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// SPDX-License-Identifier: GPL-2.0
/* This utility makes a bootblock suitable for the SRM console/miniloader */
/* Usage:
* mkbb <device> <lxboot>
*
* Where <device> is the name of the device to install the bootblock on,
* and <lxboot> is the name of a bootblock to merge in. This bootblock
* contains the offset and size of the bootloader. It must be exactly
* 512 bytes long.
*/
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
/* Minimal definition of disklabel, so we don't have to include
* asm/disklabel.h (confuses make)
*/
#ifndef MAXPARTITIONS
#define MAXPARTITIONS 8 /* max. # of partitions */
#endif
#ifndef u8
#define u8 unsigned char
#endif
#ifndef u16
#define u16 unsigned short
#endif
#ifndef u32
#define u32 unsigned int
#endif
struct disklabel {
u32 d_magic; /* must be DISKLABELMAGIC */
u16 d_type, d_subtype;
u8 d_typename[16];
u8 d_packname[16];
u32 d_secsize;
u32 d_nsectors;
u32 d_ntracks;
u32 d_ncylinders;
u32 d_secpercyl;
u32 d_secprtunit;
u16 d_sparespertrack;
u16 d_sparespercyl;
u32 d_acylinders;
u16 d_rpm, d_interleave, d_trackskew, d_cylskew;
u32 d_headswitch, d_trkseek, d_flags;
u32 d_drivedata[5];
u32 d_spare[5];
u32 d_magic2; /* must be DISKLABELMAGIC */
u16 d_checksum;
u16 d_npartitions;
u32 d_bbsize, d_sbsize;
struct d_partition {
u32 p_size;
u32 p_offset;
u32 p_fsize;
u8 p_fstype;
u8 p_frag;
u16 p_cpg;
} d_partitions[MAXPARTITIONS];
};
typedef union __bootblock {
struct {
char __pad1[64];
struct disklabel __label;
} __u1;
struct {
unsigned long __pad2[63];
unsigned long __checksum;
} __u2;
char bootblock_bytes[512];
unsigned long bootblock_quadwords[64];
} bootblock;
#define bootblock_label __u1.__label
#define bootblock_checksum __u2.__checksum
int main(int argc, char ** argv)
{
bootblock bootblock_from_disk;
bootblock bootloader_image;
int dev, fd;
int i;
int nread;
/* Make sure of the arg count */
if(argc != 3) {
fprintf(stderr, "Usage: %s device lxboot\n", argv[0]);
exit(0);
}
/* First, open the device and make sure it's accessible */
dev = open(argv[1], O_RDWR);
if(dev < 0) {
perror(argv[1]);
exit(0);
}
/* Now open the lxboot and make sure it's reasonable */
fd = open(argv[2], O_RDONLY);
if(fd < 0) {
perror(argv[2]);
close(dev);
exit(0);
}
/* Read in the lxboot */
nread = read(fd, &bootloader_image, sizeof(bootblock));
if(nread != sizeof(bootblock)) {
perror("lxboot read");
fprintf(stderr, "expected %zd, got %d\n", sizeof(bootblock), nread);
exit(0);
}
/* Read in the bootblock from disk. */
nread = read(dev, &bootblock_from_disk, sizeof(bootblock));
if(nread != sizeof(bootblock)) {
perror("bootblock read");
fprintf(stderr, "expected %zd, got %d\n", sizeof(bootblock), nread);
exit(0);
}
/* Swap the bootblock's disklabel into the bootloader */
bootloader_image.bootblock_label = bootblock_from_disk.bootblock_label;
/* Calculate the bootblock checksum */
bootloader_image.bootblock_checksum = 0;
for(i = 0; i < 63; i++) {
bootloader_image.bootblock_checksum +=
bootloader_image.bootblock_quadwords[i];
}
/* Write the whole thing out! */
lseek(dev, 0L, SEEK_SET);
if(write(dev, &bootloader_image, sizeof(bootblock)) != sizeof(bootblock)) {
perror("bootblock write");
exit(0);
}
close(fd);
close(dev);
exit(0);
}
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