/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id: mknkboot.c 17847 2008-06-28 18:10:04Z bagder $
 *
 * Copyright (C) 2007 by Dave Chapman
 *
 * Based on merge0.cpp by James Espinoza, but completely rewritten.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <inttypes.h>

/* New entry point for nk.bin - where our dualboot code is inserted */
#define NK_ENTRY_POINT 0x88200000

/* Entry point (and load address) for the main Rockbox bootloader */
#define BL_ENTRY_POINT 0x8a000000

/*

Description of nk.bin from 

http://www.xs4all.nl/~itsme/projects/xda/wince-flashfile-formats.html

these files contain most information, several non-contigouos blocks
may be present and an entrypoint in the code.

   1. a 7 character signature "B000FF\n" ( that is with 3 zeroes, and
      ending in a linefeed )
   2. DWORD for image start
   3. DWORD for image length
   4. followd by several records of this format:
         1. DWORD with address where this block is to be flashed to
         2. DWORD with the length of this block
         3. DWORD with the 32 bit checksum of this block, in perl:
            unpack("%32C*", $data);
         4. followed by <length> bytes of data 
   5. the last record has address ZERO, in the length the entrypoint
      into the rom, and ZERO as checksum.


NOTE: The Gigabeat-S nk.bin contains 171 records, plus the EOF record.

mknkboot.c appends two images:

1) A "Disable" image which overwrites a word in the EBoot image
2) Our bootloader image, which has the same load address as nk.exe

*/

/* win32 compatibility */

#ifndef O_BINARY
#define O_BINARY 0
#endif

#define DISABLE_ADDR    0x88065A10 /* in EBoot */
#define DISABLE_INSN    0xe3a00001
#define DISABLE_SUM     (0xe3+0xa0+0x00+0x01)  

/* Code to dual-boot - this is inserted at NK_ENTRY_POINT */
static uint32_t dualboot[] = 
{
    0xe59f900c,      /* ldr     r9, [pc, #12] -> 0x53fa4000 */
    0xe5999000,      /* ldr     r9, [r9] */
    0xe3190010,      /* tst     r9, #16 ; 0x10 */
#if 0
    /* Branch to Rockbox if hold is on */
    0x159ff004,      /* ldrne   pc, [pc, #4]  -> 0x89000000 */
#else
    /* Branch to Rockbox if hold is off */
    0x059ff004,      /* ldreq   pc, [pc, #4]  -> 0x89000000 */
#endif
    /* Branch to original firmware */
    0xea0003fa,      /* b 0x1000 */

    0x53fa4000,      /* GPIO3_DR */
    BL_ENTRY_POINT   /* RB bootloader load address/entry point */
};

static void put_uint32le(uint32_t x, unsigned char* p)
{
    p[0] = x & 0xff;
    p[1] = (x >> 8) & 0xff;
    p[2] = (x >> 16) & 0xff;
    p[3] = (x >> 24) & 0xff;
}

static void usage(void)
{
    printf("Usage: mknkboot <firmware file> <boot file> <output file>\n");

    exit(1);
}

static off_t filesize(int fd) {
    struct stat buf;

    if (fstat(fd,&buf) < 0) {
        perror("[ERR]  Checking filesize of input file");
        return -1;
    } else {
        return(buf.st_size);
    }
}


int main(int argc, char *argv[])
{
    char *infile, *bootfile, *outfile;
    int fdin, fdboot,fdout;
    int i,n;
    int inlength,bootlength,newlength;
    unsigned char* buf;
    unsigned char* boot;
    unsigned char* boot2;
    unsigned char* disable;
    uint32_t sum;
    
    if(argc < 3) {
        usage();
    }

    infile = argv[1];
    bootfile = argv[2];
    outfile = argv[3];

    fdin = open(infile, O_RDONLY|O_BINARY);
    if (fdin < 0)
    {
        perror(infile);
    }

    fdboot = open(bootfile, O_RDONLY|O_BINARY);
    if (fdboot < 0)
    {
        perror(bootfile);
    }

    inlength = filesize(fdin);

    bootlength = filesize(fdboot);

    /* Create buffer for original nk.bin, plus our bootloader (with 12
       byte header), plus the 16-byte "disable record", plus our dual-boot code */

    newlength = inlength + (bootlength + 12) + 16 + (12 + 28);
    buf = malloc(newlength);

    if (buf==NULL)
    {
        printf("[ERR]  Could not allocate memory, aborting\n");
        return 1;
    }

    /****** STEP 1 - Read original nk.bin into buffer */

    n = read(fdin, buf, inlength);
    if (n != inlength)
    {
        printf("[ERR] Could not read from %s\n",infile);
        return 2;
    }

    /****** STEP 2 - Move EOF record to the new EOF */
    memcpy(buf + newlength - 12, buf + inlength - 12, 12);

    /* Overwrite default entry point with NK_ENTRY_POINT */
    put_uint32le(NK_ENTRY_POINT, buf + newlength - 8);

    /****** STEP 3 - Create a record to disable the firmware signature
                check in EBoot */
    disable = buf + inlength - 12;

    put_uint32le(DISABLE_ADDR, disable);
    put_uint32le(4,            disable + 4);
    put_uint32le(DISABLE_SUM,  disable + 8);
    put_uint32le(DISABLE_INSN, disable + 12);

    /****** STEP 4 - Read the bootloader binary */
    boot = disable + 16;
    n = read(fdboot, boot + 12, bootlength);
    if (n != bootlength)
    {
        printf("[ERR] Could not read from %s\n",bootfile);
        return 3;
    }

    /****** STEP 5 - Create header for bootloader record */

    /* Calculate checksum */
    sum = 0;
    for (i = 0; i < bootlength; i++) {
        sum += boot[12 + i];
    }
    
    put_uint32le(BL_ENTRY_POINT, boot); /* Our entry point */
    put_uint32le(bootlength, boot + 4);
    put_uint32le(sum, boot + 8);

    /****** STEP 6 -  Insert our dual-boot code */
    boot2 = boot + bootlength + 12;

    /* Copy dual-boot code in an endian-safe way */
    for (i = 0; i < (signed int)sizeof(dualboot) / 4; i++) {
        put_uint32le(dualboot[i], boot2 + 12 + i*4);
    }

    /* Calculate checksum */
    sum = 0;
    for (i = 0; i < (signed int)sizeof(dualboot); i++) {
        sum += boot2[i+12];
    }
    
    put_uint32le(NK_ENTRY_POINT, boot2); /* New entry point for our nk.bin */
    put_uint32le(sizeof(dualboot), boot2 + 4);
    put_uint32le(sum, boot2 + 8);

    /****** STEP 7 -  Now write the output file */

    fdout = open(outfile, O_WRONLY|O_CREAT|O_TRUNC|O_BINARY, 0644);
    if (fdout < 0)
    {
        perror(outfile);
    }

    n = write(fdout, buf, newlength);
    if (n != newlength)
    {
        printf("[ERR] Could not write output file %s\n",outfile);
        return 3;
    }

    close(fdin);
    close(fdboot);
    close(fdout);
    
    return 0;
}
