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 
37 struct 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 
70 typedef 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 
main(int argc,char ** argv)86 int 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