/*
 * WRT400n - Firmware Generation Creator
 *
 * Creates a firmware image for the Linksys WRT400n router,
 * that can be uploaded via the firmware upload page,
 * from a kernel image file and root fs file
 *
 *	Author: Sandeep Mistry
 */
#include <arpa/inet.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

#include "cyg_crc.h"

// https://dev.openwrt.org/browser/trunk/target/linux/rdc-2.6/files/drivers/mtd/maps/rdc3210.c
static uint32_t crctab[257] =
{
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
	0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
	0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
	0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
	0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
	0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
	0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
	0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
	0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
	0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
	0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
	0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
	0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
	0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
	0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
	0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
	0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
	0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
	0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
	0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
	0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
	0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
	0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
	0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
	0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
	0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
	0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
	0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
	0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
	0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
	0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
	0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
	0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
	0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
	0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
	0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
	0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
	0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
	0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
	0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
	0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
	0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
	0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
	0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
	0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
	0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
	0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
	0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
	0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
	0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
	0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
	0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
	0
};

static uint32_t crc32(uint8_t* buf, uint32_t len)
{
	register int i;
	uint32_t sum;
	register uint32_t s0;
	s0 = ~0;
	for (i = 0; i < len; i++)
	{
		s0 = (s0 >> 8) ^ crctab[(uint8_t) (s0 & 0xFF) ^ buf[i]];
	}
	sum = ~s0;
	return sum;
}

#define HEADERSIZE	60
#define MAGIC		"GMTKRT400N"

// global variables
uint8_t kernelbuf[0x100000];	// kernel - lzma - uImage
uint8_t rootfsbuf[0x2FFFC4];	// root - squashfs

uint8_t buf[0x400000];		// buffer for image


// Header format:
//
//		GPL Tarball: http://downloads.linksysbycisco.com/downloads/WRT400N_1.0.01.19_US.tar,0.gz
//		File: WRT400N_1.0.01.19_US/FW_WRT400N_1.0.01.19_US_20081229/GTK/user/include/fw_upgrade.h
//
//
//		Struct:
//			typedef struct
//			{
//				UINT32		checksum;		/* CRC32 */
//				UINT8			magic[11];		/* The value of GTIMG_MAGIC */
//				UINT32		kernel_length;		/* The length of the kernel image */
//				//UINT32		kernel_entry_point;	/* Kernel's entry point for RedBoot's information */
//				UINT32		kernel_upgrade_flag;	/* Set to 1 if we need to upgrade the kernel parition of the Flash */
//				UINT32		rootfs_length;		/* The length of the rootfs image */
//				//UINT32		rootfs_entry_point;	/* Not in use */
//				UINT32		rootfs_upgrade_flag;	/* Set to 1 if we need to upgrade the rootfs parition of the Flash */
//
//				// Add 3 items by Vic Yu, 2006-05/10
//				UINT32		kernel_checksum;
//				UINT32		rootfs_checksum;
//				UINT32		fw_totalsize;
//				UINT32		reserved[4];
//			}imghdr_t , *pLinuxFWHeader_T;
//
//
//		Description
//			- checksum: 			CRC32 of kernel and root fs, back to back
//			- magic:				GMTKRT400N
//			- kernel_length:		kernel length in bytes
//			- kernel_upgrade_flag:	should we upgrade the kernel - set to 1
//			- rootfs_length:		root fs length in byte
//			- rootfs_upgrade_flag:	should we upgrade the root fs - set to 1
//			- kernel_checksum: 		Gary S. Brown's 32 bit CRC algorithm for kernel, with remaining bits
//									set to 0xFF upto 0x100000 bytes (total length)
//			- rootfs_checksum:		Gary S. Brown's 32 bit CRC algorithm for root fs, with remaining bits
//									set to 0xFF upto 0x2FFFC4 bytes	(total length)
//			- fw_totalsize:			total firmware image file length (header length + kernel length + root fs length)
//			- reserved[4]:			reserved ??? - set to all 0xFF



int main(int argc, char *argv[])
{
	// file descriptors ...
	int 		kernelfd		= -1;
	int 		rootfsfd			= -1;
	int			outfd			= -1;

	char*		kernelfilename	= NULL;
	char*		rootfsfilename	= NULL;
	char*		outputfilename	= NULL;

	// file sizes
	uint32_t 	kernelsize 		= 0;
	uint32_t 	rootfssize 		= 0;
	uint32_t 	totalsize 		= 0;

	// header flags
	uint32_t 	kernelflag 		= 0;
	uint32_t 	rootfsflag 		= 0;

	// checksums
	uint32_t 	kernelchecksum 	= 0;
	uint32_t 	rootfschecksum 	= 0;
	uint32_t	crc				= 0;

	if(argc != 4)
	{
		printf("Usage:\n\t%s <kernel file> <rootfs file> <output file>\n", argv[0]);
		return 1;
	}

	kernelfilename = argv[1];
	rootfsfilename = argv[2];
	outputfilename = argv[3];

	// Fill the kernel, rootfs, main buffer
	memset(kernelbuf, 0xFF, sizeof(kernelbuf));
	memset(rootfsbuf, 0xFF, sizeof(rootfsbuf));
	memset(buf, 0xFF, sizeof(buf));

	// open the kernel ..
	kernelfd = open(kernelfilename, O_RDONLY);

	if(kernelfd == -1)
	{
		printf("Error: opening '%s'\n", kernelfilename);
		goto done;
	}

	// read in the kernel ...
	kernelsize = read(kernelfd, kernelbuf, sizeof(kernelbuf));

	if(kernelsize == -1)
	{
		printf("Error: reading '%s'\n", kernelfilename);
		goto done;
	}

	// calculate the kernel checksum ...
	kernelchecksum = cyg_crc32_accumulate(0, kernelbuf, sizeof(kernelbuf));

	// print out stats
	printf("%s: size %d (0x%x), crc32 = 0x%x\n", kernelfilename, kernelsize, kernelsize, kernelchecksum);


	// open the root fs ..
	rootfsfd = open(rootfsfilename, O_RDONLY);

	if(rootfsfd == -1)
	{
		printf("Error: opening '%s'\n", rootfsfilename);
		goto done;
	}

	// read in the root fs ..
	rootfssize = read(rootfsfd, rootfsbuf, sizeof(rootfsbuf));

	if(rootfssize == -1)
	{
		printf("Error: reading '%s'\n", rootfsfilename);
		goto done;
	}

	// calculate the root fs checksum ...
	rootfschecksum = cyg_crc32_accumulate(0, rootfsbuf, sizeof(rootfsbuf));

	// print out stats
	printf("%s: size %d (0x%x), crc32 = 0x%x\n", rootfsfilename, rootfssize, rootfssize, rootfschecksum);


	// now for the header ...

	totalsize = HEADERSIZE;

	// copy over kernel
	memcpy(buf + totalsize, kernelbuf, kernelsize);
	totalsize += kernelsize;

	// copy over root fs
	memcpy(buf + totalsize, rootfsbuf, rootfssize);
	totalsize += rootfssize;

	// calculate crc
	crc = crc32(buf + HEADERSIZE, totalsize - HEADERSIZE);

	// print some stats out
	printf("crc = 0x%x, total size = %d (0x%x)\n", crc, totalsize, totalsize);

	// copy crc into header
	crc = htonl(crc);
	memcpy(buf, &crc, sizeof(crc));

	// copy over magic
	strcpy((char *)buf + 4, MAGIC);

	// copy over kernel size
	kernelsize = htonl(kernelsize);
	memcpy(buf + 16, &kernelsize, sizeof(kernelsize));

	// copy over kernal flag
	kernelflag = htonl(0x1);
	memcpy(buf + 20, &kernelflag, sizeof(kernelflag));

	// copy over root fs size
	rootfssize = htonl(rootfssize);
	memcpy(buf + 24, &rootfssize, sizeof(rootfssize));

	// copy over root fs flag
	rootfsflag = htonl(0x1);
	memcpy(buf + 28, &rootfsflag, sizeof(rootfsflag));

	// copy over kernel check sum
	kernelchecksum = htonl(kernelchecksum);
	memcpy(buf + 32, &kernelchecksum, sizeof(kernelchecksum));

	// copy over root fs checksum
	rootfschecksum = htonl(rootfschecksum);
	memcpy(buf + 36, &rootfschecksum, sizeof(rootfschecksum));

	// copy over total size
	totalsize = htonl(totalsize);
	memcpy(buf + 40, &totalsize, sizeof(totalsize));

	// undo the htonl (for write)
	totalsize = htonl(totalsize);


	// write out the file from the buffer
	outfd = open(outputfilename, O_CREAT | O_WRONLY | O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);

	if(outfd == -1)
	{
		printf("ERROR: opening '%s' for write\n", outputfilename);
	}

	write(outfd, buf, totalsize);

done:
	// close open fd's

	if(kernelfd != -1)
	{
		close(kernelfd);
		kernelfd = -1;
	}

	if(rootfsfd != -1)
	{
		close(rootfsfd);
		rootfsfd = -1;
	}

	if(outfd != -1)
	{
		close(outfd);
		outfd = -1;
	}

	return 0;
}
