mkbb.c

  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