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/*
 * dns313-header.c
 *
 * Program to add the modified U-Boot header to a binary used with
 * the D-Link DNS-313 boot loader when booting directly from an
 * EXT2 formatted hard drive.
 *
 * The DNS313 use the same header on zImage, ramdisk, rootfs.
 *
 * Written by Linus Walleij <linus.walleij@linaro.org>
 * License terms: GPLv2
 */
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

/*
 * This is the U-Boot magic number, so the U-Boot header was used
 * (obviously) as a template for this custom header.
 */
#define IH_MAGIC        0x27051956
#define HEADER_SIZE     0x68

#define OFFSET_MAGIC    0x00
#define OFFSET_HCRC     0x04
#define OFFSET_TIME     0x08
#define OFFSET_SIZE     0x0c
#define OFFSET_LOAD     0x10
#define OFFSET_EP       0x14
#define OFFSET_DCRC     0x18
#define OFFSET_OS       0x1c
#define OFFSET_ARCH     0x1d
#define OFFSET_TYPE     0x1e
#define OFFSET_COMP     0x1f
#define OFFSET_NAME     0x20
#define NAME_LEN        0x20
#define OFFSET_MODEL    0x40
#define MODEL_LEN       0x10
#define OFFSET_VERSION  0x50
#define VERSION_LEN     0x10
#define OFFSET_MAC      0x60
#define MAC_LEN         6

static const uint32_t crc32_table[256] = {
        0x00000000UL, 0x77073096UL, 0xee0e612cUL, 0x990951baUL, 0x076dc419UL,
        0x706af48fUL, 0xe963a535UL, 0x9e6495a3UL, 0x0edb8832UL, 0x79dcb8a4UL,
        0xe0d5e91eUL, 0x97d2d988UL, 0x09b64c2bUL, 0x7eb17cbdUL, 0xe7b82d07UL,
        0x90bf1d91UL, 0x1db71064UL, 0x6ab020f2UL, 0xf3b97148UL, 0x84be41deUL,
        0x1adad47dUL, 0x6ddde4ebUL, 0xf4d4b551UL, 0x83d385c7UL, 0x136c9856UL,
        0x646ba8c0UL, 0xfd62f97aUL, 0x8a65c9ecUL, 0x14015c4fUL, 0x63066cd9UL,
        0xfa0f3d63UL, 0x8d080df5UL, 0x3b6e20c8UL, 0x4c69105eUL, 0xd56041e4UL,
        0xa2677172UL, 0x3c03e4d1UL, 0x4b04d447UL, 0xd20d85fdUL, 0xa50ab56bUL,
        0x35b5a8faUL, 0x42b2986cUL, 0xdbbbc9d6UL, 0xacbcf940UL, 0x32d86ce3UL,
        0x45df5c75UL, 0xdcd60dcfUL, 0xabd13d59UL, 0x26d930acUL, 0x51de003aUL,
        0xc8d75180UL, 0xbfd06116UL, 0x21b4f4b5UL, 0x56b3c423UL, 0xcfba9599UL,
        0xb8bda50fUL, 0x2802b89eUL, 0x5f058808UL, 0xc60cd9b2UL, 0xb10be924UL,
        0x2f6f7c87UL, 0x58684c11UL, 0xc1611dabUL, 0xb6662d3dUL, 0x76dc4190UL,
        0x01db7106UL, 0x98d220bcUL, 0xefd5102aUL, 0x71b18589UL, 0x06b6b51fUL,
        0x9fbfe4a5UL, 0xe8b8d433UL, 0x7807c9a2UL, 0x0f00f934UL, 0x9609a88eUL,
        0xe10e9818UL, 0x7f6a0dbbUL, 0x086d3d2dUL, 0x91646c97UL, 0xe6635c01UL,
        0x6b6b51f4UL, 0x1c6c6162UL, 0x856530d8UL, 0xf262004eUL, 0x6c0695edUL,
        0x1b01a57bUL, 0x8208f4c1UL, 0xf50fc457UL, 0x65b0d9c6UL, 0x12b7e950UL,
        0x8bbeb8eaUL, 0xfcb9887cUL, 0x62dd1ddfUL, 0x15da2d49UL, 0x8cd37cf3UL,
        0xfbd44c65UL, 0x4db26158UL, 0x3ab551ceUL, 0xa3bc0074UL, 0xd4bb30e2UL,
        0x4adfa541UL, 0x3dd895d7UL, 0xa4d1c46dUL, 0xd3d6f4fbUL, 0x4369e96aUL,
        0x346ed9fcUL, 0xad678846UL, 0xda60b8d0UL, 0x44042d73UL, 0x33031de5UL,
        0xaa0a4c5fUL, 0xdd0d7cc9UL, 0x5005713cUL, 0x270241aaUL, 0xbe0b1010UL,
        0xc90c2086UL, 0x5768b525UL, 0x206f85b3UL, 0xb966d409UL, 0xce61e49fUL,
        0x5edef90eUL, 0x29d9c998UL, 0xb0d09822UL, 0xc7d7a8b4UL, 0x59b33d17UL,
        0x2eb40d81UL, 0xb7bd5c3bUL, 0xc0ba6cadUL, 0xedb88320UL, 0x9abfb3b6UL,
        0x03b6e20cUL, 0x74b1d29aUL, 0xead54739UL, 0x9dd277afUL, 0x04db2615UL,
        0x73dc1683UL, 0xe3630b12UL, 0x94643b84UL, 0x0d6d6a3eUL, 0x7a6a5aa8UL,
        0xe40ecf0bUL, 0x9309ff9dUL, 0x0a00ae27UL, 0x7d079eb1UL, 0xf00f9344UL,
        0x8708a3d2UL, 0x1e01f268UL, 0x6906c2feUL, 0xf762575dUL, 0x806567cbUL,
        0x196c3671UL, 0x6e6b06e7UL, 0xfed41b76UL, 0x89d32be0UL, 0x10da7a5aUL,
        0x67dd4accUL, 0xf9b9df6fUL, 0x8ebeeff9UL, 0x17b7be43UL, 0x60b08ed5UL,
        0xd6d6a3e8UL, 0xa1d1937eUL, 0x38d8c2c4UL, 0x4fdff252UL, 0xd1bb67f1UL,
        0xa6bc5767UL, 0x3fb506ddUL, 0x48b2364bUL, 0xd80d2bdaUL, 0xaf0a1b4cUL,
        0x36034af6UL, 0x41047a60UL, 0xdf60efc3UL, 0xa867df55UL, 0x316e8eefUL,
        0x4669be79UL, 0xcb61b38cUL, 0xbc66831aUL, 0x256fd2a0UL, 0x5268e236UL,
        0xcc0c7795UL, 0xbb0b4703UL, 0x220216b9UL, 0x5505262fUL, 0xc5ba3bbeUL,
        0xb2bd0b28UL, 0x2bb45a92UL, 0x5cb36a04UL, 0xc2d7ffa7UL, 0xb5d0cf31UL,
        0x2cd99e8bUL, 0x5bdeae1dUL, 0x9b64c2b0UL, 0xec63f226UL, 0x756aa39cUL,
        0x026d930aUL, 0x9c0906a9UL, 0xeb0e363fUL, 0x72076785UL, 0x05005713UL,
        0x95bf4a82UL, 0xe2b87a14UL, 0x7bb12baeUL, 0x0cb61b38UL, 0x92d28e9bUL,
        0xe5d5be0dUL, 0x7cdcefb7UL, 0x0bdbdf21UL, 0x86d3d2d4UL, 0xf1d4e242UL,
        0x68ddb3f8UL, 0x1fda836eUL, 0x81be16cdUL, 0xf6b9265bUL, 0x6fb077e1UL,
        0x18b74777UL, 0x88085ae6UL, 0xff0f6a70UL, 0x66063bcaUL, 0x11010b5cUL,
        0x8f659effUL, 0xf862ae69UL, 0x616bffd3UL, 0x166ccf45UL, 0xa00ae278UL,
        0xd70dd2eeUL, 0x4e048354UL, 0x3903b3c2UL, 0xa7672661UL, 0xd06016f7UL,
        0x4969474dUL, 0x3e6e77dbUL, 0xaed16a4aUL, 0xd9d65adcUL, 0x40df0b66UL,
        0x37d83bf0UL, 0xa9bcae53UL, 0xdebb9ec5UL, 0x47b2cf7fUL, 0x30b5ffe9UL,
        0xbdbdf21cUL, 0xcabac28aUL, 0x53b39330UL, 0x24b4a3a6UL, 0xbad03605UL,
        0xcdd70693UL, 0x54de5729UL, 0x23d967bfUL, 0xb3667a2eUL, 0xc4614ab8UL,
        0x5d681b02UL, 0x2a6f2b94UL, 0xb40bbe37UL, 0xc30c8ea1UL, 0x5a05df1bUL,
        0x2d02ef8dUL
};

static uint32_t crc32(uint32_t crc,
                      const unsigned char *buf,
                      unsigned int len)
{
        crc = crc ^ 0xffffffffUL;
        do {
                crc = crc32_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
        } while (--len);
        return crc ^ 0xffffffffUL;
}

static void be_wr(unsigned char *buf, uint32_t val)
{
        buf[0] = (val >> 24) & 0xFFU;
        buf[1] = (val >> 16) & 0xFFU;
        buf[2] = (val >> 8) & 0xFFU;
        buf[3] = val & 0xFFU;
}

int main(int argc, char **argv)
{
        int fdin;
        int fdout;
        struct stat sb;
        uint32_t filesize;
        uint32_t padding;
        int ret = 0;
        const char *pathin;
        const char *pathout;
        unsigned char *buffer;
        unsigned char *infop;
        uint32_t sum;
        size_t bufsize;
        size_t bytes;
        int i;

        if (argc < 3) {
                printf("Too few arguments.\n");
                printf("%s <infile> <outfile>\n", argv[0]);
        }

        pathin = argv[1];
        pathout = argv[2];

        ret = stat(pathin, &sb);
        if (ret < 0)
                return ret;

        filesize = sb.st_size;
        padding = filesize % 4;
        printf("INFILE: %s, size: %08x bytes\n", pathin, filesize);
        /* File + extended header size */
        bufsize = filesize + HEADER_SIZE;

        printf("Allocate %08x bytes\n", bufsize);
        buffer = malloc(bufsize);
        if (!buffer) {
                printf("OOM: could not allocate buffer\n");
                return 0;
        }

        memset(buffer, 0x00, bufsize);

        /* Read file to buffer */
        fdin = open(pathin, O_RDONLY);
        if (!fdin) {
                printf("ERROR: could not open input file\n");
                return 0;
        }
        bytes = read(fdin, buffer + HEADER_SIZE, filesize);
        if (bytes < filesize) {
                printf("ERROR: could not read entire file\n");
                return 0;
        }
        close(fdin);

        /* PREP HEADER AND FOOTER */
        infop = buffer;

        be_wr(buffer + OFFSET_MAGIC, IH_MAGIC);

        /* FIXME: use actual time */
        be_wr(buffer + OFFSET_TIME, 0x4c06738c);
        be_wr(buffer + OFFSET_SIZE, filesize);

        /* Load address & entry point */
        be_wr(buffer + OFFSET_LOAD, 0x00008000);
        be_wr(buffer + OFFSET_EP, 0x00008000);

        buffer[OFFSET_OS] = 0x05; /* Linux */
        buffer[OFFSET_ARCH] = 0x02; /* ARM */
        buffer[OFFSET_TYPE] = 0x02; /* OS kernel image */
        buffer[OFFSET_COMP] = 0x01; /* gzip */

        /* The vendor firmware just hardcodes this */
        strncpy(buffer + OFFSET_NAME, "kernel.img", NAME_LEN);
        buffer[OFFSET_NAME + NAME_LEN - 1] = '\0';
        strncpy(buffer + OFFSET_MODEL, "dns-313v3", MODEL_LEN);
        buffer[OFFSET_MODEL + MODEL_LEN - 1] = '\0';
        strncpy(buffer + OFFSET_VERSION, "2.01b04", VERSION_LEN);
        buffer[OFFSET_VERSION + VERSION_LEN - 1] = '\0';
        /* Just some MAC address from the example */
        buffer[OFFSET_MAC] = 0x00;
        buffer[OFFSET_MAC + 1] = 0x80;
        buffer[OFFSET_MAC + 2] = 0xc8;
        buffer[OFFSET_MAC + 3] = 0x16;
        buffer[OFFSET_MAC + 4] = 0x81;
        buffer[OFFSET_MAC + 5] = 0x68;

        /* Checksum payload */
        sum = crc32(0, buffer + HEADER_SIZE, filesize);
        be_wr(buffer + OFFSET_DCRC, sum);
        printf("data checksum: 0x%08x\n", sum);

        /* Checksum header, then write that into the header checksum */
        sum = crc32(0, buffer, HEADER_SIZE);
        be_wr(buffer + OFFSET_HCRC, sum);
        printf("header checksum: 0x%08x\n", sum);

        printf("OUTFILE: %s, size: %08x bytes\n", pathout, bufsize);
        fdout = open(pathout, O_RDWR|O_CREAT|O_TRUNC,S_IRWXU|S_IRGRP);
        if (!fdout) {
                printf("ERROR: could not open output file\n");
                return  0;
        }
        bytes = write(fdout, buffer, bufsize);
        if (bytes < bufsize) {
                printf("ERROR: could not write complete output file\n");
                return  0;
        }
        close(fdout);

        free(buffer);

        return 0;
}