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

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    1 /*-
    2  * Copyright (c) 1982, 1986 The Regents of the University of California.
    3  * Copyright (c) 1989, 1990 William Jolitz
    4  * Copyright (c) 1994 John Dyson
    5  * All rights reserved.
    6  *
    7  * This code is derived from software contributed to Berkeley by
    8  * the Systems Programming Group of the University of Utah Computer
    9  * Science Department, and William Jolitz.
   10  *
   11  * Redistribution and use in source and binary forms, with or without
   12  * modification, are permitted provided that the following conditions
   13  * are met:
   14  * 1. Redistributions of source code must retain the above copyright
   15  *    notice, this list of conditions and the following disclaimer.
   16  * 2. Redistributions in binary form must reproduce the above copyright
   17  *    notice, this list of conditions and the following disclaimer in the
   18  *    documentation and/or other materials provided with the distribution.
   19  * 3. All advertising materials mentioning features or use of this software
   20  *    must display the following acknowledgement:
   21  *      This product includes software developed by the University of
   22  *      California, Berkeley and its contributors.
   23  * 4. Neither the name of the University nor the names of its contributors
   24  *    may be used to endorse or promote products derived from this software
   25  *    without specific prior written permission.
   26  *
   27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   37  * SUCH DAMAGE.
   38  *
   39  *      from: @(#)vm_machdep.c  7.3 (Berkeley) 5/13/91
   40  *      Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
   41  */
   42 
   43 #include <sys/cdefs.h>
   44 __FBSDID("$FreeBSD: releng/8.2/sys/amd64/amd64/vm_machdep.c 216458 2010-12-15 15:25:56Z kib $");
   45 
   46 #include "opt_isa.h"
   47 #include "opt_cpu.h"
   48 #include "opt_compat.h"
   49 
   50 #include <sys/param.h>
   51 #include <sys/systm.h>
   52 #include <sys/bio.h>
   53 #include <sys/buf.h>
   54 #include <sys/kernel.h>
   55 #include <sys/ktr.h>
   56 #include <sys/lock.h>
   57 #include <sys/malloc.h>
   58 #include <sys/mbuf.h>
   59 #include <sys/mutex.h>
   60 #include <sys/pioctl.h>
   61 #include <sys/proc.h>
   62 #include <sys/sf_buf.h>
   63 #include <sys/smp.h>
   64 #include <sys/sysctl.h>
   65 #include <sys/sysent.h>
   66 #include <sys/unistd.h>
   67 #include <sys/vnode.h>
   68 #include <sys/vmmeter.h>
   69 
   70 #include <machine/cpu.h>
   71 #include <machine/md_var.h>
   72 #include <machine/pcb.h>
   73 #include <machine/specialreg.h>
   74 #include <machine/tss.h>
   75 
   76 #include <vm/vm.h>
   77 #include <vm/vm_extern.h>
   78 #include <vm/vm_kern.h>
   79 #include <vm/vm_page.h>
   80 #include <vm/vm_map.h>
   81 #include <vm/vm_param.h>
   82 
   83 #include <amd64/isa/isa.h>
   84 
   85 static void     cpu_reset_real(void);
   86 #ifdef SMP
   87 static void     cpu_reset_proxy(void);
   88 static u_int    cpu_reset_proxyid;
   89 static volatile u_int   cpu_reset_proxy_active;
   90 #endif
   91 
   92 /*
   93  * Finish a fork operation, with process p2 nearly set up.
   94  * Copy and update the pcb, set up the stack so that the child
   95  * ready to run and return to user mode.
   96  */
   97 void
   98 cpu_fork(td1, p2, td2, flags)
   99         register struct thread *td1;
  100         register struct proc *p2;
  101         struct thread *td2;
  102         int flags;
  103 {
  104         register struct proc *p1;
  105         struct pcb *pcb2;
  106         struct mdproc *mdp1, *mdp2;
  107         struct proc_ldt *pldt;
  108         pmap_t pmap2;
  109 
  110         p1 = td1->td_proc;
  111         if ((flags & RFPROC) == 0) {
  112                 if ((flags & RFMEM) == 0) {
  113                         /* unshare user LDT */
  114                         mdp1 = &p1->p_md;
  115                         mtx_lock(&dt_lock);
  116                         if ((pldt = mdp1->md_ldt) != NULL &&
  117                             pldt->ldt_refcnt > 1 &&
  118                             user_ldt_alloc(p1, 1) == NULL)
  119                                 panic("could not copy LDT");
  120                         mtx_unlock(&dt_lock);
  121                 }
  122                 return;
  123         }
  124 
  125         /* Ensure that td1's pcb is up to date. */
  126         fpuexit(td1);
  127 
  128         /* Point the pcb to the top of the stack */
  129         pcb2 = (struct pcb *)(td2->td_kstack +
  130             td2->td_kstack_pages * PAGE_SIZE) - 1;
  131         td2->td_pcb = pcb2;
  132 
  133         /* Copy td1's pcb */
  134         bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
  135 
  136         /* Properly initialize pcb_save */
  137         pcb2->pcb_save = &pcb2->pcb_user_save;
  138 
  139         /* Point mdproc and then copy over td1's contents */
  140         mdp2 = &p2->p_md;
  141         bcopy(&p1->p_md, mdp2, sizeof(*mdp2));
  142 
  143         /*
  144          * Create a new fresh stack for the new process.
  145          * Copy the trap frame for the return to user mode as if from a
  146          * syscall.  This copies most of the user mode register values.
  147          */
  148         td2->td_frame = (struct trapframe *)td2->td_pcb - 1;
  149         bcopy(td1->td_frame, td2->td_frame, sizeof(struct trapframe));
  150 
  151         td2->td_frame->tf_rax = 0;              /* Child returns zero */
  152         td2->td_frame->tf_rflags &= ~PSL_C;     /* success */
  153         td2->td_frame->tf_rdx = 1;
  154 
  155         /*
  156          * If the parent process has the trap bit set (i.e. a debugger had
  157          * single stepped the process to the system call), we need to clear
  158          * the trap flag from the new frame unless the debugger had set PF_FORK
  159          * on the parent.  Otherwise, the child will receive a (likely
  160          * unexpected) SIGTRAP when it executes the first instruction after
  161          * returning  to userland.
  162          */
  163         if ((p1->p_pfsflags & PF_FORK) == 0)
  164                 td2->td_frame->tf_rflags &= ~PSL_T;
  165 
  166         /*
  167          * Set registers for trampoline to user mode.  Leave space for the
  168          * return address on stack.  These are the kernel mode register values.
  169          */
  170         pmap2 = vmspace_pmap(p2->p_vmspace);
  171         pcb2->pcb_cr3 = DMAP_TO_PHYS((vm_offset_t)pmap2->pm_pml4);
  172         pcb2->pcb_r12 = (register_t)fork_return;        /* fork_trampoline argument */
  173         pcb2->pcb_rbp = 0;
  174         pcb2->pcb_rsp = (register_t)td2->td_frame - sizeof(void *);
  175         pcb2->pcb_rbx = (register_t)td2;                /* fork_trampoline argument */
  176         pcb2->pcb_rip = (register_t)fork_trampoline;
  177         /*-
  178          * pcb2->pcb_dr*:       cloned above.
  179          * pcb2->pcb_savefpu:   cloned above.
  180          * pcb2->pcb_flags:     cloned above.
  181          * pcb2->pcb_onfault:   cloned above (always NULL here?).
  182          * pcb2->pcb_[fg]sbase: cloned above
  183          */
  184 
  185         /* Setup to release spin count in fork_exit(). */
  186         td2->td_md.md_spinlock_count = 1;
  187         td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
  188 
  189         /* As an i386, do not copy io permission bitmap. */
  190         pcb2->pcb_tssp = NULL;
  191 
  192         /* New segment registers. */
  193         pcb2->pcb_full_iret = 1;
  194 
  195         /* Copy the LDT, if necessary. */
  196         mdp1 = &td1->td_proc->p_md;
  197         mdp2 = &p2->p_md;
  198         mtx_lock(&dt_lock);
  199         if (mdp1->md_ldt != NULL) {
  200                 if (flags & RFMEM) {
  201                         mdp1->md_ldt->ldt_refcnt++;
  202                         mdp2->md_ldt = mdp1->md_ldt;
  203                         bcopy(&mdp1->md_ldt_sd, &mdp2->md_ldt_sd, sizeof(struct
  204                             system_segment_descriptor));
  205                 } else {
  206                         mdp2->md_ldt = NULL;
  207                         mdp2->md_ldt = user_ldt_alloc(p2, 0);
  208                         if (mdp2->md_ldt == NULL)
  209                                 panic("could not copy LDT");
  210                         amd64_set_ldt_data(td2, 0, max_ldt_segment,
  211                             (struct user_segment_descriptor *)
  212                             mdp1->md_ldt->ldt_base);
  213                 }
  214         } else
  215                 mdp2->md_ldt = NULL;
  216         mtx_unlock(&dt_lock);
  217 
  218         /*
  219          * Now, cpu_switch() can schedule the new process.
  220          * pcb_rsp is loaded pointing to the cpu_switch() stack frame
  221          * containing the return address when exiting cpu_switch.
  222          * This will normally be to fork_trampoline(), which will have
  223          * %ebx loaded with the new proc's pointer.  fork_trampoline()
  224          * will set up a stack to call fork_return(p, frame); to complete
  225          * the return to user-mode.
  226          */
  227 }
  228 
  229 /*
  230  * Intercept the return address from a freshly forked process that has NOT
  231  * been scheduled yet.
  232  *
  233  * This is needed to make kernel threads stay in kernel mode.
  234  */
  235 void
  236 cpu_set_fork_handler(td, func, arg)
  237         struct thread *td;
  238         void (*func)(void *);
  239         void *arg;
  240 {
  241         /*
  242          * Note that the trap frame follows the args, so the function
  243          * is really called like this:  func(arg, frame);
  244          */
  245         td->td_pcb->pcb_r12 = (long) func;      /* function */
  246         td->td_pcb->pcb_rbx = (long) arg;       /* first arg */
  247 }
  248 
  249 void
  250 cpu_exit(struct thread *td)
  251 {
  252 
  253         /*
  254          * If this process has a custom LDT, release it.
  255          */
  256         mtx_lock(&dt_lock);
  257         if (td->td_proc->p_md.md_ldt != 0)
  258                 user_ldt_free(td);
  259         else
  260                 mtx_unlock(&dt_lock);
  261 }
  262 
  263 void
  264 cpu_thread_exit(struct thread *td)
  265 {
  266         struct pcb *pcb;
  267 
  268         critical_enter();
  269         if (td == PCPU_GET(fpcurthread))
  270                 fpudrop();
  271         critical_exit();
  272 
  273         pcb = td->td_pcb;
  274 
  275         /* Disable any hardware breakpoints. */
  276         if (pcb->pcb_flags & PCB_DBREGS) {
  277                 reset_dbregs();
  278                 pcb->pcb_flags &= ~PCB_DBREGS;
  279         }
  280 }
  281 
  282 void
  283 cpu_thread_clean(struct thread *td)
  284 {
  285         struct pcb *pcb;
  286 
  287         pcb = td->td_pcb;
  288 
  289         /*
  290          * Clean TSS/iomap
  291          */
  292         if (pcb->pcb_tssp != NULL) {
  293                 kmem_free(kernel_map, (vm_offset_t)pcb->pcb_tssp,
  294                     ctob(IOPAGES + 1));
  295                 pcb->pcb_tssp = NULL;
  296         }
  297 }
  298 
  299 void
  300 cpu_thread_swapin(struct thread *td)
  301 {
  302 }
  303 
  304 void
  305 cpu_thread_swapout(struct thread *td)
  306 {
  307 }
  308 
  309 void
  310 cpu_thread_alloc(struct thread *td)
  311 {
  312 
  313         td->td_pcb = (struct pcb *)(td->td_kstack +
  314             td->td_kstack_pages * PAGE_SIZE) - 1;
  315         td->td_frame = (struct trapframe *)td->td_pcb - 1;
  316         td->td_pcb->pcb_save = &td->td_pcb->pcb_user_save;
  317 }
  318 
  319 void
  320 cpu_thread_free(struct thread *td)
  321 {
  322 
  323         cpu_thread_clean(td);
  324 }
  325 
  326 void
  327 cpu_set_syscall_retval(struct thread *td, int error)
  328 {
  329 
  330         switch (error) {
  331         case 0:
  332                 td->td_frame->tf_rax = td->td_retval[0];
  333                 td->td_frame->tf_rdx = td->td_retval[1];
  334                 td->td_frame->tf_rflags &= ~PSL_C;
  335                 break;
  336 
  337         case ERESTART:
  338                 /*
  339                  * Reconstruct pc, we know that 'syscall' is 2 bytes,
  340                  * lcall $X,y is 7 bytes, int 0x80 is 2 bytes.
  341                  * We saved this in tf_err.
  342                  * %r10 (which was holding the value of %rcx) is restored
  343                  * for the next iteration.
  344                  * %r10 restore is only required for freebsd/amd64 processes,
  345                  * but shall be innocent for any ia32 ABI.
  346                  */
  347                 td->td_frame->tf_rip -= td->td_frame->tf_err;
  348                 td->td_frame->tf_r10 = td->td_frame->tf_rcx;
  349                 break;
  350 
  351         case EJUSTRETURN:
  352                 break;
  353 
  354         default:
  355                 if (td->td_proc->p_sysent->sv_errsize) {
  356                         if (error >= td->td_proc->p_sysent->sv_errsize)
  357                                 error = -1;     /* XXX */
  358                         else
  359                                 error = td->td_proc->p_sysent->sv_errtbl[error];
  360                 }
  361                 td->td_frame->tf_rax = error;
  362                 td->td_frame->tf_rflags |= PSL_C;
  363                 break;
  364         }
  365 }
  366 
  367 /*
  368  * Initialize machine state (pcb and trap frame) for a new thread about to
  369  * upcall. Put enough state in the new thread's PCB to get it to go back 
  370  * userret(), where we can intercept it again to set the return (upcall)
  371  * Address and stack, along with those from upcals that are from other sources
  372  * such as those generated in thread_userret() itself.
  373  */
  374 void
  375 cpu_set_upcall(struct thread *td, struct thread *td0)
  376 {
  377         struct pcb *pcb2;
  378 
  379         /* Point the pcb to the top of the stack. */
  380         pcb2 = td->td_pcb;
  381 
  382         /*
  383          * Copy the upcall pcb.  This loads kernel regs.
  384          * Those not loaded individually below get their default
  385          * values here.
  386          */
  387         bcopy(td0->td_pcb, pcb2, sizeof(*pcb2));
  388         pcb2->pcb_flags &= ~(PCB_FPUINITDONE | PCB_USERFPUINITDONE);
  389         pcb2->pcb_save = &pcb2->pcb_user_save;
  390         pcb2->pcb_full_iret = 1;
  391 
  392         /*
  393          * Create a new fresh stack for the new thread.
  394          */
  395         bcopy(td0->td_frame, td->td_frame, sizeof(struct trapframe));
  396 
  397         /* If the current thread has the trap bit set (i.e. a debugger had
  398          * single stepped the process to the system call), we need to clear
  399          * the trap flag from the new frame. Otherwise, the new thread will
  400          * receive a (likely unexpected) SIGTRAP when it executes the first
  401          * instruction after returning to userland.
  402          */
  403         td->td_frame->tf_rflags &= ~PSL_T;
  404 
  405         /*
  406          * Set registers for trampoline to user mode.  Leave space for the
  407          * return address on stack.  These are the kernel mode register values.
  408          */
  409         pcb2->pcb_r12 = (register_t)fork_return;            /* trampoline arg */
  410         pcb2->pcb_rbp = 0;
  411         pcb2->pcb_rsp = (register_t)td->td_frame - sizeof(void *);      /* trampoline arg */
  412         pcb2->pcb_rbx = (register_t)td;                     /* trampoline arg */
  413         pcb2->pcb_rip = (register_t)fork_trampoline;
  414         /*
  415          * If we didn't copy the pcb, we'd need to do the following registers:
  416          * pcb2->pcb_cr3:       cloned above.
  417          * pcb2->pcb_dr*:       cloned above.
  418          * pcb2->pcb_savefpu:   cloned above.
  419          * pcb2->pcb_onfault:   cloned above (always NULL here?).
  420          * pcb2->pcb_[fg]sbase: cloned above
  421          */
  422 
  423         /* Setup to release spin count in fork_exit(). */
  424         td->td_md.md_spinlock_count = 1;
  425         td->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
  426 }
  427 
  428 /*
  429  * Set that machine state for performing an upcall that has to
  430  * be done in thread_userret() so that those upcalls generated
  431  * in thread_userret() itself can be done as well.
  432  */
  433 void
  434 cpu_set_upcall_kse(struct thread *td, void (*entry)(void *), void *arg,
  435         stack_t *stack)
  436 {
  437 
  438         /* 
  439          * Do any extra cleaning that needs to be done.
  440          * The thread may have optional components
  441          * that are not present in a fresh thread.
  442          * This may be a recycled thread so make it look
  443          * as though it's newly allocated.
  444          */
  445         cpu_thread_clean(td);
  446 
  447 #ifdef COMPAT_FREEBSD32
  448         if (td->td_proc->p_sysent->sv_flags & SV_ILP32) {
  449                 /*
  450                  * Set the trap frame to point at the beginning of the uts
  451                  * function.
  452                  */
  453                 td->td_frame->tf_rbp = 0;
  454                 td->td_frame->tf_rsp =
  455                    (((uintptr_t)stack->ss_sp + stack->ss_size - 4) & ~0x0f) - 4;
  456                 td->td_frame->tf_rip = (uintptr_t)entry;
  457 
  458                 /*
  459                  * Pass the address of the mailbox for this kse to the uts
  460                  * function as a parameter on the stack.
  461                  */
  462                 suword32((void *)(td->td_frame->tf_rsp + sizeof(int32_t)),
  463                     (uint32_t)(uintptr_t)arg);
  464 
  465                 return;
  466         }
  467 #endif
  468 
  469         /*
  470          * Set the trap frame to point at the beginning of the uts
  471          * function.
  472          */
  473         td->td_frame->tf_rbp = 0;
  474         td->td_frame->tf_rsp =
  475             ((register_t)stack->ss_sp + stack->ss_size) & ~0x0f;
  476         td->td_frame->tf_rsp -= 8;
  477         td->td_frame->tf_rip = (register_t)entry;
  478         td->td_frame->tf_ds = _udatasel;
  479         td->td_frame->tf_es = _udatasel;
  480         td->td_frame->tf_fs = _ufssel;
  481         td->td_frame->tf_gs = _ugssel;
  482         td->td_frame->tf_flags = TF_HASSEGS;
  483 
  484         /*
  485          * Pass the address of the mailbox for this kse to the uts
  486          * function as a parameter on the stack.
  487          */
  488         td->td_frame->tf_rdi = (register_t)arg;
  489 }
  490 
  491 int
  492 cpu_set_user_tls(struct thread *td, void *tls_base)
  493 {
  494 
  495         if ((u_int64_t)tls_base >= VM_MAXUSER_ADDRESS)
  496                 return (EINVAL);
  497 
  498 #ifdef COMPAT_FREEBSD32
  499         if (td->td_proc->p_sysent->sv_flags & SV_ILP32) {
  500                 td->td_pcb->pcb_gsbase = (register_t)tls_base;
  501                 return (0);
  502         }
  503 #endif
  504         td->td_pcb->pcb_fsbase = (register_t)tls_base;
  505         td->td_pcb->pcb_full_iret = 1;
  506         return (0);
  507 }
  508 
  509 #ifdef SMP
  510 static void
  511 cpu_reset_proxy()
  512 {
  513 
  514         cpu_reset_proxy_active = 1;
  515         while (cpu_reset_proxy_active == 1)
  516                 ;       /* Wait for other cpu to see that we've started */
  517         stop_cpus((1<<cpu_reset_proxyid));
  518         printf("cpu_reset_proxy: Stopped CPU %d\n", cpu_reset_proxyid);
  519         DELAY(1000000);
  520         cpu_reset_real();
  521 }
  522 #endif
  523 
  524 void
  525 cpu_reset()
  526 {
  527 #ifdef SMP
  528         cpumask_t map;
  529         u_int cnt;
  530 
  531         if (smp_active) {
  532                 map = PCPU_GET(other_cpus) & ~stopped_cpus;
  533                 if (map != 0) {
  534                         printf("cpu_reset: Stopping other CPUs\n");
  535                         stop_cpus(map);
  536                 }
  537 
  538                 if (PCPU_GET(cpuid) != 0) {
  539                         cpu_reset_proxyid = PCPU_GET(cpuid);
  540                         cpustop_restartfunc = cpu_reset_proxy;
  541                         cpu_reset_proxy_active = 0;
  542                         printf("cpu_reset: Restarting BSP\n");
  543 
  544                         /* Restart CPU #0. */
  545                         atomic_store_rel_int(&started_cpus, 1 << 0);
  546 
  547                         cnt = 0;
  548                         while (cpu_reset_proxy_active == 0 && cnt < 10000000)
  549                                 cnt++;  /* Wait for BSP to announce restart */
  550                         if (cpu_reset_proxy_active == 0)
  551                                 printf("cpu_reset: Failed to restart BSP\n");
  552                         enable_intr();
  553                         cpu_reset_proxy_active = 2;
  554 
  555                         while (1);
  556                         /* NOTREACHED */
  557                 }
  558 
  559                 DELAY(1000000);
  560         }
  561 #endif
  562         cpu_reset_real();
  563         /* NOTREACHED */
  564 }
  565 
  566 static void
  567 cpu_reset_real()
  568 {
  569         struct region_descriptor null_idt;
  570         int b;
  571 
  572         disable_intr();
  573 
  574         /*
  575          * Attempt to do a CPU reset via the keyboard controller,
  576          * do not turn off GateA20, as any machine that fails
  577          * to do the reset here would then end up in no man's land.
  578          */
  579         outb(IO_KBD + 4, 0xFE);
  580         DELAY(500000);  /* wait 0.5 sec to see if that did it */
  581 
  582         /*
  583          * Attempt to force a reset via the Reset Control register at
  584          * I/O port 0xcf9.  Bit 2 forces a system reset when it
  585          * transitions from 0 to 1.  Bit 1 selects the type of reset
  586          * to attempt: 0 selects a "soft" reset, and 1 selects a
  587          * "hard" reset.  We try a "hard" reset.  The first write sets
  588          * bit 1 to select a "hard" reset and clears bit 2.  The
  589          * second write forces a 0 -> 1 transition in bit 2 to trigger
  590          * a reset.
  591          */
  592         outb(0xcf9, 0x2);
  593         outb(0xcf9, 0x6);
  594         DELAY(500000);  /* wait 0.5 sec to see if that did it */
  595 
  596         /*
  597          * Attempt to force a reset via the Fast A20 and Init register
  598          * at I/O port 0x92.  Bit 1 serves as an alternate A20 gate.
  599          * Bit 0 asserts INIT# when set to 1.  We are careful to only
  600          * preserve bit 1 while setting bit 0.  We also must clear bit
  601          * 0 before setting it if it isn't already clear.
  602          */
  603         b = inb(0x92);
  604         if (b != 0xff) {
  605                 if ((b & 0x1) != 0)
  606                         outb(0x92, b & 0xfe);
  607                 outb(0x92, b | 0x1);
  608                 DELAY(500000);  /* wait 0.5 sec to see if that did it */
  609         }
  610 
  611         printf("No known reset method worked, attempting CPU shutdown\n");
  612         DELAY(1000000); /* wait 1 sec for printf to complete */
  613 
  614         /* Wipe the IDT. */
  615         null_idt.rd_limit = 0;
  616         null_idt.rd_base = 0;
  617         lidt(&null_idt);
  618 
  619         /* "good night, sweet prince .... <THUNK!>" */
  620         breakpoint();
  621 
  622         /* NOTREACHED */
  623         while(1);
  624 }
  625 
  626 /*
  627  * Allocate an sf_buf for the given vm_page.  On this machine, however, there
  628  * is no sf_buf object.  Instead, an opaque pointer to the given vm_page is
  629  * returned.
  630  */
  631 struct sf_buf *
  632 sf_buf_alloc(struct vm_page *m, int pri)
  633 {
  634 
  635         return ((struct sf_buf *)m);
  636 }
  637 
  638 /*
  639  * Free the sf_buf.  In fact, do nothing because there are no resources
  640  * associated with the sf_buf.
  641  */
  642 void
  643 sf_buf_free(struct sf_buf *sf)
  644 {
  645 }
  646 
  647 /*
  648  * Software interrupt handler for queued VM system processing.
  649  */   
  650 void  
  651 swi_vm(void *dummy) 
  652 {     
  653         if (busdma_swi_pending != 0)
  654                 busdma_swi();
  655 }
  656 
  657 /*
  658  * Tell whether this address is in some physical memory region.
  659  * Currently used by the kernel coredump code in order to avoid
  660  * dumping the ``ISA memory hole'' which could cause indefinite hangs,
  661  * or other unpredictable behaviour.
  662  */
  663 
  664 int
  665 is_physical_memory(vm_paddr_t addr)
  666 {
  667 
  668 #ifdef DEV_ISA
  669         /* The ISA ``memory hole''. */
  670         if (addr >= 0xa0000 && addr < 0x100000)
  671                 return 0;
  672 #endif
  673 
  674         /*
  675          * stuff other tests for known memory-mapped devices (PCI?)
  676          * here
  677          */
  678 
  679         return 1;
  680 }

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