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/pioctl.h> 64 #include <sys/proc.h> 65 #include <sys/sysent.h> 66 #include <sys/sf_buf.h> 67 #include <sys/smp.h> 68 #include <sys/sched.h> 69 #include <sys/sysctl.h> 70 #include <sys/unistd.h> 71 #include <sys/vnode.h> 72 #include <sys/vmmeter.h> 73 74 #include <machine/cpu.h> 75 #include <machine/cputypes.h> 76 #include <machine/md_var.h> 77 #include <machine/pcb.h> 78 #include <machine/pcb_ext.h> 79 #include <machine/smp.h> 80 #include <machine/vm86.h> 81 82 #include <vm/vm.h> 83 #include <vm/vm_extern.h> 84 #include <vm/vm_kern.h> 85 #include <vm/vm_page.h> 86 #include <vm/vm_map.h> 87 #include <vm/vm_param.h> 88 89 #ifndef NSFBUFS 90 #define NSFBUFS (512 + maxusers * 16) 91 #endif 92 93 _Static_assert(OFFSETOF_CURTHREAD == offsetof(struct pcpu, pc_curthread), 94 "OFFSETOF_CURTHREAD does not correspond with offset of pc_curthread."); 95 _Static_assert(OFFSETOF_CURPCB == offsetof(struct pcpu, pc_curpcb), 96 "OFFSETOF_CURPCB does not correspond with offset of pc_curpcb."); 97 _Static_assert(__OFFSETOF_MONITORBUF == offsetof(struct pcpu, pc_monitorbuf), 98 "__OFFSETOF_MONITORBUF does not correspond with offset of pc_monitorbuf."); 99 100 union savefpu * 101 get_pcb_user_save_td(struct thread *td) 102 { 103 vm_offset_t p; 104 105 p = td->td_kstack + td->td_kstack_pages * PAGE_SIZE - 106 roundup2(cpu_max_ext_state_size, XSAVE_AREA_ALIGN); 107 KASSERT((p % XSAVE_AREA_ALIGN) == 0, ("Unaligned pcb_user_save area")); 108 return ((union savefpu *)p); 109 } 110 111 union savefpu * 112 get_pcb_user_save_pcb(struct pcb *pcb) 113 { 114 vm_offset_t p; 115 116 p = (vm_offset_t)(pcb + 1); 117 return ((union savefpu *)p); 118 } 119 120 struct pcb * 121 get_pcb_td(struct thread *td) 122 { 123 vm_offset_t p; 124 125 p = td->td_kstack + td->td_kstack_pages * PAGE_SIZE - 126 roundup2(cpu_max_ext_state_size, XSAVE_AREA_ALIGN) - 127 sizeof(struct pcb); 128 return ((struct pcb *)p); 129 } 130 131 void * 132 alloc_fpusave(int flags) 133 { 134 void *res; 135 struct savefpu_ymm *sf; 136 137 res = malloc(cpu_max_ext_state_size, M_DEVBUF, flags); 138 if (use_xsave) { 139 sf = (struct savefpu_ymm *)res; 140 bzero(&sf->sv_xstate.sx_hd, sizeof(sf->sv_xstate.sx_hd)); 141 sf->sv_xstate.sx_hd.xstate_bv = xsave_mask; 142 } 143 return (res); 144 } 145 /* 146 * Finish a fork operation, with process p2 nearly set up. 147 * Copy and update the pcb, set up the stack so that the child 148 * ready to run and return to user mode. 149 */ 150 void 151 cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags) 152 { 153 struct proc *p1; 154 struct pcb *pcb2; 155 struct mdproc *mdp2; 156 157 p1 = td1->td_proc; 158 if ((flags & RFPROC) == 0) { 159 if ((flags & RFMEM) == 0) { 160 /* unshare user LDT */ 161 struct mdproc *mdp1 = &p1->p_md; 162 struct proc_ldt *pldt, *pldt1; 163 164 mtx_lock_spin(&dt_lock); 165 if ((pldt1 = mdp1->md_ldt) != NULL && 166 pldt1->ldt_refcnt > 1) { 167 pldt = user_ldt_alloc(mdp1, pldt1->ldt_len); 168 if (pldt == NULL) 169 panic("could not copy LDT"); 170 mdp1->md_ldt = pldt; 171 set_user_ldt(mdp1); 172 user_ldt_deref(pldt1); 173 } else 174 mtx_unlock_spin(&dt_lock); 175 } 176 return; 177 } 178 179 /* Ensure that td1's pcb is up to date. */ 180 if (td1 == curthread) 181 td1->td_pcb->pcb_gs = rgs(); 182 critical_enter(); 183 if (PCPU_GET(fpcurthread) == td1) 184 npxsave(td1->td_pcb->pcb_save); 185 critical_exit(); 186 187 /* Point the pcb to the top of the stack */ 188 pcb2 = get_pcb_td(td2); 189 td2->td_pcb = pcb2; 190 191 /* Copy td1's pcb */ 192 bcopy(td1->td_pcb, pcb2, sizeof(*pcb2)); 193 194 /* Properly initialize pcb_save */ 195 pcb2->pcb_save = get_pcb_user_save_pcb(pcb2); 196 bcopy(get_pcb_user_save_td(td1), get_pcb_user_save_pcb(pcb2), 197 cpu_max_ext_state_size); 198 199 /* Point mdproc and then copy over td1's contents */ 200 mdp2 = &p2->p_md; 201 bcopy(&p1->p_md, mdp2, sizeof(*mdp2)); 202 203 /* 204 * Create a new fresh stack for the new process. 205 * Copy the trap frame for the return to user mode as if from a 206 * syscall. This copies most of the user mode register values. 207 * The -VM86_STACK_SPACE (-16) is so we can expand the trapframe 208 * if we go to vm86. 209 */ 210 td2->td_frame = (struct trapframe *)((caddr_t)td2->td_pcb - 211 VM86_STACK_SPACE) - 1; 212 bcopy(td1->td_frame, td2->td_frame, sizeof(struct trapframe)); 213 214 td2->td_frame->tf_eax = 0; /* Child returns zero */ 215 td2->td_frame->tf_eflags &= ~PSL_C; /* success */ 216 td2->td_frame->tf_edx = 1; 217 218 /* 219 * If the parent process has the trap bit set (i.e. a debugger had 220 * single stepped the process to the system call), we need to clear 221 * the trap flag from the new frame unless the debugger had set PF_FORK 222 * on the parent. Otherwise, the child will receive a (likely 223 * unexpected) SIGTRAP when it executes the first instruction after 224 * returning to userland. 225 */ 226 if ((p1->p_pfsflags & PF_FORK) == 0) 227 td2->td_frame->tf_eflags &= ~PSL_T; 228 229 /* 230 * Set registers for trampoline to user mode. Leave space for the 231 * return address on stack. These are the kernel mode register values. 232 */ 233 pcb2->pcb_cr3 = pmap_get_cr3(vmspace_pmap(p2->p_vmspace)); 234 pcb2->pcb_edi = 0; 235 pcb2->pcb_esi = (int)fork_return; /* fork_trampoline argument */ 236 pcb2->pcb_ebp = 0; 237 pcb2->pcb_esp = (int)td2->td_frame - sizeof(void *); 238 pcb2->pcb_ebx = (int)td2; /* fork_trampoline argument */ 239 pcb2->pcb_eip = (int)fork_trampoline + setidt_disp; 240 /*- 241 * pcb2->pcb_dr*: cloned above. 242 * pcb2->pcb_savefpu: cloned above. 243 * pcb2->pcb_flags: cloned above. 244 * pcb2->pcb_onfault: cloned above (always NULL here?). 245 * pcb2->pcb_gs: cloned above. 246 * pcb2->pcb_ext: cleared below. 247 */ 248 249 /* 250 * XXX don't copy the i/o pages. this should probably be fixed. 251 */ 252 pcb2->pcb_ext = 0; 253 254 /* Copy the LDT, if necessary. */ 255 mtx_lock_spin(&dt_lock); 256 if (mdp2->md_ldt != NULL) { 257 if (flags & RFMEM) { 258 mdp2->md_ldt->ldt_refcnt++; 259 } else { 260 mdp2->md_ldt = user_ldt_alloc(mdp2, 261 mdp2->md_ldt->ldt_len); 262 if (mdp2->md_ldt == NULL) 263 panic("could not copy LDT"); 264 } 265 } 266 mtx_unlock_spin(&dt_lock); 267 268 /* Setup to release spin count in fork_exit(). */ 269 td2->td_md.md_spinlock_count = 1; 270 td2->td_md.md_saved_flags = PSL_KERNEL | PSL_I; 271 272 /* 273 * Now, cpu_switch() can schedule the new process. 274 * pcb_esp is loaded pointing to the cpu_switch() stack frame 275 * containing the return address when exiting cpu_switch. 276 * This will normally be to fork_trampoline(), which will have 277 * %ebx loaded with the new proc's pointer. fork_trampoline() 278 * will set up a stack to call fork_return(p, frame); to complete 279 * the return to user-mode. 280 */ 281 } 282 283 /* 284 * Intercept the return address from a freshly forked process that has NOT 285 * been scheduled yet. 286 * 287 * This is needed to make kernel threads stay in kernel mode. 288 */ 289 void 290 cpu_fork_kthread_handler(struct thread *td, void (*func)(void *), void *arg) 291 { 292 /* 293 * Note that the trap frame follows the args, so the function 294 * is really called like this: func(arg, frame); 295 */ 296 td->td_pcb->pcb_esi = (int) func; /* function */ 297 td->td_pcb->pcb_ebx = (int) arg; /* first arg */ 298 } 299 300 void 301 cpu_exit(struct thread *td) 302 { 303 304 /* 305 * If this process has a custom LDT, release it. Reset pc->pcb_gs 306 * and %gs before we free it in case they refer to an LDT entry. 307 */ 308 mtx_lock_spin(&dt_lock); 309 if (td->td_proc->p_md.md_ldt) { 310 td->td_pcb->pcb_gs = _udatasel; 311 load_gs(_udatasel); 312 user_ldt_free(td); 313 } else 314 mtx_unlock_spin(&dt_lock); 315 } 316 317 void 318 cpu_thread_exit(struct thread *td) 319 { 320 321 critical_enter(); 322 if (td == PCPU_GET(fpcurthread)) 323 npxdrop(); 324 critical_exit(); 325 326 /* Disable any hardware breakpoints. */ 327 if (td->td_pcb->pcb_flags & PCB_DBREGS) { 328 reset_dbregs(); 329 td->td_pcb->pcb_flags &= ~PCB_DBREGS; 330 } 331 } 332 333 void 334 cpu_thread_clean(struct thread *td) 335 { 336 struct pcb *pcb; 337 338 pcb = td->td_pcb; 339 if (pcb->pcb_ext != NULL) { 340 /* if (pcb->pcb_ext->ext_refcount-- == 1) ?? */ 341 /* 342 * XXX do we need to move the TSS off the allocated pages 343 * before freeing them? (not done here) 344 */ 345 pmap_trm_free(pcb->pcb_ext, ctob(IOPAGES + 1)); 346 pcb->pcb_ext = NULL; 347 } 348 } 349 350 void 351 cpu_thread_swapin(struct thread *td) 352 { 353 } 354 355 void 356 cpu_thread_swapout(struct thread *td) 357 { 358 } 359 360 void 361 cpu_thread_alloc(struct thread *td) 362 { 363 struct pcb *pcb; 364 struct xstate_hdr *xhdr; 365 366 td->td_pcb = pcb = get_pcb_td(td); 367 td->td_frame = (struct trapframe *)((caddr_t)pcb - 368 VM86_STACK_SPACE) - 1; 369 pcb->pcb_ext = NULL; 370 pcb->pcb_save = get_pcb_user_save_pcb(pcb); 371 if (use_xsave) { 372 xhdr = (struct xstate_hdr *)(pcb->pcb_save + 1); 373 bzero(xhdr, sizeof(*xhdr)); 374 xhdr->xstate_bv = xsave_mask; 375 } 376 } 377 378 void 379 cpu_thread_free(struct thread *td) 380 { 381 382 cpu_thread_clean(td); 383 } 384 385 bool 386 cpu_exec_vmspace_reuse(struct proc *p __unused, vm_map_t map __unused) 387 { 388 389 return (true); 390 } 391 392 int 393 cpu_procctl(struct thread *td __unused, int idtype __unused, id_t id __unused, 394 int com __unused, void *data __unused) 395 { 396 397 return (EINVAL); 398 } 399 400 void 401 cpu_set_syscall_retval(struct thread *td, int error) 402 { 403 404 switch (error) { 405 case 0: 406 td->td_frame->tf_eax = td->td_retval[0]; 407 td->td_frame->tf_edx = td->td_retval[1]; 408 td->td_frame->tf_eflags &= ~PSL_C; 409 break; 410 411 case ERESTART: 412 /* 413 * Reconstruct pc, assuming lcall $X,y is 7 bytes, int 414 * 0x80 is 2 bytes. We saved this in tf_err. 415 */ 416 td->td_frame->tf_eip -= td->td_frame->tf_err; 417 break; 418 419 case EJUSTRETURN: 420 break; 421 422 default: 423 td->td_frame->tf_eax = SV_ABI_ERRNO(td->td_proc, error); 424 td->td_frame->tf_eflags |= PSL_C; 425 break; 426 } 427 } 428 429 /* 430 * Initialize machine state, mostly pcb and trap frame for a new 431 * thread, about to return to userspace. Put enough state in the new 432 * thread's PCB to get it to go back to the fork_return(), which 433 * finalizes the thread state and handles peculiarities of the first 434 * return to userspace for the new thread. 435 */ 436 void 437 cpu_copy_thread(struct thread *td, struct thread *td0) 438 { 439 struct pcb *pcb2; 440 441 /* Point the pcb to the top of the stack. */ 442 pcb2 = td->td_pcb; 443 444 /* 445 * Copy the upcall pcb. This loads kernel regs. 446 * Those not loaded individually below get their default 447 * values here. 448 */ 449 bcopy(td0->td_pcb, pcb2, sizeof(*pcb2)); 450 pcb2->pcb_flags &= ~(PCB_NPXINITDONE | PCB_NPXUSERINITDONE | 451 PCB_KERNNPX); 452 pcb2->pcb_save = get_pcb_user_save_pcb(pcb2); 453 bcopy(get_pcb_user_save_td(td0), pcb2->pcb_save, 454 cpu_max_ext_state_size); 455 456 /* 457 * Create a new fresh stack for the new thread. 458 */ 459 bcopy(td0->td_frame, td->td_frame, sizeof(struct trapframe)); 460 461 /* If the current thread has the trap bit set (i.e. a debugger had 462 * single stepped the process to the system call), we need to clear 463 * the trap flag from the new frame. Otherwise, the new thread will 464 * receive a (likely unexpected) SIGTRAP when it executes the first 465 * instruction after returning to userland. 466 */ 467 td->td_frame->tf_eflags &= ~PSL_T; 468 469 /* 470 * Set registers for trampoline to user mode. Leave space for the 471 * return address on stack. These are the kernel mode register values. 472 */ 473 pcb2->pcb_edi = 0; 474 pcb2->pcb_esi = (int)fork_return; /* trampoline arg */ 475 pcb2->pcb_ebp = 0; 476 pcb2->pcb_esp = (int)td->td_frame - sizeof(void *); /* trampoline arg */ 477 pcb2->pcb_ebx = (int)td; /* trampoline arg */ 478 pcb2->pcb_eip = (int)fork_trampoline + setidt_disp; 479 pcb2->pcb_gs = rgs(); 480 /* 481 * If we didn't copy the pcb, we'd need to do the following registers: 482 * pcb2->pcb_cr3: cloned above. 483 * pcb2->pcb_dr*: cloned above. 484 * pcb2->pcb_savefpu: cloned above. 485 * pcb2->pcb_flags: cloned above. 486 * pcb2->pcb_onfault: cloned above (always NULL here?). 487 * pcb2->pcb_gs: cloned above. 488 * pcb2->pcb_ext: cleared below. 489 */ 490 pcb2->pcb_ext = NULL; 491 492 /* Setup to release spin count in fork_exit(). */ 493 td->td_md.md_spinlock_count = 1; 494 td->td_md.md_saved_flags = PSL_KERNEL | PSL_I; 495 } 496 497 /* 498 * Set that machine state for performing an upcall that starts 499 * the entry function with the given argument. 500 */ 501 void 502 cpu_set_upcall(struct thread *td, void (*entry)(void *), void *arg, 503 stack_t *stack) 504 { 505 506 /* 507 * Do any extra cleaning that needs to be done. 508 * The thread may have optional components 509 * that are not present in a fresh thread. 510 * This may be a recycled thread so make it look 511 * as though it's newly allocated. 512 */ 513 cpu_thread_clean(td); 514 515 /* 516 * Set the trap frame to point at the beginning of the entry 517 * function. 518 */ 519 td->td_frame->tf_ebp = 0; 520 td->td_frame->tf_esp = 521 (((int)stack->ss_sp + stack->ss_size - 4) & ~0x0f) - 4; 522 td->td_frame->tf_eip = (int)entry; 523 524 /* Return address sentinel value to stop stack unwinding. */ 525 suword((void *)td->td_frame->tf_esp, 0); 526 527 /* Pass the argument to the entry point. */ 528 suword((void *)(td->td_frame->tf_esp + sizeof(void *)), 529 (int)arg); 530 } 531 532 int 533 cpu_set_user_tls(struct thread *td, void *tls_base) 534 { 535 struct segment_descriptor sd; 536 uint32_t base; 537 538 /* 539 * Construct a descriptor and store it in the pcb for 540 * the next context switch. Also store it in the gdt 541 * so that the load of tf_fs into %fs will activate it 542 * at return to userland. 543 */ 544 base = (uint32_t)tls_base; 545 sd.sd_lobase = base & 0xffffff; 546 sd.sd_hibase = (base >> 24) & 0xff; 547 sd.sd_lolimit = 0xffff; /* 4GB limit, wraps around */ 548 sd.sd_hilimit = 0xf; 549 sd.sd_type = SDT_MEMRWA; 550 sd.sd_dpl = SEL_UPL; 551 sd.sd_p = 1; 552 sd.sd_xx = 0; 553 sd.sd_def32 = 1; 554 sd.sd_gran = 1; 555 critical_enter(); 556 /* set %gs */ 557 td->td_pcb->pcb_gsd = sd; 558 if (td == curthread) { 559 PCPU_GET(fsgs_gdt)[1] = sd; 560 load_gs(GSEL(GUGS_SEL, SEL_UPL)); 561 } 562 critical_exit(); 563 return (0); 564 } 565 566 /* 567 * Convert kernel VA to physical address 568 */ 569 vm_paddr_t 570 kvtop(void *addr) 571 { 572 vm_paddr_t pa; 573 574 pa = pmap_kextract((vm_offset_t)addr); 575 if (pa == 0) 576 panic("kvtop: zero page frame"); 577 return (pa); 578 } 579 580 /* 581 * Get an sf_buf from the freelist. May block if none are available. 582 */ 583 void 584 sf_buf_map(struct sf_buf *sf, int flags) 585 { 586 587 pmap_sf_buf_map(sf); 588 #ifdef SMP 589 sf_buf_shootdown(sf, flags); 590 #endif 591 } 592 593 #ifdef SMP 594 void 595 sf_buf_shootdown(struct sf_buf *sf, int flags) 596 { 597 cpuset_t other_cpus; 598 u_int cpuid; 599 600 sched_pin(); 601 cpuid = PCPU_GET(cpuid); 602 if (!CPU_ISSET(cpuid, &sf->cpumask)) { 603 CPU_SET(cpuid, &sf->cpumask); 604 invlpg(sf->kva); 605 } 606 if ((flags & SFB_CPUPRIVATE) == 0) { 607 other_cpus = all_cpus; 608 CPU_CLR(cpuid, &other_cpus); 609 CPU_NAND(&other_cpus, &sf->cpumask); 610 if (!CPU_EMPTY(&other_cpus)) { 611 CPU_OR(&sf->cpumask, &other_cpus); 612 smp_masked_invlpg(other_cpus, sf->kva, kernel_pmap); 613 } 614 } 615 sched_unpin(); 616 } 617 #endif 618 619 /* 620 * MD part of sf_buf_free(). 621 */ 622 int 623 sf_buf_unmap(struct sf_buf *sf) 624 { 625 626 return (0); 627 } 628 629 static void 630 sf_buf_invalidate(struct sf_buf *sf) 631 { 632 vm_page_t m = sf->m; 633 634 /* 635 * Use pmap_qenter to update the pte for 636 * existing mapping, in particular, the PAT 637 * settings are recalculated. 638 */ 639 pmap_qenter(sf->kva, &m, 1); 640 pmap_invalidate_cache_range(sf->kva, sf->kva + PAGE_SIZE); 641 } 642 643 /* 644 * Invalidate the cache lines that may belong to the page, if 645 * (possibly old) mapping of the page by sf buffer exists. Returns 646 * TRUE when mapping was found and cache invalidated. 647 */ 648 boolean_t 649 sf_buf_invalidate_cache(vm_page_t m) 650 { 651 652 return (sf_buf_process_page(m, sf_buf_invalidate)); 653 } 654 655 /* 656 * Software interrupt handler for queued VM system processing. 657 */ 658 void 659 swi_vm(void *dummy) 660 { 661 if (busdma_swi_pending != 0) 662 busdma_swi(); 663 } 664 665 /* 666 * Tell whether this address is in some physical memory region. 667 * Currently used by the kernel coredump code in order to avoid 668 * dumping the ``ISA memory hole'' which could cause indefinite hangs, 669 * or other unpredictable behaviour. 670 */ 671 672 int 673 is_physical_memory(vm_paddr_t addr) 674 { 675 676 #ifdef DEV_ISA 677 /* The ISA ``memory hole''. */ 678 if (addr >= 0xa0000 && addr < 0x100000) 679 return 0; 680 #endif 681 682 /* 683 * stuff other tests for known memory-mapped devices (PCI?) 684 * here 685 */ 686 687 return 1; 688 } 689