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/*
2 
 * install new master boot record boot code on PC disk.
3 
 */
4 
 
5 
#include <u.h>
6 
#include <libc.h>
7 
#include <disk.h>
8 
 
9 
typedef struct {
10 
	uchar	active;			/* active flag */
11 
	uchar	starth;			/* starting head */
12 
	uchar	starts;			/* starting sector */
13 
	uchar	startc;			/* starting cylinder */
14 
	uchar	type;			/* partition type */
15 
	uchar	endh;			/* ending head */
16 
	uchar	ends;			/* ending sector */
17 
	uchar	endc;			/* ending cylinder */
18 
	uchar	lba[4];			/* starting LBA */
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	uchar	size[4];		/* size in sectors */
20 
} Tentry;
21 
 
22 
enum {
23 
	Toffset = 0x1BE,		/* offset of partition table */
24 
 
25 
	Type9	= 0x39,
26 
};
27 
 
28 
/*
29 
 * Default boot block prints an error message and reboots.
30 
 */
31 
static int ndefmbr = Toffset;
32 
static char defmbr[512] = {
33 
[0x000]	0xEB, 0x3C, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
34 
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
35 
[0x03E] 0xFA, 0xFC, 0x8C, 0xC8, 0x8E, 0xD8, 0x8E, 0xD0,
36 
	0xBC, 0x00, 0x7C, 0xBE, 0x77, 0x7C, 0xE8, 0x19,
37 
	0x00, 0x33, 0xC0, 0xCD, 0x16, 0xBB, 0x40, 0x00,
38 
	0x8E, 0xC3, 0xBB, 0x72, 0x00, 0xB8, 0x34, 0x12,
39 
	0x26, 0x89, 0x07, 0xEA, 0x00, 0x00, 0xFF, 0xFF,
40 
	0xEB, 0xD6, 0xAC, 0x0A, 0xC0, 0x74, 0x09, 0xB4,
41 
	0x0E, 0xBB, 0x07, 0x00, 0xCD, 0x10, 0xEB, 0xF2,
42 
	0xC3,  'N',  'o',  't',  ' ',  'a',  ' ',  'b',
43 
	 'o',  'o',  't',  'a',  'b',  'l',  'e',  ' ',
44 
	 'd',  'i',  's',  'c',  ' ',  'o',  'r',  ' ',
45 
	 'd',  'i',  's',  'c',  ' ',  'e',  'r',  'r',
46 
	 'o',  'r', '\r', '\n',  'P',  'r',  'e',  's',
47 
	 's',  ' ',  'a',  'l',  'm',  'o',  's',  't',
48 
	 ' ',  'a',  'n',  'y',  ' ',  'k',  'e',  'y',
49 
	 ' ',  't',  'o',  ' ',  'r',  'e',  'b',  'o',
50 
	 'o',  't',  '.',  '.',  '.', 0x00, 0x00, 0x00,
51 
};
52 
 
53 
void
54 
usage(void)
55 
{
56 
	fprint(2, "usage: disk/mbr [-m mbrfile] disk\n");
57 
	exits("usage");
58 
}
59 
 
60 
void
61 
fatal(char *fmt, ...)
62 
{
63 
	char err[ERRMAX];
64 
	va_list arg;
65 
 
66 
	va_start(arg, fmt);
67 
	vsnprint(err, ERRMAX, fmt, arg);
68 
	va_end(arg);
69 
	fprint(2, "mbr: %s\n", err);
70 
	exits(err);
71 
}
72 
 
73 
static void
74 
putle32(void* v, u32int i)
75 
{
76 
	uchar *p;
77 
 
78 
	p = v;
79 
	p[0] = i;
80 
	p[1] = i>>8;
81 
	p[2] = i>>16;
82 
	p[3] = i>>24;
83 
}
84 
 
85 
static void
86 
writechs(Disk *disk, uchar *p, vlong lba)
87 
{
88 
	int c, h, s;
89 
 
90 
	s = lba % disk->s;
91 
	h = (lba / disk->s) % disk->h;
92 
	c = lba / (disk->s * disk->h);
93 
 
94 
	if(c >= 1024) {
95 
		c = 1023;
96 
		h = disk->h - 1;
97 
		s = disk->s - 1;
98 
	}
99 
 
100 
	p[0] = h;
101 
	p[1] = ((s+1) & 0x3F) | ((c>>2) & 0xC0);
102 
	p[2] = c;
103 
}
104 
 
105 
static void
106 
wrtentry(Disk *disk, Tentry *tp, int type, u32int base, u32int lba, u32int end)
107 
{
108 
	tp->active = 0x80;		/* make this sole partition active */
109 
	tp->type = type;
110 
	writechs(disk, &tp->starth, lba);
111 
	writechs(disk, &tp->endh, end-1);
112 
	putle32(tp->lba, lba-base);
113 
	putle32(tp->size, end-lba);
114 
}
115 
 
116 
void
117 
main(int argc, char **argv)
118 
{
119 
	Disk *disk;
120 
	Tentry *tp;
121 
	uchar *mbr, *buf;
122 
	char *mbrfile;
123 
	ulong secsize;
124 
	int flag9, sysfd, nmbr;
125 
 
126 
	flag9 = 0;
127 
	mbrfile = nil;
128 
	ARGBEGIN {
129 
	case '9':
130 
		flag9 = 1;
131 
		break;
132 
	case 'm':
133 
		mbrfile = EARGF(usage());
134 
		break;
135 
	default:
136 
		usage();
137 
	} ARGEND
138 
 
139 
	if(argc < 1)
140 
		usage();
141 
 
142 
	disk = opendisk(argv[0], 0, 0);
143 
	if(disk == nil)
144 
		fatal("opendisk %s: %r", argv[0]);
145 
 
146 
	if(disk->type == Tfloppy)
147 
		fatal("will not install mbr on floppy");
148 
	/*
149 
	 * we need to cope with 4k-byte sectors on some newer disks.
150 
	 * we're only interested in 512 bytes of mbr, so
151 
	 * on 4k disks, rely on /dev/sd to read-modify-write.
152 
	 */
153 
	secsize = 512;
154 
	if(disk->secsize != secsize)
155 
		fprint(2, "%s: sector size %lld not %ld, should be okay\n",
156 
			argv0, disk->secsize, secsize);
157 
 
158 
	buf = malloc(secsize*(disk->s+1));
159 
	mbr = malloc(secsize*disk->s);
160 
	if(buf == nil || mbr == nil)
161 
		fatal("out of memory");
162 
 
163 
	/*
164 
	 * Start with initial sector from disk.
165 
	 */
166 
	if(seek(disk->fd, 0, 0) < 0)
167 
		fatal("seek to boot sector: %r\n");
168 
	if(read(disk->fd, mbr, secsize) != secsize)
169 
		fatal("reading boot sector: %r");
170 
 
171 
	if(mbrfile == nil){
172 
		nmbr = ndefmbr;
173 
		memmove(mbr, defmbr, nmbr);
174 
	} else {
175 
		memset(buf, 0, secsize*disk->s);
176 
		if((sysfd = open(mbrfile, OREAD)) < 0)
177 
			fatal("open %s: %r", mbrfile);
178 
		if((nmbr = read(sysfd, buf, secsize*(disk->s+1))) < 0)
179 
			fatal("read %s: %r", mbrfile);
180 
		if(nmbr > secsize*disk->s)
181 
			fatal("master boot record too large %d > %d", nmbr, secsize*disk->s);
182 
		if(nmbr < secsize)
183 
			nmbr = secsize;
184 
		close(sysfd);
185 
		memmove(buf+Toffset, mbr+Toffset, secsize-Toffset);
186 
		memmove(mbr, buf, nmbr);
187 
	}
188 
 
189 
	if(flag9){
190 
		tp = (Tentry*)(mbr+Toffset);
191 
		memset(tp, 0, secsize-Toffset);
192 
		wrtentry(disk, tp, Type9, 0, disk->s, disk->secs);
193 
	}
194 
	mbr[secsize-2] = 0x55;
195 
	mbr[secsize-1] = 0xAA;
196 
	nmbr = (nmbr+secsize-1)&~(secsize-1);
197 
	if(seek(disk->wfd, 0, 0) < 0)
198 
		fatal("seek to MBR sector: %r\n");
199 
	if(write(disk->wfd, mbr, nmbr) != nmbr)
200 
		fatal("writing MBR: %r");
201 
 
202 
	exits(0);
203 
}