The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/amd64/amd64/sys_machdep.c

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    1 /*-
    2  * Copyright (c) 2003 Peter Wemm.
    3  * Copyright (c) 1990 The Regents of the University of California.
    4  * All rights reserved.
    5  *
    6  * Redistribution and use in source and binary forms, with or without
    7  * modification, are permitted provided that the following conditions
    8  * are met:
    9  * 1. Redistributions of source code must retain the above copyright
   10  *    notice, this list of conditions and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 4. Neither the name of the University nor the names of its contributors
   15  *    may be used to endorse or promote products derived from this software
   16  *    without specific prior written permission.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   28  * SUCH DAMAGE.
   29  *
   30  *      from: @(#)sys_machdep.c 5.5 (Berkeley) 1/19/91
   31  */
   32 
   33 #include <sys/cdefs.h>
   34 __FBSDID("$FreeBSD: releng/9.1/sys/amd64/amd64/sys_machdep.c 231979 2012-02-21 20:56:03Z kib $");
   35 
   36 #include "opt_capsicum.h"
   37 
   38 #include <sys/param.h>
   39 #include <sys/systm.h>
   40 #include <sys/capability.h>
   41 #include <sys/kernel.h>
   42 #include <sys/lock.h>
   43 #include <sys/malloc.h>
   44 #include <sys/mutex.h>
   45 #include <sys/priv.h>
   46 #include <sys/proc.h>
   47 #include <sys/sysproto.h>
   48 #include <sys/uio.h>
   49 
   50 #include <vm/vm.h>
   51 #include <vm/pmap.h>
   52 #include <vm/vm_kern.h>         /* for kernel_map */
   53 #include <vm/vm_extern.h>
   54 
   55 #include <machine/frame.h>
   56 #include <machine/md_var.h>
   57 #include <machine/pcb.h>
   58 #include <machine/specialreg.h>
   59 #include <machine/sysarch.h>
   60 #include <machine/tss.h>
   61 #include <machine/vmparam.h>
   62 
   63 #include <security/audit/audit.h>
   64 
   65 #define MAX_LD          8192
   66 
   67 int max_ldt_segment = 1024;
   68 SYSCTL_INT(_machdep, OID_AUTO, max_ldt_segment, CTLFLAG_RDTUN,
   69     &max_ldt_segment, 0,
   70     "Maximum number of allowed LDT segments in the single address space");
   71 
   72 static void
   73 max_ldt_segment_init(void *arg __unused)
   74 {
   75 
   76         TUNABLE_INT_FETCH("machdep.max_ldt_segment", &max_ldt_segment);
   77         if (max_ldt_segment <= 0)
   78                 max_ldt_segment = 1;
   79         if (max_ldt_segment > MAX_LD)
   80                 max_ldt_segment = MAX_LD;
   81 }
   82 SYSINIT(maxldt, SI_SUB_VM_CONF, SI_ORDER_ANY, max_ldt_segment_init, NULL);
   83 
   84 #ifdef notyet
   85 #ifdef SMP
   86 static void set_user_ldt_rv(struct vmspace *vmsp);
   87 #endif
   88 #endif
   89 static void user_ldt_derefl(struct proc_ldt *pldt);
   90 
   91 #ifndef _SYS_SYSPROTO_H_
   92 struct sysarch_args {
   93         int op;
   94         char *parms;
   95 };
   96 #endif
   97 
   98 int
   99 sysarch_ldt(struct thread *td, struct sysarch_args *uap, int uap_space)
  100 {
  101         struct i386_ldt_args *largs, la;
  102         struct user_segment_descriptor *lp;
  103         int error = 0;
  104 
  105         /*
  106          * XXXKIB check that the BSM generation code knows to encode
  107          * the op argument.
  108          */
  109         AUDIT_ARG_CMD(uap->op);
  110         if (uap_space == UIO_USERSPACE) {
  111                 error = copyin(uap->parms, &la, sizeof(struct i386_ldt_args));
  112                 if (error != 0)
  113                         return (error);
  114                 largs = &la;
  115         } else
  116                 largs = (struct i386_ldt_args *)uap->parms;
  117 
  118         switch (uap->op) {
  119         case I386_GET_LDT:
  120                 error = amd64_get_ldt(td, largs);
  121                 break;
  122         case I386_SET_LDT:
  123                 if (largs->descs != NULL && largs->num > max_ldt_segment)
  124                         return (EINVAL);
  125                 set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
  126                 if (largs->descs != NULL) {
  127                         lp = malloc(largs->num * sizeof(struct
  128                             user_segment_descriptor), M_TEMP, M_WAITOK);
  129                         error = copyin(largs->descs, lp, largs->num *
  130                             sizeof(struct user_segment_descriptor));
  131                         if (error == 0)
  132                                 error = amd64_set_ldt(td, largs, lp);
  133                         free(lp, M_TEMP);
  134                 } else {
  135                         error = amd64_set_ldt(td, largs, NULL);
  136                 }
  137                 break;
  138         }
  139         return (error);
  140 }
  141 
  142 void
  143 update_gdt_gsbase(struct thread *td, uint32_t base)
  144 {
  145         struct user_segment_descriptor *sd;
  146 
  147         if (td != curthread)
  148                 return;
  149         set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
  150         critical_enter();
  151         sd = PCPU_GET(gs32p);
  152         sd->sd_lobase = base & 0xffffff;
  153         sd->sd_hibase = (base >> 24) & 0xff;
  154         critical_exit();
  155 }
  156 
  157 void
  158 update_gdt_fsbase(struct thread *td, uint32_t base)
  159 {
  160         struct user_segment_descriptor *sd;
  161 
  162         if (td != curthread)
  163                 return;
  164         set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
  165         critical_enter();
  166         sd = PCPU_GET(fs32p);
  167         sd->sd_lobase = base & 0xffffff;
  168         sd->sd_hibase = (base >> 24) & 0xff;
  169         critical_exit();
  170 }
  171 
  172 int
  173 sysarch(td, uap)
  174         struct thread *td;
  175         register struct sysarch_args *uap;
  176 {
  177         int error = 0;
  178         struct pcb *pcb = curthread->td_pcb;
  179         uint32_t i386base;
  180         uint64_t a64base;
  181         struct i386_ioperm_args iargs;
  182         struct i386_get_xfpustate i386xfpu;
  183         struct amd64_get_xfpustate a64xfpu;
  184 
  185 #ifdef CAPABILITY_MODE
  186         /*
  187          * When adding new operations, add a new case statement here to
  188          * explicitly indicate whether or not the operation is safe to
  189          * perform in capability mode.
  190          */
  191         if (IN_CAPABILITY_MODE(td)) {
  192                 switch (uap->op) {
  193                 case I386_GET_LDT:
  194                 case I386_SET_LDT:
  195                 case I386_GET_IOPERM:
  196                 case I386_GET_FSBASE:
  197                 case I386_SET_FSBASE:
  198                 case I386_GET_GSBASE:
  199                 case I386_SET_GSBASE:
  200                 case I386_GET_XFPUSTATE:
  201                 case AMD64_GET_FSBASE:
  202                 case AMD64_SET_FSBASE:
  203                 case AMD64_GET_GSBASE:
  204                 case AMD64_SET_GSBASE:
  205                 case AMD64_GET_XFPUSTATE:
  206                         break;
  207 
  208                 case I386_SET_IOPERM:
  209                 default:
  210                         return (ECAPMODE);
  211                 }
  212         }
  213 #endif
  214 
  215         if (uap->op == I386_GET_LDT || uap->op == I386_SET_LDT)
  216                 return (sysarch_ldt(td, uap, UIO_USERSPACE));
  217         /*
  218          * XXXKIB check that the BSM generation code knows to encode
  219          * the op argument.
  220          */
  221         AUDIT_ARG_CMD(uap->op);
  222         switch (uap->op) {
  223         case I386_GET_IOPERM:
  224         case I386_SET_IOPERM:
  225                 if ((error = copyin(uap->parms, &iargs,
  226                     sizeof(struct i386_ioperm_args))) != 0)
  227                         return (error);
  228                 break;
  229         case I386_GET_XFPUSTATE:
  230                 if ((error = copyin(uap->parms, &i386xfpu,
  231                     sizeof(struct i386_get_xfpustate))) != 0)
  232                         return (error);
  233                 a64xfpu.addr = (void *)(uintptr_t)i386xfpu.addr;
  234                 a64xfpu.len = i386xfpu.len;
  235                 break;
  236         case AMD64_GET_XFPUSTATE:
  237                 if ((error = copyin(uap->parms, &a64xfpu,
  238                     sizeof(struct amd64_get_xfpustate))) != 0)
  239                         return (error);
  240                 break;
  241         default:
  242                 break;
  243         }
  244 
  245         switch (uap->op) {
  246         case I386_GET_IOPERM:
  247                 error = amd64_get_ioperm(td, &iargs);
  248                 if (error == 0)
  249                         error = copyout(&iargs, uap->parms,
  250                             sizeof(struct i386_ioperm_args));
  251                 break;
  252         case I386_SET_IOPERM:
  253                 error = amd64_set_ioperm(td, &iargs);
  254                 break;
  255         case I386_GET_FSBASE:
  256                 i386base = pcb->pcb_fsbase;
  257                 error = copyout(&i386base, uap->parms, sizeof(i386base));
  258                 break;
  259         case I386_SET_FSBASE:
  260                 error = copyin(uap->parms, &i386base, sizeof(i386base));
  261                 if (!error) {
  262                         pcb->pcb_fsbase = i386base;
  263                         td->td_frame->tf_fs = _ufssel;
  264                         update_gdt_fsbase(td, i386base);
  265                 }
  266                 break;
  267         case I386_GET_GSBASE:
  268                 i386base = pcb->pcb_gsbase;
  269                 error = copyout(&i386base, uap->parms, sizeof(i386base));
  270                 break;
  271         case I386_SET_GSBASE:
  272                 error = copyin(uap->parms, &i386base, sizeof(i386base));
  273                 if (!error) {
  274                         pcb->pcb_gsbase = i386base;
  275                         td->td_frame->tf_gs = _ugssel;
  276                         update_gdt_gsbase(td, i386base);
  277                 }
  278                 break;
  279         case AMD64_GET_FSBASE:
  280                 error = copyout(&pcb->pcb_fsbase, uap->parms, sizeof(pcb->pcb_fsbase));
  281                 break;
  282                 
  283         case AMD64_SET_FSBASE:
  284                 error = copyin(uap->parms, &a64base, sizeof(a64base));
  285                 if (!error) {
  286                         if (a64base < VM_MAXUSER_ADDRESS) {
  287                                 pcb->pcb_fsbase = a64base;
  288                                 set_pcb_flags(pcb, PCB_FULL_IRET);
  289                                 td->td_frame->tf_fs = _ufssel;
  290                         } else
  291                                 error = EINVAL;
  292                 }
  293                 break;
  294 
  295         case AMD64_GET_GSBASE:
  296                 error = copyout(&pcb->pcb_gsbase, uap->parms, sizeof(pcb->pcb_gsbase));
  297                 break;
  298 
  299         case AMD64_SET_GSBASE:
  300                 error = copyin(uap->parms, &a64base, sizeof(a64base));
  301                 if (!error) {
  302                         if (a64base < VM_MAXUSER_ADDRESS) {
  303                                 pcb->pcb_gsbase = a64base;
  304                                 set_pcb_flags(pcb, PCB_FULL_IRET);
  305                                 td->td_frame->tf_gs = _ugssel;
  306                         } else
  307                                 error = EINVAL;
  308                 }
  309                 break;
  310 
  311         case I386_GET_XFPUSTATE:
  312         case AMD64_GET_XFPUSTATE:
  313                 if (a64xfpu.len > cpu_max_ext_state_size -
  314                     sizeof(struct savefpu))
  315                         return (EINVAL);
  316                 fpugetregs(td);
  317                 error = copyout((char *)(get_pcb_user_save_td(td) + 1),
  318                     a64xfpu.addr, a64xfpu.len);
  319                 return (error);
  320 
  321         default:
  322                 error = EINVAL;
  323                 break;
  324         }
  325         return (error);
  326 }
  327 
  328 int
  329 amd64_set_ioperm(td, uap)
  330         struct thread *td;
  331         struct i386_ioperm_args *uap;
  332 {
  333         int i, error;
  334         char *iomap;
  335         struct amd64tss *tssp;
  336         struct system_segment_descriptor *tss_sd;
  337         u_long *addr;
  338         struct pcb *pcb;
  339 
  340         if ((error = priv_check(td, PRIV_IO)) != 0)
  341                 return (error);
  342         if ((error = securelevel_gt(td->td_ucred, 0)) != 0)
  343                 return (error);
  344         if (uap->start + uap->length > IOPAGES * PAGE_SIZE * NBBY)
  345                 return (EINVAL);
  346 
  347         /*
  348          * XXX
  349          * While this is restricted to root, we should probably figure out
  350          * whether any other driver is using this i/o address, as so not to
  351          * cause confusion.  This probably requires a global 'usage registry'.
  352          */
  353         pcb = td->td_pcb;
  354         if (pcb->pcb_tssp == NULL) {
  355                 tssp = (struct amd64tss *)kmem_alloc(kernel_map,
  356                     ctob(IOPAGES+1));
  357                 if (tssp == NULL)
  358                         return (ENOMEM);
  359                 iomap = (char *)&tssp[1];
  360                 addr = (u_long *)iomap;
  361                 for (i = 0; i < (ctob(IOPAGES) + 1) / sizeof(u_long); i++)
  362                         *addr++ = ~0;
  363                 critical_enter();
  364                 /* Takes care of tss_rsp0. */
  365                 memcpy(tssp, &common_tss[PCPU_GET(cpuid)],
  366                     sizeof(struct amd64tss));
  367                 tssp->tss_iobase = sizeof(*tssp);
  368                 pcb->pcb_tssp = tssp;
  369                 tss_sd = PCPU_GET(tss);
  370                 tss_sd->sd_lobase = (u_long)tssp & 0xffffff;
  371                 tss_sd->sd_hibase = ((u_long)tssp >> 24) & 0xfffffffffful;
  372                 tss_sd->sd_type = SDT_SYSTSS;
  373                 ltr(GSEL(GPROC0_SEL, SEL_KPL));
  374                 PCPU_SET(tssp, tssp);
  375                 critical_exit();
  376         } else
  377                 iomap = (char *)&pcb->pcb_tssp[1];
  378         for (i = uap->start; i < uap->start + uap->length; i++) {
  379                 if (uap->enable)
  380                         iomap[i >> 3] &= ~(1 << (i & 7));
  381                 else
  382                         iomap[i >> 3] |= (1 << (i & 7));
  383         }
  384         return (error);
  385 }
  386 
  387 int
  388 amd64_get_ioperm(td, uap)
  389         struct thread *td;
  390         struct i386_ioperm_args *uap;
  391 {
  392         int i, state;
  393         char *iomap;
  394 
  395         if (uap->start >= IOPAGES * PAGE_SIZE * NBBY)
  396                 return (EINVAL);
  397         if (td->td_pcb->pcb_tssp == NULL) {
  398                 uap->length = 0;
  399                 goto done;
  400         }
  401 
  402         iomap = (char *)&td->td_pcb->pcb_tssp[1];
  403 
  404         i = uap->start;
  405         state = (iomap[i >> 3] >> (i & 7)) & 1;
  406         uap->enable = !state;
  407         uap->length = 1;
  408 
  409         for (i = uap->start + 1; i < IOPAGES * PAGE_SIZE * NBBY; i++) {
  410                 if (state != ((iomap[i >> 3] >> (i & 7)) & 1))
  411                         break;
  412                 uap->length++;
  413         }
  414 
  415 done:
  416         return (0);
  417 }
  418 
  419 /*
  420  * Update the GDT entry pointing to the LDT to point to the LDT of the
  421  * current process.
  422  */
  423 void
  424 set_user_ldt(struct mdproc *mdp)
  425 {
  426 
  427         critical_enter();
  428         *PCPU_GET(ldt) = mdp->md_ldt_sd;
  429         lldt(GSEL(GUSERLDT_SEL, SEL_KPL));
  430         critical_exit();
  431 }
  432 
  433 #ifdef notyet
  434 #ifdef SMP
  435 static void
  436 set_user_ldt_rv(struct vmspace *vmsp)
  437 {
  438         struct thread *td;
  439 
  440         td = curthread;
  441         if (vmsp != td->td_proc->p_vmspace)
  442                 return;
  443 
  444         set_user_ldt(&td->td_proc->p_md);
  445 }
  446 #endif
  447 #endif
  448 
  449 struct proc_ldt *
  450 user_ldt_alloc(struct proc *p, int force)
  451 {
  452         struct proc_ldt *pldt, *new_ldt;
  453         struct mdproc *mdp;
  454         struct soft_segment_descriptor sldt;
  455 
  456         mtx_assert(&dt_lock, MA_OWNED);
  457         mdp = &p->p_md;
  458         if (!force && mdp->md_ldt != NULL)
  459                 return (mdp->md_ldt);
  460         mtx_unlock(&dt_lock);
  461         new_ldt = malloc(sizeof(struct proc_ldt), M_SUBPROC, M_WAITOK);
  462         new_ldt->ldt_base = (caddr_t)kmem_alloc(kernel_map,
  463              max_ldt_segment * sizeof(struct user_segment_descriptor));
  464         if (new_ldt->ldt_base == NULL) {
  465                 FREE(new_ldt, M_SUBPROC);
  466                 mtx_lock(&dt_lock);
  467                 return (NULL);
  468         }
  469         new_ldt->ldt_refcnt = 1;
  470         sldt.ssd_base = (uint64_t)new_ldt->ldt_base;
  471         sldt.ssd_limit = max_ldt_segment *
  472             sizeof(struct user_segment_descriptor) - 1;
  473         sldt.ssd_type = SDT_SYSLDT;
  474         sldt.ssd_dpl = SEL_KPL;
  475         sldt.ssd_p = 1;
  476         sldt.ssd_long = 0;
  477         sldt.ssd_def32 = 0;
  478         sldt.ssd_gran = 0;
  479         mtx_lock(&dt_lock);
  480         pldt = mdp->md_ldt;
  481         if (pldt != NULL && !force) {
  482                 kmem_free(kernel_map, (vm_offset_t)new_ldt->ldt_base,
  483                     max_ldt_segment * sizeof(struct user_segment_descriptor));
  484                 free(new_ldt, M_SUBPROC);
  485                 return (pldt);
  486         }
  487 
  488         if (pldt != NULL) {
  489                 bcopy(pldt->ldt_base, new_ldt->ldt_base, max_ldt_segment *
  490                     sizeof(struct user_segment_descriptor));
  491                 user_ldt_derefl(pldt);
  492         }
  493         ssdtosyssd(&sldt, &p->p_md.md_ldt_sd);
  494         atomic_store_rel_ptr((volatile uintptr_t *)&mdp->md_ldt,
  495             (uintptr_t)new_ldt);
  496         if (p == curproc)
  497                 set_user_ldt(mdp);
  498 
  499         return (mdp->md_ldt);
  500 }
  501 
  502 void
  503 user_ldt_free(struct thread *td)
  504 {
  505         struct proc *p = td->td_proc;
  506         struct mdproc *mdp = &p->p_md;
  507         struct proc_ldt *pldt;
  508 
  509         mtx_assert(&dt_lock, MA_OWNED);
  510         if ((pldt = mdp->md_ldt) == NULL) {
  511                 mtx_unlock(&dt_lock);
  512                 return;
  513         }
  514 
  515         mdp->md_ldt = NULL;
  516         bzero(&mdp->md_ldt_sd, sizeof(mdp->md_ldt_sd));
  517         if (td == curthread)
  518                 lldt(GSEL(GNULL_SEL, SEL_KPL));
  519         user_ldt_deref(pldt);
  520 }
  521 
  522 static void
  523 user_ldt_derefl(struct proc_ldt *pldt)
  524 {
  525 
  526         if (--pldt->ldt_refcnt == 0) {
  527                 kmem_free(kernel_map, (vm_offset_t)pldt->ldt_base,
  528                     max_ldt_segment * sizeof(struct user_segment_descriptor));
  529                 free(pldt, M_SUBPROC);
  530         }
  531 }
  532 
  533 void
  534 user_ldt_deref(struct proc_ldt *pldt)
  535 {
  536 
  537         mtx_assert(&dt_lock, MA_OWNED);
  538         user_ldt_derefl(pldt);
  539         mtx_unlock(&dt_lock);
  540 }
  541 
  542 /*
  543  * Note for the authors of compat layers (linux, etc): copyout() in
  544  * the function below is not a problem since it presents data in
  545  * arch-specific format (i.e. i386-specific in this case), not in
  546  * the OS-specific one.
  547  */
  548 int
  549 amd64_get_ldt(td, uap)
  550         struct thread *td;
  551         struct i386_ldt_args *uap;
  552 {
  553         int error = 0;
  554         struct proc_ldt *pldt;
  555         int num;
  556         struct user_segment_descriptor *lp;
  557 
  558 #ifdef  DEBUG
  559         printf("amd64_get_ldt: start=%d num=%d descs=%p\n",
  560             uap->start, uap->num, (void *)uap->descs);
  561 #endif
  562 
  563         if ((pldt = td->td_proc->p_md.md_ldt) != NULL) {
  564                 lp = &((struct user_segment_descriptor *)(pldt->ldt_base))
  565                     [uap->start];
  566                 num = min(uap->num, max_ldt_segment);
  567         } else
  568                 return (EINVAL);
  569 
  570         if ((uap->start > (unsigned int)max_ldt_segment) ||
  571             ((unsigned int)num > (unsigned int)max_ldt_segment) ||
  572             ((unsigned int)(uap->start + num) > (unsigned int)max_ldt_segment))
  573                 return(EINVAL);
  574 
  575         error = copyout(lp, uap->descs, num *
  576             sizeof(struct user_segment_descriptor));
  577         if (!error)
  578                 td->td_retval[0] = num;
  579 
  580         return(error);
  581 }
  582 
  583 int
  584 amd64_set_ldt(td, uap, descs)
  585         struct thread *td;
  586         struct i386_ldt_args *uap;
  587         struct user_segment_descriptor *descs;
  588 {
  589         int error = 0, i;
  590         int largest_ld;
  591         struct mdproc *mdp = &td->td_proc->p_md;
  592         struct proc_ldt *pldt;
  593         struct user_segment_descriptor *dp;
  594         struct proc *p;
  595 
  596 #ifdef  DEBUG
  597         printf("amd64_set_ldt: start=%d num=%d descs=%p\n",
  598             uap->start, uap->num, (void *)uap->descs);
  599 #endif
  600 
  601         set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
  602         p = td->td_proc;
  603         if (descs == NULL) {
  604                 /* Free descriptors */
  605                 if (uap->start == 0 && uap->num == 0)
  606                         uap->num = max_ldt_segment;
  607                 if (uap->num == 0)
  608                         return (EINVAL);
  609                 if ((pldt = mdp->md_ldt) == NULL ||
  610                     uap->start >= max_ldt_segment)
  611                         return (0);
  612                 largest_ld = uap->start + uap->num;
  613                 if (largest_ld > max_ldt_segment)
  614                         largest_ld = max_ldt_segment;
  615                 i = largest_ld - uap->start;
  616                 mtx_lock(&dt_lock);
  617                 bzero(&((struct user_segment_descriptor *)(pldt->ldt_base))
  618                     [uap->start], sizeof(struct user_segment_descriptor) * i);
  619                 mtx_unlock(&dt_lock);
  620                 return (0);
  621         }
  622 
  623         if (!(uap->start == LDT_AUTO_ALLOC && uap->num == 1)) {
  624                 /* verify range of descriptors to modify */
  625                 largest_ld = uap->start + uap->num;
  626                 if (uap->start >= max_ldt_segment ||
  627                     largest_ld > max_ldt_segment)
  628                         return (EINVAL);
  629         }
  630 
  631         /* Check descriptors for access violations */
  632         for (i = 0; i < uap->num; i++) {
  633                 dp = &descs[i];
  634 
  635                 switch (dp->sd_type) {
  636                 case SDT_SYSNULL:       /* system null */
  637                         dp->sd_p = 0;
  638                         break;
  639                 case SDT_SYS286TSS:
  640                 case SDT_SYSLDT:
  641                 case SDT_SYS286BSY:
  642                 case SDT_SYS286CGT:
  643                 case SDT_SYSTASKGT:
  644                 case SDT_SYS286IGT:
  645                 case SDT_SYS286TGT:
  646                 case SDT_SYSNULL2:
  647                 case SDT_SYSTSS:
  648                 case SDT_SYSNULL3:
  649                 case SDT_SYSBSY:
  650                 case SDT_SYSCGT:
  651                 case SDT_SYSNULL4:
  652                 case SDT_SYSIGT:
  653                 case SDT_SYSTGT:
  654                         /* I can't think of any reason to allow a user proc
  655                          * to create a segment of these types.  They are
  656                          * for OS use only.
  657                          */
  658                         return (EACCES);
  659                         /*NOTREACHED*/
  660 
  661                 /* memory segment types */
  662                 case SDT_MEMEC:   /* memory execute only conforming */
  663                 case SDT_MEMEAC:  /* memory execute only accessed conforming */
  664                 case SDT_MEMERC:  /* memory execute read conforming */
  665                 case SDT_MEMERAC: /* memory execute read accessed conforming */
  666                          /* Must be "present" if executable and conforming. */
  667                         if (dp->sd_p == 0)
  668                                 return (EACCES);
  669                         break;
  670                 case SDT_MEMRO:   /* memory read only */
  671                 case SDT_MEMROA:  /* memory read only accessed */
  672                 case SDT_MEMRW:   /* memory read write */
  673                 case SDT_MEMRWA:  /* memory read write accessed */
  674                 case SDT_MEMROD:  /* memory read only expand dwn limit */
  675                 case SDT_MEMRODA: /* memory read only expand dwn lim accessed */
  676                 case SDT_MEMRWD:  /* memory read write expand dwn limit */
  677                 case SDT_MEMRWDA: /* memory read write expand dwn lim acessed */
  678                 case SDT_MEME:    /* memory execute only */
  679                 case SDT_MEMEA:   /* memory execute only accessed */
  680                 case SDT_MEMER:   /* memory execute read */
  681                 case SDT_MEMERA:  /* memory execute read accessed */
  682                         break;
  683                 default:
  684                         return(EINVAL);
  685                         /*NOTREACHED*/
  686                 }
  687 
  688                 /* Only user (ring-3) descriptors may be present. */
  689                 if ((dp->sd_p != 0) && (dp->sd_dpl != SEL_UPL))
  690                         return (EACCES);
  691         }
  692 
  693         if (uap->start == LDT_AUTO_ALLOC && uap->num == 1) {
  694                 /* Allocate a free slot */
  695                 mtx_lock(&dt_lock);
  696                 pldt = user_ldt_alloc(p, 0);
  697                 if (pldt == NULL) {
  698                         mtx_unlock(&dt_lock);
  699                         return (ENOMEM);
  700                 }
  701 
  702                 /*
  703                  * start scanning a bit up to leave room for NVidia and
  704                  * Wine, which still user the "Blat" method of allocation.
  705                  */
  706                 i = 16;
  707                 dp = &((struct user_segment_descriptor *)(pldt->ldt_base))[i];
  708                 for (; i < max_ldt_segment; ++i, ++dp) {
  709                         if (dp->sd_type == SDT_SYSNULL)
  710                                 break;
  711                 }
  712                 if (i >= max_ldt_segment) {
  713                         mtx_unlock(&dt_lock);
  714                         return (ENOSPC);
  715                 }
  716                 uap->start = i;
  717                 error = amd64_set_ldt_data(td, i, 1, descs);
  718                 mtx_unlock(&dt_lock);
  719         } else {
  720                 largest_ld = uap->start + uap->num;
  721                 if (largest_ld > max_ldt_segment)
  722                         return (EINVAL);
  723                 mtx_lock(&dt_lock);
  724                 if (user_ldt_alloc(p, 0) != NULL) {
  725                         error = amd64_set_ldt_data(td, uap->start, uap->num,
  726                             descs);
  727                 }
  728                 mtx_unlock(&dt_lock);
  729         }
  730         if (error == 0)
  731                 td->td_retval[0] = uap->start;
  732         return (error);
  733 }
  734 
  735 int
  736 amd64_set_ldt_data(struct thread *td, int start, int num,
  737     struct user_segment_descriptor *descs)
  738 {
  739         struct mdproc *mdp = &td->td_proc->p_md;
  740         struct proc_ldt *pldt = mdp->md_ldt;
  741 
  742         mtx_assert(&dt_lock, MA_OWNED);
  743 
  744         /* Fill in range */
  745         bcopy(descs,
  746             &((struct user_segment_descriptor *)(pldt->ldt_base))[start],
  747             num * sizeof(struct user_segment_descriptor));
  748         return (0);
  749 }

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