mkbb.c (3598B)
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