support.s revision 224187
1/*- 2 * Copyright (c) 1993 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * $FreeBSD: head/sys/i386/i386/support.s 224187 2011-07-18 15:19:40Z attilio $ 30 */ 31 32#include "opt_npx.h" 33 34#include <machine/asmacros.h> 35#include <machine/cputypes.h> 36#include <machine/intr_machdep.h> 37#include <machine/pmap.h> 38#include <machine/specialreg.h> 39 40#include "assym.s" 41 42#define IDXSHIFT 10 43 44 .text 45 46/* 47 * bcopy family 48 * void bzero(void *buf, u_int len) 49 */ 50ENTRY(bzero) 51 pushl %edi 52 movl 8(%esp),%edi 53 movl 12(%esp),%ecx 54 xorl %eax,%eax 55 shrl $2,%ecx 56 cld 57 rep 58 stosl 59 movl 12(%esp),%ecx 60 andl $3,%ecx 61 rep 62 stosb 63 popl %edi 64 ret 65END(bzero) 66 67ENTRY(sse2_pagezero) 68 pushl %ebx 69 movl 8(%esp),%ecx 70 movl %ecx,%eax 71 addl $4096,%eax 72 xor %ebx,%ebx 731: 74 movnti %ebx,(%ecx) 75 addl $4,%ecx 76 cmpl %ecx,%eax 77 jne 1b 78 sfence 79 popl %ebx 80 ret 81END(sse2_pagezero) 82 83ENTRY(i686_pagezero) 84 pushl %edi 85 pushl %ebx 86 87 movl 12(%esp),%edi 88 movl $1024,%ecx 89 cld 90 91 ALIGN_TEXT 921: 93 xorl %eax,%eax 94 repe 95 scasl 96 jnz 2f 97 98 popl %ebx 99 popl %edi 100 ret 101 102 ALIGN_TEXT 103 1042: 105 incl %ecx 106 subl $4,%edi 107 108 movl %ecx,%edx 109 cmpl $16,%ecx 110 111 jge 3f 112 113 movl %edi,%ebx 114 andl $0x3f,%ebx 115 shrl %ebx 116 shrl %ebx 117 movl $16,%ecx 118 subl %ebx,%ecx 119 1203: 121 subl %ecx,%edx 122 rep 123 stosl 124 125 movl %edx,%ecx 126 testl %edx,%edx 127 jnz 1b 128 129 popl %ebx 130 popl %edi 131 ret 132END(i686_pagezero) 133 134/* fillw(pat, base, cnt) */ 135ENTRY(fillw) 136 pushl %edi 137 movl 8(%esp),%eax 138 movl 12(%esp),%edi 139 movl 16(%esp),%ecx 140 cld 141 rep 142 stosw 143 popl %edi 144 ret 145END(fillw) 146 147ENTRY(bcopyb) 148 pushl %esi 149 pushl %edi 150 movl 12(%esp),%esi 151 movl 16(%esp),%edi 152 movl 20(%esp),%ecx 153 movl %edi,%eax 154 subl %esi,%eax 155 cmpl %ecx,%eax /* overlapping && src < dst? */ 156 jb 1f 157 cld /* nope, copy forwards */ 158 rep 159 movsb 160 popl %edi 161 popl %esi 162 ret 163 164 ALIGN_TEXT 1651: 166 addl %ecx,%edi /* copy backwards. */ 167 addl %ecx,%esi 168 decl %edi 169 decl %esi 170 std 171 rep 172 movsb 173 popl %edi 174 popl %esi 175 cld 176 ret 177END(bcopyb) 178 179/* 180 * bcopy(src, dst, cnt) 181 * ws@tools.de (Wolfgang Solfrank, TooLs GmbH) +49-228-985800 182 */ 183ENTRY(bcopy) 184 pushl %esi 185 pushl %edi 186 movl 12(%esp),%esi 187 movl 16(%esp),%edi 188 movl 20(%esp),%ecx 189 190 movl %edi,%eax 191 subl %esi,%eax 192 cmpl %ecx,%eax /* overlapping && src < dst? */ 193 jb 1f 194 195 shrl $2,%ecx /* copy by 32-bit words */ 196 cld /* nope, copy forwards */ 197 rep 198 movsl 199 movl 20(%esp),%ecx 200 andl $3,%ecx /* any bytes left? */ 201 rep 202 movsb 203 popl %edi 204 popl %esi 205 ret 206 207 ALIGN_TEXT 2081: 209 addl %ecx,%edi /* copy backwards */ 210 addl %ecx,%esi 211 decl %edi 212 decl %esi 213 andl $3,%ecx /* any fractional bytes? */ 214 std 215 rep 216 movsb 217 movl 20(%esp),%ecx /* copy remainder by 32-bit words */ 218 shrl $2,%ecx 219 subl $3,%esi 220 subl $3,%edi 221 rep 222 movsl 223 popl %edi 224 popl %esi 225 cld 226 ret 227END(bcopy) 228 229/* 230 * Note: memcpy does not support overlapping copies 231 */ 232ENTRY(memcpy) 233 pushl %edi 234 pushl %esi 235 movl 12(%esp),%edi 236 movl 16(%esp),%esi 237 movl 20(%esp),%ecx 238 movl %edi,%eax 239 shrl $2,%ecx /* copy by 32-bit words */ 240 cld /* nope, copy forwards */ 241 rep 242 movsl 243 movl 20(%esp),%ecx 244 andl $3,%ecx /* any bytes left? */ 245 rep 246 movsb 247 popl %esi 248 popl %edi 249 ret 250END(memcpy) 251 252/*****************************************************************************/ 253/* copyout and fubyte family */ 254/*****************************************************************************/ 255/* 256 * Access user memory from inside the kernel. These routines and possibly 257 * the math- and DOS emulators should be the only places that do this. 258 * 259 * We have to access the memory with user's permissions, so use a segment 260 * selector with RPL 3. For writes to user space we have to additionally 261 * check the PTE for write permission, because the 386 does not check 262 * write permissions when we are executing with EPL 0. The 486 does check 263 * this if the WP bit is set in CR0, so we can use a simpler version here. 264 * 265 * These routines set curpcb->onfault for the time they execute. When a 266 * protection violation occurs inside the functions, the trap handler 267 * returns to *curpcb->onfault instead of the function. 268 */ 269 270/* 271 * copyout(from_kernel, to_user, len) - MP SAFE 272 */ 273ENTRY(copyout) 274 movl PCPU(CURPCB),%eax 275 movl $copyout_fault,PCB_ONFAULT(%eax) 276 pushl %esi 277 pushl %edi 278 pushl %ebx 279 movl 16(%esp),%esi 280 movl 20(%esp),%edi 281 movl 24(%esp),%ebx 282 testl %ebx,%ebx /* anything to do? */ 283 jz done_copyout 284 285 /* 286 * Check explicitly for non-user addresses. If 486 write protection 287 * is being used, this check is essential because we are in kernel 288 * mode so the h/w does not provide any protection against writing 289 * kernel addresses. 290 */ 291 292 /* 293 * First, prevent address wrapping. 294 */ 295 movl %edi,%eax 296 addl %ebx,%eax 297 jc copyout_fault 298/* 299 * XXX STOP USING VM_MAXUSER_ADDRESS. 300 * It is an end address, not a max, so every time it is used correctly it 301 * looks like there is an off by one error, and of course it caused an off 302 * by one error in several places. 303 */ 304 cmpl $VM_MAXUSER_ADDRESS,%eax 305 ja copyout_fault 306 307 /* bcopy(%esi, %edi, %ebx) */ 308 movl %ebx,%ecx 309 310 shrl $2,%ecx 311 cld 312 rep 313 movsl 314 movb %bl,%cl 315 andb $3,%cl 316 rep 317 movsb 318 319done_copyout: 320 popl %ebx 321 popl %edi 322 popl %esi 323 xorl %eax,%eax 324 movl PCPU(CURPCB),%edx 325 movl %eax,PCB_ONFAULT(%edx) 326 ret 327END(copyout) 328 329 ALIGN_TEXT 330copyout_fault: 331 popl %ebx 332 popl %edi 333 popl %esi 334 movl PCPU(CURPCB),%edx 335 movl $0,PCB_ONFAULT(%edx) 336 movl $EFAULT,%eax 337 ret 338 339/* 340 * copyin(from_user, to_kernel, len) - MP SAFE 341 */ 342ENTRY(copyin) 343 movl PCPU(CURPCB),%eax 344 movl $copyin_fault,PCB_ONFAULT(%eax) 345 pushl %esi 346 pushl %edi 347 movl 12(%esp),%esi /* caddr_t from */ 348 movl 16(%esp),%edi /* caddr_t to */ 349 movl 20(%esp),%ecx /* size_t len */ 350 351 /* 352 * make sure address is valid 353 */ 354 movl %esi,%edx 355 addl %ecx,%edx 356 jc copyin_fault 357 cmpl $VM_MAXUSER_ADDRESS,%edx 358 ja copyin_fault 359 360 movb %cl,%al 361 shrl $2,%ecx /* copy longword-wise */ 362 cld 363 rep 364 movsl 365 movb %al,%cl 366 andb $3,%cl /* copy remaining bytes */ 367 rep 368 movsb 369 370 popl %edi 371 popl %esi 372 xorl %eax,%eax 373 movl PCPU(CURPCB),%edx 374 movl %eax,PCB_ONFAULT(%edx) 375 ret 376END(copyin) 377 378 ALIGN_TEXT 379copyin_fault: 380 popl %edi 381 popl %esi 382 movl PCPU(CURPCB),%edx 383 movl $0,PCB_ONFAULT(%edx) 384 movl $EFAULT,%eax 385 ret 386 387/* 388 * casuword. Compare and set user word. Returns -1 or the current value. 389 */ 390 391ALTENTRY(casuword32) 392ENTRY(casuword) 393 movl PCPU(CURPCB),%ecx 394 movl $fusufault,PCB_ONFAULT(%ecx) 395 movl 4(%esp),%edx /* dst */ 396 movl 8(%esp),%eax /* old */ 397 movl 12(%esp),%ecx /* new */ 398 399 cmpl $VM_MAXUSER_ADDRESS-4,%edx /* verify address is valid */ 400 ja fusufault 401 402#ifdef SMP 403 lock 404#endif 405 cmpxchgl %ecx,(%edx) /* Compare and set. */ 406 407 /* 408 * The old value is in %eax. If the store succeeded it will be the 409 * value we expected (old) from before the store, otherwise it will 410 * be the current value. 411 */ 412 413 movl PCPU(CURPCB),%ecx 414 movl $0,PCB_ONFAULT(%ecx) 415 ret 416END(casuword32) 417END(casuword) 418 419/* 420 * Fetch (load) a 32-bit word, a 16-bit word, or an 8-bit byte from user 421 * memory. All these functions are MPSAFE. 422 */ 423 424ALTENTRY(fuword32) 425ENTRY(fuword) 426 movl PCPU(CURPCB),%ecx 427 movl $fusufault,PCB_ONFAULT(%ecx) 428 movl 4(%esp),%edx /* from */ 429 430 cmpl $VM_MAXUSER_ADDRESS-4,%edx /* verify address is valid */ 431 ja fusufault 432 433 movl (%edx),%eax 434 movl $0,PCB_ONFAULT(%ecx) 435 ret 436END(fuword32) 437END(fuword) 438 439/* 440 * fuswintr() and suswintr() are specialized variants of fuword16() and 441 * suword16(), respectively. They are called from the profiling code, 442 * potentially at interrupt time. If they fail, that's okay; good things 443 * will happen later. They always fail for now, until the trap code is 444 * able to deal with this. 445 */ 446ALTENTRY(suswintr) 447ENTRY(fuswintr) 448 movl $-1,%eax 449 ret 450END(suswintr) 451END(fuswintr) 452 453ENTRY(fuword16) 454 movl PCPU(CURPCB),%ecx 455 movl $fusufault,PCB_ONFAULT(%ecx) 456 movl 4(%esp),%edx 457 458 cmpl $VM_MAXUSER_ADDRESS-2,%edx 459 ja fusufault 460 461 movzwl (%edx),%eax 462 movl $0,PCB_ONFAULT(%ecx) 463 ret 464END(fuword16) 465 466ENTRY(fubyte) 467 movl PCPU(CURPCB),%ecx 468 movl $fusufault,PCB_ONFAULT(%ecx) 469 movl 4(%esp),%edx 470 471 cmpl $VM_MAXUSER_ADDRESS-1,%edx 472 ja fusufault 473 474 movzbl (%edx),%eax 475 movl $0,PCB_ONFAULT(%ecx) 476 ret 477END(fubyte) 478 479 ALIGN_TEXT 480fusufault: 481 movl PCPU(CURPCB),%ecx 482 xorl %eax,%eax 483 movl %eax,PCB_ONFAULT(%ecx) 484 decl %eax 485 ret 486 487/* 488 * Store a 32-bit word, a 16-bit word, or an 8-bit byte to user memory. 489 * All these functions are MPSAFE. 490 */ 491 492ALTENTRY(suword32) 493ENTRY(suword) 494 movl PCPU(CURPCB),%ecx 495 movl $fusufault,PCB_ONFAULT(%ecx) 496 movl 4(%esp),%edx 497 498 cmpl $VM_MAXUSER_ADDRESS-4,%edx /* verify address validity */ 499 ja fusufault 500 501 movl 8(%esp),%eax 502 movl %eax,(%edx) 503 xorl %eax,%eax 504 movl PCPU(CURPCB),%ecx 505 movl %eax,PCB_ONFAULT(%ecx) 506 ret 507END(suword32) 508END(suword) 509 510ENTRY(suword16) 511 movl PCPU(CURPCB),%ecx 512 movl $fusufault,PCB_ONFAULT(%ecx) 513 movl 4(%esp),%edx 514 515 cmpl $VM_MAXUSER_ADDRESS-2,%edx /* verify address validity */ 516 ja fusufault 517 518 movw 8(%esp),%ax 519 movw %ax,(%edx) 520 xorl %eax,%eax 521 movl PCPU(CURPCB),%ecx /* restore trashed register */ 522 movl %eax,PCB_ONFAULT(%ecx) 523 ret 524END(suword16) 525 526ENTRY(subyte) 527 movl PCPU(CURPCB),%ecx 528 movl $fusufault,PCB_ONFAULT(%ecx) 529 movl 4(%esp),%edx 530 531 cmpl $VM_MAXUSER_ADDRESS-1,%edx /* verify address validity */ 532 ja fusufault 533 534 movb 8(%esp),%al 535 movb %al,(%edx) 536 xorl %eax,%eax 537 movl PCPU(CURPCB),%ecx /* restore trashed register */ 538 movl %eax,PCB_ONFAULT(%ecx) 539 ret 540END(subyte) 541 542/* 543 * copyinstr(from, to, maxlen, int *lencopied) - MP SAFE 544 * 545 * copy a string from from to to, stop when a 0 character is reached. 546 * return ENAMETOOLONG if string is longer than maxlen, and 547 * EFAULT on protection violations. If lencopied is non-zero, 548 * return the actual length in *lencopied. 549 */ 550ENTRY(copyinstr) 551 pushl %esi 552 pushl %edi 553 movl PCPU(CURPCB),%ecx 554 movl $cpystrflt,PCB_ONFAULT(%ecx) 555 556 movl 12(%esp),%esi /* %esi = from */ 557 movl 16(%esp),%edi /* %edi = to */ 558 movl 20(%esp),%edx /* %edx = maxlen */ 559 560 movl $VM_MAXUSER_ADDRESS,%eax 561 562 /* make sure 'from' is within bounds */ 563 subl %esi,%eax 564 jbe cpystrflt 565 566 /* restrict maxlen to <= VM_MAXUSER_ADDRESS-from */ 567 cmpl %edx,%eax 568 jae 1f 569 movl %eax,%edx 570 movl %eax,20(%esp) 5711: 572 incl %edx 573 cld 574 5752: 576 decl %edx 577 jz 3f 578 579 lodsb 580 stosb 581 orb %al,%al 582 jnz 2b 583 584 /* Success -- 0 byte reached */ 585 decl %edx 586 xorl %eax,%eax 587 jmp cpystrflt_x 5883: 589 /* edx is zero - return ENAMETOOLONG or EFAULT */ 590 cmpl $VM_MAXUSER_ADDRESS,%esi 591 jae cpystrflt 5924: 593 movl $ENAMETOOLONG,%eax 594 jmp cpystrflt_x 595 596cpystrflt: 597 movl $EFAULT,%eax 598 599cpystrflt_x: 600 /* set *lencopied and return %eax */ 601 movl PCPU(CURPCB),%ecx 602 movl $0,PCB_ONFAULT(%ecx) 603 movl 20(%esp),%ecx 604 subl %edx,%ecx 605 movl 24(%esp),%edx 606 testl %edx,%edx 607 jz 1f 608 movl %ecx,(%edx) 6091: 610 popl %edi 611 popl %esi 612 ret 613END(copyinstr) 614 615/* 616 * copystr(from, to, maxlen, int *lencopied) - MP SAFE 617 */ 618ENTRY(copystr) 619 pushl %esi 620 pushl %edi 621 622 movl 12(%esp),%esi /* %esi = from */ 623 movl 16(%esp),%edi /* %edi = to */ 624 movl 20(%esp),%edx /* %edx = maxlen */ 625 incl %edx 626 cld 6271: 628 decl %edx 629 jz 4f 630 lodsb 631 stosb 632 orb %al,%al 633 jnz 1b 634 635 /* Success -- 0 byte reached */ 636 decl %edx 637 xorl %eax,%eax 638 jmp 6f 6394: 640 /* edx is zero -- return ENAMETOOLONG */ 641 movl $ENAMETOOLONG,%eax 642 6436: 644 /* set *lencopied and return %eax */ 645 movl 20(%esp),%ecx 646 subl %edx,%ecx 647 movl 24(%esp),%edx 648 testl %edx,%edx 649 jz 7f 650 movl %ecx,(%edx) 6517: 652 popl %edi 653 popl %esi 654 ret 655END(copystr) 656 657ENTRY(bcmp) 658 pushl %edi 659 pushl %esi 660 movl 12(%esp),%edi 661 movl 16(%esp),%esi 662 movl 20(%esp),%edx 663 664 movl %edx,%ecx 665 shrl $2,%ecx 666 cld /* compare forwards */ 667 repe 668 cmpsl 669 jne 1f 670 671 movl %edx,%ecx 672 andl $3,%ecx 673 repe 674 cmpsb 6751: 676 setne %al 677 movsbl %al,%eax 678 popl %esi 679 popl %edi 680 ret 681END(bcmp) 682 683/* 684 * Handling of special 386 registers and descriptor tables etc 685 */ 686/* void lgdt(struct region_descriptor *rdp); */ 687ENTRY(lgdt) 688#ifndef XEN 689 /* reload the descriptor table */ 690 movl 4(%esp),%eax 691 lgdt (%eax) 692#endif 693 694 /* flush the prefetch q */ 695 jmp 1f 696 nop 6971: 698 /* reload "stale" selectors */ 699 movl $KDSEL,%eax 700 movl %eax,%ds 701 movl %eax,%es 702 movl %eax,%gs 703 movl %eax,%ss 704 movl $KPSEL,%eax 705 movl %eax,%fs 706 707 /* reload code selector by turning return into intersegmental return */ 708 movl (%esp),%eax 709 pushl %eax 710 movl $KCSEL,4(%esp) 711 MEXITCOUNT 712 lret 713END(lgdt) 714 715/* ssdtosd(*ssdp,*sdp) */ 716ENTRY(ssdtosd) 717 pushl %ebx 718 movl 8(%esp),%ecx 719 movl 8(%ecx),%ebx 720 shll $16,%ebx 721 movl (%ecx),%edx 722 roll $16,%edx 723 movb %dh,%bl 724 movb %dl,%bh 725 rorl $8,%ebx 726 movl 4(%ecx),%eax 727 movw %ax,%dx 728 andl $0xf0000,%eax 729 orl %eax,%ebx 730 movl 12(%esp),%ecx 731 movl %edx,(%ecx) 732 movl %ebx,4(%ecx) 733 popl %ebx 734 ret 735END(ssdtosd) 736 737/* void reset_dbregs() */ 738ENTRY(reset_dbregs) 739 movl $0,%eax 740 movl %eax,%dr7 /* disable all breapoints first */ 741 movl %eax,%dr0 742 movl %eax,%dr1 743 movl %eax,%dr2 744 movl %eax,%dr3 745 movl %eax,%dr6 746 ret 747END(reset_dbregs) 748 749/*****************************************************************************/ 750/* setjump, longjump */ 751/*****************************************************************************/ 752 753ENTRY(setjmp) 754 movl 4(%esp),%eax 755 movl %ebx,(%eax) /* save ebx */ 756 movl %esp,4(%eax) /* save esp */ 757 movl %ebp,8(%eax) /* save ebp */ 758 movl %esi,12(%eax) /* save esi */ 759 movl %edi,16(%eax) /* save edi */ 760 movl (%esp),%edx /* get rta */ 761 movl %edx,20(%eax) /* save eip */ 762 xorl %eax,%eax /* return(0); */ 763 ret 764END(setjmp) 765 766ENTRY(longjmp) 767 movl 4(%esp),%eax 768 movl (%eax),%ebx /* restore ebx */ 769 movl 4(%eax),%esp /* restore esp */ 770 movl 8(%eax),%ebp /* restore ebp */ 771 movl 12(%eax),%esi /* restore esi */ 772 movl 16(%eax),%edi /* restore edi */ 773 movl 20(%eax),%edx /* get rta */ 774 movl %edx,(%esp) /* put in return frame */ 775 xorl %eax,%eax /* return(1); */ 776 incl %eax 777 ret 778END(longjmp) 779 780/* 781 * Support for reading MSRs in the safe manner. 782 */ 783ENTRY(rdmsr_safe) 784/* int rdmsr_safe(u_int msr, uint64_t *data) */ 785 movl PCPU(CURPCB),%ecx 786 movl $msr_onfault,PCB_ONFAULT(%ecx) 787 788 movl 4(%esp),%ecx 789 rdmsr 790 movl 8(%esp),%ecx 791 movl %eax,(%ecx) 792 movl %edx,4(%ecx) 793 xorl %eax,%eax 794 795 movl PCPU(CURPCB),%ecx 796 movl %eax,PCB_ONFAULT(%ecx) 797 798 ret 799 800/* 801 * Support for writing MSRs in the safe manner. 802 */ 803ENTRY(wrmsr_safe) 804/* int wrmsr_safe(u_int msr, uint64_t data) */ 805 movl PCPU(CURPCB),%ecx 806 movl $msr_onfault,PCB_ONFAULT(%ecx) 807 808 movl 4(%esp),%ecx 809 movl 8(%esp),%eax 810 movl 12(%esp),%edx 811 wrmsr 812 xorl %eax,%eax 813 814 movl PCPU(CURPCB),%ecx 815 movl %eax,PCB_ONFAULT(%ecx) 816 817 ret 818 819/* 820 * MSR operations fault handler 821 */ 822 ALIGN_TEXT 823msr_onfault: 824 movl PCPU(CURPCB),%ecx 825 movl $0,PCB_ONFAULT(%ecx) 826 movl $EFAULT,%eax 827 ret 828