xref: /freebsd/sys/i386/i386/vm_machdep.c (revision dc318a4ffabcbfa23bb56a33403aad36e6de30af)
1 /*-
2  * SPDX-License-Identifier: BSD-4-Clause
3  *
4  * Copyright (c) 1982, 1986 The Regents of the University of California.
5  * Copyright (c) 1989, 1990 William Jolitz
6  * Copyright (c) 1994 John Dyson
7  * All rights reserved.
8  *
9  * This code is derived from software contributed to Berkeley by
10  * the Systems Programming Group of the University of Utah Computer
11  * Science Department, and William Jolitz.
12  *
13  * Redistribution and use in source and binary forms, with or without
14  * modification, are permitted provided that the following conditions
15  * are met:
16  * 1. Redistributions of source code must retain the above copyright
17  *    notice, this list of conditions and the following disclaimer.
18  * 2. Redistributions in binary form must reproduce the above copyright
19  *    notice, this list of conditions and the following disclaimer in the
20  *    documentation and/or other materials provided with the distribution.
21  * 3. All advertising materials mentioning features or use of this software
22  *    must display the following acknowledgement:
23  *	This product includes software developed by the University of
24  *	California, Berkeley and its contributors.
25  * 4. Neither the name of the University nor the names of its contributors
26  *    may be used to endorse or promote products derived from this software
27  *    without specific prior written permission.
28  *
29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
39  * SUCH DAMAGE.
40  *
41  *	from: @(#)vm_machdep.c	7.3 (Berkeley) 5/13/91
42  *	Utah $Hdr: vm_machdep.c 1.16.1.1 89/06/23$
43  */
44 
45 #include <sys/cdefs.h>
46 __FBSDID("$FreeBSD$");
47 
48 #include "opt_isa.h"
49 #include "opt_npx.h"
50 #include "opt_reset.h"
51 #include "opt_cpu.h"
52 
53 #include <sys/param.h>
54 #include <sys/systm.h>
55 #include <sys/bio.h>
56 #include <sys/buf.h>
57 #include <sys/kernel.h>
58 #include <sys/ktr.h>
59 #include <sys/lock.h>
60 #include <sys/malloc.h>
61 #include <sys/mbuf.h>
62 #include <sys/mutex.h>
63 #include <sys/proc.h>
64 #include <sys/sysent.h>
65 #include <sys/sf_buf.h>
66 #include <sys/smp.h>
67 #include <sys/sched.h>
68 #include <sys/sysctl.h>
69 #include <sys/unistd.h>
70 #include <sys/vnode.h>
71 #include <sys/vmmeter.h>
72 
73 #include <machine/cpu.h>
74 #include <machine/cputypes.h>
75 #include <machine/md_var.h>
76 #include <machine/pcb.h>
77 #include <machine/pcb_ext.h>
78 #include <machine/smp.h>
79 #include <machine/vm86.h>
80 
81 #include <vm/vm.h>
82 #include <vm/vm_extern.h>
83 #include <vm/vm_kern.h>
84 #include <vm/vm_page.h>
85 #include <vm/vm_map.h>
86 #include <vm/vm_param.h>
87 
88 _Static_assert(__OFFSETOF_MONITORBUF == offsetof(struct pcpu, pc_monitorbuf),
89     "__OFFSETOF_MONITORBUF does not correspond with offset of pc_monitorbuf.");
90 
91 union savefpu *
92 get_pcb_user_save_td(struct thread *td)
93 {
94 	vm_offset_t p;
95 
96 	p = td->td_kstack + td->td_kstack_pages * PAGE_SIZE -
97 	    roundup2(cpu_max_ext_state_size, XSAVE_AREA_ALIGN);
98 	KASSERT((p % XSAVE_AREA_ALIGN) == 0, ("Unaligned pcb_user_save area"));
99 	return ((union savefpu *)p);
100 }
101 
102 union savefpu *
103 get_pcb_user_save_pcb(struct pcb *pcb)
104 {
105 	vm_offset_t p;
106 
107 	p = (vm_offset_t)(pcb + 1);
108 	return ((union savefpu *)p);
109 }
110 
111 struct pcb *
112 get_pcb_td(struct thread *td)
113 {
114 	vm_offset_t p;
115 
116 	p = td->td_kstack + td->td_kstack_pages * PAGE_SIZE -
117 	    roundup2(cpu_max_ext_state_size, XSAVE_AREA_ALIGN) -
118 	    sizeof(struct pcb);
119 	return ((struct pcb *)p);
120 }
121 
122 void *
123 alloc_fpusave(int flags)
124 {
125 	void *res;
126 	struct savefpu_ymm *sf;
127 
128 	res = malloc(cpu_max_ext_state_size, M_DEVBUF, flags);
129 	if (use_xsave) {
130 		sf = (struct savefpu_ymm *)res;
131 		bzero(&sf->sv_xstate.sx_hd, sizeof(sf->sv_xstate.sx_hd));
132 		sf->sv_xstate.sx_hd.xstate_bv = xsave_mask;
133 	}
134 	return (res);
135 }
136 
137 /*
138  * Common code shared between cpu_fork() and cpu_copy_thread() for
139  * initializing a thread.
140  */
141 static void
142 copy_thread(struct thread *td1, struct thread *td2)
143 {
144 	struct pcb *pcb2;
145 
146 	pcb2 = td2->td_pcb;
147 
148 	/* Ensure that td1's pcb is up to date for user threads. */
149 	if ((td2->td_pflags & TDP_KTHREAD) == 0) {
150 		MPASS(td1 == curthread);
151 		td1->td_pcb->pcb_gs = rgs();
152 		critical_enter();
153 		if (PCPU_GET(fpcurthread) == td1)
154 			npxsave(td1->td_pcb->pcb_save);
155 		critical_exit();
156 	}
157 
158 	/* Copy td1's pcb */
159 	bcopy(td1->td_pcb, pcb2, sizeof(*pcb2));
160 
161 	/* Properly initialize pcb_save */
162 	pcb2->pcb_save = get_pcb_user_save_pcb(pcb2);
163 
164 	/* Kernel threads start with clean NPX and segment bases. */
165 	if ((td2->td_pflags & TDP_KTHREAD) != 0) {
166 		pcb2->pcb_gs = _udatasel;
167 		set_fsbase(td2, 0);
168 		set_gsbase(td2, 0);
169 		pcb2->pcb_flags &= ~(PCB_NPXINITDONE | PCB_NPXUSERINITDONE |
170 		    PCB_KERNNPX | PCB_KERNNPX_THR);
171 	} else {
172 		MPASS((pcb2->pcb_flags & (PCB_KERNNPX | PCB_KERNNPX_THR)) == 0);
173 		bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2),
174 		    cpu_max_ext_state_size);
175 	}
176 
177 	/*
178 	 * Set registers for trampoline to user mode.  Leave space for the
179 	 * return address on stack.  These are the kernel mode register values.
180 	 */
181 	pcb2->pcb_edi = 0;
182 	pcb2->pcb_esi = (int)fork_return;		    /* trampoline arg */
183 	pcb2->pcb_ebp = 0;
184 	pcb2->pcb_esp = (int)td2->td_frame - sizeof(void *); /* trampoline arg */
185 	pcb2->pcb_ebx = (int)td2;			    /* trampoline arg */
186 	pcb2->pcb_eip = (int)fork_trampoline + setidt_disp;
187 	/*
188 	 * If we didn't copy the pcb, we'd need to do the following registers:
189 	 * pcb2->pcb_cr3:	cloned above.
190 	 * pcb2->pcb_dr*:	cloned above.
191 	 * pcb2->pcb_savefpu:	cloned above.
192 	 * pcb2->pcb_flags:	cloned above.
193 	 * pcb2->pcb_onfault:	cloned above (always NULL here?).
194 	 * pcb2->pcb_gs:	cloned above.
195 	 * pcb2->pcb_ext:	cleared below.
196 	 */
197 	pcb2->pcb_ext = NULL;
198 
199 	/* Setup to release spin count in fork_exit(). */
200 	td2->td_md.md_spinlock_count = 1;
201 	td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I;
202 }
203 
204 /*
205  * Finish a fork operation, with process p2 nearly set up.
206  * Copy and update the pcb, set up the stack so that the child
207  * ready to run and return to user mode.
208  */
209 void
210 cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
211 {
212 	struct proc *p1;
213 	struct pcb *pcb2;
214 	struct mdproc *mdp2;
215 
216 	p1 = td1->td_proc;
217 	if ((flags & RFPROC) == 0) {
218 		if ((flags & RFMEM) == 0) {
219 			/* unshare user LDT */
220 			struct mdproc *mdp1 = &p1->p_md;
221 			struct proc_ldt *pldt, *pldt1;
222 
223 			mtx_lock_spin(&dt_lock);
224 			if ((pldt1 = mdp1->md_ldt) != NULL &&
225 			    pldt1->ldt_refcnt > 1) {
226 				pldt = user_ldt_alloc(mdp1, pldt1->ldt_len);
227 				if (pldt == NULL)
228 					panic("could not copy LDT");
229 				mdp1->md_ldt = pldt;
230 				set_user_ldt(mdp1);
231 				user_ldt_deref(pldt1);
232 			} else
233 				mtx_unlock_spin(&dt_lock);
234 		}
235 		return;
236 	}
237 
238 	/* Point the pcb to the top of the stack */
239 	pcb2 = get_pcb_td(td2);
240 	td2->td_pcb = pcb2;
241 
242 	copy_thread(td1, td2);
243 
244 	/* Reset debug registers in the new process */
245 	x86_clear_dbregs(pcb2);
246 
247 	/* Point mdproc and then copy over td1's contents */
248 	mdp2 = &p2->p_md;
249 	bcopy(&p1->p_md, mdp2, sizeof(*mdp2));
250 
251 	/*
252 	 * Copy the trap frame for the return to user mode as if from a
253 	 * syscall.  This copies most of the user mode register values.
254 	 * The -VM86_STACK_SPACE (-16) is so we can expand the trapframe
255 	 * if we go to vm86.
256 	 */
257 	td2->td_frame = (struct trapframe *)((caddr_t)td2->td_pcb -
258 	    VM86_STACK_SPACE) - 1;
259 	bcopy(td1->td_frame, td2->td_frame, sizeof(struct trapframe));
260 
261 	td2->td_frame->tf_eax = 0;		/* Child returns zero */
262 	td2->td_frame->tf_eflags &= ~PSL_C;	/* success */
263 	td2->td_frame->tf_edx = 1;
264 
265 	/*
266 	 * If the parent process has the trap bit set (i.e. a debugger
267 	 * had single stepped the process to the system call), we need
268 	 * to clear the trap flag from the new frame.
269 	 */
270 	td2->td_frame->tf_eflags &= ~PSL_T;
271 
272 	/* Set cr3 for the new process. */
273 	pcb2->pcb_cr3 = pmap_get_cr3(vmspace_pmap(p2->p_vmspace));
274 
275 	/*
276 	 * XXX don't copy the i/o pages.  this should probably be fixed.
277 	 */
278 	pcb2->pcb_ext = NULL;
279 
280 	/* Copy the LDT, if necessary. */
281 	mtx_lock_spin(&dt_lock);
282 	if (mdp2->md_ldt != NULL) {
283 		if (flags & RFMEM) {
284 			mdp2->md_ldt->ldt_refcnt++;
285 		} else {
286 			mdp2->md_ldt = user_ldt_alloc(mdp2,
287 			    mdp2->md_ldt->ldt_len);
288 			if (mdp2->md_ldt == NULL)
289 				panic("could not copy LDT");
290 		}
291 	}
292 	mtx_unlock_spin(&dt_lock);
293 
294 	/*
295 	 * Now, cpu_switch() can schedule the new process.
296 	 * pcb_esp is loaded pointing to the cpu_switch() stack frame
297 	 * containing the return address when exiting cpu_switch.
298 	 * This will normally be to fork_trampoline(), which will have
299 	 * %ebx loaded with the new proc's pointer.  fork_trampoline()
300 	 * will set up a stack to call fork_return(p, frame); to complete
301 	 * the return to user-mode.
302 	 */
303 }
304 
305 /*
306  * Intercept the return address from a freshly forked process that has NOT
307  * been scheduled yet.
308  *
309  * This is needed to make kernel threads stay in kernel mode.
310  */
311 void
312 cpu_fork_kthread_handler(struct thread *td, void (*func)(void *), void *arg)
313 {
314 	/*
315 	 * Note that the trap frame follows the args, so the function
316 	 * is really called like this:  func(arg, frame);
317 	 */
318 	td->td_pcb->pcb_esi = (int) func;	/* function */
319 	td->td_pcb->pcb_ebx = (int) arg;	/* first arg */
320 }
321 
322 void
323 cpu_exit(struct thread *td)
324 {
325 
326 	/*
327 	 * If this process has a custom LDT, release it.  Reset pc->pcb_gs
328 	 * and %gs before we free it in case they refer to an LDT entry.
329 	 */
330 	mtx_lock_spin(&dt_lock);
331 	if (td->td_proc->p_md.md_ldt) {
332 		td->td_pcb->pcb_gs = _udatasel;
333 		load_gs(_udatasel);
334 		user_ldt_free(td);
335 	} else
336 		mtx_unlock_spin(&dt_lock);
337 }
338 
339 void
340 cpu_thread_exit(struct thread *td)
341 {
342 
343 	critical_enter();
344 	if (td == PCPU_GET(fpcurthread))
345 		npxdrop();
346 	critical_exit();
347 
348 	/* Disable any hardware breakpoints. */
349 	if (td->td_pcb->pcb_flags & PCB_DBREGS) {
350 		reset_dbregs();
351 		td->td_pcb->pcb_flags &= ~PCB_DBREGS;
352 	}
353 }
354 
355 void
356 cpu_thread_clean(struct thread *td)
357 {
358 	struct pcb *pcb;
359 
360 	pcb = td->td_pcb;
361 	if (pcb->pcb_ext != NULL) {
362 		/* if (pcb->pcb_ext->ext_refcount-- == 1) ?? */
363 		/*
364 		 * XXX do we need to move the TSS off the allocated pages
365 		 * before freeing them?  (not done here)
366 		 */
367 		pmap_trm_free(pcb->pcb_ext, ctob(IOPAGES + 1));
368 		pcb->pcb_ext = NULL;
369 	}
370 }
371 
372 void
373 cpu_thread_swapin(struct thread *td)
374 {
375 }
376 
377 void
378 cpu_thread_swapout(struct thread *td)
379 {
380 }
381 
382 void
383 cpu_thread_alloc(struct thread *td)
384 {
385 	struct pcb *pcb;
386 	struct xstate_hdr *xhdr;
387 
388 	td->td_pcb = pcb = get_pcb_td(td);
389 	td->td_frame = (struct trapframe *)((caddr_t)pcb -
390 	    VM86_STACK_SPACE) - 1;
391 	pcb->pcb_ext = NULL;
392 	pcb->pcb_save = get_pcb_user_save_pcb(pcb);
393 	if (use_xsave) {
394 		xhdr = (struct xstate_hdr *)(pcb->pcb_save + 1);
395 		bzero(xhdr, sizeof(*xhdr));
396 		xhdr->xstate_bv = xsave_mask;
397 	}
398 }
399 
400 void
401 cpu_thread_free(struct thread *td)
402 {
403 
404 	cpu_thread_clean(td);
405 }
406 
407 bool
408 cpu_exec_vmspace_reuse(struct proc *p __unused, vm_map_t map __unused)
409 {
410 
411 	return (true);
412 }
413 
414 int
415 cpu_procctl(struct thread *td __unused, int idtype __unused, id_t id __unused,
416     int com __unused, void *data __unused)
417 {
418 
419 	return (EINVAL);
420 }
421 
422 void
423 cpu_set_syscall_retval(struct thread *td, int error)
424 {
425 
426 	switch (error) {
427 	case 0:
428 		td->td_frame->tf_eax = td->td_retval[0];
429 		td->td_frame->tf_edx = td->td_retval[1];
430 		td->td_frame->tf_eflags &= ~PSL_C;
431 		break;
432 
433 	case ERESTART:
434 		/*
435 		 * Reconstruct pc, assuming lcall $X,y is 7 bytes, int
436 		 * 0x80 is 2 bytes. We saved this in tf_err.
437 		 */
438 		td->td_frame->tf_eip -= td->td_frame->tf_err;
439 		break;
440 
441 	case EJUSTRETURN:
442 		break;
443 
444 	default:
445 		td->td_frame->tf_eax = error;
446 		td->td_frame->tf_eflags |= PSL_C;
447 		break;
448 	}
449 }
450 
451 /*
452  * Initialize machine state, mostly pcb and trap frame for a new
453  * thread, about to return to userspace.  Put enough state in the new
454  * thread's PCB to get it to go back to the fork_return(), which
455  * finalizes the thread state and handles peculiarities of the first
456  * return to userspace for the new thread.
457  */
458 void
459 cpu_copy_thread(struct thread *td, struct thread *td0)
460 {
461 	copy_thread(td0, td);
462 
463 	/*
464 	 * Copy user general-purpose registers.
465 	 *
466 	 * Some of these registers are rewritten by cpu_set_upcall()
467 	 * and linux_set_upcall().
468 	 */
469 	bcopy(td0->td_frame, td->td_frame, sizeof(struct trapframe));
470 
471 	/* If the current thread has the trap bit set (i.e. a debugger had
472 	 * single stepped the process to the system call), we need to clear
473 	 * the trap flag from the new frame. Otherwise, the new thread will
474 	 * receive a (likely unexpected) SIGTRAP when it executes the first
475 	 * instruction after returning to userland.
476 	 */
477 	td->td_frame->tf_eflags &= ~PSL_T;
478 }
479 
480 /*
481  * Set that machine state for performing an upcall that starts
482  * the entry function with the given argument.
483  */
484 void
485 cpu_set_upcall(struct thread *td, void (*entry)(void *), void *arg,
486     stack_t *stack)
487 {
488 
489 	/*
490 	 * Do any extra cleaning that needs to be done.
491 	 * The thread may have optional components
492 	 * that are not present in a fresh thread.
493 	 * This may be a recycled thread so make it look
494 	 * as though it's newly allocated.
495 	 */
496 	cpu_thread_clean(td);
497 
498 	/*
499 	 * Set the trap frame to point at the beginning of the entry
500 	 * function.
501 	 */
502 	td->td_frame->tf_ebp = 0;
503 	td->td_frame->tf_esp =
504 	    (((int)stack->ss_sp + stack->ss_size - 4) & ~0x0f) - 4;
505 	td->td_frame->tf_eip = (int)entry;
506 
507 	/* Return address sentinel value to stop stack unwinding. */
508 	suword((void *)td->td_frame->tf_esp, 0);
509 
510 	/* Pass the argument to the entry point. */
511 	suword((void *)(td->td_frame->tf_esp + sizeof(void *)),
512 	    (int)arg);
513 }
514 
515 int
516 cpu_set_user_tls(struct thread *td, void *tls_base)
517 {
518 	struct segment_descriptor sd;
519 	uint32_t base;
520 
521 	/*
522 	 * Construct a descriptor and store it in the pcb for
523 	 * the next context switch.  Also store it in the gdt
524 	 * so that the load of tf_fs into %fs will activate it
525 	 * at return to userland.
526 	 */
527 	base = (uint32_t)tls_base;
528 	sd.sd_lobase = base & 0xffffff;
529 	sd.sd_hibase = (base >> 24) & 0xff;
530 	sd.sd_lolimit = 0xffff;	/* 4GB limit, wraps around */
531 	sd.sd_hilimit = 0xf;
532 	sd.sd_type  = SDT_MEMRWA;
533 	sd.sd_dpl   = SEL_UPL;
534 	sd.sd_p     = 1;
535 	sd.sd_xx    = 0;
536 	sd.sd_def32 = 1;
537 	sd.sd_gran  = 1;
538 	critical_enter();
539 	/* set %gs */
540 	td->td_pcb->pcb_gsd = sd;
541 	if (td == curthread) {
542 		PCPU_GET(fsgs_gdt)[1] = sd;
543 		load_gs(GSEL(GUGS_SEL, SEL_UPL));
544 	}
545 	critical_exit();
546 	return (0);
547 }
548 
549 /*
550  * Convert kernel VA to physical address
551  */
552 vm_paddr_t
553 kvtop(void *addr)
554 {
555 	vm_paddr_t pa;
556 
557 	pa = pmap_kextract((vm_offset_t)addr);
558 	if (pa == 0)
559 		panic("kvtop: zero page frame");
560 	return (pa);
561 }
562 
563 /*
564  * Get an sf_buf from the freelist.  May block if none are available.
565  */
566 void
567 sf_buf_map(struct sf_buf *sf, int flags)
568 {
569 
570 	pmap_sf_buf_map(sf);
571 #ifdef SMP
572 	sf_buf_shootdown(sf, flags);
573 #endif
574 }
575 
576 #ifdef SMP
577 static void
578 sf_buf_shootdown_curcpu_cb(pmap_t pmap __unused,
579     vm_offset_t addr1 __unused, vm_offset_t addr2 __unused)
580 {
581 }
582 
583 void
584 sf_buf_shootdown(struct sf_buf *sf, int flags)
585 {
586 	cpuset_t other_cpus;
587 	u_int cpuid;
588 
589 	sched_pin();
590 	cpuid = PCPU_GET(cpuid);
591 	if (!CPU_ISSET(cpuid, &sf->cpumask)) {
592 		CPU_SET(cpuid, &sf->cpumask);
593 		invlpg(sf->kva);
594 	}
595 	if ((flags & SFB_CPUPRIVATE) == 0) {
596 		other_cpus = all_cpus;
597 		CPU_CLR(cpuid, &other_cpus);
598 		CPU_ANDNOT(&other_cpus, &sf->cpumask);
599 		if (!CPU_EMPTY(&other_cpus)) {
600 			CPU_OR(&sf->cpumask, &other_cpus);
601 			smp_masked_invlpg(other_cpus, sf->kva, kernel_pmap,
602 			    sf_buf_shootdown_curcpu_cb);
603 		}
604 	}
605 	sched_unpin();
606 }
607 #endif
608 
609 /*
610  * MD part of sf_buf_free().
611  */
612 int
613 sf_buf_unmap(struct sf_buf *sf)
614 {
615 
616 	return (0);
617 }
618 
619 static void
620 sf_buf_invalidate(struct sf_buf *sf)
621 {
622 	vm_page_t m = sf->m;
623 
624 	/*
625 	 * Use pmap_qenter to update the pte for
626 	 * existing mapping, in particular, the PAT
627 	 * settings are recalculated.
628 	 */
629 	pmap_qenter(sf->kva, &m, 1);
630 	pmap_invalidate_cache_range(sf->kva, sf->kva + PAGE_SIZE);
631 }
632 
633 /*
634  * Invalidate the cache lines that may belong to the page, if
635  * (possibly old) mapping of the page by sf buffer exists.  Returns
636  * TRUE when mapping was found and cache invalidated.
637  */
638 boolean_t
639 sf_buf_invalidate_cache(vm_page_t m)
640 {
641 
642 	return (sf_buf_process_page(m, sf_buf_invalidate));
643 }
644 
645 /*
646  * Software interrupt handler for queued VM system processing.
647  */
648 void
649 swi_vm(void *dummy)
650 {
651 	if (busdma_swi_pending != 0)
652 		busdma_swi();
653 }
654 
655 /*
656  * Tell whether this address is in some physical memory region.
657  * Currently used by the kernel coredump code in order to avoid
658  * dumping the ``ISA memory hole'' which could cause indefinite hangs,
659  * or other unpredictable behaviour.
660  */
661 
662 int
663 is_physical_memory(vm_paddr_t addr)
664 {
665 
666 #ifdef DEV_ISA
667 	/* The ISA ``memory hole''. */
668 	if (addr >= 0xa0000 && addr < 0x100000)
669 		return 0;
670 #endif
671 
672 	/*
673 	 * stuff other tests for known memory-mapped devices (PCI?)
674 	 * here
675 	 */
676 
677 	return 1;
678 }
679