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1.1     ! root        1: /* 
        !             2:  * Mach Operating System
        !             3:  * Copyright (c) 1991,1990,1989, 1988 Carnegie Mellon University
        !             4:  * All Rights Reserved.
        !             5:  * 
        !             6:  * Permission to use, copy, modify and distribute this software and its
        !             7:  * documentation is hereby granted, provided that both the copyright
        !             8:  * notice and this permission notice appear in all copies of the
        !             9:  * software, derivative works or modified versions, and any portions
        !            10:  * thereof, and that both notices appear in supporting documentation.
        !            11:  * 
        !            12:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
        !            13:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
        !            14:  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            15:  * 
        !            16:  * Carnegie Mellon requests users of this software to return to
        !            17:  * 
        !            18:  *  Software Distribution Coordinator  or  [email protected]
        !            19:  *  School of Computer Science
        !            20:  *  Carnegie Mellon University
        !            21:  *  Pittsburgh PA 15213-3890
        !            22:  * 
        !            23:  * any improvements or extensions that they make and grant Carnegie Mellon
        !            24:  * the rights to redistribute these changes.
        !            25:  */
        !            26: /*
        !            27:  *     File:   model_dep.c
        !            28:  *     Author: Avadis Tevanian, Jr., Michael Wayne Young
        !            29:  *
        !            30:  *     Copyright (C) 1986, Avadis Tevanian, Jr., Michael Wayne Young
        !            31:  *
        !            32:  *     Basic initialization for I386 - ISA bus machines.
        !            33:  */
        !            34: 
        !            35: #include <platforms.h>
        !            36: #include <mach_kdb.h>
        !            37: 
        !            38: #include <mach/vm_param.h>
        !            39: #include <mach/vm_prot.h>
        !            40: #include <mach/machine.h>
        !            41: #include <mach/machine/multiboot.h>
        !            42: 
        !            43: #include "vm_param.h"
        !            44: #include <kern/time_out.h>
        !            45: #include <sys/time.h>
        !            46: #include <vm/vm_page.h>
        !            47: #include <i386/machspl.h>
        !            48: #include <i386/pmap.h>
        !            49: #include "proc_reg.h"
        !            50: 
        !            51: /* Location of the kernel's symbol table.
        !            52:    Both of these are 0 if none is available.  */
        !            53: #if MACH_KDB
        !            54: static vm_offset_t kern_sym_start, kern_sym_end;
        !            55: #else
        !            56: #define kern_sym_start 0
        !            57: #define kern_sym_end   0
        !            58: #endif
        !            59: 
        !            60: /* These indicate the total extent of physical memory addresses we're using.
        !            61:    They are page-aligned.  */
        !            62: vm_offset_t phys_first_addr = 0;
        !            63: vm_offset_t phys_last_addr;
        !            64: 
        !            65: /* Virtual address of physical memory, for the kvtophys/phystokv macros.  */
        !            66: vm_offset_t phys_mem_va;
        !            67: 
        !            68: struct multiboot_info *boot_info;
        !            69: 
        !            70: /* Command line supplied to kernel.  */
        !            71: char *kernel_cmdline = "";
        !            72: 
        !            73: /* This is used for memory initialization:
        !            74:    it gets bumped up through physical memory
        !            75:    that exists and is not occupied by boot gunk.
        !            76:    It is not necessarily page-aligned.  */
        !            77: static vm_offset_t avail_next = 0x1000; /* XX end of BIOS data area */
        !            78: 
        !            79: /* Possibly overestimated amount of available memory
        !            80:    still remaining to be handed to the VM system.  */
        !            81: static vm_size_t avail_remaining;
        !            82: 
        !            83: /* Configuration parameter:
        !            84:    if zero, only use physical memory in the low 16MB of addresses.
        !            85:    Only SCSI still has DMA problems.  */
        !            86: #ifdef LINUX_DEV
        !            87: int use_all_mem = 1;
        !            88: #else
        !            89: #include "nscsi.h"
        !            90: #if    NSCSI > 0
        !            91: int use_all_mem = 0;
        !            92: #else
        !            93: int use_all_mem = 1;
        !            94: #endif
        !            95: #endif
        !            96: 
        !            97: extern char    version[];
        !            98: 
        !            99: extern void    setup_main();
        !           100: 
        !           101: void           inittodr();     /* forward */
        !           102: 
        !           103: int            rebootflag = 0; /* exported to kdintr */
        !           104: 
        !           105: /* XX interrupt stack pointer and highwater mark, for locore.S.  */
        !           106: vm_offset_t int_stack_top, int_stack_high;
        !           107: 
        !           108: #ifdef LINUX_DEV
        !           109: extern void linux_init(void);
        !           110: #endif
        !           111: 
        !           112: /*
        !           113:  * Find devices.  The system is alive.
        !           114:  */
        !           115: void machine_init()
        !           116: {
        !           117:        /*
        !           118:         * Initialize the console.
        !           119:         */
        !           120:        cninit();
        !           121: 
        !           122:        /*
        !           123:         * Set up to use floating point.
        !           124:         */
        !           125:        init_fpu();
        !           126: 
        !           127: #ifdef LINUX_DEV
        !           128:        /*
        !           129:         * Initialize Linux drivers.
        !           130:         */
        !           131:        linux_init();
        !           132: #endif
        !           133: 
        !           134:        /*
        !           135:         * Find the devices
        !           136:         */
        !           137:        probeio();
        !           138: 
        !           139:        /*
        !           140:         * Get the time
        !           141:         */
        !           142:        inittodr();
        !           143: 
        !           144:        /*
        !           145:         * Tell the BIOS not to clear and test memory.
        !           146:         */
        !           147:        *(unsigned short *)phystokv(0x472) = 0x1234;
        !           148: 
        !           149:        /*
        !           150:         * Unmap page 0 to trap NULL references.
        !           151:         */
        !           152:        pmap_unmap_page_zero();
        !           153: }
        !           154: 
        !           155: /*
        !           156:  * Halt a cpu.
        !           157:  */
        !           158: halt_cpu()
        !           159: {
        !           160:        asm volatile("cli");
        !           161:        while(1);
        !           162: }
        !           163: 
        !           164: /*
        !           165:  * Halt the system or reboot.
        !           166:  */
        !           167: halt_all_cpus(reboot)
        !           168:        boolean_t       reboot;
        !           169: {
        !           170:        if (reboot) {
        !           171:            kdreboot();
        !           172:        }
        !           173:        else {
        !           174:            rebootflag = 1;
        !           175:            printf("In tight loop: hit ctl-alt-del to reboot\n");
        !           176:            (void) spl0();
        !           177:        }
        !           178:        for (;;)
        !           179:            continue;
        !           180: }
        !           181: 
        !           182: void exit(int rc)
        !           183: {
        !           184:        halt_all_cpus(0);
        !           185: }
        !           186: 
        !           187: void db_reset_cpu()
        !           188: {
        !           189:        halt_all_cpus(1);
        !           190: }
        !           191: 
        !           192: 
        !           193: /*
        !           194:  * Compute physical memory size and other parameters.
        !           195:  */
        !           196: void
        !           197: mem_size_init()
        !           198: {
        !           199:        /* Physical memory on all PCs starts at physical address 0.
        !           200:           XX make it a constant.  */
        !           201:        phys_first_addr = 0;
        !           202: 
        !           203:        phys_last_addr = 0x100000 + (boot_info->mem_upper * 0x400);
        !           204:        avail_remaining
        !           205:          = phys_last_addr - (0x100000 - (boot_info->mem_lower * 0x400)
        !           206:                              - 0x1000);
        !           207: 
        !           208:        printf("AT386 boot: physical memory from 0x%x to 0x%x\n",
        !           209:               phys_first_addr, phys_last_addr);
        !           210: 
        !           211:        if ((!use_all_mem) && phys_last_addr > 16 * 1024*1024) {
        !           212:                printf("** Limiting useable memory to 16 Meg to avoid DMA problems.\n");
        !           213:                /* This is actually enforced below, in init_alloc_aligned.  */
        !           214:        }
        !           215: 
        !           216:        phys_first_addr = round_page(phys_first_addr);
        !           217:        phys_last_addr = trunc_page(phys_last_addr);
        !           218: }
        !           219: 
        !           220: /*
        !           221:  * Basic PC VM initialization.
        !           222:  * Turns on paging and changes the kernel segments to use high linear addresses.
        !           223:  */
        !           224: i386at_init()
        !           225: {
        !           226:        /* XXX move to intel/pmap.h */
        !           227:        extern pt_entry_t *kernel_page_dir;
        !           228: 
        !           229:        /*
        !           230:         * Initialize the PIC prior to any possible call to an spl.
        !           231:         */
        !           232:        picinit();
        !           233: 
        !           234:        /*
        !           235:         * Find memory size parameters.
        !           236:         */
        !           237:        mem_size_init();
        !           238: 
        !           239:        /*
        !           240:         *      Initialize kernel physical map, mapping the
        !           241:         *      region from loadpt to avail_start.
        !           242:         *      Kernel virtual address starts at VM_KERNEL_MIN_ADDRESS.
        !           243:         *      XXX make the BIOS page (page 0) read-only.
        !           244:         */
        !           245:        pmap_bootstrap();
        !           246: 
        !           247:        /*
        !           248:         * Turn paging on.
        !           249:         * We'll have to temporarily install a direct mapping
        !           250:         * between physical memory and low linear memory,
        !           251:         * until we start using our new kernel segment descriptors.
        !           252:         * One page table (4MB) should do the trick.
        !           253:         * Also, set the WP bit so that on 486 or better processors
        !           254:         * page-level write protection works in kernel mode.
        !           255:         */
        !           256:        kernel_page_dir[lin2pdenum(0)] =
        !           257:                kernel_page_dir[lin2pdenum(LINEAR_MIN_KERNEL_ADDRESS)];
        !           258:        set_cr3((unsigned)kernel_page_dir);
        !           259:        set_cr0(get_cr0() | CR0_PG | CR0_WP);
        !           260:        flush_instr_queue();
        !           261: 
        !           262:        /*
        !           263:         * Initialize and activate the real i386 protected-mode structures.
        !           264:         */
        !           265:        gdt_init();
        !           266:        idt_init();
        !           267:        int_init();
        !           268:        ldt_init();
        !           269:        ktss_init();
        !           270: 
        !           271:        /* Get rid of the temporary direct mapping and flush it out of the TLB.  */
        !           272:        kernel_page_dir[lin2pdenum(0)] = 0;
        !           273:        set_cr3((unsigned)kernel_page_dir);
        !           274: 
        !           275: 
        !           276: 
        !           277:        /* XXX We'll just use the initialization stack we're already running on
        !           278:           as the interrupt stack for now.  Later this will have to change,
        !           279:           because the init stack will get freed after bootup.  */
        !           280:        asm("movl %%esp,%0" : "=m" (int_stack_top));
        !           281: 
        !           282:        /* Interrupt stacks are allocated in physical memory,
        !           283:           while kernel stacks are allocated in kernel virtual memory,
        !           284:           so phys_last_addr serves as a convenient dividing point.  */
        !           285:        int_stack_high = phys_last_addr;
        !           286: }
        !           287: 
        !           288: /*
        !           289:  *     C boot entrypoint - called by boot_entry in boothdr.S.
        !           290:  *     Running in 32-bit flat mode, but without paging yet.
        !           291:  */
        !           292: void c_boot_entry(vm_offset_t bi)
        !           293: {
        !           294:        /* Stash the boot_image_info pointer.  */
        !           295:        boot_info = (struct multiboot_info*)phystokv(bi);
        !           296: 
        !           297:        /* XXX we currently assume phys_mem_va is always 0 here -
        !           298:           if it isn't, we must tweak the pointers in the boot_info.  */
        !           299: 
        !           300:        /* Before we do _anything_ else, print the hello message.
        !           301:           If there are no initialized console devices yet,
        !           302:           it will be stored and printed at the first opportunity.  */
        !           303:        printf(version);
        !           304:        printf("\n");
        !           305: 
        !           306:        /* Find the kernel command line, if there is one.  */
        !           307:        if (boot_info->flags & MULTIBOOT_CMDLINE)
        !           308:                kernel_cmdline = (char*)phystokv(boot_info->cmdline);
        !           309: 
        !           310: #if    MACH_KDB
        !           311:        /*
        !           312:         * Locate the kernel's symbol table, if the boot loader provided it.
        !           313:         * We need to do this before i386at_init()
        !           314:         * so that the symbol table's memory won't be stomped on.
        !           315:         */
        !           316:        if ((boot_info->flags & MULTIBOOT_AOUT_SYMS)
        !           317:            && boot_info->syms.a.addr)
        !           318:        {
        !           319:                vm_size_t symtab_size, strtab_size;
        !           320: 
        !           321:                kern_sym_start = (vm_offset_t)phystokv(boot_info->syms.a.addr);
        !           322:                symtab_size = (vm_offset_t)phystokv(boot_info->syms.a.tabsize);
        !           323:                strtab_size = (vm_offset_t)phystokv(boot_info->syms.a.strsize);
        !           324:                kern_sym_end = kern_sym_start + 4 + symtab_size + strtab_size;
        !           325: 
        !           326:                printf("kernel symbol table at %08x-%08x (%d,%d)\n",
        !           327:                       kern_sym_start, kern_sym_end,
        !           328:                       symtab_size, strtab_size);
        !           329:        }
        !           330: #endif MACH_KDB
        !           331: 
        !           332:        /*
        !           333:         * Do basic VM initialization
        !           334:         */
        !           335:        i386at_init();
        !           336: 
        !           337: #if    MACH_KDB
        !           338:        /*
        !           339:         * Initialize the kernel debugger's kernel symbol table.
        !           340:         */
        !           341:        if (kern_sym_start)
        !           342:        {
        !           343:                aout_db_sym_init(kern_sym_start, kern_sym_end, "mach", 0);
        !           344:        }
        !           345: 
        !           346:        /*
        !           347:         * Cause a breakpoint trap to the debugger before proceeding
        !           348:         * any further if the proper option flag was specified
        !           349:         * on the kernel's command line.
        !           350:         * XXX check for surrounding spaces.
        !           351:         */
        !           352:        if (strstr(kernel_cmdline, "-d ")) {
        !           353:                cninit();               /* need console for debugger */
        !           354:                Debugger();
        !           355:        }
        !           356: #endif MACH_KDB
        !           357: 
        !           358:        machine_slot[0].is_cpu = TRUE;
        !           359:        machine_slot[0].running = TRUE;
        !           360:        machine_slot[0].cpu_type = CPU_TYPE_I386;
        !           361:        machine_slot[0].cpu_subtype = CPU_SUBTYPE_AT386;
        !           362: 
        !           363:        /*
        !           364:         * Start the system.
        !           365:         */
        !           366:        setup_main();
        !           367: 
        !           368: }
        !           369: 
        !           370: #include <mach/vm_prot.h>
        !           371: #include <vm/pmap.h>
        !           372: #include <mach/time_value.h>
        !           373: 
        !           374: timemmap(dev,off,prot)
        !           375:        vm_prot_t prot;
        !           376: {
        !           377:        extern time_value_t *mtime;
        !           378: 
        !           379: #ifdef lint
        !           380:        dev++; off++;
        !           381: #endif lint
        !           382: 
        !           383:        if (prot & VM_PROT_WRITE) return (-1);
        !           384: 
        !           385:        return (i386_btop(pmap_extract(pmap_kernel(), (vm_offset_t) mtime)));
        !           386: }
        !           387: 
        !           388: startrtclock()
        !           389: {
        !           390:        clkstart();
        !           391: }
        !           392: 
        !           393: void
        !           394: inittodr()
        !           395: {
        !           396:        time_value_t    new_time;
        !           397: 
        !           398:        new_time.seconds = 0;
        !           399:        new_time.microseconds = 0;
        !           400: 
        !           401:        (void) readtodc(&new_time.seconds);
        !           402: 
        !           403:        {
        !           404:            spl_t       s = splhigh();
        !           405:            time = new_time;
        !           406:            splx(s);
        !           407:        }
        !           408: }
        !           409: 
        !           410: void
        !           411: resettodr()
        !           412: {
        !           413:        writetodc();
        !           414: }
        !           415: 
        !           416: unsigned int pmap_free_pages()
        !           417: {
        !           418:        return atop(avail_remaining);
        !           419: }
        !           420: 
        !           421: /* Always returns page-aligned regions.  */
        !           422: boolean_t
        !           423: init_alloc_aligned(vm_size_t size, vm_offset_t *addrp)
        !           424: {
        !           425:        vm_offset_t addr;
        !           426:        extern char start[], end[];
        !           427:        int i;
        !           428: 
        !           429:        /* Memory regions to skip.  */
        !           430:        vm_offset_t boot_info_start_pa = kvtophys(boot_info);
        !           431:        vm_offset_t boot_info_end_pa = boot_info_start_pa + sizeof(*boot_info);
        !           432:        vm_offset_t cmdline_start_pa = boot_info->flags & MULTIBOOT_CMDLINE
        !           433:                ? boot_info->cmdline : 0;
        !           434:        vm_offset_t cmdline_end_pa = cmdline_start_pa
        !           435:                ? cmdline_start_pa+strlen((char*)phystokv(cmdline_start_pa))+1
        !           436:                : 0;
        !           437:        vm_offset_t mods_start_pa = boot_info->flags & MULTIBOOT_MODS
        !           438:                ? boot_info->mods_addr : 0;
        !           439:        vm_offset_t mods_end_pa = mods_start_pa
        !           440:                ? mods_start_pa
        !           441:                  + boot_info->mods_count * sizeof(struct multiboot_module)
        !           442:                : 0;
        !           443: 
        !           444:        retry:
        !           445: 
        !           446:        /* Page-align the start address.  */
        !           447:        avail_next = round_page(avail_next);
        !           448: 
        !           449:        /* Check if we have reached the end of memory.  */
        !           450:        if (avail_next == phys_last_addr)
        !           451:                return FALSE;
        !           452: 
        !           453:        /* Tentatively assign the current location to the caller.  */
        !           454:        addr = avail_next;
        !           455: 
        !           456:        /* Bump the pointer past the newly allocated region
        !           457:           and see where that puts us.  */
        !           458:        avail_next += size;
        !           459: 
        !           460:        /* Skip past the I/O and ROM area.  */
        !           461:        if ((avail_next > (boot_info->mem_lower * 0x400)) && (addr < 0x100000))
        !           462:        {
        !           463:                avail_next = 0x100000;
        !           464:                goto retry;
        !           465:        }
        !           466: 
        !           467:        /* If we're only supposed to use the low 16 megs, enforce that.  */
        !           468:        if ((!use_all_mem) && (addr >= 16 * 1024*1024)) {
        !           469:                return FALSE;
        !           470:        }
        !           471: 
        !           472:        /* Skip our own kernel code, data, and bss.  */
        !           473:        if ((avail_next >= (vm_offset_t)start) && (addr < (vm_offset_t)end))
        !           474:        {
        !           475:                avail_next = (vm_offset_t)end;
        !           476:                goto retry;
        !           477:        }
        !           478: 
        !           479:        /* Skip any areas occupied by valuable boot_info data.  */
        !           480:        if ((avail_next > boot_info_start_pa) && (addr < boot_info_end_pa))
        !           481:        {
        !           482:                avail_next = boot_info_end_pa;
        !           483:                goto retry;
        !           484:        }
        !           485:        if ((avail_next > cmdline_start_pa) && (addr < cmdline_end_pa))
        !           486:        {
        !           487:                avail_next = cmdline_end_pa;
        !           488:                goto retry;
        !           489:        }
        !           490:        if ((avail_next > mods_start_pa) && (addr < mods_end_pa))
        !           491:        {
        !           492:                avail_next = mods_end_pa;
        !           493:                goto retry;
        !           494:        }
        !           495:        if ((avail_next > kern_sym_start) && (addr < kern_sym_end))
        !           496:        {
        !           497:                avail_next = kern_sym_end;
        !           498:                goto retry;
        !           499:        }
        !           500:        if (boot_info->flags & MULTIBOOT_MODS)
        !           501:        {
        !           502:                struct multiboot_module *m = (struct multiboot_module *)
        !           503:                        phystokv(boot_info->mods_addr);
        !           504:                for (i = 0; i < boot_info->mods_count; i++)
        !           505:                {
        !           506:                        if ((avail_next > m[i].mod_start)
        !           507:                            && (addr < m[i].mod_end))
        !           508:                        {
        !           509:                                avail_next = m[i].mod_end;
        !           510:                                goto retry;
        !           511:                        }
        !           512:                        /* XXX string */
        !           513:                }
        !           514:        }
        !           515: 
        !           516:        avail_remaining -= size;
        !           517: 
        !           518:        *addrp = addr;
        !           519:        return TRUE;
        !           520: }
        !           521: 
        !           522: boolean_t pmap_next_page(addrp)
        !           523:        vm_offset_t *addrp;
        !           524: {
        !           525:        return init_alloc_aligned(PAGE_SIZE, addrp);
        !           526: }
        !           527: 
        !           528: /* Grab a physical page:
        !           529:    the standard memory allocation mechanism
        !           530:    during system initialization.  */
        !           531: vm_offset_t
        !           532: pmap_grab_page()
        !           533: {
        !           534:        vm_offset_t addr;
        !           535:        if (!pmap_next_page(&addr))
        !           536:                panic("Not enough memory to initialize Mach");
        !           537:        return addr;
        !           538: }
        !           539: 
        !           540: boolean_t pmap_valid_page(x)
        !           541:        vm_offset_t x;
        !           542: {
        !           543:        /* XXX is this OK?  What does it matter for?  */
        !           544:        return (((phys_first_addr <= x) && (x < phys_last_addr)) &&
        !           545:                !(((boot_info->mem_lower * 1024) <= x) && (x < 1024*1024)));
        !           546: }
        !           547: 
        !           548: #ifndef NBBY
        !           549: #define NBBY   8
        !           550: #endif
        !           551: #ifndef NBPW
        !           552: #define NBPW   (NBBY * sizeof(int))
        !           553: #endif
        !           554: #define DMA_MAX        (16*1024*1024)
        !           555: 
        !           556: /*
        !           557:  * Allocate contiguous pages below 16 MB
        !           558:  * starting at specified boundary for DMA.
        !           559:  */
        !           560: vm_offset_t
        !           561: alloc_dma_mem(size, align)
        !           562:        vm_size_t size;
        !           563:        vm_offset_t align;
        !           564: {
        !           565:        int *bits, i, j, k, n;
        !           566:        int npages, count, bit, mask;
        !           567:        int first_page, last_page;
        !           568:        vm_offset_t addr;
        !           569:        vm_page_t p, prevp;
        !           570: 
        !           571:        npages = round_page(size) / PAGE_SIZE;
        !           572:        mask = align ? (align - 1) / PAGE_SIZE : 0;
        !           573: 
        !           574:        /*
        !           575:         * Allocate bit array.
        !           576:         */
        !           577:        n = ((DMA_MAX / PAGE_SIZE) + NBPW - 1) / NBPW;
        !           578:        i = n * NBPW;
        !           579:        bits = (unsigned *)kalloc(i);
        !           580:        if (bits == 0) {
        !           581:                printf("alloc_dma_mem: unable alloc bit array\n");
        !           582:                return (0);
        !           583:        }
        !           584:        bzero((char *)bits, i);
        !           585: 
        !           586:        /*
        !           587:         * Walk the page free list and set a bit for
        !           588:         * every usable page in bit array.
        !           589:         */
        !           590:        simple_lock(&vm_page_queue_free_lock);
        !           591:        for (p = vm_page_queue_free; p; p = (vm_page_t)p->pageq.next) {
        !           592:                if (p->phys_addr < DMA_MAX) {
        !           593:                        i = p->phys_addr / PAGE_SIZE;
        !           594:                        bits[i / NBPW] |= 1 << (i % NBPW);
        !           595:                }
        !           596:        }
        !           597: 
        !           598:        /*
        !           599:         * Search for contiguous pages by scanning bit array.
        !           600:         */
        !           601:        for (i = 0, first_page = -1; i < n; i++) {
        !           602:                for (bit = 1, j = 0; j < NBPW; j++, bit <<= 1) {
        !           603:                        if (bits[i] & bit) {
        !           604:                                if (first_page < 0) {
        !           605:                                        k = i * NBPW + j;
        !           606:                                        if (!mask
        !           607:                                            || (((k & mask) + npages)
        !           608:                                                <= mask + 1)) {
        !           609:                                                first_page = k;
        !           610:                                                if (npages == 1)
        !           611:                                                        goto found;
        !           612:                                                count = 1;
        !           613:                                        }
        !           614:                                } else if (++count == npages)
        !           615:                                        goto found;
        !           616:                        } else
        !           617:                                first_page = -1;
        !           618:                }
        !           619:        }
        !           620:        addr = 0;
        !           621:        goto out;
        !           622: 
        !           623:  found:
        !           624:        /*
        !           625:         * Remove pages from the free list.
        !           626:         */
        !           627:        addr = first_page * PAGE_SIZE;
        !           628:        last_page = first_page + npages;
        !           629:        vm_page_free_count -= npages;
        !           630:        p = vm_page_queue_free;
        !           631:        prevp = 0;
        !           632:        while (1) {
        !           633:                i = p->phys_addr / PAGE_SIZE;
        !           634:                if (i >= first_page && i < last_page) {
        !           635:                        if (prevp)
        !           636:                                prevp->pageq.next = p->pageq.next;
        !           637:                        else
        !           638:                                vm_page_queue_free = (vm_page_t)p->pageq.next;
        !           639:                        p->free = FALSE;
        !           640:                        if (--npages == 0)
        !           641:                                break;
        !           642:                } else
        !           643:                        prevp = p;
        !           644:                p = (vm_page_t)p->pageq.next;
        !           645:        }
        !           646: 
        !           647:  out:
        !           648:        simple_unlock(&vm_page_queue_free_lock);
        !           649:        kfree((vm_offset_t)bits, n * NBPW);
        !           650:        return (addr);
        !           651: }

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