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