The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: 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  * Copyright (c) 1990 The Regents of the University of California.
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    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  * 3. 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.
   16  *
   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
   27  * SUCH DAMAGE.
   28  *
   29  *      from: @(#)sys_machdep.c 5.5 (Berkeley) 1/19/91
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __FBSDID("$FreeBSD: releng/11.2/sys/i386/i386/sys_machdep.c 331722 2018-03-29 02:50:57Z eadler $");
   34 
   35 #include "opt_capsicum.h"
   36 #include "opt_kstack_pages.h"
   37 
   38 #include <sys/param.h>
   39 #include <sys/capsicum.h>
   40 #include <sys/systm.h>
   41 #include <sys/lock.h>
   42 #include <sys/malloc.h>
   43 #include <sys/mutex.h>
   44 #include <sys/priv.h>
   45 #include <sys/proc.h>
   46 #include <sys/smp.h>
   47 #include <sys/sysproto.h>
   48 
   49 #include <vm/vm.h>
   50 #include <vm/pmap.h>
   51 #include <vm/vm_map.h>
   52 #include <vm/vm_extern.h>
   53 
   54 #include <machine/atomic.h>
   55 #include <machine/cpu.h>
   56 #include <machine/pcb.h>
   57 #include <machine/pcb_ext.h>
   58 #include <machine/proc.h>
   59 #include <machine/sysarch.h>
   60 
   61 #include <security/audit/audit.h>
   62 
   63 #include <vm/vm_kern.h>         /* for kernel_map */
   64 
   65 #define MAX_LD 8192
   66 #define LD_PER_PAGE 512
   67 #define NEW_MAX_LD(num)  rounddown2(num + LD_PER_PAGE, LD_PER_PAGE)
   68 #define SIZE_FROM_LARGEST_LD(num) (NEW_MAX_LD(num) << 3)
   69 #define NULL_LDT_BASE   ((caddr_t)NULL)
   70 
   71 #ifdef SMP
   72 static void set_user_ldt_rv(void *arg);
   73 #endif
   74 static int i386_set_ldt_data(struct thread *, int start, int num,
   75     union descriptor *descs);
   76 static int i386_ldt_grow(struct thread *td, int len);
   77 
   78 void
   79 fill_based_sd(struct segment_descriptor *sdp, uint32_t base)
   80 {
   81 
   82         sdp->sd_lobase = base & 0xffffff;
   83         sdp->sd_hibase = (base >> 24) & 0xff;
   84         sdp->sd_lolimit = 0xffff;       /* 4GB limit, wraps around */
   85         sdp->sd_hilimit = 0xf;
   86         sdp->sd_type = SDT_MEMRWA;
   87         sdp->sd_dpl = SEL_UPL;
   88         sdp->sd_p = 1;
   89         sdp->sd_xx = 0;
   90         sdp->sd_def32 = 1;
   91         sdp->sd_gran = 1;
   92 }
   93 
   94 /*
   95  * Construct special descriptors for "base" selectors.  Store them in
   96  * the PCB for later use by cpu_switch().  Store them in the GDT for
   97  * more immediate use.  The GDT entries are part of the current
   98  * context.  Callers must load related segment registers to complete
   99  * setting up the current context.
  100  */
  101 void
  102 set_fsbase(struct thread *td, uint32_t base)
  103 {
  104         struct segment_descriptor sd;
  105 
  106         fill_based_sd(&sd, base);
  107         critical_enter();
  108         td->td_pcb->pcb_fsd = sd;
  109         PCPU_GET(fsgs_gdt)[0] = sd;
  110         critical_exit();
  111 }
  112 
  113 void
  114 set_gsbase(struct thread *td, uint32_t base)
  115 {
  116         struct segment_descriptor sd;
  117 
  118         fill_based_sd(&sd, base);
  119         critical_enter();
  120         td->td_pcb->pcb_gsd = sd;
  121         PCPU_GET(fsgs_gdt)[1] = sd;
  122         critical_exit();
  123 }
  124 
  125 #ifndef _SYS_SYSPROTO_H_
  126 struct sysarch_args {
  127         int op;
  128         char *parms;
  129 };
  130 #endif
  131 
  132 int
  133 sysarch(struct thread *td, struct sysarch_args *uap)
  134 {
  135         int error;
  136         union descriptor *lp;
  137         union {
  138                 struct i386_ldt_args largs;
  139                 struct i386_ioperm_args iargs;
  140                 struct i386_get_xfpustate xfpu;
  141         } kargs;
  142         uint32_t base;
  143         struct segment_descriptor *sdp;
  144 
  145         AUDIT_ARG_CMD(uap->op);
  146 
  147 #ifdef CAPABILITY_MODE
  148         /*
  149          * When adding new operations, add a new case statement here to
  150          * explicitly indicate whether or not the operation is safe to
  151          * perform in capability mode.
  152          */
  153         if (IN_CAPABILITY_MODE(td)) {
  154                 switch (uap->op) {
  155                 case I386_GET_LDT:
  156                 case I386_SET_LDT:
  157                 case I386_GET_IOPERM:
  158                 case I386_GET_FSBASE:
  159                 case I386_SET_FSBASE:
  160                 case I386_GET_GSBASE:
  161                 case I386_SET_GSBASE:
  162                 case I386_GET_XFPUSTATE:
  163                         break;
  164 
  165                 case I386_SET_IOPERM:
  166                 default:
  167 #ifdef KTRACE
  168                         if (KTRPOINT(td, KTR_CAPFAIL))
  169                                 ktrcapfail(CAPFAIL_SYSCALL, NULL, NULL);
  170 #endif
  171                         return (ECAPMODE);
  172                 }
  173         }
  174 #endif
  175 
  176         switch (uap->op) {
  177         case I386_GET_IOPERM:
  178         case I386_SET_IOPERM:
  179                 if ((error = copyin(uap->parms, &kargs.iargs,
  180                     sizeof(struct i386_ioperm_args))) != 0)
  181                         return (error);
  182                 break;
  183         case I386_GET_LDT:
  184         case I386_SET_LDT:
  185                 if ((error = copyin(uap->parms, &kargs.largs,
  186                     sizeof(struct i386_ldt_args))) != 0)
  187                         return (error);
  188                 break;
  189         case I386_GET_XFPUSTATE:
  190                 if ((error = copyin(uap->parms, &kargs.xfpu,
  191                     sizeof(struct i386_get_xfpustate))) != 0)
  192                         return (error);
  193                 break;
  194         default:
  195                 break;
  196         }
  197 
  198         switch (uap->op) {
  199         case I386_GET_LDT:
  200                 error = i386_get_ldt(td, &kargs.largs);
  201                 break;
  202         case I386_SET_LDT:
  203                 if (kargs.largs.descs != NULL) {
  204                         if (kargs.largs.num > MAX_LD)
  205                                 return (EINVAL);
  206                         lp = malloc(kargs.largs.num * sizeof(union descriptor),
  207                             M_TEMP, M_WAITOK);
  208                         error = copyin(kargs.largs.descs, lp,
  209                             kargs.largs.num * sizeof(union descriptor));
  210                         if (error == 0)
  211                                 error = i386_set_ldt(td, &kargs.largs, lp);
  212                         free(lp, M_TEMP);
  213                 } else {
  214                         error = i386_set_ldt(td, &kargs.largs, NULL);
  215                 }
  216                 break;
  217         case I386_GET_IOPERM:
  218                 error = i386_get_ioperm(td, &kargs.iargs);
  219                 if (error == 0)
  220                         error = copyout(&kargs.iargs, uap->parms,
  221                             sizeof(struct i386_ioperm_args));
  222                 break;
  223         case I386_SET_IOPERM:
  224                 error = i386_set_ioperm(td, &kargs.iargs);
  225                 break;
  226         case I386_VM86:
  227                 error = vm86_sysarch(td, uap->parms);
  228                 break;
  229         case I386_GET_FSBASE:
  230                 sdp = &td->td_pcb->pcb_fsd;
  231                 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
  232                 error = copyout(&base, uap->parms, sizeof(base));
  233                 break;
  234         case I386_SET_FSBASE:
  235                 error = copyin(uap->parms, &base, sizeof(base));
  236                 if (error == 0) {
  237                         /*
  238                          * Construct the special descriptor for fsbase
  239                          * and arrange for doreti to load its selector
  240                          * soon enough.
  241                          */
  242                         set_fsbase(td, base);
  243                         td->td_frame->tf_fs = GSEL(GUFS_SEL, SEL_UPL);
  244                 }
  245                 break;
  246         case I386_GET_GSBASE:
  247                 sdp = &td->td_pcb->pcb_gsd;
  248                 base = sdp->sd_hibase << 24 | sdp->sd_lobase;
  249                 error = copyout(&base, uap->parms, sizeof(base));
  250                 break;
  251         case I386_SET_GSBASE:
  252                 error = copyin(uap->parms, &base, sizeof(base));
  253                 if (error == 0) {
  254                         /*
  255                          * Construct the special descriptor for gsbase.
  256                          * The selector is loaded immediately, since we
  257                          * normally only reload %gs on context switches.
  258                          */
  259                         set_gsbase(td, base);
  260                         load_gs(GSEL(GUGS_SEL, SEL_UPL));
  261                 }
  262                 break;
  263         case I386_GET_XFPUSTATE:
  264                 if (kargs.xfpu.len > cpu_max_ext_state_size -
  265                     sizeof(union savefpu))
  266                         return (EINVAL);
  267                 npxgetregs(td);
  268                 error = copyout((char *)(get_pcb_user_save_td(td) + 1),
  269                     kargs.xfpu.addr, kargs.xfpu.len);
  270                 break;
  271         default:
  272                 error = EINVAL;
  273                 break;
  274         }
  275         return (error);
  276 }
  277 
  278 int
  279 i386_extend_pcb(struct thread *td)
  280 {
  281         int i, offset;
  282         u_long *addr;
  283         struct pcb_ext *ext;
  284         struct soft_segment_descriptor ssd = {
  285                 0,                      /* segment base address (overwritten) */
  286                 ctob(IOPAGES + 1) - 1,  /* length */
  287                 SDT_SYS386TSS,          /* segment type */
  288                 0,                      /* priority level */
  289                 1,                      /* descriptor present */
  290                 0, 0,
  291                 0,                      /* default 32 size */
  292                 0                       /* granularity */
  293         };
  294 
  295         ext = (struct pcb_ext *)kmem_malloc(kernel_arena, ctob(IOPAGES+1),
  296             M_WAITOK | M_ZERO);
  297         /* -16 is so we can convert a trapframe into vm86trapframe inplace */
  298         ext->ext_tss.tss_esp0 = (vm_offset_t)td->td_pcb - 16;
  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         td->td_pcb->pcb_ext = ext;
  325         PCPU_SET(private_tss, 1);
  326         *PCPU_GET(tss_gdt) = ext->ext_tssd;
  327         ltr(GSEL(GPROC0_SEL, SEL_KPL));
  328         critical_exit();
  329 
  330         return 0;
  331 }
  332 
  333 int
  334 i386_set_ioperm(td, uap)
  335         struct thread *td;
  336         struct i386_ioperm_args *uap;
  337 {
  338         char *iomap;
  339         u_int i;
  340         int error;
  341 
  342         if ((error = priv_check(td, PRIV_IO)) != 0)
  343                 return (error);
  344         if ((error = securelevel_gt(td->td_ucred, 0)) != 0)
  345                 return (error);
  346         /*
  347          * XXX 
  348          * While this is restricted to root, we should probably figure out
  349          * whether any other driver is using this i/o address, as so not to
  350          * cause confusion.  This probably requires a global 'usage registry'.
  351          */
  352 
  353         if (td->td_pcb->pcb_ext == 0)
  354                 if ((error = i386_extend_pcb(td)) != 0)
  355                         return (error);
  356         iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
  357 
  358         if (uap->start > uap->start + uap->length ||
  359             uap->start + uap->length > IOPAGES * PAGE_SIZE * NBBY)
  360                 return (EINVAL);
  361 
  362         for (i = uap->start; i < uap->start + uap->length; i++) {
  363                 if (uap->enable)
  364                         iomap[i >> 3] &= ~(1 << (i & 7));
  365                 else
  366                         iomap[i >> 3] |= (1 << (i & 7));
  367         }
  368         return (error);
  369 }
  370 
  371 int
  372 i386_get_ioperm(td, uap)
  373         struct thread *td;
  374         struct i386_ioperm_args *uap;
  375 {
  376         int i, state;
  377         char *iomap;
  378 
  379         if (uap->start >= IOPAGES * PAGE_SIZE * NBBY)
  380                 return (EINVAL);
  381 
  382         if (td->td_pcb->pcb_ext == 0) {
  383                 uap->length = 0;
  384                 goto done;
  385         }
  386 
  387         iomap = (char *)td->td_pcb->pcb_ext->ext_iomap;
  388 
  389         i = uap->start;
  390         state = (iomap[i >> 3] >> (i & 7)) & 1;
  391         uap->enable = !state;
  392         uap->length = 1;
  393 
  394         for (i = uap->start + 1; i < IOPAGES * PAGE_SIZE * NBBY; i++) {
  395                 if (state != ((iomap[i >> 3] >> (i & 7)) & 1))
  396                         break;
  397                 uap->length++;
  398         }
  399 
  400 done:
  401         return (0);
  402 }
  403 
  404 /*
  405  * Update the GDT entry pointing to the LDT to point to the LDT of the
  406  * current process. Manage dt_lock holding/unholding autonomously.
  407  */   
  408 static void
  409 set_user_ldt_locked(struct mdproc *mdp)
  410 {
  411         struct proc_ldt *pldt;
  412         int gdt_idx;
  413 
  414         mtx_assert(&dt_lock, MA_OWNED);
  415 
  416         pldt = mdp->md_ldt;
  417         gdt_idx = GUSERLDT_SEL;
  418         gdt_idx += PCPU_GET(cpuid) * NGDT;      /* always 0 on UP */
  419         gdt[gdt_idx].sd = pldt->ldt_sd;
  420         lldt(GSEL(GUSERLDT_SEL, SEL_KPL));
  421         PCPU_SET(currentldt, GSEL(GUSERLDT_SEL, SEL_KPL));
  422 }
  423 
  424 void
  425 set_user_ldt(struct mdproc *mdp)
  426 {
  427 
  428         mtx_lock_spin(&dt_lock);
  429         set_user_ldt_locked(mdp);
  430         mtx_unlock_spin(&dt_lock);
  431 }
  432 
  433 #ifdef SMP
  434 static void
  435 set_user_ldt_rv(void *arg)
  436 {
  437         struct proc *p;
  438 
  439         p = curproc;
  440         if (arg == p->p_vmspace)
  441                 set_user_ldt(&p->p_md);
  442 }
  443 #endif
  444 
  445 /*
  446  * dt_lock must be held. Returns with dt_lock held.
  447  */
  448 struct proc_ldt *
  449 user_ldt_alloc(struct mdproc *mdp, int len)
  450 {
  451         struct proc_ldt *pldt, *new_ldt;
  452 
  453         mtx_assert(&dt_lock, MA_OWNED);
  454         mtx_unlock_spin(&dt_lock);
  455         new_ldt = malloc(sizeof(struct proc_ldt), M_SUBPROC, M_WAITOK);
  456 
  457         new_ldt->ldt_len = len = NEW_MAX_LD(len);
  458         new_ldt->ldt_base = (caddr_t)kmem_malloc(kernel_arena,
  459             len * sizeof(union descriptor), M_WAITOK | M_ZERO);
  460         new_ldt->ldt_refcnt = 1;
  461         new_ldt->ldt_active = 0;
  462 
  463         mtx_lock_spin(&dt_lock);
  464         gdt_segs[GUSERLDT_SEL].ssd_base = (unsigned)new_ldt->ldt_base;
  465         gdt_segs[GUSERLDT_SEL].ssd_limit = len * sizeof(union descriptor) - 1;
  466         ssdtosd(&gdt_segs[GUSERLDT_SEL], &new_ldt->ldt_sd);
  467 
  468         if ((pldt = mdp->md_ldt) != NULL) {
  469                 if (len > pldt->ldt_len)
  470                         len = pldt->ldt_len;
  471                 bcopy(pldt->ldt_base, new_ldt->ldt_base,
  472                     len * sizeof(union descriptor));
  473         } else
  474                 bcopy(ldt, new_ldt->ldt_base, sizeof(ldt));
  475         
  476         return (new_ldt);
  477 }
  478 
  479 /*
  480  * Must be called with dt_lock held.  Returns with dt_lock unheld.
  481  */
  482 void
  483 user_ldt_free(struct thread *td)
  484 {
  485         struct mdproc *mdp;
  486         struct proc_ldt *pldt;
  487 
  488         mtx_assert(&dt_lock, MA_OWNED);
  489         mdp = &td->td_proc->p_md;
  490         if ((pldt = mdp->md_ldt) == NULL) {
  491                 mtx_unlock_spin(&dt_lock);
  492                 return;
  493         }
  494 
  495         if (td == curthread) {
  496                 lldt(_default_ldt);
  497                 PCPU_SET(currentldt, _default_ldt);
  498         }
  499 
  500         mdp->md_ldt = NULL;
  501         user_ldt_deref(pldt);
  502 }
  503 
  504 void
  505 user_ldt_deref(struct proc_ldt *pldt)
  506 {
  507 
  508         mtx_assert(&dt_lock, MA_OWNED);
  509         if (--pldt->ldt_refcnt == 0) {
  510                 mtx_unlock_spin(&dt_lock);
  511                 kmem_free(kernel_arena, (vm_offset_t)pldt->ldt_base,
  512                         pldt->ldt_len * sizeof(union descriptor));
  513                 free(pldt, M_SUBPROC);
  514         } else
  515                 mtx_unlock_spin(&dt_lock);
  516 }
  517 
  518 /*
  519  * Note for the authors of compat layers (linux, etc): copyout() in
  520  * the function below is not a problem since it presents data in
  521  * arch-specific format (i.e. i386-specific in this case), not in
  522  * the OS-specific one.
  523  */
  524 int
  525 i386_get_ldt(struct thread *td, struct i386_ldt_args *uap)
  526 {
  527         struct proc_ldt *pldt;
  528         char *data;
  529         u_int nldt, num;
  530         int error;
  531 
  532 #ifdef DEBUG
  533         printf("i386_get_ldt: start=%u num=%u descs=%p\n",
  534             uap->start, uap->num, (void *)uap->descs);
  535 #endif
  536 
  537         num = min(uap->num, MAX_LD);
  538         data = malloc(num * sizeof(union descriptor), M_TEMP, M_WAITOK);
  539         mtx_lock_spin(&dt_lock);
  540         pldt = td->td_proc->p_md.md_ldt;
  541         nldt = pldt != NULL ? pldt->ldt_len : nitems(ldt);
  542         if (uap->start >= nldt) {
  543                 num = 0;
  544         } else {
  545                 num = min(num, nldt - uap->start);
  546                 bcopy(pldt != NULL ?
  547                     &((union descriptor *)(pldt->ldt_base))[uap->start] :
  548                     &ldt[uap->start], data, num * sizeof(union descriptor));
  549         }
  550         mtx_unlock_spin(&dt_lock);
  551         error = copyout(data, uap->descs, num * sizeof(union descriptor));
  552         if (error == 0)
  553                 td->td_retval[0] = num;
  554         free(data, M_TEMP);
  555         return (error);
  556 }
  557 
  558 int
  559 i386_set_ldt(struct thread *td, struct i386_ldt_args *uap,
  560     union descriptor *descs)
  561 {
  562         struct mdproc *mdp;
  563         struct proc_ldt *pldt;
  564         union descriptor *dp;
  565         u_int largest_ld, i;
  566         int error;
  567 
  568 #ifdef DEBUG
  569         printf("i386_set_ldt: start=%u num=%u descs=%p\n",
  570             uap->start, uap->num, (void *)uap->descs);
  571 #endif
  572         error = 0;
  573         mdp = &td->td_proc->p_md;
  574 
  575         if (descs == NULL) {
  576                 /* Free descriptors */
  577                 if (uap->start == 0 && uap->num == 0) {
  578                         /*
  579                          * Treat this as a special case, so userland needn't
  580                          * know magic number NLDT.
  581                          */
  582                         uap->start = NLDT;
  583                         uap->num = MAX_LD - NLDT;
  584                 }
  585                 mtx_lock_spin(&dt_lock);
  586                 if ((pldt = mdp->md_ldt) == NULL ||
  587                     uap->start >= pldt->ldt_len) {
  588                         mtx_unlock_spin(&dt_lock);
  589                         return (0);
  590                 }
  591                 largest_ld = uap->start + uap->num;
  592                 if (largest_ld > pldt->ldt_len)
  593                         largest_ld = pldt->ldt_len;
  594                 for (i = uap->start; i < largest_ld; i++)
  595                         atomic_store_rel_64(&((uint64_t *)(pldt->ldt_base))[i],
  596                             0);
  597                 mtx_unlock_spin(&dt_lock);
  598                 return (0);
  599         }
  600 
  601         if (uap->start != LDT_AUTO_ALLOC || uap->num != 1) {
  602                 /* verify range of descriptors to modify */
  603                 largest_ld = uap->start + uap->num;
  604                 if (uap->start >= MAX_LD || largest_ld > MAX_LD)
  605                         return (EINVAL);
  606         }
  607 
  608         /* Check descriptors for access violations */
  609         for (i = 0; i < uap->num; i++) {
  610                 dp = &descs[i];
  611 
  612                 switch (dp->sd.sd_type) {
  613                 case SDT_SYSNULL:       /* system null */ 
  614                         dp->sd.sd_p = 0;
  615                         break;
  616                 case SDT_SYS286TSS: /* system 286 TSS available */
  617                 case SDT_SYSLDT:    /* system local descriptor table */
  618                 case SDT_SYS286BSY: /* system 286 TSS busy */
  619                 case SDT_SYSTASKGT: /* system task gate */
  620                 case SDT_SYS286IGT: /* system 286 interrupt gate */
  621                 case SDT_SYS286TGT: /* system 286 trap gate */
  622                 case SDT_SYSNULL2:  /* undefined by Intel */ 
  623                 case SDT_SYS386TSS: /* system 386 TSS available */
  624                 case SDT_SYSNULL3:  /* undefined by Intel */
  625                 case SDT_SYS386BSY: /* system 386 TSS busy */
  626                 case SDT_SYSNULL4:  /* undefined by Intel */ 
  627                 case SDT_SYS386IGT: /* system 386 interrupt gate */
  628                 case SDT_SYS386TGT: /* system 386 trap gate */
  629                 case SDT_SYS286CGT: /* system 286 call gate */ 
  630                 case SDT_SYS386CGT: /* system 386 call gate */
  631                         return (EACCES);
  632 
  633                 /* memory segment types */
  634                 case SDT_MEMEC:   /* memory execute only conforming */
  635                 case SDT_MEMEAC:  /* memory execute only accessed conforming */
  636                 case SDT_MEMERC:  /* memory execute read conforming */
  637                 case SDT_MEMERAC: /* memory execute read accessed conforming */
  638                          /* Must be "present" if executable and conforming. */
  639                         if (dp->sd.sd_p == 0)
  640                                 return (EACCES);
  641                         break;
  642                 case SDT_MEMRO:   /* memory read only */
  643                 case SDT_MEMROA:  /* memory read only accessed */
  644                 case SDT_MEMRW:   /* memory read write */
  645                 case SDT_MEMRWA:  /* memory read write accessed */
  646                 case SDT_MEMROD:  /* memory read only expand dwn limit */
  647                 case SDT_MEMRODA: /* memory read only expand dwn lim accessed */
  648                 case SDT_MEMRWD:  /* memory read write expand dwn limit */  
  649                 case SDT_MEMRWDA: /* memory read write expand dwn lim acessed */
  650                 case SDT_MEME:    /* memory execute only */ 
  651                 case SDT_MEMEA:   /* memory execute only accessed */
  652                 case SDT_MEMER:   /* memory execute read */
  653                 case SDT_MEMERA:  /* memory execute read accessed */
  654                         break;
  655                 default:
  656                         return (EINVAL);
  657                 }
  658 
  659                 /* Only user (ring-3) descriptors may be present. */
  660                 if (dp->sd.sd_p != 0 && dp->sd.sd_dpl != SEL_UPL)
  661                         return (EACCES);
  662         }
  663 
  664         if (uap->start == LDT_AUTO_ALLOC && uap->num == 1) {
  665                 /* Allocate a free slot */
  666                 mtx_lock_spin(&dt_lock);
  667                 if ((pldt = mdp->md_ldt) == NULL) {
  668                         if ((error = i386_ldt_grow(td, NLDT + 1))) {
  669                                 mtx_unlock_spin(&dt_lock);
  670                                 return (error);
  671                         }
  672                         pldt = mdp->md_ldt;
  673                 }
  674 again:
  675                 /*
  676                  * start scanning a bit up to leave room for NVidia and
  677                  * Wine, which still user the "Blat" method of allocation.
  678                  */
  679                 dp = &((union descriptor *)(pldt->ldt_base))[NLDT];
  680                 for (i = NLDT; i < pldt->ldt_len; ++i) {
  681                         if (dp->sd.sd_type == SDT_SYSNULL)
  682                                 break;
  683                         dp++;
  684                 }
  685                 if (i >= pldt->ldt_len) {
  686                         if ((error = i386_ldt_grow(td, pldt->ldt_len+1))) {
  687                                 mtx_unlock_spin(&dt_lock);
  688                                 return (error);
  689                         }
  690                         goto again;
  691                 }
  692                 uap->start = i;
  693                 error = i386_set_ldt_data(td, i, 1, descs);
  694                 mtx_unlock_spin(&dt_lock);
  695         } else {
  696                 largest_ld = uap->start + uap->num;
  697                 mtx_lock_spin(&dt_lock);
  698                 if (!(error = i386_ldt_grow(td, largest_ld))) {
  699                         error = i386_set_ldt_data(td, uap->start, uap->num,
  700                             descs);
  701                 }
  702                 mtx_unlock_spin(&dt_lock);
  703         }
  704         if (error == 0)
  705                 td->td_retval[0] = uap->start;
  706         return (error);
  707 }
  708 
  709 static int
  710 i386_set_ldt_data(struct thread *td, int start, int num,
  711     union descriptor *descs)
  712 {
  713         struct mdproc *mdp;
  714         struct proc_ldt *pldt;
  715         uint64_t *dst, *src;
  716         int i;
  717 
  718         mtx_assert(&dt_lock, MA_OWNED);
  719 
  720         mdp = &td->td_proc->p_md;
  721         pldt = mdp->md_ldt;
  722         dst = (uint64_t *)(pldt->ldt_base);
  723         src = (uint64_t *)descs;
  724 
  725         /*
  726          * Atomic(9) is used only to get 64bit atomic store with
  727          * cmpxchg8b when available.  There is no op without release
  728          * semantic.
  729          */
  730         for (i = 0; i < num; i++)
  731                 atomic_store_rel_64(&dst[start + i], src[i]);
  732         return (0);
  733 }
  734 
  735 static int
  736 i386_ldt_grow(struct thread *td, int len) 
  737 {
  738         struct mdproc *mdp;
  739         struct proc_ldt *new_ldt, *pldt;
  740         caddr_t old_ldt_base;
  741         int old_ldt_len;
  742 
  743         mtx_assert(&dt_lock, MA_OWNED);
  744 
  745         if (len > MAX_LD)
  746                 return (ENOMEM);
  747         if (len < NLDT + 1)
  748                 len = NLDT + 1;
  749 
  750         mdp = &td->td_proc->p_md;
  751         old_ldt_base = NULL_LDT_BASE;
  752         old_ldt_len = 0;
  753 
  754         /* Allocate a user ldt. */
  755         if ((pldt = mdp->md_ldt) == NULL || len > pldt->ldt_len) {
  756                 new_ldt = user_ldt_alloc(mdp, len);
  757                 if (new_ldt == NULL)
  758                         return (ENOMEM);
  759                 pldt = mdp->md_ldt;
  760 
  761                 if (pldt != NULL) {
  762                         if (new_ldt->ldt_len <= pldt->ldt_len) {
  763                                 /*
  764                                  * We just lost the race for allocation, so
  765                                  * free the new object and return.
  766                                  */
  767                                 mtx_unlock_spin(&dt_lock);
  768                                 kmem_free(kernel_arena,
  769                                    (vm_offset_t)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                         kmem_free(kernel_arena, (vm_offset_t)old_ldt_base,
  803                             old_ldt_len * sizeof(union descriptor));
  804                         free(new_ldt, M_SUBPROC);
  805                 }
  806                 mtx_lock_spin(&dt_lock);
  807         }
  808         return (0);
  809 }

Cache object: 3411a25e029fa0a483b6efb44cce14e6


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