2 * Copyright (c) 1990 The Regents of the University of California.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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
29 * from: @(#)sys_machdep.c 5.5 (Berkeley) 1/19/91
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
35 #include "opt_capsicum.h"
36 #include "opt_kstack_pages.h"
38 #include <sys/param.h>
39 #include <sys/capability.h>
40 #include <sys/systm.h>
42 #include <sys/malloc.h>
43 #include <sys/mutex.h>
47 #include <sys/sysproto.h>
51 #include <vm/vm_map.h>
52 #include <vm/vm_extern.h>
54 #include <machine/cpu.h>
55 #include <machine/pcb.h>
56 #include <machine/pcb_ext.h>
57 #include <machine/proc.h>
58 #include <machine/sysarch.h>
60 #include <security/audit/audit.h>
63 #include <machine/xen/xenfunc.h>
65 void i386_reset_ldt(struct proc_ldt *pldt);
68 i386_reset_ldt(struct proc_ldt *pldt)
70 xen_set_ldt((vm_offset_t)pldt->ldt_base, pldt->ldt_len);
73 #define i386_reset_ldt(x)
76 #include <vm/vm_kern.h> /* for kernel_map */
79 #define LD_PER_PAGE 512
80 #define NEW_MAX_LD(num) ((num + LD_PER_PAGE) & ~(LD_PER_PAGE-1))
81 #define SIZE_FROM_LARGEST_LD(num) (NEW_MAX_LD(num) << 3)
82 #define NULL_LDT_BASE ((caddr_t)NULL)
85 static void set_user_ldt_rv(struct vmspace *vmsp);
87 static int i386_set_ldt_data(struct thread *, int start, int num,
88 union descriptor *descs);
89 static int i386_ldt_grow(struct thread *td, int len);
91 #ifndef _SYS_SYSPROTO_H_
101 register struct sysarch_args *uap;
104 union descriptor *lp;
106 struct i386_ldt_args largs;
107 struct i386_ioperm_args iargs;
110 struct segment_descriptor sd, *sdp;
112 AUDIT_ARG_CMD(uap->op);
114 #ifdef CAPABILITY_MODE
116 * When adding new operations, add a new case statement here to
117 * explicitly indicate whether or not the operation is safe to
118 * perform in capability mode.
120 if (IN_CAPABILITY_MODE(td)) {
124 case I386_GET_IOPERM:
125 case I386_GET_FSBASE:
126 case I386_SET_FSBASE:
127 case I386_GET_GSBASE:
128 case I386_SET_GSBASE:
131 case I386_SET_IOPERM:
134 if (KTRPOINT(td, KTR_CAPFAIL))
135 ktrcapfail(CAPFAIL_SYSCALL, NULL, NULL);
143 case I386_GET_IOPERM:
144 case I386_SET_IOPERM:
145 if ((error = copyin(uap->parms, &kargs.iargs,
146 sizeof(struct i386_ioperm_args))) != 0)
151 if ((error = copyin(uap->parms, &kargs.largs,
152 sizeof(struct i386_ldt_args))) != 0)
154 if (kargs.largs.num > MAX_LD || kargs.largs.num <= 0)
163 error = i386_get_ldt(td, &kargs.largs);
166 if (kargs.largs.descs != NULL) {
167 lp = (union descriptor *)kmem_malloc(kernel_arena,
168 kargs.largs.num * sizeof(union descriptor),
174 error = copyin(kargs.largs.descs, lp,
175 kargs.largs.num * sizeof(union descriptor));
177 error = i386_set_ldt(td, &kargs.largs, lp);
178 kmem_free(kernel_arena, (vm_offset_t)lp,
179 kargs.largs.num * sizeof(union descriptor));
181 error = i386_set_ldt(td, &kargs.largs, NULL);
184 case I386_GET_IOPERM:
185 error = i386_get_ioperm(td, &kargs.iargs);
187 error = copyout(&kargs.iargs, uap->parms,
188 sizeof(struct i386_ioperm_args));
190 case I386_SET_IOPERM:
191 error = i386_set_ioperm(td, &kargs.iargs);
194 error = vm86_sysarch(td, uap->parms);
196 case I386_GET_FSBASE:
197 sdp = &td->td_pcb->pcb_fsd;
198 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
199 error = copyout(&base, uap->parms, sizeof(base));
201 case I386_SET_FSBASE:
202 error = copyin(uap->parms, &base, sizeof(base));
205 * Construct a descriptor and store it in the pcb for
206 * the next context switch. Also store it in the gdt
207 * so that the load of tf_fs into %fs will activate it
208 * at return to userland.
210 sd.sd_lobase = base & 0xffffff;
211 sd.sd_hibase = (base >> 24) & 0xff;
213 /* need to do nosegneg like Linux */
214 sd.sd_lolimit = (HYPERVISOR_VIRT_START >> 12) & 0xffff;
216 sd.sd_lolimit = 0xffff; /* 4GB limit, wraps around */
219 sd.sd_type = SDT_MEMRWA;
226 td->td_pcb->pcb_fsd = sd;
228 HYPERVISOR_update_descriptor(vtomach(&PCPU_GET(fsgs_gdt)[0]),
231 PCPU_GET(fsgs_gdt)[0] = sd;
234 td->td_frame->tf_fs = GSEL(GUFS_SEL, SEL_UPL);
237 case I386_GET_GSBASE:
238 sdp = &td->td_pcb->pcb_gsd;
239 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
240 error = copyout(&base, uap->parms, sizeof(base));
242 case I386_SET_GSBASE:
243 error = copyin(uap->parms, &base, sizeof(base));
246 * Construct a descriptor and store it in the pcb for
247 * the next context switch. Also store it in the gdt
248 * because we have to do a load_gs() right now.
250 sd.sd_lobase = base & 0xffffff;
251 sd.sd_hibase = (base >> 24) & 0xff;
254 /* need to do nosegneg like Linux */
255 sd.sd_lolimit = (HYPERVISOR_VIRT_START >> 12) & 0xffff;
257 sd.sd_lolimit = 0xffff; /* 4GB limit, wraps around */
260 sd.sd_type = SDT_MEMRWA;
267 td->td_pcb->pcb_gsd = sd;
269 HYPERVISOR_update_descriptor(vtomach(&PCPU_GET(fsgs_gdt)[1]),
272 PCPU_GET(fsgs_gdt)[1] = sd;
275 load_gs(GSEL(GUGS_SEL, SEL_UPL));
286 i386_extend_pcb(struct thread *td)
291 struct soft_segment_descriptor ssd = {
292 0, /* segment base address (overwritten) */
293 ctob(IOPAGES + 1) - 1, /* length */
294 SDT_SYS386TSS, /* segment type */
295 0, /* priority level */
296 1, /* descriptor present */
298 0, /* default 32 size */
302 ext = (struct pcb_ext *)kmem_malloc(kernel_arena, ctob(IOPAGES+1),
306 bzero(ext, sizeof(struct pcb_ext));
307 /* -16 is so we can convert a trapframe into vm86trapframe inplace */
308 ext->ext_tss.tss_esp0 = td->td_kstack + ctob(KSTACK_PAGES) -
309 sizeof(struct pcb) - 16;
310 ext->ext_tss.tss_ss0 = GSEL(GDATA_SEL, SEL_KPL);
312 * The last byte of the i/o map must be followed by an 0xff byte.
313 * We arbitrarily allocate 16 bytes here, to keep the starting
314 * address on a doubleword boundary.
316 offset = PAGE_SIZE - 16;
317 ext->ext_tss.tss_ioopt =
318 (offset - ((unsigned)&ext->ext_tss - (unsigned)ext)) << 16;
319 ext->ext_iomap = (caddr_t)ext + offset;
320 ext->ext_vm86.vm86_intmap = (caddr_t)ext + offset - 32;
322 addr = (u_long *)ext->ext_vm86.vm86_intmap;
323 for (i = 0; i < (ctob(IOPAGES) + 32 + 16) / sizeof(u_long); i++)
326 ssd.ssd_base = (unsigned)&ext->ext_tss;
327 ssd.ssd_limit -= ((unsigned)&ext->ext_tss - (unsigned)ext);
328 ssdtosd(&ssd, &ext->ext_tssd);
330 KASSERT(td == curthread, ("giving TSS to !curthread"));
331 KASSERT(td->td_pcb->pcb_ext == 0, ("already have a TSS!"));
333 /* Switch to the new TSS. */
335 td->td_pcb->pcb_ext = ext;
336 PCPU_SET(private_tss, 1);
337 *PCPU_GET(tss_gdt) = ext->ext_tssd;
338 ltr(GSEL(GPROC0_SEL, SEL_KPL));
345 i386_set_ioperm(td, uap)
347 struct i386_ioperm_args *uap;
352 if ((error = priv_check(td, PRIV_IO)) != 0)
354 if ((error = securelevel_gt(td->td_ucred, 0)) != 0)
358 * While this is restricted to root, we should probably figure out
359 * whether any other driver is using this i/o address, as so not to
360 * cause confusion. This probably requires a global 'usage registry'.
363 if (td->td_pcb->pcb_ext == 0)
364 if ((error = i386_extend_pcb(td)) != 0)
366 iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
368 if (uap->start + uap->length > IOPAGES * PAGE_SIZE * NBBY)
371 for (i = uap->start; i < uap->start + uap->length; i++) {
373 iomap[i >> 3] &= ~(1 << (i & 7));
375 iomap[i >> 3] |= (1 << (i & 7));
381 i386_get_ioperm(td, uap)
383 struct i386_ioperm_args *uap;
388 if (uap->start >= IOPAGES * PAGE_SIZE * NBBY)
391 if (td->td_pcb->pcb_ext == 0) {
396 iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
399 state = (iomap[i >> 3] >> (i & 7)) & 1;
400 uap->enable = !state;
403 for (i = uap->start + 1; i < IOPAGES * PAGE_SIZE * NBBY; i++) {
404 if (state != ((iomap[i >> 3] >> (i & 7)) & 1))
414 * Update the GDT entry pointing to the LDT to point to the LDT of the
415 * current process. Manage dt_lock holding/unholding autonomously.
418 set_user_ldt(struct mdproc *mdp)
420 struct proc_ldt *pldt;
424 if (!mtx_owned(&dt_lock)) {
425 mtx_lock_spin(&dt_lock);
431 i386_reset_ldt(pldt);
432 PCPU_SET(currentldt, (int)pldt);
435 gdt[PCPU_GET(cpuid) * NGDT + GUSERLDT_SEL].sd = pldt->ldt_sd;
437 gdt[GUSERLDT_SEL].sd = pldt->ldt_sd;
439 lldt(GSEL(GUSERLDT_SEL, SEL_KPL));
440 PCPU_SET(currentldt, GSEL(GUSERLDT_SEL, SEL_KPL));
443 mtx_unlock_spin(&dt_lock);
448 set_user_ldt_rv(struct vmspace *vmsp)
453 if (vmsp != td->td_proc->p_vmspace)
456 set_user_ldt(&td->td_proc->p_md);
463 * dt_lock must be held. Returns with dt_lock held.
466 user_ldt_alloc(struct mdproc *mdp, int len)
468 struct proc_ldt *pldt, *new_ldt;
470 mtx_assert(&dt_lock, MA_OWNED);
471 mtx_unlock_spin(&dt_lock);
472 new_ldt = malloc(sizeof(struct proc_ldt),
473 M_SUBPROC, M_WAITOK);
475 new_ldt->ldt_len = len = NEW_MAX_LD(len);
476 new_ldt->ldt_base = (caddr_t)kmem_malloc(kernel_arena,
477 round_page(len * sizeof(union descriptor)), M_WAITOK);
478 if (new_ldt->ldt_base == NULL) {
479 free(new_ldt, M_SUBPROC);
480 mtx_lock_spin(&dt_lock);
483 new_ldt->ldt_refcnt = 1;
484 new_ldt->ldt_active = 0;
486 mtx_lock_spin(&dt_lock);
487 if ((pldt = mdp->md_ldt)) {
488 if (len > pldt->ldt_len)
490 bcopy(pldt->ldt_base, new_ldt->ldt_base,
491 len * sizeof(union descriptor));
493 bcopy(ldt, new_ldt->ldt_base, PAGE_SIZE);
495 mtx_unlock_spin(&dt_lock); /* XXX kill once pmap locking fixed. */
496 pmap_map_readonly(kernel_pmap, (vm_offset_t)new_ldt->ldt_base,
497 new_ldt->ldt_len*sizeof(union descriptor));
498 mtx_lock_spin(&dt_lock); /* XXX kill once pmap locking fixed. */
503 * dt_lock must be held. Returns with dt_lock held.
506 user_ldt_alloc(struct mdproc *mdp, int len)
508 struct proc_ldt *pldt, *new_ldt;
510 mtx_assert(&dt_lock, MA_OWNED);
511 mtx_unlock_spin(&dt_lock);
512 new_ldt = malloc(sizeof(struct proc_ldt),
513 M_SUBPROC, M_WAITOK);
515 new_ldt->ldt_len = len = NEW_MAX_LD(len);
516 new_ldt->ldt_base = (caddr_t)kmem_malloc(kernel_arena,
517 len * sizeof(union descriptor), M_WAITOK);
518 if (new_ldt->ldt_base == NULL) {
519 free(new_ldt, M_SUBPROC);
520 mtx_lock_spin(&dt_lock);
523 new_ldt->ldt_refcnt = 1;
524 new_ldt->ldt_active = 0;
526 mtx_lock_spin(&dt_lock);
527 gdt_segs[GUSERLDT_SEL].ssd_base = (unsigned)new_ldt->ldt_base;
528 gdt_segs[GUSERLDT_SEL].ssd_limit = len * sizeof(union descriptor) - 1;
529 ssdtosd(&gdt_segs[GUSERLDT_SEL], &new_ldt->ldt_sd);
531 if ((pldt = mdp->md_ldt) != NULL) {
532 if (len > pldt->ldt_len)
534 bcopy(pldt->ldt_base, new_ldt->ldt_base,
535 len * sizeof(union descriptor));
537 bcopy(ldt, new_ldt->ldt_base, sizeof(ldt));
544 * Must be called with dt_lock held. Returns with dt_lock unheld.
547 user_ldt_free(struct thread *td)
549 struct mdproc *mdp = &td->td_proc->p_md;
550 struct proc_ldt *pldt;
552 mtx_assert(&dt_lock, MA_OWNED);
553 if ((pldt = mdp->md_ldt) == NULL) {
554 mtx_unlock_spin(&dt_lock);
558 if (td == curthread) {
560 i386_reset_ldt(&default_proc_ldt);
561 PCPU_SET(currentldt, (int)&default_proc_ldt);
564 PCPU_SET(currentldt, _default_ldt);
569 user_ldt_deref(pldt);
573 user_ldt_deref(struct proc_ldt *pldt)
576 mtx_assert(&dt_lock, MA_OWNED);
577 if (--pldt->ldt_refcnt == 0) {
578 mtx_unlock_spin(&dt_lock);
579 kmem_free(kernel_arena, (vm_offset_t)pldt->ldt_base,
580 pldt->ldt_len * sizeof(union descriptor));
581 free(pldt, M_SUBPROC);
583 mtx_unlock_spin(&dt_lock);
587 * Note for the authors of compat layers (linux, etc): copyout() in
588 * the function below is not a problem since it presents data in
589 * arch-specific format (i.e. i386-specific in this case), not in
590 * the OS-specific one.
593 i386_get_ldt(td, uap)
595 struct i386_ldt_args *uap;
598 struct proc_ldt *pldt;
600 union descriptor *lp;
603 printf("i386_get_ldt: start=%d num=%d descs=%p\n",
604 uap->start, uap->num, (void *)uap->descs);
607 mtx_lock_spin(&dt_lock);
608 if ((pldt = td->td_proc->p_md.md_ldt) != NULL) {
609 nldt = pldt->ldt_len;
610 lp = &((union descriptor *)(pldt->ldt_base))[uap->start];
611 mtx_unlock_spin(&dt_lock);
612 num = min(uap->num, nldt);
614 mtx_unlock_spin(&dt_lock);
615 nldt = sizeof(ldt)/sizeof(ldt[0]);
616 num = min(uap->num, nldt);
617 lp = &ldt[uap->start];
620 if ((uap->start > (unsigned int)nldt) ||
621 ((unsigned int)num > (unsigned int)nldt) ||
622 ((unsigned int)(uap->start + num) > (unsigned int)nldt))
625 error = copyout(lp, uap->descs, num * sizeof(union descriptor));
627 td->td_retval[0] = num;
633 i386_set_ldt(td, uap, descs)
635 struct i386_ldt_args *uap;
636 union descriptor *descs;
640 struct mdproc *mdp = &td->td_proc->p_md;
641 struct proc_ldt *pldt;
642 union descriptor *dp;
645 printf("i386_set_ldt: start=%d num=%d descs=%p\n",
646 uap->start, uap->num, (void *)uap->descs);
650 /* Free descriptors */
651 if (uap->start == 0 && uap->num == 0) {
653 * Treat this as a special case, so userland needn't
654 * know magic number NLDT.
657 uap->num = MAX_LD - NLDT;
661 mtx_lock_spin(&dt_lock);
662 if ((pldt = mdp->md_ldt) == NULL ||
663 uap->start >= pldt->ldt_len) {
664 mtx_unlock_spin(&dt_lock);
667 largest_ld = uap->start + uap->num;
668 if (largest_ld > pldt->ldt_len)
669 largest_ld = pldt->ldt_len;
670 i = largest_ld - uap->start;
671 bzero(&((union descriptor *)(pldt->ldt_base))[uap->start],
672 sizeof(union descriptor) * i);
673 mtx_unlock_spin(&dt_lock);
677 if (!(uap->start == LDT_AUTO_ALLOC && uap->num == 1)) {
678 /* verify range of descriptors to modify */
679 largest_ld = uap->start + uap->num;
680 if (uap->start >= MAX_LD || largest_ld > MAX_LD) {
685 /* Check descriptors for access violations */
686 for (i = 0; i < uap->num; i++) {
689 switch (dp->sd.sd_type) {
690 case SDT_SYSNULL: /* system null */
693 case SDT_SYS286TSS: /* system 286 TSS available */
694 case SDT_SYSLDT: /* system local descriptor table */
695 case SDT_SYS286BSY: /* system 286 TSS busy */
696 case SDT_SYSTASKGT: /* system task gate */
697 case SDT_SYS286IGT: /* system 286 interrupt gate */
698 case SDT_SYS286TGT: /* system 286 trap gate */
699 case SDT_SYSNULL2: /* undefined by Intel */
700 case SDT_SYS386TSS: /* system 386 TSS available */
701 case SDT_SYSNULL3: /* undefined by Intel */
702 case SDT_SYS386BSY: /* system 386 TSS busy */
703 case SDT_SYSNULL4: /* undefined by Intel */
704 case SDT_SYS386IGT: /* system 386 interrupt gate */
705 case SDT_SYS386TGT: /* system 386 trap gate */
706 case SDT_SYS286CGT: /* system 286 call gate */
707 case SDT_SYS386CGT: /* system 386 call gate */
708 /* I can't think of any reason to allow a user proc
709 * to create a segment of these types. They are
715 /* memory segment types */
716 case SDT_MEMEC: /* memory execute only conforming */
717 case SDT_MEMEAC: /* memory execute only accessed conforming */
718 case SDT_MEMERC: /* memory execute read conforming */
719 case SDT_MEMERAC: /* memory execute read accessed conforming */
720 /* Must be "present" if executable and conforming. */
721 if (dp->sd.sd_p == 0)
724 case SDT_MEMRO: /* memory read only */
725 case SDT_MEMROA: /* memory read only accessed */
726 case SDT_MEMRW: /* memory read write */
727 case SDT_MEMRWA: /* memory read write accessed */
728 case SDT_MEMROD: /* memory read only expand dwn limit */
729 case SDT_MEMRODA: /* memory read only expand dwn lim accessed */
730 case SDT_MEMRWD: /* memory read write expand dwn limit */
731 case SDT_MEMRWDA: /* memory read write expand dwn lim acessed */
732 case SDT_MEME: /* memory execute only */
733 case SDT_MEMEA: /* memory execute only accessed */
734 case SDT_MEMER: /* memory execute read */
735 case SDT_MEMERA: /* memory execute read accessed */
742 /* Only user (ring-3) descriptors may be present. */
743 if ((dp->sd.sd_p != 0) && (dp->sd.sd_dpl != SEL_UPL))
747 if (uap->start == LDT_AUTO_ALLOC && uap->num == 1) {
748 /* Allocate a free slot */
749 mtx_lock_spin(&dt_lock);
750 if ((pldt = mdp->md_ldt) == NULL) {
751 if ((error = i386_ldt_grow(td, NLDT + 1))) {
752 mtx_unlock_spin(&dt_lock);
759 * start scanning a bit up to leave room for NVidia and
760 * Wine, which still user the "Blat" method of allocation.
762 dp = &((union descriptor *)(pldt->ldt_base))[NLDT];
763 for (i = NLDT; i < pldt->ldt_len; ++i) {
764 if (dp->sd.sd_type == SDT_SYSNULL)
768 if (i >= pldt->ldt_len) {
769 if ((error = i386_ldt_grow(td, pldt->ldt_len+1))) {
770 mtx_unlock_spin(&dt_lock);
776 error = i386_set_ldt_data(td, i, 1, descs);
777 mtx_unlock_spin(&dt_lock);
779 largest_ld = uap->start + uap->num;
780 mtx_lock_spin(&dt_lock);
781 if (!(error = i386_ldt_grow(td, largest_ld))) {
782 error = i386_set_ldt_data(td, uap->start, uap->num,
785 mtx_unlock_spin(&dt_lock);
788 td->td_retval[0] = uap->start;
793 i386_set_ldt_data(struct thread *td, int start, int num,
794 union descriptor *descs)
796 struct mdproc *mdp = &td->td_proc->p_md;
797 struct proc_ldt *pldt = mdp->md_ldt;
799 mtx_assert(&dt_lock, MA_OWNED);
802 xen_update_descriptor(
803 &((union descriptor *)(pldt->ldt_base))[start],
813 i386_set_ldt_data(struct thread *td, int start, int num,
814 union descriptor *descs)
816 struct mdproc *mdp = &td->td_proc->p_md;
817 struct proc_ldt *pldt = mdp->md_ldt;
819 mtx_assert(&dt_lock, MA_OWNED);
823 &((union descriptor *)(pldt->ldt_base))[start],
824 num * sizeof(union descriptor));
830 i386_ldt_grow(struct thread *td, int len)
832 struct mdproc *mdp = &td->td_proc->p_md;
833 struct proc_ldt *new_ldt, *pldt;
834 caddr_t old_ldt_base = NULL_LDT_BASE;
837 mtx_assert(&dt_lock, MA_OWNED);
844 /* Allocate a user ldt. */
845 if ((pldt = mdp->md_ldt) == NULL || len > pldt->ldt_len) {
846 new_ldt = user_ldt_alloc(mdp, len);
852 if (new_ldt->ldt_len <= pldt->ldt_len) {
854 * We just lost the race for allocation, so
855 * free the new object and return.
857 mtx_unlock_spin(&dt_lock);
858 kmem_free(kernel_arena,
859 (vm_offset_t)new_ldt->ldt_base,
860 new_ldt->ldt_len * sizeof(union descriptor));
861 free(new_ldt, M_SUBPROC);
862 mtx_lock_spin(&dt_lock);
867 * We have to substitute the current LDT entry for
868 * curproc with the new one since its size grew.
870 old_ldt_base = pldt->ldt_base;
871 old_ldt_len = pldt->ldt_len;
872 pldt->ldt_sd = new_ldt->ldt_sd;
873 pldt->ldt_base = new_ldt->ldt_base;
874 pldt->ldt_len = new_ldt->ldt_len;
876 mdp->md_ldt = pldt = new_ldt;
879 * Signal other cpus to reload ldt. We need to unlock dt_lock
880 * here because other CPU will contest on it since their
881 * curthreads won't hold the lock and will block when trying
884 mtx_unlock_spin(&dt_lock);
885 smp_rendezvous(NULL, (void (*)(void *))set_user_ldt_rv,
886 NULL, td->td_proc->p_vmspace);
888 set_user_ldt(&td->td_proc->p_md);
889 mtx_unlock_spin(&dt_lock);
891 if (old_ldt_base != NULL_LDT_BASE) {
892 kmem_free(kernel_arena, (vm_offset_t)old_ldt_base,
893 old_ldt_len * sizeof(union descriptor));
894 free(new_ldt, M_SUBPROC);
896 mtx_lock_spin(&dt_lock);