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
153
154