The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/sys_machdep.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1990 The Regents of the University of California.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the University nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      from: @(#)sys_machdep.c 5.5 (Berkeley) 1/19/91
   32  */
   33 
   34 #include <sys/cdefs.h>
   35 __FBSDID("$FreeBSD: releng/12.0/sys/i386/i386/sys_machdep.c 332489 2018-04-13 20:30:49Z kib $");
   36 
   37 #include "opt_capsicum.h"
   38 #include "opt_kstack_pages.h"
   39 
   40 #include <sys/param.h>
   41 #include <sys/capsicum.h>
   42 #include <sys/systm.h>
   43 #include <sys/lock.h>
   44 #include <sys/malloc.h>
   45 #include <sys/mutex.h>
   46 #include <sys/priv.h>
   47 #include <sys/proc.h>
   48 #include <sys/smp.h>
   49 #include <sys/sysproto.h>
   50 
   51 #include <vm/vm.h>
   52 #include <vm/pmap.h>
   53 #include <vm/vm_map.h>
   54 #include <vm/vm_extern.h>
   55 
   56 #include <machine/atomic.h>
   57 #include <machine/cpu.h>
   58 #include <machine/pcb.h>
   59 #include <machine/pcb_ext.h>
   60 #include <machine/proc.h>
   61 #include <machine/sysarch.h>
   62 
   63 #include <security/audit/audit.h>
   64 
   65 #include <vm/vm_kern.h>         /* for kernel_map */
   66 
   67 #define MAX_LD 8192
   68 #define LD_PER_PAGE 512
   69 #define NEW_MAX_LD(num)  rounddown2(num + LD_PER_PAGE, LD_PER_PAGE)
   70 #define SIZE_FROM_LARGEST_LD(num) (NEW_MAX_LD(num) << 3)
   71 #define NULL_LDT_BASE   ((caddr_t)NULL)
   72 
   73 #ifdef SMP
   74 static void set_user_ldt_rv(void *arg);
   75 #endif
   76 static int i386_set_ldt_data(struct thread *, int start, int num,
   77     union descriptor *descs);
   78 static int i386_ldt_grow(struct thread *td, int len);
   79 
   80 void
   81 fill_based_sd(struct segment_descriptor *sdp, uint32_t base)
   82 {
   83 
   84         sdp->sd_lobase = base & 0xffffff;
   85         sdp->sd_hibase = (base >> 24) & 0xff;
   86         sdp->sd_lolimit = 0xffff;       /* 4GB limit, wraps around */
   87         sdp->sd_hilimit = 0xf;
   88         sdp->sd_type = SDT_MEMRWA;
   89         sdp->sd_dpl = SEL_UPL;
   90         sdp->sd_p = 1;
   91         sdp->sd_xx = 0;
   92         sdp->sd_def32 = 1;
   93         sdp->sd_gran = 1;
   94 }
   95 
   96 /*
   97  * Construct special descriptors for "base" selectors.  Store them in
   98  * the PCB for later use by cpu_switch().  Store them in the GDT for
   99  * more immediate use.  The GDT entries are part of the current
  100  * context.  Callers must load related segment registers to complete
  101  * setting up the current context.
  102  */
  103 void
  104 set_fsbase(struct thread *td, uint32_t base)
  105 {
  106         struct segment_descriptor sd;
  107 
  108         fill_based_sd(&sd, base);
  109         critical_enter();
  110         td->td_pcb->pcb_fsd = sd;
  111         PCPU_GET(fsgs_gdt)[0] = sd;
  112         critical_exit();
  113 }
  114 
  115 void
  116 set_gsbase(struct thread *td, uint32_t base)
  117 {
  118         struct segment_descriptor sd;
  119 
  120         fill_based_sd(&sd, base);
  121         critical_enter();
  122         td->td_pcb->pcb_gsd = sd;
  123         PCPU_GET(fsgs_gdt)[1] = sd;
  124         critical_exit();
  125 }
  126 
  127 #ifndef _SYS_SYSPROTO_H_
  128 struct sysarch_args {
  129         int op;
  130         char *parms;
  131 };
  132 #endif
  133 
  134 int
  135 sysarch(struct thread *td, struct sysarch_args *uap)
  136 {
  137         int error;
  138         union descriptor *lp;
  139         union {
  140                 struct i386_ldt_args largs;
  141                 struct i386_ioperm_args iargs;
  142                 struct i386_get_xfpustate xfpu;
  143         } kargs;
  144         uint32_t base;
  145         struct segment_descriptor *sdp;
  146 
  147         AUDIT_ARG_CMD(uap->op);
  148 
  149 #ifdef CAPABILITY_MODE
  150         /*
  151          * When adding new operations, add a new case statement here to
  152          * explicitly indicate whether or not the operation is safe to
  153          * perform in capability mode.
  154          */
  155         if (IN_CAPABILITY_MODE(td)) {
  156                 switch (uap->op) {
  157                 case I386_GET_LDT:
  158                 case I386_SET_LDT:
  159                 case I386_GET_IOPERM:
  160                 case I386_GET_FSBASE:
  161                 case I386_SET_FSBASE:
  162                 case I386_GET_GSBASE:
  163                 case I386_SET_GSBASE:
  164                 case I386_GET_XFPUSTATE:
  165                         break;
  166 
  167                 case I386_SET_IOPERM:
  168                 default:
  169 #ifdef KTRACE
  170                         if (KTRPOINT(td, KTR_CAPFAIL))
  171                                 ktrcapfail(CAPFAIL_SYSCALL, NULL, NULL);
  172 #endif
  173                         return (ECAPMODE);
  174                 }
  175         }
  176 #endif
  177 
  178         switch (uap->op) {
  179         case I386_GET_IOPERM:
  180         case I386_SET_IOPERM:
  181                 if ((error = copyin(uap->parms, &kargs.iargs,
  182                     sizeof(struct i386_ioperm_args))) != 0)
  183                         return (error);
  184                 break;
  185         case I386_GET_LDT:
  186         case I386_SET_LDT:
  187                 if ((error = copyin(uap->parms, &kargs.largs,
  188                     sizeof(struct i386_ldt_args))) != 0)
  189                         return (error);
  190                 break;
  191         case I386_GET_XFPUSTATE:
  192                 if ((error = copyin(uap->parms, &kargs.xfpu,
  193                     sizeof(struct i386_get_xfpustate))) != 0)
  194                         return (error);
  195                 break;
  196         default:
  197                 break;
  198         }
  199 
  200         switch (uap->op) {
  201         case I386_GET_LDT:
  202                 error = i386_get_ldt(td, &kargs.largs);
  203                 break;
  204         case I386_SET_LDT:
  205                 if (kargs.largs.descs != NULL) {
  206                         if (kargs.largs.num > MAX_LD)
  207                                 return (EINVAL);
  208                         lp = malloc(kargs.largs.num * sizeof(union descriptor),
  209                             M_TEMP, M_WAITOK);
  210                         error = copyin(kargs.largs.descs, lp,
  211                             kargs.largs.num * sizeof(union descriptor));
  212                         if (error == 0)
  213                                 error = i386_set_ldt(td, &kargs.largs, lp);
  214                         free(lp, M_TEMP);
  215                 } else {
  216                         error = i386_set_ldt(td, &kargs.largs, NULL);
  217                 }
  218                 break;
  219         case I386_GET_IOPERM:
  220                 error = i386_get_ioperm(td, &kargs.iargs);
  221                 if (error == 0)
  222                         error = copyout(&kargs.iargs, uap->parms,
  223                             sizeof(struct i386_ioperm_args));
  224                 break;
  225         case I386_SET_IOPERM:
  226                 error = i386_set_ioperm(td, &kargs.iargs);
  227                 break;
  228         case I386_VM86:
  229                 error = vm86_sysarch(td, uap->parms);
  230                 break;
  231         case I386_GET_FSBASE:
  232                 sdp = &td->td_pcb->pcb_fsd;
  233                 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
  234                 error = copyout(&base, uap->parms, sizeof(base));
  235                 break;
  236         case I386_SET_FSBASE:
  237                 error = copyin(uap->parms, &base, sizeof(base));
  238                 if (error == 0) {
  239                         /*
  240                          * Construct the special descriptor for fsbase
  241                          * and arrange for doreti to load its selector
  242                          * soon enough.
  243                          */
  244                         set_fsbase(td, base);
  245                         td->td_frame->tf_fs = GSEL(GUFS_SEL, SEL_UPL);
  246                 }
  247                 break;
  248         case I386_GET_GSBASE:
  249                 sdp = &td->td_pcb->pcb_gsd;
  250                 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
  251                 error = copyout(&base, uap->parms, sizeof(base));
  252                 break;
  253         case I386_SET_GSBASE:
  254                 error = copyin(uap->parms, &base, sizeof(base));
  255                 if (error == 0) {
  256                         /*
  257                          * Construct the special descriptor for gsbase.
  258                          * The selector is loaded immediately, since we
  259                          * normally only reload %gs on context switches.
  260                          */
  261                         set_gsbase(td, base);
  262                         load_gs(GSEL(GUGS_SEL, SEL_UPL));
  263                 }
  264                 break;
  265         case I386_GET_XFPUSTATE:
  266                 if (kargs.xfpu.len > cpu_max_ext_state_size -
  267                     sizeof(union savefpu))
  268                         return (EINVAL);
  269                 npxgetregs(td);
  270                 error = copyout((char *)(get_pcb_user_save_td(td) + 1),
  271                     kargs.xfpu.addr, kargs.xfpu.len);
  272                 break;
  273         default:
  274                 error = EINVAL;
  275                 break;
  276         }
  277         return (error);
  278 }
  279 
  280 int
  281 i386_extend_pcb(struct thread *td)
  282 {
  283         int i, offset;
  284         u_long *addr;
  285         struct pcb_ext *ext;
  286         struct soft_segment_descriptor ssd = {
  287                 0,                      /* segment base address (overwritten) */
  288                 ctob(IOPAGES + 1) - 1,  /* length */
  289                 SDT_SYS386TSS,          /* segment type */
  290                 0,                      /* priority level */
  291                 1,                      /* descriptor present */
  292                 0, 0,
  293                 0,                      /* default 32 size */
  294                 0                       /* granularity */
  295         };
  296 
  297         ext = pmap_trm_alloc(ctob(IOPAGES + 1), M_WAITOK | M_ZERO);
  298         /* -16 is so we can convert a trapframe into vm86trapframe inplace */
  299         ext->ext_tss.tss_ss0 = GSEL(GDATA_SEL, SEL_KPL);
  300         /*
  301          * The last byte of the i/o map must be followed by an 0xff byte.
  302          * We arbitrarily allocate 16 bytes here, to keep the starting
  303          * address on a doubleword boundary.
  304          */
  305         offset = PAGE_SIZE - 16;
  306         ext->ext_tss.tss_ioopt = 
  307             (offset - ((unsigned)&ext->ext_tss - (unsigned)ext)) << 16;
  308         ext->ext_iomap = (caddr_t)ext + offset;
  309         ext->ext_vm86.vm86_intmap = (caddr_t)ext + offset - 32;
  310 
  311         addr = (u_long *)ext->ext_vm86.vm86_intmap;
  312         for (i = 0; i < (ctob(IOPAGES) + 32 + 16) / sizeof(u_long); i++)
  313                 *addr++ = ~0;
  314 
  315         ssd.ssd_base = (unsigned)&ext->ext_tss;
  316         ssd.ssd_limit -= ((unsigned)&ext->ext_tss - (unsigned)ext);
  317         ssdtosd(&ssd, &ext->ext_tssd);
  318 
  319         KASSERT(td == curthread, ("giving TSS to !curthread"));
  320         KASSERT(td->td_pcb->pcb_ext == 0, ("already have a TSS!"));
  321 
  322         /* Switch to the new TSS. */
  323         critical_enter();
  324         ext->ext_tss.tss_esp0 = PCPU_GET(trampstk);
  325         td->td_pcb->pcb_ext = ext;
  326         PCPU_SET(private_tss, 1);
  327         *PCPU_GET(tss_gdt) = ext->ext_tssd;
  328         ltr(GSEL(GPROC0_SEL, SEL_KPL));
  329         critical_exit();
  330 
  331         return 0;
  332 }
  333 
  334 int
  335 i386_set_ioperm(td, uap)
  336         struct thread *td;
  337         struct i386_ioperm_args *uap;
  338 {
  339         char *iomap;
  340         u_int i;
  341         int error;
  342 
  343         if ((error = priv_check(td, PRIV_IO)) != 0)
  344                 return (error);
  345         if ((error = securelevel_gt(td->td_ucred, 0)) != 0)
  346                 return (error);
  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 
  354         if (td->td_pcb->pcb_ext == 0)
  355                 if ((error = i386_extend_pcb(td)) != 0)
  356                         return (error);
  357         iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
  358 
  359         if (uap->start > uap->start + uap->length ||
  360             uap->start + uap->length > IOPAGES * PAGE_SIZE * NBBY)
  361                 return (EINVAL);
  362 
  363         for (i = uap->start; i < uap->start + uap->length; i++) {
  364                 if (uap->enable)
  365                         iomap[i >> 3] &= ~(1 << (i & 7));
  366                 else
  367                         iomap[i >> 3] |= (1 << (i & 7));
  368         }
  369         return (error);
  370 }
  371 
  372 int
  373 i386_get_ioperm(td, uap)
  374         struct thread *td;
  375         struct i386_ioperm_args *uap;
  376 {
  377         int i, state;
  378         char *iomap;
  379 
  380         if (uap->start >= IOPAGES * PAGE_SIZE * NBBY)
  381                 return (EINVAL);
  382 
  383         if (td->td_pcb->pcb_ext == 0) {
  384                 uap->length = 0;
  385                 goto done;
  386         }
  387 
  388         iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
  389 
  390         i = uap->start;
  391         state = (iomap[i >> 3] >> (i & 7)) & 1;
  392         uap->enable = !state;
  393         uap->length = 1;
  394 
  395         for (i = uap->start + 1; i < IOPAGES * PAGE_SIZE * NBBY; i++) {
  396                 if (state != ((iomap[i >> 3] >> (i & 7)) & 1))
  397                         break;
  398                 uap->length++;
  399         }
  400 
  401 done:
  402         return (0);
  403 }
  404 
  405 /*
  406  * Update the GDT entry pointing to the LDT to point to the LDT of the
  407  * current process. Manage dt_lock holding/unholding autonomously.
  408  */   
  409 static void
  410 set_user_ldt_locked(struct mdproc *mdp)
  411 {
  412         struct proc_ldt *pldt;
  413         int gdt_idx;
  414 
  415         mtx_assert(&dt_lock, MA_OWNED);
  416 
  417         pldt = mdp->md_ldt;
  418         gdt_idx = GUSERLDT_SEL;
  419         gdt_idx += PCPU_GET(cpuid) * NGDT;      /* always 0 on UP */
  420         gdt[gdt_idx].sd = pldt->ldt_sd;
  421         lldt(GSEL(GUSERLDT_SEL, SEL_KPL));
  422         PCPU_SET(currentldt, GSEL(GUSERLDT_SEL, SEL_KPL));
  423 }
  424 
  425 void
  426 set_user_ldt(struct mdproc *mdp)
  427 {
  428 
  429         mtx_lock_spin(&dt_lock);
  430         set_user_ldt_locked(mdp);
  431         mtx_unlock_spin(&dt_lock);
  432 }
  433 
  434 #ifdef SMP
  435 static void
  436 set_user_ldt_rv(void *arg)
  437 {
  438         struct proc *p;
  439 
  440         p = curproc;
  441         if (arg == p->p_vmspace)
  442                 set_user_ldt(&p->p_md);
  443 }
  444 #endif
  445 
  446 /*
  447  * dt_lock must be held. Returns with dt_lock held.
  448  */
  449 struct proc_ldt *
  450 user_ldt_alloc(struct mdproc *mdp, int len)
  451 {
  452         struct proc_ldt *pldt, *new_ldt;
  453 
  454         mtx_assert(&dt_lock, MA_OWNED);
  455         mtx_unlock_spin(&dt_lock);
  456         new_ldt = malloc(sizeof(struct proc_ldt), M_SUBPROC, M_WAITOK);
  457 
  458         new_ldt->ldt_len = len = NEW_MAX_LD(len);
  459         new_ldt->ldt_base = pmap_trm_alloc(len * sizeof(union descriptor),
  460             M_WAITOK | M_ZERO);
  461         new_ldt->ldt_refcnt = 1;
  462         new_ldt->ldt_active = 0;
  463 
  464         mtx_lock_spin(&dt_lock);
  465         gdt_segs[GUSERLDT_SEL].ssd_base = (unsigned)new_ldt->ldt_base;
  466         gdt_segs[GUSERLDT_SEL].ssd_limit = len * sizeof(union descriptor) - 1;
  467         ssdtosd(&gdt_segs[GUSERLDT_SEL], &new_ldt->ldt_sd);
  468 
  469         if ((pldt = mdp->md_ldt) != NULL) {
  470                 if (len > pldt->ldt_len)
  471                         len = pldt->ldt_len;
  472                 bcopy(pldt->ldt_base, new_ldt->ldt_base,
  473                     len * sizeof(union descriptor));
  474         } else
  475                 bcopy(ldt, new_ldt->ldt_base, sizeof(union descriptor) * NLDT);
  476         
  477         return (new_ldt);
  478 }
  479 
  480 /*
  481  * Must be called with dt_lock held.  Returns with dt_lock unheld.
  482  */
  483 void
  484 user_ldt_free(struct thread *td)
  485 {
  486         struct mdproc *mdp;
  487         struct proc_ldt *pldt;
  488 
  489         mtx_assert(&dt_lock, MA_OWNED);
  490         mdp = &td->td_proc->p_md;
  491         if ((pldt = mdp->md_ldt) == NULL) {
  492                 mtx_unlock_spin(&dt_lock);
  493                 return;
  494         }
  495 
  496         if (td == curthread) {
  497                 lldt(_default_ldt);
  498                 PCPU_SET(currentldt, _default_ldt);
  499         }
  500 
  501         mdp->md_ldt = NULL;
  502         user_ldt_deref(pldt);
  503 }
  504 
  505 void
  506 user_ldt_deref(struct proc_ldt *pldt)
  507 {
  508 
  509         mtx_assert(&dt_lock, MA_OWNED);
  510         if (--pldt->ldt_refcnt == 0) {
  511                 mtx_unlock_spin(&dt_lock);
  512                 pmap_trm_free(pldt->ldt_base, pldt->ldt_len *
  513                     sizeof(union descriptor));
  514                 free(pldt, M_SUBPROC);
  515         } else
  516                 mtx_unlock_spin(&dt_lock);
  517 }
  518 
  519 /*
  520  * Note for the authors of compat layers (linux, etc): copyout() in
  521  * the function below is not a problem since it presents data in
  522  * arch-specific format (i.e. i386-specific in this case), not in
  523  * the OS-specific one.
  524  */
  525 int
  526 i386_get_ldt(struct thread *td, struct i386_ldt_args *uap)
  527 {
  528         struct proc_ldt *pldt;
  529         char *data;
  530         u_int nldt, num;
  531         int error;
  532 
  533 #ifdef DEBUG
  534         printf("i386_get_ldt: start=%u num=%u descs=%p\n",
  535             uap->start, uap->num, (void *)uap->descs);
  536 #endif
  537 
  538         num = min(uap->num, MAX_LD);
  539         data = malloc(num * sizeof(union descriptor), M_TEMP, M_WAITOK);
  540         mtx_lock_spin(&dt_lock);
  541         pldt = td->td_proc->p_md.md_ldt;
  542         nldt = pldt != NULL ? pldt->ldt_len : nitems(ldt);
  543         if (uap->start >= nldt) {
  544                 num = 0;
  545         } else {
  546                 num = min(num, nldt - uap->start);
  547                 bcopy(pldt != NULL ?
  548                     &((union descriptor *)(pldt->ldt_base))[uap->start] :
  549                     &ldt[uap->start], data, num * sizeof(union descriptor));
  550         }
  551         mtx_unlock_spin(&dt_lock);
  552         error = copyout(data, uap->descs, num * sizeof(union descriptor));
  553         if (error == 0)
  554                 td->td_retval[0] = num;
  555         free(data, M_TEMP);
  556         return (error);
  557 }
  558 
  559 int
  560 i386_set_ldt(struct thread *td, struct i386_ldt_args *uap,
  561     union descriptor *descs)
  562 {
  563         struct mdproc *mdp;
  564         struct proc_ldt *pldt;
  565         union descriptor *dp;
  566         u_int largest_ld, i;
  567         int error;
  568 
  569 #ifdef DEBUG
  570         printf("i386_set_ldt: start=%u num=%u descs=%p\n",
  571             uap->start, uap->num, (void *)uap->descs);
  572 #endif
  573         error = 0;
  574         mdp = &td->td_proc->p_md;
  575 
  576         if (descs == NULL) {
  577                 /* Free descriptors */
  578                 if (uap->start == 0 && uap->num == 0) {
  579                         /*
  580                          * Treat this as a special case, so userland needn't
  581                          * know magic number NLDT.
  582                          */
  583                         uap->start = NLDT;
  584                         uap->num = MAX_LD - NLDT;
  585                 }
  586                 mtx_lock_spin(&dt_lock);
  587                 if ((pldt = mdp->md_ldt) == NULL ||
  588                     uap->start >= pldt->ldt_len) {
  589                         mtx_unlock_spin(&dt_lock);
  590                         return (0);
  591                 }
  592                 largest_ld = uap->start + uap->num;
  593                 if (largest_ld > pldt->ldt_len)
  594                         largest_ld = pldt->ldt_len;
  595                 for (i = uap->start; i < largest_ld; i++)
  596                         atomic_store_rel_64(&((uint64_t *)(pldt->ldt_base))[i],
  597                             0);
  598                 mtx_unlock_spin(&dt_lock);
  599                 return (0);
  600         }
  601 
  602         if (uap->start != LDT_AUTO_ALLOC || uap->num != 1) {
  603                 /* verify range of descriptors to modify */
  604                 largest_ld = uap->start + uap->num;
  605                 if (uap->start >= MAX_LD || largest_ld > MAX_LD)
  606                         return (EINVAL);
  607         }
  608 
  609         /* Check descriptors for access violations */
  610         for (i = 0; i < uap->num; i++) {
  611                 dp = &descs[i];
  612 
  613                 switch (dp->sd.sd_type) {
  614                 case SDT_SYSNULL:       /* system null */ 
  615                         dp->sd.sd_p = 0;
  616                         break;
  617                 case SDT_SYS286TSS: /* system 286 TSS available */
  618                 case SDT_SYSLDT:    /* system local descriptor table */
  619                 case SDT_SYS286BSY: /* system 286 TSS busy */
  620                 case SDT_SYSTASKGT: /* system task gate */
  621                 case SDT_SYS286IGT: /* system 286 interrupt gate */
  622                 case SDT_SYS286TGT: /* system 286 trap gate */
  623                 case SDT_SYSNULL2:  /* undefined by Intel */ 
  624                 case SDT_SYS386TSS: /* system 386 TSS available */
  625                 case SDT_SYSNULL3:  /* undefined by Intel */
  626                 case SDT_SYS386BSY: /* system 386 TSS busy */
  627                 case SDT_SYSNULL4:  /* undefined by Intel */ 
  628                 case SDT_SYS386IGT: /* system 386 interrupt gate */
  629                 case SDT_SYS386TGT: /* system 386 trap gate */
  630                 case SDT_SYS286CGT: /* system 286 call gate */ 
  631                 case SDT_SYS386CGT: /* system 386 call gate */
  632                         return (EACCES);
  633 
  634                 /* memory segment types */
  635                 case SDT_MEMEC:   /* memory execute only conforming */
  636                 case SDT_MEMEAC:  /* memory execute only accessed conforming */
  637                 case SDT_MEMERC:  /* memory execute read conforming */
  638                 case SDT_MEMERAC: /* memory execute read accessed conforming */
  639                          /* Must be "present" if executable and conforming. */
  640                         if (dp->sd.sd_p == 0)
  641                                 return (EACCES);
  642                         break;
  643                 case SDT_MEMRO:   /* memory read only */
  644                 case SDT_MEMROA:  /* memory read only accessed */
  645                 case SDT_MEMRW:   /* memory read write */
  646                 case SDT_MEMRWA:  /* memory read write accessed */
  647                 case SDT_MEMROD:  /* memory read only expand dwn limit */
  648                 case SDT_MEMRODA: /* memory read only expand dwn lim accessed */
  649                 case SDT_MEMRWD:  /* memory read write expand dwn limit */  
  650                 case SDT_MEMRWDA: /* memory read write expand dwn lim acessed */
  651                 case SDT_MEME:    /* memory execute only */ 
  652                 case SDT_MEMEA:   /* memory execute only accessed */
  653                 case SDT_MEMER:   /* memory execute read */
  654                 case SDT_MEMERA:  /* memory execute read accessed */
  655                         break;
  656                 default:
  657                         return (EINVAL);
  658                 }
  659 
  660                 /* Only user (ring-3) descriptors may be present. */
  661                 if (dp->sd.sd_p != 0 && dp->sd.sd_dpl != SEL_UPL)
  662                         return (EACCES);
  663         }
  664 
  665         if (uap->start == LDT_AUTO_ALLOC && uap->num == 1) {
  666                 /* Allocate a free slot */
  667                 mtx_lock_spin(&dt_lock);
  668                 if ((pldt = mdp->md_ldt) == NULL) {
  669                         if ((error = i386_ldt_grow(td, NLDT + 1))) {
  670                                 mtx_unlock_spin(&dt_lock);
  671                                 return (error);
  672                         }
  673                         pldt = mdp->md_ldt;
  674                 }
  675 again:
  676                 /*
  677                  * start scanning a bit up to leave room for NVidia and
  678                  * Wine, which still user the "Blat" method of allocation.
  679                  */
  680                 dp = &((union descriptor *)(pldt->ldt_base))[NLDT];
  681                 for (i = NLDT; i < pldt->ldt_len; ++i) {
  682                         if (dp->sd.sd_type == SDT_SYSNULL)
  683                                 break;
  684                         dp++;
  685                 }
  686                 if (i >= pldt->ldt_len) {
  687                         if ((error = i386_ldt_grow(td, pldt->ldt_len+1))) {
  688                                 mtx_unlock_spin(&dt_lock);
  689                                 return (error);
  690                         }
  691                         goto again;
  692                 }
  693                 uap->start = i;
  694                 error = i386_set_ldt_data(td, i, 1, descs);
  695                 mtx_unlock_spin(&dt_lock);
  696         } else {
  697                 largest_ld = uap->start + uap->num;
  698                 mtx_lock_spin(&dt_lock);
  699                 if (!(error = i386_ldt_grow(td, largest_ld))) {
  700                         error = i386_set_ldt_data(td, uap->start, uap->num,
  701                             descs);
  702                 }
  703                 mtx_unlock_spin(&dt_lock);
  704         }
  705         if (error == 0)
  706                 td->td_retval[0] = uap->start;
  707         return (error);
  708 }
  709 
  710 static int
  711 i386_set_ldt_data(struct thread *td, int start, int num,
  712     union descriptor *descs)
  713 {
  714         struct mdproc *mdp;
  715         struct proc_ldt *pldt;
  716         uint64_t *dst, *src;
  717         int i;
  718 
  719         mtx_assert(&dt_lock, MA_OWNED);
  720 
  721         mdp = &td->td_proc->p_md;
  722         pldt = mdp->md_ldt;
  723         dst = (uint64_t *)(pldt->ldt_base);
  724         src = (uint64_t *)descs;
  725 
  726         /*
  727          * Atomic(9) is used only to get 64bit atomic store with
  728          * cmpxchg8b when available.  There is no op without release
  729          * semantic.
  730          */
  731         for (i = 0; i < num; i++)
  732                 atomic_store_rel_64(&dst[start + i], src[i]);
  733         return (0);
  734 }
  735 
  736 static int
  737 i386_ldt_grow(struct thread *td, int len) 
  738 {
  739         struct mdproc *mdp;
  740         struct proc_ldt *new_ldt, *pldt;
  741         caddr_t old_ldt_base;
  742         int old_ldt_len;
  743 
  744         mtx_assert(&dt_lock, MA_OWNED);
  745 
  746         if (len > MAX_LD)
  747                 return (ENOMEM);
  748         if (len < NLDT + 1)
  749                 len = NLDT + 1;
  750 
  751         mdp = &td->td_proc->p_md;
  752         old_ldt_base = NULL_LDT_BASE;
  753         old_ldt_len = 0;
  754 
  755         /* Allocate a user ldt. */
  756         if ((pldt = mdp->md_ldt) == NULL || len > pldt->ldt_len) {
  757                 new_ldt = user_ldt_alloc(mdp, len);
  758                 if (new_ldt == NULL)
  759                         return (ENOMEM);
  760                 pldt = mdp->md_ldt;
  761 
  762                 if (pldt != NULL) {
  763                         if (new_ldt->ldt_len <= pldt->ldt_len) {
  764                                 /*
  765                                  * We just lost the race for allocation, so
  766                                  * free the new object and return.
  767                                  */
  768                                 mtx_unlock_spin(&dt_lock);
  769                                 pmap_trm_free(new_ldt->ldt_base,
  770                                    new_ldt->ldt_len * sizeof(union descriptor));
  771                                 free(new_ldt, M_SUBPROC);
  772                                 mtx_lock_spin(&dt_lock);
  773                                 return (0);
  774                         }
  775 
  776                         /*
  777                          * We have to substitute the current LDT entry for
  778                          * curproc with the new one since its size grew.
  779                          */
  780                         old_ldt_base = pldt->ldt_base;
  781                         old_ldt_len = pldt->ldt_len;
  782                         pldt->ldt_sd = new_ldt->ldt_sd;
  783                         pldt->ldt_base = new_ldt->ldt_base;
  784                         pldt->ldt_len = new_ldt->ldt_len;
  785                 } else
  786                         mdp->md_ldt = pldt = new_ldt;
  787 #ifdef SMP
  788                 /*
  789                  * Signal other cpus to reload ldt.  We need to unlock dt_lock
  790                  * here because other CPU will contest on it since their
  791                  * curthreads won't hold the lock and will block when trying
  792                  * to acquire it.
  793                  */
  794                 mtx_unlock_spin(&dt_lock);
  795                 smp_rendezvous(NULL, set_user_ldt_rv, NULL,
  796                     td->td_proc->p_vmspace);
  797 #else
  798                 set_user_ldt_locked(&td->td_proc->p_md);
  799                 mtx_unlock_spin(&dt_lock);
  800 #endif
  801                 if (old_ldt_base != NULL_LDT_BASE) {
  802                         pmap_trm_free(old_ldt_base, old_ldt_len *
  803                             sizeof(union descriptor));
  804                         free(new_ldt, M_SUBPROC);
  805                 }
  806                 mtx_lock_spin(&dt_lock);
  807         }
  808         return (0);
  809 }

Cache object: b49e422c8d4730e5feeaf3bc100fe53f


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