/*
 * Linksys boot counter reset code for mtd
 *
 * Copyright (C) 2013 Jonas Gorski <jogo@openwrt.org>
 * Portions Copyright (c) 2019, Jeff Kletsky
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License v2
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <endian.h>
#include <string.h>
#include <errno.h>
#include <stdint.h>
#include <syslog.h>

#include <sys/ioctl.h>
#include <mtd/mtd-user.h>

#include "mtd.h"

#define BOOTCOUNT_MAGIC	0x20110811

/*
 * EA6350v3, and potentially other NOR-boot devices,
 * use an offset increment of 16 between records,
 * not mtd_info_user.writesize (often 1 on NOR devices).
 */

#define BC_OFFSET_INCREMENT_MIN 16



#define DLOG_OPEN()

#define DLOG_ERR(...) do {						       \
		fprintf(stderr, "ERROR: " __VA_ARGS__); fprintf(stderr, "\n"); \
	} while (0)

#define DLOG_NOTICE(...) do {						\
		fprintf(stderr, __VA_ARGS__); fprintf(stderr, "\n");	\
	} while (0)

#define DLOG_DEBUG(...)



struct bootcounter {
	uint32_t magic;
	uint32_t count;
	uint32_t checksum;
};

int mtd_resetbc(const char *mtd)
{
	struct mtd_info_user mtd_info;
	struct bootcounter *curr = NULL;
	unsigned int i;
	unsigned int bc_offset_increment;
	int last_count = 0;
	int num_bc;
	int fd;
	int ret;
	int retval = 0;

	DLOG_OPEN();

	fd = mtd_check_open(mtd, true);

	if (ioctl(fd, MEMGETINFO, &mtd_info) < 0) {
		DLOG_ERR("Unable to obtain mtd_info for given partition name.");

		retval = -1;
		goto out;
	}


	/* Detect need to override increment (for EA6350v3) */

	if (mtd_info.writesize < BC_OFFSET_INCREMENT_MIN) {

		bc_offset_increment = BC_OFFSET_INCREMENT_MIN;
		DLOG_DEBUG("Offset increment set to %i for writesize of %i",
			   bc_offset_increment, mtd_info.writesize);
	} else {

		bc_offset_increment = mtd_info.writesize;
	}

	num_bc = mtd_info.size / bc_offset_increment;
	curr = malloc(bc_offset_increment);

	if(curr == NULL) {
		DLOG_ERR("Failed to allocate %u bytes from memory.", bc_offset_increment);

		retval = -6;
		goto out;
	}

	for (i = 0; i < num_bc; i++) {
		ret = pread(fd, curr, sizeof(struct bootcounter), i * bc_offset_increment);

		if(ret != sizeof(struct bootcounter)) {
			DLOG_ERR("Failed to read boot-count log at offset 0x%08x.", i * bc_offset_increment);

			retval = -5;
			goto out;
		}

		/* Existing code assumes erase is to 0xff; left as-is (2019) */
		if (curr->magic == 0xffffffff)
			break;

		if (curr->magic != BOOTCOUNT_MAGIC || curr->checksum != curr->magic + curr->count) {
			DLOG_ERR("Unexpected boot-count log at offset 0x%08x: magic 0x%08x boot count 0x%08x checksum 0x%08x; aborting.",
				 i * bc_offset_increment, curr->magic, curr->count, curr->checksum);

			retval = -2;
			goto out;
		}

		last_count = curr->count;
	}


	if (last_count == 0) {	/* bootcount is already 0 */

		retval = 0;
		goto out;
	}


	if (i == num_bc) {
		DLOG_NOTICE("Boot-count log full with %i entries; erasing (expected occasionally).",
			    i);

		struct erase_info_user erase_info;
		erase_info.start = 0;
		erase_info.length = mtd_info.size;

		ret = ioctl(fd, MEMERASE, &erase_info);
		if (ret < 0) {
			DLOG_ERR("Failed to erase boot-count log MTD; ioctl() MEMERASE returned %i",
				 ret);

			retval = -3;
			goto out;
		}

		i = 0;
	}

	memset(curr, 0xff, bc_offset_increment);

	curr->magic = BOOTCOUNT_MAGIC;
	curr->count = 0;
	curr->checksum = BOOTCOUNT_MAGIC;

	/* Assumes bc_offset_increment is a multiple of mtd_info.writesize */

	ret = pwrite(fd, curr, bc_offset_increment, i * bc_offset_increment);
	if (ret < 0) {
		DLOG_ERR("Failed to write boot-count log entry; pwrite() returned %i",
			 errno);
		retval = -4;
		goto out;

	} else {
		sync();

		DLOG_NOTICE("Boot count sucessfully reset to zero.");

		retval = 0;
		goto out;
	}

out:
	if (curr != NULL)
		free(curr);

	close(fd);
	return retval;
}
