boot/tools/mkbb.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /* This utility makes a bootblock suitable for the SRM console/miniloader */
0003
0004 /* Usage:
0005  *  mkbb <device> <lxboot>
0006  *
0007  * Where <device> is the name of the device to install the bootblock on,
0008  * and <lxboot> is the name of a bootblock to merge in.  This bootblock
0009  * contains the offset and size of the bootloader.  It must be exactly
0010  * 512 bytes long.
0011  */
0012
0013 #include <fcntl.h>
0014 #include <unistd.h>
0015 #include <stdlib.h>
0016 #include <stdio.h>
0017
0018 /* Minimal definition of disklabel, so we don't have to include
0019  * asm/disklabel.h (confuses make)
0020  */
0021 #ifndef MAXPARTITIONS
0022 #define MAXPARTITIONS   8                       /* max. # of partitions */
0023 #endif
0024
0025 #ifndef u8
0026 #define u8 unsigned char
0027 #endif
0028
0029 #ifndef u16
0030 #define u16 unsigned short
0031 #endif
0032
0033 #ifndef u32
0034 #define u32 unsigned int
0035 #endif
0036
0037 struct disklabel {
0038     u32 d_magic;                /* must be DISKLABELMAGIC */
0039     u16 d_type, d_subtype;
0040     u8  d_typename[16];
0041     u8  d_packname[16];
0042     u32 d_secsize;
0043     u32 d_nsectors;
0044     u32 d_ntracks;
0045     u32 d_ncylinders;
0046     u32 d_secpercyl;
0047     u32 d_secprtunit;
0048     u16 d_sparespertrack;
0049     u16 d_sparespercyl;
0050     u32 d_acylinders;
0051     u16 d_rpm, d_interleave, d_trackskew, d_cylskew;
0052     u32 d_headswitch, d_trkseek, d_flags;
0053     u32 d_drivedata[5];
0054     u32 d_spare[5];
0055     u32 d_magic2;               /* must be DISKLABELMAGIC */
0056     u16 d_checksum;
0057     u16 d_npartitions;
0058     u32 d_bbsize, d_sbsize;
0059     struct d_partition {
0060     u32 p_size;
0061     u32 p_offset;
0062     u32 p_fsize;
0063     u8  p_fstype;
0064     u8  p_frag;
0065     u16 p_cpg;
0066     } d_partitions[MAXPARTITIONS];
0067 };
0068
0069
0070 typedef union __bootblock {
0071     struct {
0072         char            __pad1[64];
0073         struct disklabel    __label;
0074     } __u1;
0075     struct {
0076     unsigned long       __pad2[63];
0077     unsigned long       __checksum;
0078     } __u2;
0079     char        bootblock_bytes[512];
0080     unsigned long   bootblock_quadwords[64];
0081 } bootblock;
0082
0083 #define bootblock_label     __u1.__label
0084 #define bootblock_checksum  __u2.__checksum
0085
0086 int main(int argc, char ** argv)
0087 {
0088     bootblock       bootblock_from_disk;
0089     bootblock       bootloader_image;
0090     int         dev, fd;
0091     int         i;
0092     int         nread;
0093
0094     /* Make sure of the arg count */
0095     if(argc != 3) {
0096     fprintf(stderr, "Usage: %s device lxboot\n", argv[0]);
0097     exit(0);
0098     }
0099
0100     /* First, open the device and make sure it's accessible */
0101     dev = open(argv[1], O_RDWR);
0102     if(dev < 0) {
0103     perror(argv[1]);
0104     exit(0);
0105     }
0106
0107     /* Now open the lxboot and make sure it's reasonable */
0108     fd = open(argv[2], O_RDONLY);
0109     if(fd < 0) {
0110     perror(argv[2]);
0111     close(dev);
0112     exit(0);
0113     }
0114
0115     /* Read in the lxboot */
0116     nread = read(fd, &bootloader_image, sizeof(bootblock));
0117     if(nread != sizeof(bootblock)) {
0118     perror("lxboot read");
0119     fprintf(stderr, "expected %zd, got %d\n", sizeof(bootblock), nread);
0120     exit(0);
0121     }
0122
0123     /* Read in the bootblock from disk. */
0124     nread = read(dev, &bootblock_from_disk, sizeof(bootblock));
0125     if(nread != sizeof(bootblock)) {
0126     perror("bootblock read");
0127     fprintf(stderr, "expected %zd, got %d\n", sizeof(bootblock), nread);
0128     exit(0);
0129     }
0130
0131     /* Swap the bootblock's disklabel into the bootloader */
0132     bootloader_image.bootblock_label = bootblock_from_disk.bootblock_label;
0133
0134     /* Calculate the bootblock checksum */
0135     bootloader_image.bootblock_checksum = 0;
0136     for(i = 0; i < 63; i++) {
0137     bootloader_image.bootblock_checksum +=
0138             bootloader_image.bootblock_quadwords[i];
0139     }
0140
0141     /* Write the whole thing out! */
0142     lseek(dev, 0L, SEEK_SET);
0143     if(write(dev, &bootloader_image, sizeof(bootblock)) != sizeof(bootblock)) {
0144     perror("bootblock write");
0145     exit(0);
0146     }
0147
0148     close(fd);
0149     close(dev);
0150     exit(0);
0151 }
0152
0153