// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2014  Claudio Leite <leitec@staticky.com>
 */

/*
 * Builds a proper flash image for routers using some Gemtek
 * OEM boards. These include the Airlink101 AR725W, the
 * Asante SmartHub 600 (AWRT-600N), and Linksys WRT100/110.
 *
 * The resulting image is compatible with the factory firmware
 * web upgrade and TFTP interface.
 *
 * To build:
 *  gcc -O2 -o mkheader_gemtek mkheader_gemtek.c -lz
 *
 * Claudio Leite <leitec@staticky.com>
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>

#include <zlib.h>		/* for crc32() */

/*
 * The header is in little-endian format. In case
 * we are on a BE host, we need to swap binary
 * values.
 */
#ifdef __APPLE__
# include <libkern/OSByteOrder.h>
# define le32 OSSwapHostToLittleInt32
#else
# if defined(__linux__)
#  include <endian.h>
#  if __BYTE_ORDER == __BIG_ENDIAN
#   define CPU_BIG_ENDIAN
#  endif
# else
#  include <sys/endian.h>		/* BSD's should have this */
#  if _BYTE_ORDER == _BIG_ENDIAN
#   define CPU_BIG_ENDIAN
#  endif
# endif
# ifdef CPU_BIG_ENDIAN
#  define le32(x) (((x & 0xff000000) >> 24) | \
                   ((x & 0x00ff0000) >> 8)  | \
                   ((x & 0x0000ff00) << 8)  | \
                   ((x & 0x000000ff) << 24))
# else
#  define le32(x) (x)
# endif
#endif

struct gemtek_header {
	uint8_t 	magic[4];
	uint8_t 	version[4];
	uint32_t 	product_id;
	uint32_t 	imagesz;
	uint32_t 	checksum;
	uint32_t 	fast_checksum;
	uint8_t 	build[4];
	uint8_t 	lang[4];
};

#define HDRLEN	sizeof(struct gemtek_header)

struct machines {
	char           *desc;
	char           *id;
	uint32_t 	maxsize;
	struct gemtek_header header;
};

struct machines mach_def[] = {
	{"Airlink101 AR725W", "ar725w", 0x340000,
		{"GMTK", "1003", le32(0x03000001), 0, 0,
		  0, "01\0\0", "EN\0\0"}},
	{"Asante AWRT-600N", "awrt600n", 0x340000,
		{"A600", "1005", le32(0x03000001), 0, 0,
		  0, "01\0\0", "EN\0\0"}},
	{"Linksys WRT100", "wrt100", 0x320000,
		{"GMTK", "1007", le32(0x03040001), 0, 0,
		  0, "2\0\0\0", "EN\0\0"}},
	{"Linksys WRT110", "wrt110", 0x320000,
		{"GMTK", "1007", le32(0x03040001), 0, 0,
		  0, "2\0\0\0", "EN\0\0"}},
	{0}
};

int
main(int argc, char *argv[])
{
	unsigned long 	res, flen;
	struct gemtek_header my_hdr;
	FILE           *f, *f_out;
	int 		image_type = -1, index;
	uint8_t        *buf;
	uint32_t 	crc;

	if (argc < 3) {
		fprintf(stderr, "mkheader_gemtek <uImage> <webflash image> [machine ID]\n");
		fprintf(stderr, "  where [machine ID] is one of:\n");
		for (index = 0; mach_def[index].desc != 0; index++) {
			fprintf(stderr, "    %-10s  %s", mach_def[index].id, mach_def[index].desc);
			if (index == 0)
				fprintf(stderr, " (default)\n");
			else
				fprintf(stderr, "\n");
		}

		exit(-1);
	}

	if (argc == 4) {
		for(index = 0; mach_def[index].id != 0; index++) {
			if(strcmp(mach_def[index].id, argv[3]) == 0) {
				image_type = index;
				break;
			}
		}

		if(image_type == -1) {
			fprintf(stderr, "\nERROR: invalid machine type\n");
			exit(-1);
		}
	} else
		image_type = 0;

	printf("Opening %s...\n", argv[1]);

	f = fopen(argv[1], "r");
	if(!f) {
		fprintf(stderr, "\nERROR: couldn't open input image\n");
		exit(-1);
	}

	fseek(f, 0, SEEK_END);
	flen = (unsigned long) ftell(f);

	printf("  %lu (0x%lX) bytes long\n", flen, flen);

	if (flen > mach_def[image_type].maxsize) {
		fprintf(stderr, "\nERROR: image exceeds maximum compatible size\n");
		goto f_error;
	}

	buf = malloc(flen + HDRLEN);
	if (!buf) {
		fprintf(stderr, "\nERROR: couldn't allocate buffer\n");
		goto f_error;
	}
	rewind(f);
	res = fread(buf + HDRLEN, 1, flen, f);
	if (res != flen) {
		perror("Couldn't read entire file: fread()");
		goto f_error;
	}
	fclose(f);

	printf("\nCreating %s...\n", argv[2]);

	memcpy(&my_hdr, &mach_def[image_type].header, HDRLEN);

	printf("  Using %s magic\n", mach_def[image_type].desc);

	my_hdr.imagesz = le32(flen + HDRLEN);
	memcpy(my_hdr.lang, "EN", 2);

	memcpy(buf, &my_hdr, HDRLEN);

	crc = crc32(0, buf, flen + HDRLEN);
	printf("  CRC32: %08X\n", crc);

	my_hdr.checksum = le32(crc);
	memcpy(buf, &my_hdr, HDRLEN);

	printf("  Writing...\n");

	f_out = fopen(argv[2], "w");
	if(!f_out) {
		fprintf(stderr, "\nERROR: couldn't open output image\n");
		exit(-1);
	}

	fwrite(buf, 1, flen + HDRLEN, f_out);

	fclose(f_out);

	free(buf);
	return 0;

f_error:
	fclose(f);
	exit(-1);
}