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("$FreeBSD$");
   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/smp.h>
   63 #include <sys/sysctl.h>
   64 #include <sys/sysent.h>
   65 #include <sys/unistd.h>
   66 #include <sys/vnode.h>
   67 #include <sys/vmmeter.h>
   68 
   69 #include <machine/cpu.h>
   70 #include <machine/md_var.h>
   71 #include <machine/pcb.h>
   72 #include <machine/smp.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 <x86/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 _Static_assert(OFFSETOF_CURTHREAD == offsetof(struct pcpu, pc_curthread),
   93     "OFFSETOF_CURTHREAD does not correspond with offset of pc_curthread.");
   94 _Static_assert(OFFSETOF_CURPCB == offsetof(struct pcpu, pc_curpcb),
   95     "OFFSETOF_CURPCB does not correspond with offset of pc_curpcb.");
   96 
   97 struct savefpu *
   98 get_pcb_user_save_td(struct thread *td)
   99 {
  100         vm_offset_t p;
  101 
  102         p = td->td_kstack + td->td_kstack_pages * PAGE_SIZE -
  103             roundup2(cpu_max_ext_state_size, XSAVE_AREA_ALIGN);
  104         KASSERT((p % XSAVE_AREA_ALIGN) == 0, ("Unaligned pcb_user_save area"));
  105         return ((struct savefpu *)p);
  106 }
  107 
  108 struct savefpu *
  109 get_pcb_user_save_pcb(struct pcb *pcb)
  110 {
  111         vm_offset_t p;
  112 
  113         p = (vm_offset_t)(pcb + 1);
  114         return ((struct savefpu *)p);
  115 }
  116 
  117 struct pcb *
  118 get_pcb_td(struct thread *td)
  119 {
  120         vm_offset_t p;
  121 
  122         p = td->td_kstack + td->td_kstack_pages * PAGE_SIZE -
  123             roundup2(cpu_max_ext_state_size, XSAVE_AREA_ALIGN) -
  124             sizeof(struct pcb);
  125         return ((struct pcb *)p);
  126 }
  127 
  128 void *
  129 alloc_fpusave(int flags)
  130 {
  131         void *res;
  132         struct savefpu_ymm *sf;
  133 
  134         res = malloc(cpu_max_ext_state_size, M_DEVBUF, flags);
  135         if (use_xsave) {
  136                 sf = (struct savefpu_ymm *)res;
  137                 bzero(&sf->sv_xstate.sx_hd, sizeof(sf->sv_xstate.sx_hd));
  138                 sf->sv_xstate.sx_hd.xstate_bv = xsave_mask;
  139         }
  140         return (res);
  141 }
  142 
  143 /*
  144  * Finish a fork operation, with process p2 nearly set up.
  145  * Copy and update the pcb, set up the stack so that the child
  146  * ready to run and return to user mode.
  147  */
  148 void
  149 cpu_fork(td1, p2, td2, flags)
  150         register struct thread *td1;
  151         register struct proc *p2;
  152         struct thread *td2;
  153         int flags;
  154 {
  155         register struct proc *p1;
  156         struct pcb *pcb2;
  157         struct mdproc *mdp1, *mdp2;
  158         struct proc_ldt *pldt;
  159         pmap_t pmap2;
  160 
  161         p1 = td1->td_proc;
  162         if ((flags & RFPROC) == 0) {
  163                 if ((flags & RFMEM) == 0) {
  164                         /* unshare user LDT */
  165                         mdp1 = &p1->p_md;
  166                         mtx_lock(&dt_lock);
  167                         if ((pldt = mdp1->md_ldt) != NULL &&
  168                             pldt->ldt_refcnt > 1 &&
  169                             user_ldt_alloc(p1, 1) == NULL)
  170                                 panic("could not copy LDT");
  171                         mtx_unlock(&dt_lock);
  172                 }
  173                 return;
  174         }
  175 
  176         /* Ensure that td1's pcb is up to date. */
  177         fpuexit(td1);
  178 
  179         /* Point the pcb to the top of the stack */
  180         pcb2 = get_pcb_td(td2);
  181         td2->td_pcb = pcb2;
  182 
  183         /* Copy td1's pcb */
  184         bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
  185 
  186         /* Properly initialize pcb_save */
  187         pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
  188         bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
  189             cpu_max_ext_state_size);
  190 
  191         /* Point mdproc and then copy over td1's contents */
  192         mdp2 = &p2->p_md;
  193         bcopy(&p1->p_md, mdp2, sizeof(*mdp2));
  194 
  195         /*
  196          * Create a new fresh stack for the new process.
  197          * Copy the trap frame for the return to user mode as if from a
  198          * syscall.  This copies most of the user mode register values.
  199          */
  200         td2->td_frame = (struct trapframe *)td2->td_pcb - 1;
  201         bcopy(td1->td_frame, td2->td_frame, sizeof(struct trapframe));
  202 
  203         td2->td_frame->tf_rax = 0;              /* Child returns zero */
  204         td2->td_frame->tf_rflags &= ~PSL_C;     /* success */
  205         td2->td_frame->tf_rdx = 1;
  206 
  207         /*
  208          * If the parent process has the trap bit set (i.e. a debugger had
  209          * single stepped the process to the system call), we need to clear
  210          * the trap flag from the new frame unless the debugger had set PF_FORK
  211          * on the parent.  Otherwise, the child will receive a (likely
  212          * unexpected) SIGTRAP when it executes the first instruction after
  213          * returning  to userland.
  214          */
  215         if ((p1->p_pfsflags & PF_FORK) == 0)
  216                 td2->td_frame->tf_rflags &= ~PSL_T;
  217 
  218         /*
  219          * Set registers for trampoline to user mode.  Leave space for the
  220          * return address on stack.  These are the kernel mode register values.
  221          */
  222         pmap2 = vmspace_pmap(p2->p_vmspace);
  223         pcb2->pcb_cr3 = pmap2->pm_cr3;
  224         pcb2->pcb_r12 = (register_t)fork_return;        /* fork_trampoline argument */
  225         pcb2->pcb_rbp = 0;
  226         pcb2->pcb_rsp = (register_t)td2->td_frame - sizeof(void *);
  227         pcb2->pcb_rbx = (register_t)td2;                /* fork_trampoline argument */
  228         pcb2->pcb_rip = (register_t)fork_trampoline;
  229         /*-
  230          * pcb2->pcb_dr*:       cloned above.
  231          * pcb2->pcb_savefpu:   cloned above.
  232          * pcb2->pcb_flags:     cloned above.
  233          * pcb2->pcb_onfault:   cloned above (always NULL here?).
  234          * pcb2->pcb_[fg]sbase: cloned above
  235          */
  236 
  237         /* Setup to release spin count in fork_exit(). */
  238         td2->td_md.md_spinlock_count = 1;
  239         td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
  240 
  241         /* As an i386, do not copy io permission bitmap. */
  242         pcb2->pcb_tssp = NULL;
  243 
  244         /* New segment registers. */
  245         set_pcb_flags(pcb2, PCB_FULL_IRET);
  246 
  247         /* Copy the LDT, if necessary. */
  248         mdp1 = &td1->td_proc->p_md;
  249         mdp2 = &p2->p_md;
  250         mtx_lock(&dt_lock);
  251         if (mdp1->md_ldt != NULL) {
  252                 if (flags & RFMEM) {
  253                         mdp1->md_ldt->ldt_refcnt++;
  254                         mdp2->md_ldt = mdp1->md_ldt;
  255                         bcopy(&mdp1->md_ldt_sd, &mdp2->md_ldt_sd, sizeof(struct
  256                             system_segment_descriptor));
  257                 } else {
  258                         mdp2->md_ldt = NULL;
  259                         mdp2->md_ldt = user_ldt_alloc(p2, 0);
  260                         if (mdp2->md_ldt == NULL)
  261                                 panic("could not copy LDT");
  262                         amd64_set_ldt_data(td2, 0, max_ldt_segment,
  263                             (struct user_segment_descriptor *)
  264                             mdp1->md_ldt->ldt_base);
  265                 }
  266         } else
  267                 mdp2->md_ldt = NULL;
  268         mtx_unlock(&dt_lock);
  269 
  270         /*
  271          * Now, cpu_switch() can schedule the new process.
  272          * pcb_rsp is loaded pointing to the cpu_switch() stack frame
  273          * containing the return address when exiting cpu_switch.
  274          * This will normally be to fork_trampoline(), which will have
  275          * %ebx loaded with the new proc's pointer.  fork_trampoline()
  276          * will set up a stack to call fork_return(p, frame); to complete
  277          * the return to user-mode.
  278          */
  279 }
  280 
  281 /*
  282  * Intercept the return address from a freshly forked process that has NOT
  283  * been scheduled yet.
  284  *
  285  * This is needed to make kernel threads stay in kernel mode.
  286  */
  287 void
  288 cpu_set_fork_handler(td, func, arg)
  289         struct thread *td;
  290         void (*func)(void *);
  291         void *arg;
  292 {
  293         /*
  294          * Note that the trap frame follows the args, so the function
  295          * is really called like this:  func(arg, frame);
  296          */
  297         td->td_pcb->pcb_r12 = (long) func;      /* function */
  298         td->td_pcb->pcb_rbx = (long) arg;       /* first arg */
  299 }
  300 
  301 void
  302 cpu_exit(struct thread *td)
  303 {
  304 
  305         /*
  306          * If this process has a custom LDT, release it.
  307          */
  308         mtx_lock(&dt_lock);
  309         if (td->td_proc->p_md.md_ldt != 0)
  310                 user_ldt_free(td);
  311         else
  312                 mtx_unlock(&dt_lock);
  313 }
  314 
  315 void
  316 cpu_thread_exit(struct thread *td)
  317 {
  318         struct pcb *pcb;
  319 
  320         critical_enter();
  321         if (td == PCPU_GET(fpcurthread))
  322                 fpudrop();
  323         critical_exit();
  324 
  325         pcb = td->td_pcb;
  326 
  327         /* Disable any hardware breakpoints. */
  328         if (pcb->pcb_flags & PCB_DBREGS) {
  329                 reset_dbregs();
  330                 clear_pcb_flags(pcb, PCB_DBREGS);
  331         }
  332 }
  333 
  334 void
  335 cpu_thread_clean(struct thread *td)
  336 {
  337         struct pcb *pcb;
  338 
  339         pcb = td->td_pcb;
  340 
  341         /*
  342          * Clean TSS/iomap
  343          */
  344         if (pcb->pcb_tssp != NULL) {
  345                 kmem_free(kernel_arena, (vm_offset_t)pcb->pcb_tssp,
  346                     ctob(IOPAGES + 1));
  347                 pcb->pcb_tssp = NULL;
  348         }
  349 }
  350 
  351 void
  352 cpu_thread_swapin(struct thread *td)
  353 {
  354 }
  355 
  356 void
  357 cpu_thread_swapout(struct thread *td)
  358 {
  359 }
  360 
  361 void
  362 cpu_thread_alloc(struct thread *td)
  363 {
  364         struct pcb *pcb;
  365         struct xstate_hdr *xhdr;
  366 
  367         td->td_pcb = pcb = get_pcb_td(td);
  368         td->td_frame = (struct trapframe *)pcb - 1;
  369         pcb->pcb_save = get_pcb_user_save_pcb(pcb);
  370         if (use_xsave) {
  371                 xhdr = (struct xstate_hdr *)(pcb->pcb_save + 1);
  372                 bzero(xhdr, sizeof(*xhdr));
  373                 xhdr->xstate_bv = xsave_mask;
  374         }
  375 }
  376 
  377 void
  378 cpu_thread_free(struct thread *td)
  379 {
  380 
  381         cpu_thread_clean(td);
  382 }
  383 
  384 void
  385 cpu_set_syscall_retval(struct thread *td, int error)
  386 {
  387 
  388         switch (error) {
  389         case 0:
  390                 td->td_frame->tf_rax = td->td_retval[0];
  391                 td->td_frame->tf_rdx = td->td_retval[1];
  392                 td->td_frame->tf_rflags &= ~PSL_C;
  393                 break;
  394 
  395         case ERESTART:
  396                 /*
  397                  * Reconstruct pc, we know that 'syscall' is 2 bytes,
  398                  * lcall $X,y is 7 bytes, int 0x80 is 2 bytes.
  399                  * We saved this in tf_err.
  400                  * %r10 (which was holding the value of %rcx) is restored
  401                  * for the next iteration.
  402                  * %r10 restore is only required for freebsd/amd64 processes,
  403                  * but shall be innocent for any ia32 ABI.
  404                  *
  405                  * Require full context restore to get the arguments
  406                  * in the registers reloaded at return to usermode.
  407                  */
  408                 td->td_frame->tf_rip -= td->td_frame->tf_err;
  409                 td->td_frame->tf_r10 = td->td_frame->tf_rcx;
  410                 set_pcb_flags(td->td_pcb, PCB_FULL_IRET);
  411                 break;
  412 
  413         case EJUSTRETURN:
  414                 break;
  415 
  416         default:
  417                 td->td_frame->tf_rax = SV_ABI_ERRNO(td->td_proc, error);
  418                 td->td_frame->tf_rflags |= PSL_C;
  419                 break;
  420         }
  421 }
  422 
  423 /*
  424  * Initialize machine state (pcb and trap frame) for a new thread about to
  425  * upcall. Put enough state in the new thread's PCB to get it to go back 
  426  * userret(), where we can intercept it again to set the return (upcall)
  427  * Address and stack, along with those from upcals that are from other sources
  428  * such as those generated in thread_userret() itself.
  429  */
  430 void
  431 cpu_set_upcall(struct thread *td, struct thread *td0)
  432 {
  433         struct pcb *pcb2;
  434 
  435         /* Point the pcb to the top of the stack. */
  436         pcb2 = td->td_pcb;
  437 
  438         /*
  439          * Copy the upcall pcb.  This loads kernel regs.
  440          * Those not loaded individually below get their default
  441          * values here.
  442          */
  443         bcopy(td0->td_pcb, pcb2, sizeof(*pcb2));
  444         clear_pcb_flags(pcb2, PCB_FPUINITDONE | PCB_USERFPUINITDONE |
  445             PCB_KERNFPU);
  446         pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
  447         bcopy(get_pcb_user_save_td(td0), pcb2->pcb_save,
  448             cpu_max_ext_state_size);
  449         set_pcb_flags(pcb2, PCB_FULL_IRET);
  450 
  451         /*
  452          * Create a new fresh stack for the new thread.
  453          */
  454         bcopy(td0->td_frame, td->td_frame, sizeof(struct trapframe));
  455 
  456         /* If the current thread has the trap bit set (i.e. a debugger had
  457          * single stepped the process to the system call), we need to clear
  458          * the trap flag from the new frame. Otherwise, the new thread will
  459          * receive a (likely unexpected) SIGTRAP when it executes the first
  460          * instruction after returning to userland.
  461          */
  462         td->td_frame->tf_rflags &= ~PSL_T;
  463 
  464         /*
  465          * Set registers for trampoline to user mode.  Leave space for the
  466          * return address on stack.  These are the kernel mode register values.
  467          */
  468         pcb2->pcb_r12 = (register_t)fork_return;            /* trampoline arg */
  469         pcb2->pcb_rbp = 0;
  470         pcb2->pcb_rsp = (register_t)td->td_frame - sizeof(void *);      /* trampoline arg */
  471         pcb2->pcb_rbx = (register_t)td;                     /* trampoline arg */
  472         pcb2->pcb_rip = (register_t)fork_trampoline;
  473         /*
  474          * If we didn't copy the pcb, we'd need to do the following registers:
  475          * pcb2->pcb_cr3:       cloned above.
  476          * pcb2->pcb_dr*:       cloned above.
  477          * pcb2->pcb_savefpu:   cloned above.
  478          * pcb2->pcb_onfault:   cloned above (always NULL here?).
  479          * pcb2->pcb_[fg]sbase: cloned above
  480          */
  481 
  482         /* Setup to release spin count in fork_exit(). */
  483         td->td_md.md_spinlock_count = 1;
  484         td->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
  485 }
  486 
  487 /*
  488  * Set that machine state for performing an upcall that has to
  489  * be done in thread_userret() so that those upcalls generated
  490  * in thread_userret() itself can be done as well.
  491  */
  492 void
  493 cpu_set_upcall_kse(struct thread *td, void (*entry)(void *), void *arg,
  494         stack_t *stack)
  495 {
  496 
  497         /* 
  498          * Do any extra cleaning that needs to be done.
  499          * The thread may have optional components
  500          * that are not present in a fresh thread.
  501          * This may be a recycled thread so make it look
  502          * as though it's newly allocated.
  503          */
  504         cpu_thread_clean(td);
  505 
  506 #ifdef COMPAT_FREEBSD32
  507         if (SV_PROC_FLAG(td->td_proc, SV_ILP32)) {
  508                 /*
  509                  * Set the trap frame to point at the beginning of the uts
  510                  * function.
  511                  */
  512                 td->td_frame->tf_rbp = 0;
  513                 td->td_frame->tf_rsp =
  514                    (((uintptr_t)stack->ss_sp + stack->ss_size - 4) & ~0x0f) - 4;
  515                 td->td_frame->tf_rip = (uintptr_t)entry;
  516 
  517                 /*
  518                  * Pass the address of the mailbox for this kse to the uts
  519                  * function as a parameter on the stack.
  520                  */
  521                 suword32((void *)(td->td_frame->tf_rsp + sizeof(int32_t)),
  522                     (uint32_t)(uintptr_t)arg);
  523 
  524                 return;
  525         }
  526 #endif
  527 
  528         /*
  529          * Set the trap frame to point at the beginning of the uts
  530          * function.
  531          */
  532         td->td_frame->tf_rbp = 0;
  533         td->td_frame->tf_rsp =
  534             ((register_t)stack->ss_sp + stack->ss_size) & ~0x0f;
  535         td->td_frame->tf_rsp -= 8;
  536         td->td_frame->tf_rip = (register_t)entry;
  537         td->td_frame->tf_ds = _udatasel;
  538         td->td_frame->tf_es = _udatasel;
  539         td->td_frame->tf_fs = _ufssel;
  540         td->td_frame->tf_gs = _ugssel;
  541         td->td_frame->tf_flags = TF_HASSEGS;
  542 
  543         /*
  544          * Pass the address of the mailbox for this kse to the uts
  545          * function as a parameter on the stack.
  546          */
  547         td->td_frame->tf_rdi = (register_t)arg;
  548 }
  549 
  550 int
  551 cpu_set_user_tls(struct thread *td, void *tls_base)
  552 {
  553         struct pcb *pcb;
  554 
  555         if ((u_int64_t)tls_base >= VM_MAXUSER_ADDRESS)
  556                 return (EINVAL);
  557 
  558         pcb = td->td_pcb;
  559         set_pcb_flags(pcb, PCB_FULL_IRET);
  560 #ifdef COMPAT_FREEBSD32
  561         if (SV_PROC_FLAG(td->td_proc, SV_ILP32)) {
  562                 pcb->pcb_gsbase = (register_t)tls_base;
  563                 return (0);
  564         }
  565 #endif
  566         pcb->pcb_fsbase = (register_t)tls_base;
  567         return (0);
  568 }
  569 
  570 #ifdef SMP
  571 static void
  572 cpu_reset_proxy()
  573 {
  574 
  575         cpu_reset_proxy_active = 1;
  576         while (cpu_reset_proxy_active == 1)
  577                 ia32_pause(); /* Wait for other cpu to see that we've started */
  578 
  579         printf("cpu_reset_proxy: Stopped CPU %d\n", cpu_reset_proxyid);
  580         DELAY(1000000);
  581         cpu_reset_real();
  582 }
  583 #endif
  584 
  585 void
  586 cpu_reset()
  587 {
  588 #ifdef SMP
  589         cpuset_t map;
  590         u_int cnt;
  591 
  592         if (smp_started) {
  593                 map = all_cpus;
  594                 CPU_CLR(PCPU_GET(cpuid), &map);
  595                 CPU_NAND(&map, &stopped_cpus);
  596                 if (!CPU_EMPTY(&map)) {
  597                         printf("cpu_reset: Stopping other CPUs\n");
  598                         stop_cpus(map);
  599                 }
  600 
  601                 if (PCPU_GET(cpuid) != 0) {
  602                         cpu_reset_proxyid = PCPU_GET(cpuid);
  603                         cpustop_restartfunc = cpu_reset_proxy;
  604                         cpu_reset_proxy_active = 0;
  605                         printf("cpu_reset: Restarting BSP\n");
  606 
  607                         /* Restart CPU #0. */
  608                         CPU_SETOF(0, &started_cpus);
  609                         wmb();
  610 
  611                         cnt = 0;
  612                         while (cpu_reset_proxy_active == 0 && cnt < 10000000) {
  613                                 ia32_pause();
  614                                 cnt++;  /* Wait for BSP to announce restart */
  615                         }
  616                         if (cpu_reset_proxy_active == 0) {
  617                                 printf("cpu_reset: Failed to restart BSP\n");
  618                         } else {
  619                                 cpu_reset_proxy_active = 2;
  620                                 while (1)
  621                                         ia32_pause();
  622                                 /* NOTREACHED */
  623                         }
  624                 }
  625 
  626                 DELAY(1000000);
  627         }
  628 #endif
  629         cpu_reset_real();
  630         /* NOTREACHED */
  631 }
  632 
  633 static void
  634 cpu_reset_real()
  635 {
  636         struct region_descriptor null_idt;
  637         int b;
  638 
  639         disable_intr();
  640 
  641         /*
  642          * Attempt to do a CPU reset via the keyboard controller,
  643          * do not turn off GateA20, as any machine that fails
  644          * to do the reset here would then end up in no man's land.
  645          */
  646         outb(IO_KBD + 4, 0xFE);
  647         DELAY(500000);  /* wait 0.5 sec to see if that did it */
  648 
  649         /*
  650          * Attempt to force a reset via the Reset Control register at
  651          * I/O port 0xcf9.  Bit 2 forces a system reset when it
  652          * transitions from 0 to 1.  Bit 1 selects the type of reset
  653          * to attempt: 0 selects a "soft" reset, and 1 selects a
  654          * "hard" reset.  We try a "hard" reset.  The first write sets
  655          * bit 1 to select a "hard" reset and clears bit 2.  The
  656          * second write forces a 0 -> 1 transition in bit 2 to trigger
  657          * a reset.
  658          */
  659         outb(0xcf9, 0x2);
  660         outb(0xcf9, 0x6);
  661         DELAY(500000);  /* wait 0.5 sec to see if that did it */
  662 
  663         /*
  664          * Attempt to force a reset via the Fast A20 and Init register
  665          * at I/O port 0x92.  Bit 1 serves as an alternate A20 gate.
  666          * Bit 0 asserts INIT# when set to 1.  We are careful to only
  667          * preserve bit 1 while setting bit 0.  We also must clear bit
  668          * 0 before setting it if it isn't already clear.
  669          */
  670         b = inb(0x92);
  671         if (b != 0xff) {
  672                 if ((b & 0x1) != 0)
  673                         outb(0x92, b & 0xfe);
  674                 outb(0x92, b | 0x1);
  675                 DELAY(500000);  /* wait 0.5 sec to see if that did it */
  676         }
  677 
  678         printf("No known reset method worked, attempting CPU shutdown\n");
  679         DELAY(1000000); /* wait 1 sec for printf to complete */
  680 
  681         /* Wipe the IDT. */
  682         null_idt.rd_limit = 0;
  683         null_idt.rd_base = 0;
  684         lidt(&null_idt);
  685 
  686         /* "good night, sweet prince .... <THUNK!>" */
  687         breakpoint();
  688 
  689         /* NOTREACHED */
  690         while(1);
  691 }
  692 
  693 /*
  694  * Software interrupt handler for queued VM system processing.
  695  */   
  696 void  
  697 swi_vm(void *dummy) 
  698 {     
  699         if (busdma_swi_pending != 0)
  700                 busdma_swi();
  701 }
  702 
  703 /*
  704  * Tell whether this address is in some physical memory region.
  705  * Currently used by the kernel coredump code in order to avoid
  706  * dumping the ``ISA memory hole'' which could cause indefinite hangs,
  707  * or other unpredictable behaviour.
  708  */
  709 
  710 int
  711 is_physical_memory(vm_paddr_t addr)
  712 {
  713 
  714 #ifdef DEV_ISA
  715         /* The ISA ``memory hole''. */
  716         if (addr >= 0xa0000 && addr < 0x100000)
  717                 return 0;
  718 #endif
  719 
  720         /*
  721          * stuff other tests for known memory-mapped devices (PCI?)
  722          * here
  723          */
  724 
  725         return 1;
  726 }

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