2 * install new master boot record boot code on PC disk.
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 */
19 uchar size[4]; /* size in sectors */
23 Toffset = 0x1BE, /* offset of partition table */
29 * Default boot block prints an error message and reboots.
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,
56 fprint(2, "usage: disk/mbr [-m mbrfile] disk\n");
67 vsnprint(err, ERRMAX, fmt, arg);
69 fprint(2, "mbr: %s\n", err);
74 putle32(void* v, u32int i)
86 writechs(Disk *disk, uchar *p, vlong lba)
91 h = (lba / disk->s) % disk->h;
92 c = lba / (disk->s * disk->h);
101 p[1] = ((s+1) & 0x3F) | ((c>>2) & 0xC0);
106 wrtentry(Disk *disk, Tentry *tp, int type, u32int base, u32int lba, u32int end)
108 tp->active = 0x80; /* make this sole partition active */
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);
117 main(int argc, char **argv)
124 int flag9, sysfd, nmbr;
133 mbrfile = EARGF(usage());
142 disk = opendisk(argv[0], 0, 0);
144 fatal("opendisk %s: %r", argv[0]);
146 if(disk->type == Tfloppy)
147 fatal("will not install mbr on floppy");
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.
154 if(disk->secsize != secsize)
155 fprint(2, "%s: sector size %lld not %ld, should be okay\n",
156 argv0, disk->secsize, secsize);
158 buf = malloc(secsize*(disk->s+1));
159 mbr = malloc(secsize*disk->s);
160 if(buf == nil || mbr == nil)
161 fatal("out of memory");
164 * Start with initial sector from disk.
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");
173 memmove(mbr, defmbr, nmbr);
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);
185 memmove(buf+Toffset, mbr+Toffset, secsize-Toffset);
186 memmove(mbr, buf, nmbr);
190 tp = (Tentry*)(mbr+Toffset);
191 memset(tp, 0, secsize-Toffset);
192 wrtentry(disk, tp, Type9, 0, disk->s, disk->secs);
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");