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153 lines · 3.5 KiB

1// SPDX-License-Identifier: GPL-2.0
2/* This utility makes a bootblock suitable for the SRM console/miniloader */
3
4/* Usage:
5 * mkbb <device> <lxboot>
6 *
7 * Where <device> is the name of the device to install the bootblock on,
8 * and <lxboot> is the name of a bootblock to merge in. This bootblock
9 * contains the offset and size of the bootloader. It must be exactly
10 * 512 bytes long.
11 */
12
13#include <fcntl.h>
14#include <unistd.h>
15#include <stdlib.h>
16#include <stdio.h>
17
18/* Minimal definition of disklabel, so we don't have to include
19 * asm/disklabel.h (confuses make)
20 */
21#ifndef MAXPARTITIONS
22#define MAXPARTITIONS 8 /* max. # of partitions */
23#endif
24
25#ifndef u8
26#define u8 unsigned char
27#endif
28
29#ifndef u16
30#define u16 unsigned short
31#endif
32
33#ifndef u32
34#define u32 unsigned int
35#endif
36
37struct disklabel {
38 u32 d_magic; /* must be DISKLABELMAGIC */
39 u16 d_type, d_subtype;
40 u8 d_typename[16];
41 u8 d_packname[16];
42 u32 d_secsize;
43 u32 d_nsectors;
44 u32 d_ntracks;
45 u32 d_ncylinders;
46 u32 d_secpercyl;
47 u32 d_secprtunit;
48 u16 d_sparespertrack;
49 u16 d_sparespercyl;
50 u32 d_acylinders;
51 u16 d_rpm, d_interleave, d_trackskew, d_cylskew;
52 u32 d_headswitch, d_trkseek, d_flags;
53 u32 d_drivedata[5];
54 u32 d_spare[5];
55 u32 d_magic2; /* must be DISKLABELMAGIC */
56 u16 d_checksum;
57 u16 d_npartitions;
58 u32 d_bbsize, d_sbsize;
59 struct d_partition {
60 u32 p_size;
61 u32 p_offset;
62 u32 p_fsize;
63 u8 p_fstype;
64 u8 p_frag;
65 u16 p_cpg;
66 } d_partitions[MAXPARTITIONS];
67};
68
69
70typedef union __bootblock {
71 struct {
72 char __pad1[64];
73 struct disklabel __label;
74 } __u1;
75 struct {
76 unsigned long __pad2[63];
77 unsigned long __checksum;
78 } __u2;
79 char bootblock_bytes[512];
80 unsigned long bootblock_quadwords[64];
81} bootblock;
82
83#define bootblock_label __u1.__label
84#define bootblock_checksum __u2.__checksum
85
86int main(int argc, char ** argv)
87{
88 bootblock bootblock_from_disk;
89 bootblock bootloader_image;
90 int dev, fd;
91 int i;
92 int nread;
93
94 /* Make sure of the arg count */
95 if(argc != 3) {
96 fprintf(stderr, "Usage: %s device lxboot\n", argv[0]);
97 exit(0);
98 }
99
100 /* First, open the device and make sure it's accessible */
101 dev = open(argv[1], O_RDWR);
102 if(dev < 0) {
103 perror(argv[1]);
104 exit(0);
105 }
106
107 /* Now open the lxboot and make sure it's reasonable */
108 fd = open(argv[2], O_RDONLY);
109 if(fd < 0) {
110 perror(argv[2]);
111 close(dev);
112 exit(0);
113 }
114
115 /* Read in the lxboot */
116 nread = read(fd, &bootloader_image, sizeof(bootblock));
117 if(nread != sizeof(bootblock)) {
118 perror("lxboot read");
119 fprintf(stderr, "expected %zd, got %d\n", sizeof(bootblock), nread);
120 exit(0);
121 }
122
123 /* Read in the bootblock from disk. */
124 nread = read(dev, &bootblock_from_disk, sizeof(bootblock));
125 if(nread != sizeof(bootblock)) {
126 perror("bootblock read");
127 fprintf(stderr, "expected %zd, got %d\n", sizeof(bootblock), nread);
128 exit(0);
129 }
130
131 /* Swap the bootblock's disklabel into the bootloader */
132 bootloader_image.bootblock_label = bootblock_from_disk.bootblock_label;
133
134 /* Calculate the bootblock checksum */
135 bootloader_image.bootblock_checksum = 0;
136 for(i = 0; i < 63; i++) {
137 bootloader_image.bootblock_checksum +=
138 bootloader_image.bootblock_quadwords[i];
139 }
140
141 /* Write the whole thing out! */
142 lseek(dev, 0L, SEEK_SET);
143 if(write(dev, &bootloader_image, sizeof(bootblock)) != sizeof(bootblock)) {
144 perror("bootblock write");
145 exit(0);
146 }
147
148 close(fd);
149 close(dev);
150 exit(0);
151}
152
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