113 lines
3.9 KiB
C
113 lines
3.9 KiB
C
/*
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* aarch64-rpi/mkboot.c
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*
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* Copyright (C) 2017 - 2021 bzt (bztsrc@gitlab)
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use, copy,
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* modify, merge, publish, distribute, sublicense, and/or sell copies
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* of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*
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* This file is part of the BOOTBOOT Protocol package.
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* @brief Little tool to create a RPi compatible MBR for ESP
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*
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*/
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <unistd.h>
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/* entry point */
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int main(int argc, char** argv)
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{
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// variables
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unsigned char data[65536];
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unsigned int np,sp,i,es,ee;
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int f;
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// check arguments
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if(argc < 2) {
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printf( "BOOTBOOT mkboot utility - bztsrc@gitlab\n\nUsage:\n"
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" ./mkboot <disk>\n\n"
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"Maps GPT EFI System Partition into MBR so that Raspberry Pi\n"
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"firmware can find it's files and boot from it.\n"
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"Examples:\n"
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" ./mkboot diskimage.dd - modify a disk image file\n"
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" ./mkboot /dev/sda - modify a real disk\n");
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return 1;
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}
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// open file
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f = open(argv[1], O_RDONLY);
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if(f < 0) {
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fprintf(stderr, "mkboot: file not found\n");
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return 2;
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}
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// read the partitioning tables
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if(read(f, data, 65536)==-1) {
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close(f);
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fprintf(stderr, "mkboot: unable to read file\n");
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return 2;
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}
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close(f);
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if(memcmp((void*)&data[512], "EFI PART", 8)) {
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fprintf(stderr, "mkboot: GPT partitioning table not found\n");
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return 2;
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}
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// get number of partitions and size of partition entry
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np=*((unsigned int*)&data[512+80]); sp=*((unsigned int*)&data[512+84]);
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i=*((unsigned int*)&data[512+72])*512; es=ee=0;
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// get esp start and esp end sectors
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while(np--) {
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if(*((unsigned int*)&data[i])==0xC12A7328 && *((unsigned int*)&data[i+4])==0x11D2F81F) {
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es=*((unsigned int*)&data[i+32]); ee=*((unsigned int*)&data[i+40]); break;
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}
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i+=sp;
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}
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if(es==0 || ee==0 || ee<es+1) {
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fprintf(stderr, "mkboot: ESP not found in GPT\n");
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return 2;
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}
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// if first MBR partition is not a FAT, make space for it
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if(data[0x1C2]!=0xC/*FAT32 LBA*/ && data[0x1C2]!=0xE/*FAT16 LBA*/) {
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memcpy((void*)&data+0x1EE, (void*)&data+0x1DE, 16);
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memcpy((void*)&data+0x1DE, (void*)&data+0x1CE, 16);
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memcpy((void*)&data+0x1CE, (void*)&data+0x1BE, 16);
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data[0x1C2]=0xC;
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}
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// check if it's already pointing to ESP
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ee-=sp-1;
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if(*((unsigned int*)&data[0x1C6])==es && *((unsigned int*)&data[0x1CA])==ee) {
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fprintf(stderr, "mkboot: ESP already mapped to MBR, nothing to do\n");
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return 0;
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}
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*((unsigned int*)&data[0x1C6])=es;
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*((unsigned int*)&data[0x1CA])=ee;
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// save boot record
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f = open(argv[1], O_WRONLY);
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if(f < 0 || write(f, data, 512) <= 0) {
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fprintf(stderr, "mkboot: unable to write MBR\n");
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return 3;
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}
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close(f);
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// all went well
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printf("mkboot: GPT ESP mapped to MBR successfully\n");
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}
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