(%rcx)
 653 7:
 654         ret
 655
 656 /*
 657  * Handling of special x86_64 registers and descriptor tables etc
 658  * %rdi
 659  */
 660 /* void lgdt(struct region_descriptor *rdp); */
 661 ENTRY(lgdt)
 662         /* reload the descriptor table */
 663         lgdt    (%rdi)
 664
 665         /* flush the prefetch q */
 666         jmp     1f
 667         nop
 668 1:
 669         movl    $KDSEL,%eax
 670         movl    %eax,%ds
 671         movl    %eax,%es
 672         movl    %eax,%fs        /* Beware, use wrmsr to set 64 bit base */
 673         movl    %eax,%gs        /* Beware, use wrmsr to set 64 bit base */
 674         movl    %eax,%ss
 675
 676         /* reload code selector by turning return into intersegmental return */
 677         popq    %rax
 678         pushq   $KCSEL
 679         pushq   %rax
 680         MEXITCOUNT
 681         lretq
 682
 683 /*****************************************************************************/
 684 /* setjmp, longjmp                                                           */
 685 /*****************************************************************************/
 686
 687 ENTRY(setjmp)
 688         movq    %rbx,0(%rdi)                    /* save rbx */
 689         movq    %rsp,8(%rdi)                    /* save rsp */
 690         movq    %rbp,16(%rdi)                   /* save rbp */
 691         movq    %r12,24(%rdi)                   /* save r12 */
 692         movq    %r13,32(%rdi)                   /* save r13 */
 693         movq    %r14,40(%rdi)                   /* save r14 */
 694         movq    %r15,48(%rdi)                   /* save r15 */
 695         movq    0(%rsp),%rdx                    /* get rta */
 696         movq    %rdx,56(%rdi)                   /* save rip */
 697         xorl    %eax,%eax                       /* return(0); */
 698         ret
 699
 700 ENTRY(longjmp)
 701         movq    0(%rdi),%rbx                    /* restore rbx */
 702         movq    8(%rdi),%rsp                    /* restore rsp */
 703         movq    16(%rdi),%rbp                   /* restore rbp */
 704         movq    24(%rdi),%r12                   /* restore r12 */
 705         movq    32(%rdi),%r13                   /* restore r13 */
 706         movq    40(%rdi),%r14                   /* restore r14 */
 707         movq    48(%rdi),%r15                   /* restore r15 */
 708         movq    56(%rdi),%rdx                   /* get rta */
 709         movq    %rdx,0(%rsp)                    /* put in return frame */
 710         xorl    %eax,%eax                       /* return(1); */
 711         incl    %eax
 712         ret
 713
 714 /*
 715  * Support for reading MSRs in the safe manner.
 716  */
 717 ENTRY(rdmsr_safe)
 718 /* int rdmsr_safe(u_int msr, uint64_t *data) */
 719         movq    PCPU(curthread),%r8
 720         movq    TD_PCB(%r8), %r8
 721         movq    $msr_onfault,PCB_ONFAULT(%r8)
 722         movq    %rsp,PCB_ONFAULT_SP(%r8)
 723         movl    %edi,%ecx
 724         rdmsr                   /* Read MSR pointed by %ecx. Returns
 725                                    hi byte in edx, lo in %eax */
 726         salq    $32,%rdx        /* sign-shift %rdx left */
 727         movl    %eax,%eax       /* zero-extend %eax -> %rax */
 728         orq     %rdx,%rax
 729         movq    %rax,(%rsi)
 730         xorq    %rax,%rax
 731         movq    %rax,PCB_ONFAULT(%r8)
 732         ret
 733
 734 /*
 735  * Support for writing MSRs in the safe manner.
 736  */
 737 ENTRY(wrmsr_safe)
 738 /* int wrmsr_safe(u_int msr, uint64_t data) */
 739         movq    PCPU(curthread),%r8
 740         movq    TD_PCB(%r8), %r8
 741         movq    $msr_onfault,PCB_ONFAULT(%r8)
 742         movq    %rsp,PCB_ONFAULT_SP(%rcx)
 743         movl    %edi,%ecx
 744         movl    %esi,%eax
 745         sarq    $32,%rsi
 746         movl    %esi,%edx
 747         wrmsr                   /* Write MSR pointed by %ecx. Accepts
 748                                    hi byte in edx, lo in %eax. */
 749         xorq    %rax,%rax
 750         movq    %rax,PCB_ONFAULT(%r8)
 751         ret
 752
 753 /*
 754  * MSR operations fault handler
 755  */
 756         ALIGN_TEXT
 757 msr_onfault:
 758         movq    PCPU(curthread),%r8
 759         movq    TD_PCB(%r8), %r8
 760         movq    $0,PCB_ONFAULT(%r8)
 761         movl    $EFAULT,%eax
 762         ret
 763
 764 /*
 765  * Support for BB-profiling (gcc -a).  The kernbb program will extract
 766  * the data from the kernel.
 767  */
 768
 769         .data
 770         ALIGN_DATA
 771         .globl bbhead
 772 bbhead:
 773         .quad 0
 774
 775         .text
 776 NON_GPROF_ENTRY(__bb_init_func)
 777         movq    $1,(%rdi)
 778         movq    bbhead,%rax
 779         movq    %rax,32(%rdi)
 780         movq    %rdi,bbhead
 781         NON_GPROF_RET