xref: /titanic_52/usr/src/uts/intel/ia32/os/sundep.c (revision 1cb6af97c6f66f456d4f726ef056e1ebc0f73305)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License, Version 1.0 only
6  * (the "License").  You may not use this file except in compliance
7  * with the License.
8  *
9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10  * or http://www.opensolaris.org/os/licensing.
11  * See the License for the specific language governing permissions
12  * and limitations under the License.
13  *
14  * When distributing Covered Code, include this CDDL HEADER in each
15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16  * If applicable, add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your own identifying
18  * information: Portions Copyright [yyyy] [name of copyright owner]
19  *
20  * CDDL HEADER END
21  */
22 /*
23  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
28 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T   */
29 /*	All Rights Reserved   */
30 
31 #pragma ident	"%Z%%M%	%I%	%E% SMI"
32 
33 #include <sys/types.h>
34 #include <sys/param.h>
35 #include <sys/sysmacros.h>
36 #include <sys/signal.h>
37 #include <sys/systm.h>
38 #include <sys/user.h>
39 #include <sys/mman.h>
40 #include <sys/class.h>
41 #include <sys/proc.h>
42 #include <sys/procfs.h>
43 #include <sys/buf.h>
44 #include <sys/kmem.h>
45 #include <sys/cred.h>
46 #include <sys/archsystm.h>
47 #include <sys/vmparam.h>
48 #include <sys/prsystm.h>
49 #include <sys/reboot.h>
50 #include <sys/uadmin.h>
51 #include <sys/vfs.h>
52 #include <sys/vnode.h>
53 #include <sys/file.h>
54 #include <sys/session.h>
55 #include <sys/ucontext.h>
56 #include <sys/dnlc.h>
57 #include <sys/var.h>
58 #include <sys/cmn_err.h>
59 #include <sys/debugreg.h>
60 #include <sys/thread.h>
61 #include <sys/vtrace.h>
62 #include <sys/consdev.h>
63 #include <sys/psw.h>
64 #include <sys/regset.h>
65 #include <sys/privregs.h>
66 #include <sys/stack.h>
67 #include <sys/swap.h>
68 #include <vm/hat.h>
69 #include <vm/anon.h>
70 #include <vm/as.h>
71 #include <vm/page.h>
72 #include <vm/seg.h>
73 #include <vm/seg_kmem.h>
74 #include <vm/seg_map.h>
75 #include <vm/seg_vn.h>
76 #include <sys/exec.h>
77 #include <sys/acct.h>
78 #include <sys/core.h>
79 #include <sys/corectl.h>
80 #include <sys/modctl.h>
81 #include <sys/tuneable.h>
82 #include <c2/audit.h>
83 #include <sys/bootconf.h>
84 #include <sys/dumphdr.h>
85 #include <sys/promif.h>
86 #include <sys/systeminfo.h>
87 #include <sys/kdi.h>
88 #include <sys/contract_impl.h>
89 #include <sys/x86_archext.h>
90 #include <sys/segments.h>
91 
92 /*
93  * Compare the version of boot that boot says it is against
94  * the version of boot the kernel expects.
95  */
96 int
97 check_boot_version(int boots_version)
98 {
99 	if (boots_version == BO_VERSION)
100 		return (0);
101 
102 	prom_printf("Wrong boot interface - kernel needs v%d found v%d\n",
103 	    BO_VERSION, boots_version);
104 	prom_panic("halting");
105 	/*NOTREACHED*/
106 }
107 
108 /*
109  * Process the physical installed list for boot.
110  * Finds:
111  * 1) the pfn of the highest installed physical page,
112  * 2) the number of pages installed
113  * 3) the number of distinct contiguous regions these pages fall into.
114  */
115 void
116 installed_top_size(
117 	struct memlist *list,	/* pointer to start of installed list */
118 	pfn_t *high_pfn,	/* return ptr for top value */
119 	pgcnt_t *pgcnt,		/* return ptr for sum of installed pages */
120 	int	*ranges)	/* return ptr for the count of contig. ranges */
121 {
122 	pfn_t top = 0;
123 	pgcnt_t sumpages = 0;
124 	pfn_t highp;		/* high page in a chunk */
125 	int cnt = 0;
126 
127 	for (; list; list = list->next) {
128 		++cnt;
129 		highp = (list->address + list->size - 1) >> PAGESHIFT;
130 		if (top < highp)
131 			top = highp;
132 		sumpages += btop(list->size);
133 	}
134 
135 	*high_pfn = top;
136 	*pgcnt = sumpages;
137 	*ranges = cnt;
138 }
139 
140 /*
141  * Copy in a memory list from boot to kernel, with a filter function
142  * to remove pages. The filter function can increase the address and/or
143  * decrease the size to filter out pages.
144  */
145 void
146 copy_memlist_filter(
147 	struct memlist *src,
148 	struct memlist **dstp,
149 	void (*filter)(uint64_t *, uint64_t *))
150 {
151 	struct memlist *dst, *prev;
152 	uint64_t addr;
153 	uint64_t size;
154 	uint64_t eaddr;
155 
156 	dst = *dstp;
157 	prev = dst;
158 
159 	/*
160 	 * Move through the memlist applying a filter against
161 	 * each range of memory. Note that we may apply the
162 	 * filter multiple times against each memlist entry.
163 	 */
164 	for (; src; src = src->next) {
165 		addr = src->address;
166 		eaddr = addr + src->size;
167 		while (addr < eaddr) {
168 			size = eaddr - addr;
169 			if (filter != NULL)
170 				filter(&addr, &size);
171 			if (size == 0)
172 				break;
173 			dst->address = addr;
174 			dst->size = size;
175 			dst->next = 0;
176 			if (prev == dst) {
177 				dst->prev = 0;
178 				dst++;
179 			} else {
180 				dst->prev = prev;
181 				prev->next = dst;
182 				dst++;
183 				prev++;
184 			}
185 			addr += size;
186 		}
187 	}
188 
189 	*dstp = dst;
190 }
191 
192 /*
193  * Kernel setup code, called from startup().
194  */
195 void
196 kern_setup1(void)
197 {
198 	proc_t *pp;
199 
200 	pp = &p0;
201 
202 	proc_sched = pp;
203 
204 	/*
205 	 * Initialize process 0 data structures
206 	 */
207 	pp->p_stat = SRUN;
208 	pp->p_flag = SSYS;
209 
210 	pp->p_pidp = &pid0;
211 	pp->p_pgidp = &pid0;
212 	pp->p_sessp = &session0;
213 	pp->p_tlist = &t0;
214 	pid0.pid_pglink = pp;
215 
216 	/*
217 	 * XXX - we asssume that the u-area is zeroed out except for
218 	 * ttolwp(curthread)->lwp_regs.
219 	 */
220 	u.u_cmask = (mode_t)CMASK;
221 
222 	thread_init();		/* init thread_free list */
223 	pid_init();		/* initialize pid (proc) table */
224 	contract_init();	/* initialize contracts */
225 
226 	init_pages_pp_maximum();
227 }
228 
229 /*
230  * Load a procedure into a thread.
231  */
232 void
233 thread_load(kthread_t *t, void (*start)(), caddr_t arg, size_t len)
234 {
235 	caddr_t sp;
236 	size_t framesz;
237 	caddr_t argp;
238 	long *p;
239 	extern void thread_start();
240 
241 	/*
242 	 * Push a "c" call frame onto the stack to represent
243 	 * the caller of "start".
244 	 */
245 	sp = t->t_stk;
246 	ASSERT(((uintptr_t)t->t_stk & (STACK_ENTRY_ALIGN - 1)) == 0);
247 	if (len != 0) {
248 		/*
249 		 * the object that arg points at is copied into the
250 		 * caller's frame.
251 		 */
252 		framesz = SA(len);
253 		sp -= framesz;
254 		ASSERT(sp > t->t_stkbase);
255 		argp = sp + SA(MINFRAME);
256 		bcopy(arg, argp, len);
257 		arg = argp;
258 	}
259 	/*
260 	 * Set up arguments (arg and len) on the caller's stack frame.
261 	 */
262 	p = (long *)sp;
263 
264 	*--p = 0;		/* fake call */
265 	*--p = 0;		/* null frame pointer terminates stack trace */
266 	*--p = (long)len;
267 	*--p = (intptr_t)arg;
268 	*--p = (intptr_t)start;
269 
270 	/*
271 	 * initialize thread to resume at thread_start() which will
272 	 * turn around and invoke (*start)(arg, len).
273 	 */
274 	t->t_pc = (uintptr_t)thread_start;
275 	t->t_sp = (uintptr_t)p;
276 
277 	ASSERT((t->t_sp & (STACK_ENTRY_ALIGN - 1)) == 0);
278 }
279 
280 /*
281  * load user registers into lwp.
282  */
283 /*ARGSUSED2*/
284 void
285 lwp_load(klwp_t *lwp, gregset_t grp, uintptr_t thrptr)
286 {
287 	struct regs *rp = lwptoregs(lwp);
288 
289 	setgregs(lwp, grp);
290 	rp->r_ps = PSL_USER;
291 
292 	/*
293 	 * For 64-bit lwps, we allow one magic %fs selector value, and one
294 	 * magic %gs selector to point anywhere in the address space using
295 	 * %fsbase and %gsbase behind the scenes.  libc uses %fs to point
296 	 * at the ulwp_t structure.
297 	 *
298 	 * For 32-bit lwps, libc wedges its lwp thread pointer into the
299 	 * ucontext ESP slot (which is otherwise irrelevant to setting a
300 	 * ucontext) and LWPGS_SEL value into gregs[REG_GS].  This is so
301 	 * syslwp_create() can atomically setup %gs.
302 	 *
303 	 * See setup_context() in libc.
304 	 */
305 #ifdef _SYSCALL32_IMPL
306 	if (lwp_getdatamodel(lwp) == DATAMODEL_ILP32) {
307 		if (grp[REG_GS] == LWPGS_SEL)
308 			(void) lwp_setprivate(lwp, _LWP_GSBASE, thrptr);
309 	}
310 #else
311 	if (grp[GS] == LWPGS_SEL)
312 		(void) lwp_setprivate(lwp, _LWP_GSBASE, thrptr);
313 #endif
314 
315 	lwp->lwp_eosys = JUSTRETURN;
316 	lwptot(lwp)->t_post_sys = 1;
317 }
318 
319 /*
320  * set syscall()'s return values for a lwp.
321  */
322 void
323 lwp_setrval(klwp_t *lwp, int v1, int v2)
324 {
325 	lwptoregs(lwp)->r_ps &= ~PS_C;
326 	lwptoregs(lwp)->r_r0 = v1;
327 	lwptoregs(lwp)->r_r1 = v2;
328 }
329 
330 /*
331  * set syscall()'s return values for a lwp.
332  */
333 void
334 lwp_setsp(klwp_t *lwp, caddr_t sp)
335 {
336 	lwptoregs(lwp)->r_sp = (intptr_t)sp;
337 }
338 
339 /*
340  * Copy regs from parent to child.
341  */
342 void
343 lwp_forkregs(klwp_t *lwp, klwp_t *clwp)
344 {
345 #if defined(__amd64)
346 	clwp->lwp_pcb.pcb_flags |= RUPDATE_PENDING;
347 	lwptot(clwp)->t_post_sys = 1;
348 #endif
349 	bcopy(lwp->lwp_regs, clwp->lwp_regs, sizeof (struct regs));
350 }
351 
352 /*
353  * This function is currently unused on x86.
354  */
355 /*ARGSUSED*/
356 void
357 lwp_freeregs(klwp_t *lwp, int isexec)
358 {}
359 
360 /*
361  * This function is currently unused on x86.
362  */
363 void
364 lwp_pcb_exit(void)
365 {}
366 
367 /*
368  * Lwp context ops for segment registers.
369  */
370 
371 /*
372  * Every time we come into the kernel (syscall, interrupt or trap
373  * but not fast-traps) we capture the current values of the user's
374  * segment registers into the lwp's reg structure. This includes
375  * lcall for i386 generic system call support since it is handled
376  * as a segment-not-present trap.
377  *
378  * Here we save the current values from the lwp regs into the pcb
379  * and set the RUPDATE_PENDING bit to tell the rest of the kernel
380  * that the pcb copy of the segment registers is the current one.
381  * This ensures the lwp's next trip to user land via update_sregs.
382  * Finally we set t_post_sys to ensure that no system call fast-path's
383  * its way out of the kernel via sysret.
384  *
385  * (This means that we need to have interrupts disabled when we test
386  * t->t_post_sys in the syscall handlers; if the test fails, we need
387  * to keep interrupts disabled until we return to userland so we can't
388  * be switched away.)
389  *
390  * As a result of all this, we don't really have to do a whole lot if
391  * the thread is just mucking about in the kernel, switching on and
392  * off the cpu for whatever reason it feels like. And yet we still
393  * preserve fast syscalls, cause if we -don't- get descheduled,
394  * we never come here either.
395  */
396 
397 #define	VALID_LWP_DESC(udp) ((udp)->usd_type == SDT_MEMRWA && \
398 	    (udp)->usd_p == 1 && (udp)->usd_dpl == SEL_UPL)
399 
400 void
401 lwp_segregs_save(klwp_t *lwp)
402 {
403 #if defined(__amd64)
404 	pcb_t *pcb = &lwp->lwp_pcb;
405 	struct regs *rp;
406 
407 	ASSERT(VALID_LWP_DESC(&pcb->pcb_fsdesc));
408 	ASSERT(VALID_LWP_DESC(&pcb->pcb_gsdesc));
409 
410 	if ((pcb->pcb_flags & RUPDATE_PENDING) == 0) {
411 		rp = lwptoregs(lwp);
412 
413 		/*
414 		 * If there's no update already pending, capture the current
415 		 * %ds/%es/%fs/%gs values from lwp's regs in case the user
416 		 * changed them; %fsbase and %gsbase are privileged so the
417 		 * kernel versions of these registers in pcb_fsbase and
418 		 * pcb_gsbase are always up-to-date.
419 		 */
420 		pcb->pcb_ds = rp->r_ds;
421 		pcb->pcb_es = rp->r_es;
422 		pcb->pcb_fs = rp->r_fs;
423 		pcb->pcb_gs = rp->r_gs;
424 		pcb->pcb_flags |= RUPDATE_PENDING;
425 		lwp->lwp_thread->t_post_sys = 1;
426 	}
427 #endif	/* __amd64 */
428 
429 	ASSERT(bcmp(&CPU->cpu_gdt[GDT_LWPFS], &lwp->lwp_pcb.pcb_fsdesc,
430 	    sizeof (lwp->lwp_pcb.pcb_fsdesc)) == 0);
431 	ASSERT(bcmp(&CPU->cpu_gdt[GDT_LWPGS], &lwp->lwp_pcb.pcb_gsdesc,
432 	    sizeof (lwp->lwp_pcb.pcb_gsdesc)) == 0);
433 }
434 
435 /*
436  * Restore lwp private fs and gs segment descriptors
437  * on current cpu's GDT.
438  */
439 static void
440 lwp_segregs_restore(klwp_t *lwp)
441 {
442 	cpu_t *cpu = CPU;
443 	pcb_t *pcb = &lwp->lwp_pcb;
444 
445 	ASSERT(VALID_LWP_DESC(&pcb->pcb_fsdesc));
446 	ASSERT(VALID_LWP_DESC(&pcb->pcb_gsdesc));
447 
448 	cpu->cpu_gdt[GDT_LWPFS] = pcb->pcb_fsdesc;
449 	cpu->cpu_gdt[GDT_LWPGS] = pcb->pcb_gsdesc;
450 
451 #if defined(__amd64)
452 	/*
453 	 * Make it impossible for a process to change its data model.
454 	 * We do this by toggling the present bits for the 32 and
455 	 * 64-bit user code descriptors. That way if a user lwp attempts
456 	 * to change its data model (by using the wrong code descriptor in
457 	 * %cs) it will fault immediately. This also allows us to simplify
458 	 * assertions and checks in the kernel.
459 	 */
460 	cpu->cpu_gdt[GDT_UCODE].usd_p = 1;
461 	cpu->cpu_gdt[GDT_U32CODE].usd_p = 0;
462 #endif	/* __amd64 */
463 }
464 
465 #ifdef _SYSCALL32_IMPL
466 
467 static void
468 lwp_segregs_restore32(klwp_t *lwp)
469 {
470 	cpu_t *cpu = CPU;
471 	pcb_t *pcb = &lwp->lwp_pcb;
472 
473 	ASSERT(VALID_LWP_DESC(&pcb->pcb_fsdesc));
474 	ASSERT(VALID_LWP_DESC(&pcb->pcb_gsdesc));
475 
476 	cpu->cpu_gdt[GDT_LWPFS] = pcb->pcb_fsdesc;
477 	cpu->cpu_gdt[GDT_LWPGS] = pcb->pcb_gsdesc;
478 	cpu->cpu_gdt[GDT_UCODE].usd_p = 0;
479 	cpu->cpu_gdt[GDT_U32CODE].usd_p = 1;
480 }
481 
482 #endif	/* _SYSCALL32_IMPL */
483 
484 /*
485  * Add any lwp-associated context handlers to the lwp at the beginning
486  * of the lwp's useful life.
487  *
488  * All paths which create lwp's invoke lwp_create(); lwp_create()
489  * invokes lwp_stk_init() which initializes the stack, sets up
490  * lwp_regs, and invokes this routine.
491  *
492  * All paths which destroy lwp's invoke lwp_exit() to rip the lwp
493  * apart and put it on 'lwp_deathrow'; if the lwp is destroyed it
494  * ends up in thread_free() which invokes freectx(t, 0) before
495  * invoking lwp_stk_fini().  When the lwp is recycled from death
496  * row, lwp_stk_fini() is invoked, then thread_free(), and thus
497  * freectx(t, 0) as before.
498  *
499  * In the case of exec, the surviving lwp is thoroughly scrubbed
500  * clean; exec invokes freectx(t, 1) to destroy associated contexts.
501  * On the way back to the new image, it invokes setregs() which
502  * in turn invokes this routine.
503  */
504 void
505 lwp_installctx(klwp_t *lwp)
506 {
507 	kthread_t *t = lwptot(lwp);
508 	int thisthread = t == curthread;
509 #ifdef _SYSCALL32_IMPL
510 	void (*restop)(klwp_t *) = lwp_getdatamodel(lwp) == DATAMODEL_NATIVE ?
511 	    lwp_segregs_restore : lwp_segregs_restore32;
512 #else
513 	void (*restop)(klwp_t *) = lwp_segregs_restore;
514 #endif
515 
516 	/*
517 	 * Install the basic lwp context handlers on each lwp.
518 	 *
519 	 * On the amd64 kernel, the context handlers are responsible for
520 	 * virtualizing %ds, %es, %fs, and %gs to the lwp.  The register
521 	 * values are only ever changed via sys_rtt when the
522 	 * RUPDATE_PENDING bit is set.  Only sys_rtt gets to clear the bit.
523 	 *
524 	 * On the i386 kernel, the context handlers are responsible for
525 	 * virtualizing %gs/%fs to the lwp by updating the per-cpu GDTs
526 	 */
527 	ASSERT(removectx(t, lwp, lwp_segregs_save, restop,
528 	    NULL, NULL, NULL, NULL) == 0);
529 	if (thisthread)
530 		kpreempt_disable();
531 	installctx(t, lwp, lwp_segregs_save, restop,
532 	    NULL, NULL, NULL, NULL);
533 	if (thisthread) {
534 		/*
535 		 * Since we're the right thread, set the values in the GDT
536 		 */
537 		restop(lwp);
538 		kpreempt_enable();
539 	}
540 
541 	/*
542 	 * If we have sysenter/sysexit instructions enabled, we need
543 	 * to ensure that the hardware mechanism is kept up-to-date with the
544 	 * lwp's kernel stack pointer across context switches.
545 	 *
546 	 * sep_save zeros the sysenter stack pointer msr; sep_restore sets
547 	 * it to the lwp's kernel stack pointer (kstktop).
548 	 */
549 	if (x86_feature & X86_SEP) {
550 #if defined(__amd64)
551 		caddr_t kstktop = (caddr_t)lwp->lwp_regs;
552 #elif defined(__i386)
553 		caddr_t kstktop = ((caddr_t)lwp->lwp_regs - MINFRAME) +
554 		    SA(sizeof (struct regs) + MINFRAME);
555 #endif
556 		ASSERT(removectx(t, kstktop,
557 		    sep_save, sep_restore, NULL, NULL, NULL, NULL) == 0);
558 
559 		if (thisthread)
560 			kpreempt_disable();
561 		installctx(t, kstktop,
562 		    sep_save, sep_restore, NULL, NULL, NULL, NULL);
563 		if (thisthread) {
564 			/*
565 			 * We're the right thread, so set the stack pointer
566 			 * for the first sysenter instruction to use
567 			 */
568 			sep_restore(kstktop);
569 			kpreempt_enable();
570 		}
571 	}
572 }
573 
574 /*
575  * Clear registers on exec(2).
576  */
577 void
578 setregs(uarg_t *args)
579 {
580 	struct regs *rp;
581 	kthread_t *t = curthread;
582 	klwp_t *lwp = ttolwp(t);
583 	pcb_t *pcb = &lwp->lwp_pcb;
584 	greg_t sp;
585 
586 	/*
587 	 * Initialize user registers
588 	 */
589 	(void) save_syscall_args();	/* copy args from registers first */
590 	rp = lwptoregs(lwp);
591 	sp = rp->r_sp;
592 	bzero(rp, sizeof (*rp));
593 
594 	rp->r_ss = UDS_SEL;
595 	rp->r_sp = sp;
596 	rp->r_pc = args->entry;
597 	rp->r_ps = PSL_USER;
598 
599 #if defined(__amd64)
600 
601 	pcb->pcb_fs = pcb->pcb_gs = 0;
602 	pcb->pcb_fsbase = pcb->pcb_gsbase = 0;
603 
604 	if (ttoproc(t)->p_model == DATAMODEL_NATIVE) {
605 		cpu_t *cpu;
606 
607 		rp->r_cs = UCS_SEL;
608 
609 		/*
610 		 * Only allow 64-bit user code descriptor to be present.
611 		 */
612 		kpreempt_disable();
613 		cpu = CPU;
614 		cpu->cpu_gdt[GDT_UCODE].usd_p = 1;
615 		cpu->cpu_gdt[GDT_U32CODE].usd_p = 0;
616 		kpreempt_enable();
617 
618 		/*
619 		 * Arrange that the virtualized %fs and %gs GDT descriptors
620 		 * have a well-defined initial state (present, ring 3
621 		 * and of type data).
622 		 */
623 		pcb->pcb_fsdesc = pcb->pcb_gsdesc = zero_udesc;
624 
625 		/*
626 		 * thrptr is either NULL or a value used by DTrace.
627 		 * 64-bit processes use %fs as their "thread" register.
628 		 */
629 		if (args->thrptr)
630 			(void) lwp_setprivate(lwp, _LWP_FSBASE, args->thrptr);
631 
632 	} else {
633 		cpu_t *cpu;
634 
635 		rp->r_cs = U32CS_SEL;
636 		rp->r_ds = rp->r_es = UDS_SEL;
637 
638 		/*
639 		 * only allow 32-bit user code selector to be present.
640 		 */
641 		kpreempt_disable();
642 		cpu = CPU;
643 		cpu->cpu_gdt[GDT_UCODE].usd_p = 0;
644 		cpu->cpu_gdt[GDT_U32CODE].usd_p = 1;
645 		kpreempt_enable();
646 
647 		pcb->pcb_fsdesc = pcb->pcb_gsdesc = zero_u32desc;
648 
649 		/*
650 		 * thrptr is either NULL or a value used by DTrace.
651 		 * 32-bit processes use %gs as their "thread" register.
652 		 */
653 		if (args->thrptr)
654 			(void) lwp_setprivate(lwp, _LWP_GSBASE, args->thrptr);
655 
656 	}
657 
658 
659 	pcb->pcb_ds = rp->r_ds;
660 	pcb->pcb_es = rp->r_es;
661 	pcb->pcb_flags |= RUPDATE_PENDING;
662 
663 #elif defined(__i386)
664 
665 	rp->r_cs = UCS_SEL;
666 	rp->r_ds = rp->r_es = UDS_SEL;
667 
668 	/*
669 	 * Arrange that the virtualized %fs and %gs GDT descriptors
670 	 * have a well-defined initial state (present, ring 3
671 	 * and of type data).
672 	 */
673 	pcb->pcb_fsdesc = pcb->pcb_gsdesc = zero_udesc;
674 
675 
676 	/*
677 	 * For %gs we need to reset LWP_GSBASE in pcb and the
678 	 * per-cpu GDT descriptor. thrptr is either NULL
679 	 * or a value used by DTrace.
680 	 */
681 	if (args->thrptr)
682 		(void) lwp_setprivate(lwp, _LWP_GSBASE, args->thrptr);
683 #endif
684 
685 	lwp->lwp_eosys = JUSTRETURN;
686 	t->t_post_sys = 1;
687 
688 	/*
689 	 * Here we initialize minimal fpu state.
690 	 * The rest is done at the first floating
691 	 * point instruction that a process executes.
692 	 */
693 	pcb->pcb_fpu.fpu_flags = 0;
694 
695 	/*
696 	 * Add the lwp context handlers that virtualize segment registers,
697 	 * and/or system call stacks etc.
698 	 */
699 	lwp_installctx(lwp);
700 }
701 
702 #if !defined(lwp_getdatamodel)
703 
704 /*
705  * Return the datamodel of the given lwp.
706  */
707 /*ARGSUSED*/
708 model_t
709 lwp_getdatamodel(klwp_t *lwp)
710 {
711 	return (lwp->lwp_procp->p_model);
712 }
713 
714 #endif	/* !lwp_getdatamodel */
715 
716 #if !defined(get_udatamodel)
717 
718 model_t
719 get_udatamodel(void)
720 {
721 	return (curproc->p_model);
722 }
723 
724 #endif	/* !get_udatamodel */
725