gptboot.c revision 42519 
1/*
2 * Copyright (c) 1998 Robert Nordier
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms are freely
6 * permitted provided that the above copyright notice and this
7 * paragraph and the following disclaimer are duplicated in all
8 * such forms.
9 *
10 * This software is provided "AS IS" and without any express or
11 * implied warranties, including, without limitation, the implied
12 * warranties of merchantability and fitness for a particular
13 * purpose.
14 */
15
16/*
17 *	$Id: boot2.c,v 1.17 1999/01/10 13:29:52 peter Exp $
18 */
19
20#include <sys/param.h>
21#include <sys/reboot.h>
22#include <sys/diskslice.h>
23#include <sys/disklabel.h>
24#include <sys/dirent.h>
25#include <machine/bootinfo.h>
26
27#include <ufs/ffs/fs.h>
28#include <ufs/ufs/dinode.h>
29
30#include <stdarg.h>
31
32#include <a.out.h>
33#include <elf.h>
34
35#include <btxv86.h>
36
37#include "lib.h"
38
39#define RBX_ASKNAME	0x0	/* -a */
40#define RBX_SINGLE	0x1	/* -s */
41#define RBX_DFLTROOT	0x5	/* -r */
42#define RBX_KDB 	0x6	/* -d */
43#define RBX_CONFIG	0xa	/* -c */
44#define RBX_VERBOSE	0xb	/* -v */
45#define RBX_SERIAL	0xc	/* -h */
46#define RBX_CDROM	0xd	/* -C */
47#define RBX_GDB 	0xf	/* -g */
48#define RBX_DUAL	0x1d	/* -D */
49#define RBX_PROBEKBD	0x1e	/* -P */
50
51#define RBX_MASK	0xffff
52
53#define PATH_CONFIG	"/boot.config"
54#define PATH_BOOT3	"/boot/loader"
55#define PATH_KERNEL	"/kernel"
56
57#define ARGS		0x900
58#define NOPT		11
59#define BSIZEMAX	8192
60#define NDEV		5
61#define MEM_BASE	0x12
62#define MEM_EXT 	0x15
63#define V86_CY(x)	((x) & 1)
64#define V86_ZR(x)	((x) & 0x40)
65
66#define DRV_HARD	0x80
67#define DRV_MASK	0x7f
68
69#define MAJ_WD		0
70#define MAJ_WFD 	1
71#define MAJ_FD		2
72#define MAJ_DA		4
73
74extern uint32_t _end;
75
76static const char optstr[NOPT] = "DhaCcdgPrsv";
77static const unsigned char flags[NOPT] = {
78    RBX_DUAL,
79    RBX_SERIAL,
80    RBX_ASKNAME,
81    RBX_CDROM,
82    RBX_CONFIG,
83    RBX_KDB,
84    RBX_GDB,
85    RBX_PROBEKBD,
86    RBX_DFLTROOT,
87    RBX_SINGLE,
88    RBX_VERBOSE
89};
90
91static const char *const dev_nm[] = {"wd", "  ", "fd", "  ", "da"};
92
93static struct dsk {
94    unsigned drive;
95    unsigned type;
96    unsigned unit;
97    unsigned slice;
98    unsigned part;
99    unsigned start;
100    int init;
101    int meta;
102} dsk;
103static char cmd[512];
104static char kname[1024];
105static uint32_t opts;
106static struct bootinfo bootinfo;
107static int ls;
108static uint32_t fs_off;
109static uint8_t ioctrl = 0x1;
110
111void exit(int);
112static void load(const char *);
113static int parse(char *);
114static void readfile(const char *, void *, size_t);
115static ino_t lookup(const char *);
116static int fsfind(const char *, ino_t *);
117static int xfsread(ino_t, void *, size_t);
118static ssize_t fsread(ino_t, void *, size_t);
119static int dskread(void *, unsigned, unsigned);
120static int printf(const char *,...);
121static void getstr(char *, int);
122static int putchar(int);
123static int getchar(void);
124static void *memcpy(void *, const void *, size_t);
125static int strcmp(const char *, const char *);
126static void *malloc(size_t);
127static uint32_t memsize(int);
128static uint32_t drvinfo(int);
129static int drvread(void *, unsigned, unsigned);
130static int keyhit(unsigned);
131static int xputc(int);
132static int xgetc(int);
133static void putc(int);
134static int getc(int);
135
136int
137main(void)
138{
139    int autoboot, i;
140
141    v86.ctl = V86_FLAGS;
142    dsk.drive = *(uint8_t *)PTOV(ARGS);
143    dsk.type = dsk.drive & DRV_HARD ? MAJ_WD : MAJ_FD;
144    dsk.unit = dsk.drive & DRV_MASK;
145    dsk.slice = *(uint8_t *)PTOV(ARGS + 1) + 1;
146    bootinfo.bi_version = BOOTINFO_VERSION;
147    bootinfo.bi_size = sizeof(bootinfo);
148    bootinfo.bi_basemem = memsize(MEM_BASE);
149    bootinfo.bi_extmem = memsize(MEM_EXT);
150    bootinfo.bi_memsizes_valid++;
151    for (i = 0; i < N_BIOS_GEOM; i++)
152	bootinfo.bi_bios_geom[i] = drvinfo(i);
153    autoboot = 2;
154    readfile(PATH_CONFIG, cmd, sizeof(cmd));
155    if (*cmd) {
156	printf("%s: %s", PATH_CONFIG, cmd);
157	if (parse(cmd))
158	    autoboot = 0;
159	*cmd = 0;
160    }
161    if (autoboot && !*kname) {
162	if (autoboot == 2) {
163	    memcpy(kname, PATH_BOOT3, sizeof(PATH_BOOT3));
164	    if (!keyhit(0x37)) {
165		load(kname);
166		autoboot = 1;
167	    }
168	}
169	if (autoboot == 1)
170	    memcpy(kname, PATH_KERNEL, sizeof(PATH_KERNEL));
171    }
172    for (;;) {
173	printf(" \n>> FreeBSD/i386 BOOT\n"
174	       "Default: %u:%s(%u,%c)%s\n"
175	       "boot: ",
176	       dsk.drive & DRV_MASK, dev_nm[dsk.type], dsk.unit,
177	       'a' + dsk.part, kname);
178	if (ioctrl & 0x2)
179	    sio_flush();
180	if (!autoboot || keyhit(0x5a))
181	    getstr(cmd, sizeof(cmd));
182	else
183	    putchar('\n');
184	autoboot = 0;
185	if (parse(cmd))
186	    putchar('\a');
187	else
188	    load(kname);
189    }
190}
191
192void
193exit(int x)
194{
195}
196
197static void
198load(const char *fname)
199{
200    union {
201	struct exec ex;
202	Elf32_Ehdr eh;
203    } hdr;
204    Elf32_Phdr ep[2];
205    Elf32_Shdr es[2];
206    caddr_t p;
207    ino_t ino;
208    uint32_t addr, x;
209    int fmt, i, j;
210
211    if (!(ino = lookup(fname))) {
212	if (!ls)
213	    printf("No %s\n", fname);
214	return;
215    }
216    if (xfsread(ino, &hdr, sizeof(hdr)))
217	return;
218    if (N_GETMAGIC(hdr.ex) == ZMAGIC)
219	fmt = 0;
220    else if (IS_ELF(hdr.eh))
221	fmt = 1;
222    else {
223	printf("Invalid %s\n", "format");
224	return;
225    }
226    if (fmt == 0) {
227	addr = hdr.ex.a_entry & 0xffffff;
228	p = PTOV(addr);
229	fs_off = PAGE_SIZE;
230	if (xfsread(ino, p, hdr.ex.a_text))
231	    return;
232	p += roundup2(hdr.ex.a_text, PAGE_SIZE);
233	if (xfsread(ino, p, hdr.ex.a_data))
234	    return;
235	p += hdr.ex.a_data + roundup2(hdr.ex.a_bss, PAGE_SIZE);
236	bootinfo.bi_symtab = VTOP(p);
237	memcpy(p, &hdr.ex.a_syms, sizeof(hdr.ex.a_syms));
238	p += sizeof(hdr.ex.a_syms);
239	if (hdr.ex.a_syms) {
240	    if (xfsread(ino, p, hdr.ex.a_syms))
241		return;
242	    p += hdr.ex.a_syms;
243	    if (xfsread(ino, p, sizeof(int)))
244		return;
245	    x = *(uint32_t *)p;
246	    p += sizeof(int);
247	    x -= sizeof(int);
248	    if (xfsread(ino, p, x))
249		return;
250	    p += x;
251	}
252    } else {
253	fs_off = hdr.eh.e_phoff;
254	for (j = i = 0; i < hdr.eh.e_phoff && j < 2; i++) {
255	    if (xfsread(ino, ep + j, sizeof(ep[0])))
256		return;
257	    if (ep[j].p_type == PT_LOAD)
258		j++;
259	}
260	for (i = 0; i < 2; i++) {
261	    p = PTOV(ep[i].p_paddr & 0xffffff);
262	    fs_off = ep[i].p_offset;
263	    if (xfsread(ino, p, ep[i].p_filesz))
264		return;
265	}
266	p += roundup2(ep[1].p_memsz, PAGE_SIZE);
267	bootinfo.bi_symtab = VTOP(p);
268	if (hdr.eh.e_shnum == hdr.eh.e_shstrndx + 3) {
269	    fs_off = hdr.eh.e_shoff + sizeof(es[0]) *
270		(hdr.eh.e_shstrndx + 1);
271	    if (xfsread(ino, &es, sizeof(es)))
272		return;
273	    for (i = 0; i < 2; i++) {
274		memcpy(p, &es[i].sh_size, sizeof(es[i].sh_size));
275		p += sizeof(es[i].sh_size);
276		fs_off = es[i].sh_offset;
277		if (xfsread(ino, p, es[i].sh_size))
278		    return;
279		p += es[i].sh_size;
280	    }
281	}
282	addr = hdr.eh.e_entry & 0xffffff;
283    }
284    bootinfo.bi_esymtab = VTOP(p);
285    bootinfo.bi_kernelname = VTOP(fname);
286    __exec((caddr_t)addr, RB_BOOTINFO | (opts & RBX_MASK),
287	   MAKEBOOTDEV(dsk.type, 0, dsk.slice, dsk.unit, dsk.part),
288	   0, 0, 0, VTOP(&bootinfo));
289}
290
291static int
292parse(char *arg)
293{
294    char *p, *q;
295    int drv, c, i;
296
297    while ((c = *arg++)) {
298	if (c == ' ')
299	    continue;
300	for (p = arg; *p && *p != '\n' && *p != ' '; p++);
301	if (*p)
302	    *p++ = 0;
303	if (c == '-') {
304	    while ((c = *arg++)) {
305		for (i = 0; c != optstr[i]; i++)
306		    if (i == NOPT - 1)
307			return -1;
308		opts ^= 1 << flags[i];
309	    }
310	    if (opts & 1 << RBX_PROBEKBD) {
311		i = *(uint8_t *)PTOV(0x496) & 0x10;
312		printf("Keyboard: %s\n", i ? "yes" : "no");
313		if (!i)
314		    opts |= 1 << RBX_DUAL | 1 << RBX_SERIAL;
315		opts &= ~(1 << RBX_PROBEKBD);
316	    }
317	    ioctrl = opts & 1 << RBX_DUAL ? 0x3 :
318		     opts & 1 << RBX_SERIAL ? 0x2 : 0x1;
319	    if (ioctrl & 0x2)
320	        sio_init();
321	} else {
322	    for (q = arg--; *q && *q != '('; q++);
323	    if (*q) {
324		drv = -1;
325		if (arg[1] == ':') {
326		    if (*arg < '0' || *arg > '9')
327			return -1;
328		    drv = *arg - '0';
329		    arg += 2;
330		}
331		if (q - arg != 2)
332		    return -1;
333		for (i = 0; arg[0] != dev_nm[i][0] ||
334			    arg[1] != dev_nm[i][1]; i++)
335		    if (i == NDEV - 1)
336			return -1;
337		dsk.type = i;
338		arg += 3;
339		if (arg[1] != ',' || *arg < '0' || *arg > '9')
340		    return -1;
341		dsk.unit = *arg - '0';
342		arg += 2;
343		dsk.slice = WHOLE_DISK_SLICE;
344		if (arg[1] == ',') {
345		    if (*arg < '0' || *arg > '0' + NDOSPART)
346			return -1;
347		    if ((dsk.slice = *arg - '0'))
348			dsk.slice++;
349		    arg += 2;
350		}
351		if (arg[1] != ')' || *arg < 'a' || *arg > 'p')
352		    return -1;
353		dsk.part = *arg - 'a';
354		arg += 2;
355		if (drv == -1)
356		    drv = dsk.unit;
357		dsk.drive = (dsk.type == MAJ_WD ||
358			     dsk.type == MAJ_DA ? DRV_HARD : 0) + drv;
359		dsk.meta = 0;
360		fsread(0, NULL, 0);
361	    }
362	    if ((i = p - arg - !*(p - 1))) {
363		if (i >= sizeof(kname))
364		    return -1;
365		memcpy(kname, arg, i + 1);
366	    }
367	}
368	arg = p;
369    }
370    return 0;
371}
372
373static void
374readfile(const char *fname, void *buf, size_t size)
375{
376    ino_t ino;
377
378    if ((ino = lookup(fname)))
379	fsread(ino, buf, size);
380}
381
382static ino_t
383lookup(const char *path)
384{
385    char name[MAXNAMLEN + 1];
386    const char *s;
387    ino_t ino;
388    ssize_t n;
389    int dt;
390
391    ino = ROOTINO;
392    dt = DT_DIR;
393    for (;;) {
394	if (*path == '/')
395	    path++;
396	if (!*path)
397	    break;
398	for (s = path; *s && *s != '/'; s++);
399	if ((n = s - path) > MAXNAMLEN)
400	    return 0;
401	ls = *path == '?' && n == 1 && !*s;
402	memcpy(name, path, n);
403	name[n] = 0;
404	if ((dt = fsfind(name, &ino)) <= 0)
405	    break;
406	path = s;
407    }
408    return dt == DT_REG ? ino : 0;
409}
410
411static int
412fsfind(const char *name, ino_t * ino)
413{
414    char buf[DEV_BSIZE];
415    struct dirent *d;
416    char *s;
417    ssize_t n;
418
419    fs_off = 0;
420    while ((n = fsread(*ino, buf, DEV_BSIZE)) > 0)
421	for (s = buf; s < buf + DEV_BSIZE;) {
422	    d = (void *)s;
423	    if (ls)
424		printf("%s ", d->d_name);
425	    else if (!strcmp(name, d->d_name)) {
426		*ino = d->d_fileno;
427		return d->d_type;
428	    }
429	    s += d->d_reclen;
430	}
431    if (n != -1 && ls)
432	putchar('\n');
433    return 0;
434}
435
436static int
437xfsread(ino_t inode, void *buf, size_t nbyte)
438{
439    if (fsread(inode, buf, nbyte) != nbyte) {
440	printf("Invalid %s\n", "format");
441	return -1;
442    }
443    return 0;
444}
445
446static ssize_t
447fsread(ino_t inode, void *buf, size_t nbyte)
448{
449    static struct fs fs;
450    static struct dinode din;
451    static char *blkbuf;
452    static ufs_daddr_t *indbuf;
453    static ino_t inomap;
454    static ufs_daddr_t blkmap, indmap;
455    static unsigned fsblks;
456    char *s;
457    ufs_daddr_t lbn, addr;
458    size_t n, nb, off;
459
460    if (!dsk.meta) {
461	if (!blkbuf)
462	    blkbuf = malloc(BSIZEMAX);
463	inomap = 0;
464	if (dskread(blkbuf, SBOFF / DEV_BSIZE, SBSIZE / DEV_BSIZE))
465	    return -1;
466	memcpy(&fs, blkbuf, sizeof(fs));
467	if (fs.fs_magic != FS_MAGIC) {
468	    printf("Not ufs\n");
469	    return -1;
470	}
471	fsblks = fs.fs_bsize >> DEV_BSHIFT;
472	dsk.meta++;
473    }
474    if (!inode)
475	return 0;
476    if (inomap != inode) {
477	if (dskread(blkbuf, fsbtodb(&fs, ino_to_fsba(&fs, inode)),
478		    fsblks))
479	    return -1;
480	din = ((struct dinode *)blkbuf)[inode % INOPB(&fs)];
481	inomap = inode;
482	fs_off = 0;
483	blkmap = indmap = 0;
484    }
485    s = buf;
486    if (nbyte > (n = din.di_size - fs_off))
487	nbyte = n;
488    nb = nbyte;
489    while (nb) {
490	lbn = lblkno(&fs, fs_off);
491	if (lbn < NDADDR)
492	    addr = din.di_db[lbn];
493	else {
494	    if (indmap != din.di_ib[0]) {
495		if (!indbuf)
496		    indbuf = malloc(BSIZEMAX);
497		if (dskread(indbuf, fsbtodb(&fs, din.di_ib[0]),
498			    fsblks))
499		    return -1;
500		indmap = din.di_ib[0];
501	    }
502	    addr = indbuf[(lbn - NDADDR) % NINDIR(&fs)];
503	}
504	n = dblksize(&fs, &din, lbn);
505	if (blkmap != addr) {
506	    if (dskread(blkbuf, fsbtodb(&fs, addr), n >> DEV_BSHIFT))
507		return -1;
508	    blkmap = addr;
509	}
510	off = blkoff(&fs, fs_off);
511	n -= off;
512	if (n > nb)
513	    n = nb;
514	memcpy(s, blkbuf + off, n);
515	s += n;
516	fs_off += n;
517	nb -= n;
518    }
519    return nbyte;
520}
521
522static int
523dskread(void *buf, unsigned lba, unsigned nblk)
524{
525    static char *sec;
526    struct dos_partition *dp;
527    struct disklabel *d;
528    unsigned sl, i;
529
530    if (!dsk.meta) {
531	if (!sec)
532	    sec = malloc(DEV_BSIZE);
533	dsk.start = 0;
534	if (drvread(sec, DOSBBSECTOR, 1))
535	    return -1;
536	dp = (void *)(sec + DOSPARTOFF);
537	sl = dsk.slice;
538	if (sl < BASE_SLICE) {
539	    for (i = 0; i < NDOSPART; i++)
540		if (dp[i].dp_typ == DOSPTYP_386BSD &&
541		    (dp[i].dp_flag & 0x80 || sl < BASE_SLICE)) {
542		    sl = BASE_SLICE + i;
543		    if (dp[i].dp_flag & 0x80 ||
544			dsk.slice == COMPATIBILITY_SLICE)
545			break;
546		}
547	    if (dsk.slice == WHOLE_DISK_SLICE)
548		dsk.slice = sl;
549	}
550	if (sl != WHOLE_DISK_SLICE) {
551	    if (sl != COMPATIBILITY_SLICE)
552		dp += sl - BASE_SLICE;
553	    if (dp->dp_typ != DOSPTYP_386BSD) {
554		printf("Invalid %s\n", "slice");
555		return -1;
556	    }
557	    dsk.start = dp->dp_start;
558	}
559	if (drvread(sec, dsk.start + LABELSECTOR, 1))
560		return -1;
561	d = (void *)(sec + LABELOFFSET);
562	if (d->d_magic != DISKMAGIC || d->d_magic2 != DISKMAGIC) {
563	    if (dsk.part != RAW_PART) {
564		printf("Invalid %s\n", "label");
565		return -1;
566	    }
567	} else {
568	    if (!dsk.init) {
569		if (d->d_type == DTYPE_SCSI)
570		    dsk.type = MAJ_DA;
571		dsk.init++;
572	    }
573	    if (dsk.part >= d->d_npartitions) {
574		printf("Invalid %s\n", "partition");
575		return -1;
576	    }
577	    dsk.start = d->d_partitions[dsk.part].p_offset;
578	}
579    }
580    return drvread(buf, dsk.start + lba, nblk);
581}
582
583static int
584printf(const char *fmt,...)
585{
586    static const char digits[16] = "0123456789abcdef";
587    va_list ap;
588    char buf[10];
589    char *s;
590    unsigned r, u;
591    int c;
592
593    va_start(ap, fmt);
594    while ((c = *fmt++)) {
595	if (c == '%') {
596	    c = *fmt++;
597	    switch (c) {
598	    case 'c':
599		putchar(va_arg(ap, int));
600		continue;
601	    case 's':
602		for (s = va_arg(ap, char *); *s; s++)
603		    putchar(*s);
604		continue;
605	    case 'u':
606	    case 'x':
607		r = c == 'u' ? 10U : 16U;
608		u = va_arg(ap, unsigned);
609		s = buf;
610		do
611		    *s++ = digits[u % r];
612		while (u /= r);
613		while (--s >= buf)
614		    putchar(*s);
615		continue;
616	    }
617	}
618	putchar(c);
619    }
620    va_end(ap);
621    return 0;
622}
623
624static void
625getstr(char *str, int size)
626{
627    char *s;
628    int c;
629
630    s = str;
631    do {
632	switch (c = getchar()) {
633	case 0:
634	    break;
635	case '\b':
636	    if (s > str) {
637		s--;
638		putchar(c);
639		putchar(' ');
640	    } else
641		c = 0;
642	    break;
643	case '\n':
644	    *s = 0;
645	    break;
646	default:
647	    if (s - str < size - 1)
648		*s++ = c;
649	}
650	if (c)
651	    putchar(c);
652    } while (c != '\n');
653}
654
655static int
656putchar(int c)
657{
658    if (c == '\n')
659	xputc('\r');
660    return xputc(c);
661}
662
663static int
664getchar(void)
665{
666    int c;
667
668    c = xgetc(0);
669    if (c == '\r')
670	c = '\n';
671    return c;
672}
673
674static void *
675memcpy(void *dst, const void *src, size_t size)
676{
677    const char *s;
678    char *d;
679
680    for (d = dst, s = src; size; size--)
681	*d++ = *s++;
682    return dst;
683}
684
685static int
686strcmp(const char *s1, const char *s2)
687{
688    for (; *s1 == *s2 && *s1; s1++, s2++);
689    return (u_char)*s1 - (u_char)*s2;
690}
691
692static void *
693malloc(size_t size)
694{
695    static uint32_t next;
696    void *p;
697
698    if (!next)
699	next = roundup2(__base + _end, 0x10000) - __base;
700    p = (void *)next;
701    next += size;
702    return p;
703}
704
705static uint32_t
706memsize(int type)
707{
708    v86.addr = type;
709    v86.eax = 0x8800;
710    v86int();
711    return v86.eax;
712}
713
714static uint32_t
715drvinfo(int drive)
716{
717    v86.addr = 0x13;
718    v86.eax = 0x800;
719    v86.edx = DRV_HARD + drive;
720    v86int();
721    if (V86_CY(v86.efl))
722	return 0x4f010f;
723    return ((v86.ecx & 0xc0) << 18) | ((v86.ecx & 0xff00) << 8) |
724	   (v86.edx & 0xff00) | (v86.ecx & 0x3f);
725}
726
727static int
728drvread(void *buf, unsigned lba, unsigned nblk)
729{
730    static unsigned c = 0x2d5c7c2f;
731
732    printf("%c\b", c = c << 8 | c >> 24);
733    v86.ctl = V86_ADDR | V86_CALLF | V86_FLAGS;
734    v86.addr = 0x704;		/* call to xread in boot1 */
735    v86.es = VTOPSEG(buf);
736    v86.eax = lba;
737    v86.ebx = VTOPOFF(buf);
738    v86.ecx = lba >> 16;
739    v86.edx = nblk << 8 | dsk.drive;
740    v86int();
741    v86.ctl = V86_FLAGS;
742    if (V86_CY(v86.efl)) {
743	printf("Disk error 0x%x (lba=0x%x)\n", v86.eax >> 8 & 0xff,
744	       lba);
745	return -1;
746    }
747    return 0;
748}
749
750static int
751keyhit(unsigned ticks)
752{
753    uint32_t t0, t1;
754
755    t0 = 0;
756    for (;;) {
757	if (xgetc(1))
758	    return 1;
759	t1 = *(uint32_t *)PTOV(0x46c);
760	if (!t0)
761	    t0 = t1;
762	if (t1 < t0 || t1 >= t0 + ticks)
763	    return 0;
764    }
765}
766
767static int
768xputc(int c)
769{
770    if (ioctrl & 0x1)
771	putc(c);
772    if (ioctrl & 0x2)
773	sio_putc(c);
774    return c;
775}
776
777static int
778xgetc(int fn)
779{
780    for (;;) {
781	if (ioctrl & 0x1 && getc(1))
782	    return fn ? 1 : getc(0);
783	if (ioctrl & 0x2 && sio_ischar())
784	    return fn ? 1 : sio_getc();
785	if (fn)
786	    return 0;
787    }
788}
789
790static void
791putc(int c)
792{
793    v86.addr = 0x10;
794    v86.eax = 0xe00 | (c & 0xff);
795    v86.ebx = 0x7;
796    v86int();
797}
798
799static int
800getc(int fn)
801{
802    v86.addr = 0x16;
803    v86.eax = fn << 8;
804    v86int();
805    return fn == 0 ? v86.eax & 0xff : !V86_ZR(v86.efl);
806}
807