support.s revision 253328 
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 253328 2013-07-13 19:42:52Z kib $
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	%ebp
185	movl	%esp,%ebp
186	pushl	%esi
187	pushl	%edi
188	movl	8(%ebp),%esi
189	movl	12(%ebp),%edi
190	movl	16(%ebp),%ecx
191
192	movl	%edi,%eax
193	subl	%esi,%eax
194	cmpl	%ecx,%eax			/* overlapping && src < dst? */
195	jb	1f
196
197	shrl	$2,%ecx				/* copy by 32-bit words */
198	cld					/* nope, copy forwards */
199	rep
200	movsl
201	movl	16(%ebp),%ecx
202	andl	$3,%ecx				/* any bytes left? */
203	rep
204	movsb
205	popl	%edi
206	popl	%esi
207	popl	%ebp
208	ret
209
210	ALIGN_TEXT
2111:
212	addl	%ecx,%edi			/* copy backwards */
213	addl	%ecx,%esi
214	decl	%edi
215	decl	%esi
216	andl	$3,%ecx				/* any fractional bytes? */
217	std
218	rep
219	movsb
220	movl	16(%ebp),%ecx			/* copy remainder by 32-bit words */
221	shrl	$2,%ecx
222	subl	$3,%esi
223	subl	$3,%edi
224	rep
225	movsl
226	popl	%edi
227	popl	%esi
228	cld
229	popl	%ebp
230	ret
231END(bcopy)
232
233/*
234 * Note: memcpy does not support overlapping copies
235 */
236ENTRY(memcpy)
237	pushl	%edi
238	pushl	%esi
239	movl	12(%esp),%edi
240	movl	16(%esp),%esi
241	movl	20(%esp),%ecx
242	movl	%edi,%eax
243	shrl	$2,%ecx				/* copy by 32-bit words */
244	cld					/* nope, copy forwards */
245	rep
246	movsl
247	movl	20(%esp),%ecx
248	andl	$3,%ecx				/* any bytes left? */
249	rep
250	movsb
251	popl	%esi
252	popl	%edi
253	ret
254END(memcpy)
255
256/*****************************************************************************/
257/* copyout and fubyte family                                                 */
258/*****************************************************************************/
259/*
260 * Access user memory from inside the kernel. These routines and possibly
261 * the math- and DOS emulators should be the only places that do this.
262 *
263 * We have to access the memory with user's permissions, so use a segment
264 * selector with RPL 3. For writes to user space we have to additionally
265 * check the PTE for write permission, because the 386 does not check
266 * write permissions when we are executing with EPL 0. The 486 does check
267 * this if the WP bit is set in CR0, so we can use a simpler version here.
268 *
269 * These routines set curpcb->pcb_onfault for the time they execute. When a
270 * protection violation occurs inside the functions, the trap handler
271 * returns to *curpcb->pcb_onfault instead of the function.
272 */
273
274/*
275 * copyout(from_kernel, to_user, len)  - MP SAFE
276 */
277ENTRY(copyout)
278	movl	PCPU(CURPCB),%eax
279	movl	$copyout_fault,PCB_ONFAULT(%eax)
280	pushl	%esi
281	pushl	%edi
282	pushl	%ebx
283	movl	16(%esp),%esi
284	movl	20(%esp),%edi
285	movl	24(%esp),%ebx
286	testl	%ebx,%ebx			/* anything to do? */
287	jz	done_copyout
288
289	/*
290	 * Check explicitly for non-user addresses.  If 486 write protection
291	 * is being used, this check is essential because we are in kernel
292	 * mode so the h/w does not provide any protection against writing
293	 * kernel addresses.
294	 */
295
296	/*
297	 * First, prevent address wrapping.
298	 */
299	movl	%edi,%eax
300	addl	%ebx,%eax
301	jc	copyout_fault
302/*
303 * XXX STOP USING VM_MAXUSER_ADDRESS.
304 * It is an end address, not a max, so every time it is used correctly it
305 * looks like there is an off by one error, and of course it caused an off
306 * by one error in several places.
307 */
308	cmpl	$VM_MAXUSER_ADDRESS,%eax
309	ja	copyout_fault
310
311	/* bcopy(%esi, %edi, %ebx) */
312	movl	%ebx,%ecx
313
314	shrl	$2,%ecx
315	cld
316	rep
317	movsl
318	movb	%bl,%cl
319	andb	$3,%cl
320	rep
321	movsb
322
323done_copyout:
324	popl	%ebx
325	popl	%edi
326	popl	%esi
327	xorl	%eax,%eax
328	movl	PCPU(CURPCB),%edx
329	movl	%eax,PCB_ONFAULT(%edx)
330	ret
331END(copyout)
332
333	ALIGN_TEXT
334copyout_fault:
335	popl	%ebx
336	popl	%edi
337	popl	%esi
338	movl	PCPU(CURPCB),%edx
339	movl	$0,PCB_ONFAULT(%edx)
340	movl	$EFAULT,%eax
341	ret
342
343/*
344 * copyin(from_user, to_kernel, len) - MP SAFE
345 */
346ENTRY(copyin)
347	movl	PCPU(CURPCB),%eax
348	movl	$copyin_fault,PCB_ONFAULT(%eax)
349	pushl	%esi
350	pushl	%edi
351	movl	12(%esp),%esi			/* caddr_t from */
352	movl	16(%esp),%edi			/* caddr_t to */
353	movl	20(%esp),%ecx			/* size_t  len */
354
355	/*
356	 * make sure address is valid
357	 */
358	movl	%esi,%edx
359	addl	%ecx,%edx
360	jc	copyin_fault
361	cmpl	$VM_MAXUSER_ADDRESS,%edx
362	ja	copyin_fault
363
364	movb	%cl,%al
365	shrl	$2,%ecx				/* copy longword-wise */
366	cld
367	rep
368	movsl
369	movb	%al,%cl
370	andb	$3,%cl				/* copy remaining bytes */
371	rep
372	movsb
373
374	popl	%edi
375	popl	%esi
376	xorl	%eax,%eax
377	movl	PCPU(CURPCB),%edx
378	movl	%eax,PCB_ONFAULT(%edx)
379	ret
380END(copyin)
381
382	ALIGN_TEXT
383copyin_fault:
384	popl	%edi
385	popl	%esi
386	movl	PCPU(CURPCB),%edx
387	movl	$0,PCB_ONFAULT(%edx)
388	movl	$EFAULT,%eax
389	ret
390
391/*
392 * casuword.  Compare and set user word.  Returns -1 or the current value.
393 */
394
395ALTENTRY(casuword32)
396ENTRY(casuword)
397	movl	PCPU(CURPCB),%ecx
398	movl	$fusufault,PCB_ONFAULT(%ecx)
399	movl	4(%esp),%edx			/* dst */
400	movl	8(%esp),%eax			/* old */
401	movl	12(%esp),%ecx			/* new */
402
403	cmpl	$VM_MAXUSER_ADDRESS-4,%edx	/* verify address is valid */
404	ja	fusufault
405
406#ifdef SMP
407	lock
408#endif
409	cmpxchgl %ecx,(%edx)			/* Compare and set. */
410
411	/*
412	 * The old value is in %eax.  If the store succeeded it will be the
413	 * value we expected (old) from before the store, otherwise it will
414	 * be the current value.
415	 */
416
417	movl	PCPU(CURPCB),%ecx
418	movl	$0,PCB_ONFAULT(%ecx)
419	ret
420END(casuword32)
421END(casuword)
422
423/*
424 * Fetch (load) a 32-bit word, a 16-bit word, or an 8-bit byte from user
425 * memory.  All these functions are MPSAFE.
426 */
427
428ALTENTRY(fuword32)
429ENTRY(fuword)
430	movl	PCPU(CURPCB),%ecx
431	movl	$fusufault,PCB_ONFAULT(%ecx)
432	movl	4(%esp),%edx			/* from */
433
434	cmpl	$VM_MAXUSER_ADDRESS-4,%edx	/* verify address is valid */
435	ja	fusufault
436
437	movl	(%edx),%eax
438	movl	$0,PCB_ONFAULT(%ecx)
439	ret
440END(fuword32)
441END(fuword)
442
443/*
444 * fuswintr() and suswintr() are specialized variants of fuword16() and
445 * suword16(), respectively.  They are called from the profiling code,
446 * potentially at interrupt time.  If they fail, that's okay; good things
447 * will happen later.  They always fail for now, until the trap code is
448 * able to deal with this.
449 */
450ALTENTRY(suswintr)
451ENTRY(fuswintr)
452	movl	$-1,%eax
453	ret
454END(suswintr)
455END(fuswintr)
456
457ENTRY(fuword16)
458	movl	PCPU(CURPCB),%ecx
459	movl	$fusufault,PCB_ONFAULT(%ecx)
460	movl	4(%esp),%edx
461
462	cmpl	$VM_MAXUSER_ADDRESS-2,%edx
463	ja	fusufault
464
465	movzwl	(%edx),%eax
466	movl	$0,PCB_ONFAULT(%ecx)
467	ret
468END(fuword16)
469
470ENTRY(fubyte)
471	movl	PCPU(CURPCB),%ecx
472	movl	$fusufault,PCB_ONFAULT(%ecx)
473	movl	4(%esp),%edx
474
475	cmpl	$VM_MAXUSER_ADDRESS-1,%edx
476	ja	fusufault
477
478	movzbl	(%edx),%eax
479	movl	$0,PCB_ONFAULT(%ecx)
480	ret
481END(fubyte)
482
483	ALIGN_TEXT
484fusufault:
485	movl	PCPU(CURPCB),%ecx
486	xorl	%eax,%eax
487	movl	%eax,PCB_ONFAULT(%ecx)
488	decl	%eax
489	ret
490
491/*
492 * Store a 32-bit word, a 16-bit word, or an 8-bit byte to user memory.
493 * All these functions are MPSAFE.
494 */
495
496ALTENTRY(suword32)
497ENTRY(suword)
498	movl	PCPU(CURPCB),%ecx
499	movl	$fusufault,PCB_ONFAULT(%ecx)
500	movl	4(%esp),%edx
501
502	cmpl	$VM_MAXUSER_ADDRESS-4,%edx	/* verify address validity */
503	ja	fusufault
504
505	movl	8(%esp),%eax
506	movl	%eax,(%edx)
507	xorl	%eax,%eax
508	movl	PCPU(CURPCB),%ecx
509	movl	%eax,PCB_ONFAULT(%ecx)
510	ret
511END(suword32)
512END(suword)
513
514ENTRY(suword16)
515	movl	PCPU(CURPCB),%ecx
516	movl	$fusufault,PCB_ONFAULT(%ecx)
517	movl	4(%esp),%edx
518
519	cmpl	$VM_MAXUSER_ADDRESS-2,%edx	/* verify address validity */
520	ja	fusufault
521
522	movw	8(%esp),%ax
523	movw	%ax,(%edx)
524	xorl	%eax,%eax
525	movl	PCPU(CURPCB),%ecx		/* restore trashed register */
526	movl	%eax,PCB_ONFAULT(%ecx)
527	ret
528END(suword16)
529
530ENTRY(subyte)
531	movl	PCPU(CURPCB),%ecx
532	movl	$fusufault,PCB_ONFAULT(%ecx)
533	movl	4(%esp),%edx
534
535	cmpl	$VM_MAXUSER_ADDRESS-1,%edx	/* verify address validity */
536	ja	fusufault
537
538	movb	8(%esp),%al
539	movb	%al,(%edx)
540	xorl	%eax,%eax
541	movl	PCPU(CURPCB),%ecx		/* restore trashed register */
542	movl	%eax,PCB_ONFAULT(%ecx)
543	ret
544END(subyte)
545
546/*
547 * copyinstr(from, to, maxlen, int *lencopied) - MP SAFE
548 *
549 *	copy a string from from to to, stop when a 0 character is reached.
550 *	return ENAMETOOLONG if string is longer than maxlen, and
551 *	EFAULT on protection violations. If lencopied is non-zero,
552 *	return the actual length in *lencopied.
553 */
554ENTRY(copyinstr)
555	pushl	%esi
556	pushl	%edi
557	movl	PCPU(CURPCB),%ecx
558	movl	$cpystrflt,PCB_ONFAULT(%ecx)
559
560	movl	12(%esp),%esi			/* %esi = from */
561	movl	16(%esp),%edi			/* %edi = to */
562	movl	20(%esp),%edx			/* %edx = maxlen */
563
564	movl	$VM_MAXUSER_ADDRESS,%eax
565
566	/* make sure 'from' is within bounds */
567	subl	%esi,%eax
568	jbe	cpystrflt
569
570	/* restrict maxlen to <= VM_MAXUSER_ADDRESS-from */
571	cmpl	%edx,%eax
572	jae	1f
573	movl	%eax,%edx
574	movl	%eax,20(%esp)
5751:
576	incl	%edx
577	cld
578
5792:
580	decl	%edx
581	jz	3f
582
583	lodsb
584	stosb
585	orb	%al,%al
586	jnz	2b
587
588	/* Success -- 0 byte reached */
589	decl	%edx
590	xorl	%eax,%eax
591	jmp	cpystrflt_x
5923:
593	/* edx is zero - return ENAMETOOLONG or EFAULT */
594	cmpl	$VM_MAXUSER_ADDRESS,%esi
595	jae	cpystrflt
5964:
597	movl	$ENAMETOOLONG,%eax
598	jmp	cpystrflt_x
599
600cpystrflt:
601	movl	$EFAULT,%eax
602
603cpystrflt_x:
604	/* set *lencopied and return %eax */
605	movl	PCPU(CURPCB),%ecx
606	movl	$0,PCB_ONFAULT(%ecx)
607	movl	20(%esp),%ecx
608	subl	%edx,%ecx
609	movl	24(%esp),%edx
610	testl	%edx,%edx
611	jz	1f
612	movl	%ecx,(%edx)
6131:
614	popl	%edi
615	popl	%esi
616	ret
617END(copyinstr)
618
619/*
620 * copystr(from, to, maxlen, int *lencopied) - MP SAFE
621 */
622ENTRY(copystr)
623	pushl	%esi
624	pushl	%edi
625
626	movl	12(%esp),%esi			/* %esi = from */
627	movl	16(%esp),%edi			/* %edi = to */
628	movl	20(%esp),%edx			/* %edx = maxlen */
629	incl	%edx
630	cld
6311:
632	decl	%edx
633	jz	4f
634	lodsb
635	stosb
636	orb	%al,%al
637	jnz	1b
638
639	/* Success -- 0 byte reached */
640	decl	%edx
641	xorl	%eax,%eax
642	jmp	6f
6434:
644	/* edx is zero -- return ENAMETOOLONG */
645	movl	$ENAMETOOLONG,%eax
646
6476:
648	/* set *lencopied and return %eax */
649	movl	20(%esp),%ecx
650	subl	%edx,%ecx
651	movl	24(%esp),%edx
652	testl	%edx,%edx
653	jz	7f
654	movl	%ecx,(%edx)
6557:
656	popl	%edi
657	popl	%esi
658	ret
659END(copystr)
660
661ENTRY(bcmp)
662	pushl	%edi
663	pushl	%esi
664	movl	12(%esp),%edi
665	movl	16(%esp),%esi
666	movl	20(%esp),%edx
667
668	movl	%edx,%ecx
669	shrl	$2,%ecx
670	cld					/* compare forwards */
671	repe
672	cmpsl
673	jne	1f
674
675	movl	%edx,%ecx
676	andl	$3,%ecx
677	repe
678	cmpsb
6791:
680	setne	%al
681	movsbl	%al,%eax
682	popl	%esi
683	popl	%edi
684	ret
685END(bcmp)
686
687/*
688 * Handling of special 386 registers and descriptor tables etc
689 */
690/* void lgdt(struct region_descriptor *rdp); */
691ENTRY(lgdt)
692#ifndef XEN
693	/* reload the descriptor table */
694	movl	4(%esp),%eax
695	lgdt	(%eax)
696#endif
697
698	/* flush the prefetch q */
699	jmp	1f
700	nop
7011:
702	/* reload "stale" selectors */
703	movl	$KDSEL,%eax
704	movl	%eax,%ds
705	movl	%eax,%es
706	movl	%eax,%gs
707	movl	%eax,%ss
708	movl	$KPSEL,%eax
709	movl	%eax,%fs
710
711	/* reload code selector by turning return into intersegmental return */
712	movl	(%esp),%eax
713	pushl	%eax
714	movl	$KCSEL,4(%esp)
715	MEXITCOUNT
716	lret
717END(lgdt)
718
719/* ssdtosd(*ssdp,*sdp) */
720ENTRY(ssdtosd)
721	pushl	%ebx
722	movl	8(%esp),%ecx
723	movl	8(%ecx),%ebx
724	shll	$16,%ebx
725	movl	(%ecx),%edx
726	roll	$16,%edx
727	movb	%dh,%bl
728	movb	%dl,%bh
729	rorl	$8,%ebx
730	movl	4(%ecx),%eax
731	movw	%ax,%dx
732	andl	$0xf0000,%eax
733	orl	%eax,%ebx
734	movl	12(%esp),%ecx
735	movl	%edx,(%ecx)
736	movl	%ebx,4(%ecx)
737	popl	%ebx
738	ret
739END(ssdtosd)
740
741/* void reset_dbregs() */
742ENTRY(reset_dbregs)
743	movl    $0,%eax
744	movl    %eax,%dr7     /* disable all breapoints first */
745	movl    %eax,%dr0
746	movl    %eax,%dr1
747	movl    %eax,%dr2
748	movl    %eax,%dr3
749	movl    %eax,%dr6
750	ret
751END(reset_dbregs)
752
753/*****************************************************************************/
754/* setjump, longjump                                                         */
755/*****************************************************************************/
756
757ENTRY(setjmp)
758	movl	4(%esp),%eax
759	movl	%ebx,(%eax)			/* save ebx */
760	movl	%esp,4(%eax)			/* save esp */
761	movl	%ebp,8(%eax)			/* save ebp */
762	movl	%esi,12(%eax)			/* save esi */
763	movl	%edi,16(%eax)			/* save edi */
764	movl	(%esp),%edx			/* get rta */
765	movl	%edx,20(%eax)			/* save eip */
766	xorl	%eax,%eax			/* return(0); */
767	ret
768END(setjmp)
769
770ENTRY(longjmp)
771	movl	4(%esp),%eax
772	movl	(%eax),%ebx			/* restore ebx */
773	movl	4(%eax),%esp			/* restore esp */
774	movl	8(%eax),%ebp			/* restore ebp */
775	movl	12(%eax),%esi			/* restore esi */
776	movl	16(%eax),%edi			/* restore edi */
777	movl	20(%eax),%edx			/* get rta */
778	movl	%edx,(%esp)			/* put in return frame */
779	xorl	%eax,%eax			/* return(1); */
780	incl	%eax
781	ret
782END(longjmp)
783
784/*
785 * Support for reading MSRs in the safe manner.
786 */
787ENTRY(rdmsr_safe)
788/* int rdmsr_safe(u_int msr, uint64_t *data) */
789	movl	PCPU(CURPCB),%ecx
790	movl	$msr_onfault,PCB_ONFAULT(%ecx)
791
792	movl	4(%esp),%ecx
793	rdmsr
794	movl	8(%esp),%ecx
795	movl	%eax,(%ecx)
796	movl	%edx,4(%ecx)
797	xorl	%eax,%eax
798
799	movl	PCPU(CURPCB),%ecx
800	movl	%eax,PCB_ONFAULT(%ecx)
801
802	ret
803
804/*
805 * Support for writing MSRs in the safe manner.
806 */
807ENTRY(wrmsr_safe)
808/* int wrmsr_safe(u_int msr, uint64_t data) */
809	movl	PCPU(CURPCB),%ecx
810	movl	$msr_onfault,PCB_ONFAULT(%ecx)
811
812	movl	4(%esp),%ecx
813	movl	8(%esp),%eax
814	movl	12(%esp),%edx
815	wrmsr
816	xorl	%eax,%eax
817
818	movl	PCPU(CURPCB),%ecx
819	movl	%eax,PCB_ONFAULT(%ecx)
820
821	ret
822
823/*
824 * MSR operations fault handler
825 */
826	ALIGN_TEXT
827msr_onfault:
828	movl	PCPU(CURPCB),%ecx
829	movl	$0,PCB_ONFAULT(%ecx)
830	movl	$EFAULT,%eax
831	ret
832