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, 0, 0);
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_alloc(kernel_map,
168 kargs.largs.num * sizeof(union descriptor));
173 error = copyin(kargs.largs.descs, lp,
174 kargs.largs.num * sizeof(union descriptor));
176 error = i386_set_ldt(td, &kargs.largs, lp);
177 kmem_free(kernel_map, (vm_offset_t)lp,
178 kargs.largs.num * sizeof(union descriptor));
180 error = i386_set_ldt(td, &kargs.largs, NULL);
183 case I386_GET_IOPERM:
184 error = i386_get_ioperm(td, &kargs.iargs);
186 error = copyout(&kargs.iargs, uap->parms,
187 sizeof(struct i386_ioperm_args));
189 case I386_SET_IOPERM:
190 error = i386_set_ioperm(td, &kargs.iargs);
193 error = vm86_sysarch(td, uap->parms);
195 case I386_GET_FSBASE:
196 sdp = &td->td_pcb->pcb_fsd;
197 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
198 error = copyout(&base, uap->parms, sizeof(base));
200 case I386_SET_FSBASE:
201 error = copyin(uap->parms, &base, sizeof(base));
204 * Construct a descriptor and store it in the pcb for
205 * the next context switch. Also store it in the gdt
206 * so that the load of tf_fs into %fs will activate it
207 * at return to userland.
209 sd.sd_lobase = base & 0xffffff;
210 sd.sd_hibase = (base >> 24) & 0xff;
212 /* need to do nosegneg like Linux */
213 sd.sd_lolimit = (HYPERVISOR_VIRT_START >> 12) & 0xffff;
215 sd.sd_lolimit = 0xffff; /* 4GB limit, wraps around */
218 sd.sd_type = SDT_MEMRWA;
225 td->td_pcb->pcb_fsd = sd;
227 HYPERVISOR_update_descriptor(vtomach(&PCPU_GET(fsgs_gdt)[0]),
230 PCPU_GET(fsgs_gdt)[0] = sd;
233 td->td_frame->tf_fs = GSEL(GUFS_SEL, SEL_UPL);
236 case I386_GET_GSBASE:
237 sdp = &td->td_pcb->pcb_gsd;
238 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
239 error = copyout(&base, uap->parms, sizeof(base));
241 case I386_SET_GSBASE:
242 error = copyin(uap->parms, &base, sizeof(base));
245 * Construct a descriptor and store it in the pcb for
246 * the next context switch. Also store it in the gdt
247 * because we have to do a load_gs() right now.
249 sd.sd_lobase = base & 0xffffff;
250 sd.sd_hibase = (base >> 24) & 0xff;
253 /* need to do nosegneg like Linux */
254 sd.sd_lolimit = (HYPERVISOR_VIRT_START >> 12) & 0xffff;
256 sd.sd_lolimit = 0xffff; /* 4GB limit, wraps around */
259 sd.sd_type = SDT_MEMRWA;
266 td->td_pcb->pcb_gsd = sd;
268 HYPERVISOR_update_descriptor(vtomach(&PCPU_GET(fsgs_gdt)[1]),
271 PCPU_GET(fsgs_gdt)[1] = sd;
274 load_gs(GSEL(GUGS_SEL, SEL_UPL));
285 i386_extend_pcb(struct thread *td)
290 struct soft_segment_descriptor ssd = {
291 0, /* segment base address (overwritten) */
292 ctob(IOPAGES + 1) - 1, /* length */
293 SDT_SYS386TSS, /* segment type */
294 0, /* priority level */
295 1, /* descriptor present */
297 0, /* default 32 size */
301 ext = (struct pcb_ext *)kmem_alloc(kernel_map, ctob(IOPAGES+1));
304 bzero(ext, sizeof(struct pcb_ext));
305 /* -16 is so we can convert a trapframe into vm86trapframe inplace */
306 ext->ext_tss.tss_esp0 = td->td_kstack + ctob(KSTACK_PAGES) -
307 sizeof(struct pcb) - 16;
308 ext->ext_tss.tss_ss0 = GSEL(GDATA_SEL, SEL_KPL);
310 * The last byte of the i/o map must be followed by an 0xff byte.
311 * We arbitrarily allocate 16 bytes here, to keep the starting
312 * address on a doubleword boundary.
314 offset = PAGE_SIZE - 16;
315 ext->ext_tss.tss_ioopt =
316 (offset - ((unsigned)&ext->ext_tss - (unsigned)ext)) << 16;
317 ext->ext_iomap = (caddr_t)ext + offset;
318 ext->ext_vm86.vm86_intmap = (caddr_t)ext + offset - 32;
320 addr = (u_long *)ext->ext_vm86.vm86_intmap;
321 for (i = 0; i < (ctob(IOPAGES) + 32 + 16) / sizeof(u_long); i++)
324 ssd.ssd_base = (unsigned)&ext->ext_tss;
325 ssd.ssd_limit -= ((unsigned)&ext->ext_tss - (unsigned)ext);
326 ssdtosd(&ssd, &ext->ext_tssd);
328 KASSERT(td == curthread, ("giving TSS to !curthread"));
329 KASSERT(td->td_pcb->pcb_ext == 0, ("already have a TSS!"));
331 /* Switch to the new TSS. */
333 td->td_pcb->pcb_ext = ext;
334 PCPU_SET(private_tss, 1);
335 *PCPU_GET(tss_gdt) = ext->ext_tssd;
336 ltr(GSEL(GPROC0_SEL, SEL_KPL));
343 i386_set_ioperm(td, uap)
345 struct i386_ioperm_args *uap;
350 if ((error = priv_check(td, PRIV_IO)) != 0)
352 if ((error = securelevel_gt(td->td_ucred, 0)) != 0)
356 * While this is restricted to root, we should probably figure out
357 * whether any other driver is using this i/o address, as so not to
358 * cause confusion. This probably requires a global 'usage registry'.
361 if (td->td_pcb->pcb_ext == 0)
362 if ((error = i386_extend_pcb(td)) != 0)
364 iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
366 if (uap->start + uap->length > IOPAGES * PAGE_SIZE * NBBY)
369 for (i = uap->start; i < uap->start + uap->length; i++) {
371 iomap[i >> 3] &= ~(1 << (i & 7));
373 iomap[i >> 3] |= (1 << (i & 7));
379 i386_get_ioperm(td, uap)
381 struct i386_ioperm_args *uap;
386 if (uap->start >= IOPAGES * PAGE_SIZE * NBBY)
389 if (td->td_pcb->pcb_ext == 0) {
394 iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
397 state = (iomap[i >> 3] >> (i & 7)) & 1;
398 uap->enable = !state;
401 for (i = uap->start + 1; i < IOPAGES * PAGE_SIZE * NBBY; i++) {
402 if (state != ((iomap[i >> 3] >> (i & 7)) & 1))
412 * Update the GDT entry pointing to the LDT to point to the LDT of the
413 * current process. Manage dt_lock holding/unholding autonomously.
416 set_user_ldt(struct mdproc *mdp)
418 struct proc_ldt *pldt;
422 if (!mtx_owned(&dt_lock)) {
423 mtx_lock_spin(&dt_lock);
429 i386_reset_ldt(pldt);
430 PCPU_SET(currentldt, (int)pldt);
433 gdt[PCPU_GET(cpuid) * NGDT + GUSERLDT_SEL].sd = pldt->ldt_sd;
435 gdt[GUSERLDT_SEL].sd = pldt->ldt_sd;
437 lldt(GSEL(GUSERLDT_SEL, SEL_KPL));
438 PCPU_SET(currentldt, GSEL(GUSERLDT_SEL, SEL_KPL));
441 mtx_unlock_spin(&dt_lock);
446 set_user_ldt_rv(struct vmspace *vmsp)
451 if (vmsp != td->td_proc->p_vmspace)
454 set_user_ldt(&td->td_proc->p_md);
461 * dt_lock must be held. Returns with dt_lock held.
464 user_ldt_alloc(struct mdproc *mdp, int len)
466 struct proc_ldt *pldt, *new_ldt;
468 mtx_assert(&dt_lock, MA_OWNED);
469 mtx_unlock_spin(&dt_lock);
470 new_ldt = malloc(sizeof(struct proc_ldt),
471 M_SUBPROC, M_WAITOK);
473 new_ldt->ldt_len = len = NEW_MAX_LD(len);
474 new_ldt->ldt_base = (caddr_t)kmem_alloc(kernel_map,
475 round_page(len * sizeof(union descriptor)));
476 if (new_ldt->ldt_base == NULL) {
477 free(new_ldt, M_SUBPROC);
478 mtx_lock_spin(&dt_lock);
481 new_ldt->ldt_refcnt = 1;
482 new_ldt->ldt_active = 0;
484 mtx_lock_spin(&dt_lock);
485 if ((pldt = mdp->md_ldt)) {
486 if (len > pldt->ldt_len)
488 bcopy(pldt->ldt_base, new_ldt->ldt_base,
489 len * sizeof(union descriptor));
491 bcopy(ldt, new_ldt->ldt_base, PAGE_SIZE);
493 mtx_unlock_spin(&dt_lock); /* XXX kill once pmap locking fixed. */
494 pmap_map_readonly(kernel_pmap, (vm_offset_t)new_ldt->ldt_base,
495 new_ldt->ldt_len*sizeof(union descriptor));
496 mtx_lock_spin(&dt_lock); /* XXX kill once pmap locking fixed. */
501 * dt_lock must be held. Returns with dt_lock held.
504 user_ldt_alloc(struct mdproc *mdp, int len)
506 struct proc_ldt *pldt, *new_ldt;
508 mtx_assert(&dt_lock, MA_OWNED);
509 mtx_unlock_spin(&dt_lock);
510 new_ldt = malloc(sizeof(struct proc_ldt),
511 M_SUBPROC, M_WAITOK);
513 new_ldt->ldt_len = len = NEW_MAX_LD(len);
514 new_ldt->ldt_base = (caddr_t)kmem_alloc(kernel_map,
515 len * sizeof(union descriptor));
516 if (new_ldt->ldt_base == NULL) {
517 free(new_ldt, M_SUBPROC);
518 mtx_lock_spin(&dt_lock);
521 new_ldt->ldt_refcnt = 1;
522 new_ldt->ldt_active = 0;
524 mtx_lock_spin(&dt_lock);
525 gdt_segs[GUSERLDT_SEL].ssd_base = (unsigned)new_ldt->ldt_base;
526 gdt_segs[GUSERLDT_SEL].ssd_limit = len * sizeof(union descriptor) - 1;
527 ssdtosd(&gdt_segs[GUSERLDT_SEL], &new_ldt->ldt_sd);
529 if ((pldt = mdp->md_ldt) != NULL) {
530 if (len > pldt->ldt_len)
532 bcopy(pldt->ldt_base, new_ldt->ldt_base,
533 len * sizeof(union descriptor));
535 bcopy(ldt, new_ldt->ldt_base, sizeof(ldt));
542 * Must be called with dt_lock held. Returns with dt_lock unheld.
545 user_ldt_free(struct thread *td)
547 struct mdproc *mdp = &td->td_proc->p_md;
548 struct proc_ldt *pldt;
550 mtx_assert(&dt_lock, MA_OWNED);
551 if ((pldt = mdp->md_ldt) == NULL) {
552 mtx_unlock_spin(&dt_lock);
556 if (td == curthread) {
558 i386_reset_ldt(&default_proc_ldt);
559 PCPU_SET(currentldt, (int)&default_proc_ldt);
562 PCPU_SET(currentldt, _default_ldt);
567 user_ldt_deref(pldt);
571 user_ldt_deref(struct proc_ldt *pldt)
574 mtx_assert(&dt_lock, MA_OWNED);
575 if (--pldt->ldt_refcnt == 0) {
576 mtx_unlock_spin(&dt_lock);
577 kmem_free(kernel_map, (vm_offset_t)pldt->ldt_base,
578 pldt->ldt_len * sizeof(union descriptor));
579 free(pldt, M_SUBPROC);
581 mtx_unlock_spin(&dt_lock);
585 * Note for the authors of compat layers (linux, etc): copyout() in
586 * the function below is not a problem since it presents data in
587 * arch-specific format (i.e. i386-specific in this case), not in
588 * the OS-specific one.
591 i386_get_ldt(td, uap)
593 struct i386_ldt_args *uap;
596 struct proc_ldt *pldt;
598 union descriptor *lp;
601 printf("i386_get_ldt: start=%d num=%d descs=%p\n",
602 uap->start, uap->num, (void *)uap->descs);
605 mtx_lock_spin(&dt_lock);
606 if ((pldt = td->td_proc->p_md.md_ldt) != NULL) {
607 nldt = pldt->ldt_len;
608 lp = &((union descriptor *)(pldt->ldt_base))[uap->start];
609 mtx_unlock_spin(&dt_lock);
610 num = min(uap->num, nldt);
612 mtx_unlock_spin(&dt_lock);
613 nldt = sizeof(ldt)/sizeof(ldt[0]);
614 num = min(uap->num, nldt);
615 lp = &ldt[uap->start];
618 if ((uap->start > (unsigned int)nldt) ||
619 ((unsigned int)num > (unsigned int)nldt) ||
620 ((unsigned int)(uap->start + num) > (unsigned int)nldt))
623 error = copyout(lp, uap->descs, num * sizeof(union descriptor));
625 td->td_retval[0] = num;
631 i386_set_ldt(td, uap, descs)
633 struct i386_ldt_args *uap;
634 union descriptor *descs;
638 struct mdproc *mdp = &td->td_proc->p_md;
639 struct proc_ldt *pldt;
640 union descriptor *dp;
643 printf("i386_set_ldt: start=%d num=%d descs=%p\n",
644 uap->start, uap->num, (void *)uap->descs);
648 /* Free descriptors */
649 if (uap->start == 0 && uap->num == 0) {
651 * Treat this as a special case, so userland needn't
652 * know magic number NLDT.
655 uap->num = MAX_LD - NLDT;
659 mtx_lock_spin(&dt_lock);
660 if ((pldt = mdp->md_ldt) == NULL ||
661 uap->start >= pldt->ldt_len) {
662 mtx_unlock_spin(&dt_lock);
665 largest_ld = uap->start + uap->num;
666 if (largest_ld > pldt->ldt_len)
667 largest_ld = pldt->ldt_len;
668 i = largest_ld - uap->start;
669 bzero(&((union descriptor *)(pldt->ldt_base))[uap->start],
670 sizeof(union descriptor) * i);
671 mtx_unlock_spin(&dt_lock);
675 if (!(uap->start == LDT_AUTO_ALLOC && uap->num == 1)) {
676 /* verify range of descriptors to modify */
677 largest_ld = uap->start + uap->num;
678 if (uap->start >= MAX_LD || largest_ld > MAX_LD) {
683 /* Check descriptors for access violations */
684 for (i = 0; i < uap->num; i++) {
687 switch (dp->sd.sd_type) {
688 case SDT_SYSNULL: /* system null */
691 case SDT_SYS286TSS: /* system 286 TSS available */
692 case SDT_SYSLDT: /* system local descriptor table */
693 case SDT_SYS286BSY: /* system 286 TSS busy */
694 case SDT_SYSTASKGT: /* system task gate */
695 case SDT_SYS286IGT: /* system 286 interrupt gate */
696 case SDT_SYS286TGT: /* system 286 trap gate */
697 case SDT_SYSNULL2: /* undefined by Intel */
698 case SDT_SYS386TSS: /* system 386 TSS available */
699 case SDT_SYSNULL3: /* undefined by Intel */
700 case SDT_SYS386BSY: /* system 386 TSS busy */
701 case SDT_SYSNULL4: /* undefined by Intel */
702 case SDT_SYS386IGT: /* system 386 interrupt gate */
703 case SDT_SYS386TGT: /* system 386 trap gate */
704 case SDT_SYS286CGT: /* system 286 call gate */
705 case SDT_SYS386CGT: /* system 386 call gate */
706 /* I can't think of any reason to allow a user proc
707 * to create a segment of these types. They are
713 /* memory segment types */
714 case SDT_MEMEC: /* memory execute only conforming */
715 case SDT_MEMEAC: /* memory execute only accessed conforming */
716 case SDT_MEMERC: /* memory execute read conforming */
717 case SDT_MEMERAC: /* memory execute read accessed conforming */
718 /* Must be "present" if executable and conforming. */
719 if (dp->sd.sd_p == 0)
722 case SDT_MEMRO: /* memory read only */
723 case SDT_MEMROA: /* memory read only accessed */
724 case SDT_MEMRW: /* memory read write */
725 case SDT_MEMRWA: /* memory read write accessed */
726 case SDT_MEMROD: /* memory read only expand dwn limit */
727 case SDT_MEMRODA: /* memory read only expand dwn lim accessed */
728 case SDT_MEMRWD: /* memory read write expand dwn limit */
729 case SDT_MEMRWDA: /* memory read write expand dwn lim acessed */
730 case SDT_MEME: /* memory execute only */
731 case SDT_MEMEA: /* memory execute only accessed */
732 case SDT_MEMER: /* memory execute read */
733 case SDT_MEMERA: /* memory execute read accessed */
740 /* Only user (ring-3) descriptors may be present. */
741 if ((dp->sd.sd_p != 0) && (dp->sd.sd_dpl != SEL_UPL))
745 if (uap->start == LDT_AUTO_ALLOC && uap->num == 1) {
746 /* Allocate a free slot */
747 mtx_lock_spin(&dt_lock);
748 if ((pldt = mdp->md_ldt) == NULL) {
749 if ((error = i386_ldt_grow(td, NLDT + 1))) {
750 mtx_unlock_spin(&dt_lock);
757 * start scanning a bit up to leave room for NVidia and
758 * Wine, which still user the "Blat" method of allocation.
760 dp = &((union descriptor *)(pldt->ldt_base))[NLDT];
761 for (i = NLDT; i < pldt->ldt_len; ++i) {
762 if (dp->sd.sd_type == SDT_SYSNULL)
766 if (i >= pldt->ldt_len) {
767 if ((error = i386_ldt_grow(td, pldt->ldt_len+1))) {
768 mtx_unlock_spin(&dt_lock);
774 error = i386_set_ldt_data(td, i, 1, descs);
775 mtx_unlock_spin(&dt_lock);
777 largest_ld = uap->start + uap->num;
778 mtx_lock_spin(&dt_lock);
779 if (!(error = i386_ldt_grow(td, largest_ld))) {
780 error = i386_set_ldt_data(td, uap->start, uap->num,
783 mtx_unlock_spin(&dt_lock);
786 td->td_retval[0] = uap->start;
791 i386_set_ldt_data(struct thread *td, int start, int num,
792 union descriptor *descs)
794 struct mdproc *mdp = &td->td_proc->p_md;
795 struct proc_ldt *pldt = mdp->md_ldt;
797 mtx_assert(&dt_lock, MA_OWNED);
800 xen_update_descriptor(
801 &((union descriptor *)(pldt->ldt_base))[start],
811 i386_set_ldt_data(struct thread *td, int start, int num,
812 union descriptor *descs)
814 struct mdproc *mdp = &td->td_proc->p_md;
815 struct proc_ldt *pldt = mdp->md_ldt;
817 mtx_assert(&dt_lock, MA_OWNED);
821 &((union descriptor *)(pldt->ldt_base))[start],
822 num * sizeof(union descriptor));
828 i386_ldt_grow(struct thread *td, int len)
830 struct mdproc *mdp = &td->td_proc->p_md;
831 struct proc_ldt *new_ldt, *pldt;
832 caddr_t old_ldt_base = NULL_LDT_BASE;
835 mtx_assert(&dt_lock, MA_OWNED);
842 /* Allocate a user ldt. */
843 if ((pldt = mdp->md_ldt) == NULL || len > pldt->ldt_len) {
844 new_ldt = user_ldt_alloc(mdp, len);
850 if (new_ldt->ldt_len <= pldt->ldt_len) {
852 * We just lost the race for allocation, so
853 * free the new object and return.
855 mtx_unlock_spin(&dt_lock);
856 kmem_free(kernel_map,
857 (vm_offset_t)new_ldt->ldt_base,
858 new_ldt->ldt_len * sizeof(union descriptor));
859 free(new_ldt, M_SUBPROC);
860 mtx_lock_spin(&dt_lock);
865 * We have to substitute the current LDT entry for
866 * curproc with the new one since its size grew.
868 old_ldt_base = pldt->ldt_base;
869 old_ldt_len = pldt->ldt_len;
870 pldt->ldt_sd = new_ldt->ldt_sd;
871 pldt->ldt_base = new_ldt->ldt_base;
872 pldt->ldt_len = new_ldt->ldt_len;
874 mdp->md_ldt = pldt = new_ldt;
877 * Signal other cpus to reload ldt. We need to unlock dt_lock
878 * here because other CPU will contest on it since their
879 * curthreads won't hold the lock and will block when trying
882 mtx_unlock_spin(&dt_lock);
883 smp_rendezvous(NULL, (void (*)(void *))set_user_ldt_rv,
884 NULL, td->td_proc->p_vmspace);
886 set_user_ldt(&td->td_proc->p_md);
887 mtx_unlock_spin(&dt_lock);
889 if (old_ldt_base != NULL_LDT_BASE) {
890 kmem_free(kernel_map, (vm_offset_t)old_ldt_base,
891 old_ldt_len * sizeof(union descriptor));
892 free(new_ldt, M_SUBPROC);
894 mtx_lock_spin(&dt_lock);