/*
 * This file is part of the coreboot project.
 *
 * Copyright (C) 2014 The ChromiumOS Authors.  All rights reserved.
 *
 * 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; version 2 of the License.
 *
 * 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <2api.h>
#include <cbfs.h>
#include <cbfs_core.h>
#include <console/console.h>
#include <spi_flash.h>
#include <string.h>
#include <vboot_nvstorage.h>
#include "chromeos.h"

#if IS_ENABLED(CONFIG_VBOOT_VERIFY_FIRMWARE)
#define BLOB_SIZE VBNV_BLOCK_SIZE
#elif IS_ENABLED(CONFIG_VBOOT2_VERIFY_FIRMWARE)
#define BLOB_SIZE VB2_NVDATA_SIZE
#else
#error unable to determine BLOB_SIZE
#endif

/* FMAP descriptor of the NVRAM area */
static struct vboot_region nvram_region;

/* offset of the current nvdata in nvram */
static int blob_offset = -1;

/* cache of the current nvdata */
static uint8_t cache[BLOB_SIZE];

/* spi_flash struct used when saving data */
static struct spi_flash *spi_flash = NULL;

/*
 * This code assumes that flash is erased to 1-bits, and write operations can
 * only change 1-bits to 0-bits. So if the new contents only change 1-bits to
 * 0-bits, we can reuse the current blob.
 */
static inline uint8_t erase_value(void)
{
	return 0xff;
}

static inline int can_overwrite(uint8_t current, uint8_t new)
{
	return (current & new) == new;
}

static inline int is_initialized(void)
{
	return blob_offset >= 0;
}

static int init_vbnv(void)
{
	uint8_t buf[BLOB_SIZE];
	uint8_t empty_blob[BLOB_SIZE];
	int offset;
	int i;

	vboot_locate_region("RW_NVRAM", &nvram_region);
	if (nvram_region.size < BLOB_SIZE) {
		printk(BIOS_ERR, "%s: failed to locate NVRAM\n", __func__);
		return 1;
	}

	/* Prepare an empty blob to compare against. */
	for (i = 0; i < BLOB_SIZE; i++)
		empty_blob[i] = erase_value();

	/*
	 * after the loop, offset is supposed to point the blob right before the
	 * first empty blob, the last blob in the nvram if there is no empty
	 * blob, or 0 if the nvram has never been used.
	 */
	for (i = 0, offset = 0; i <= nvram_region.size - BLOB_SIZE;
			i += BLOB_SIZE) {
		if (vboot_get_region(i, BLOB_SIZE, buf) == NULL) {
			printk(BIOS_ERR, "failed to read nvdata\n");
			return 1;
		}
		if (!memcmp(buf, empty_blob, BLOB_SIZE))
			break;
		offset = i;
	}

	/* reread the nvdata and write it to the cache */
	if (vboot_get_region(offset, BLOB_SIZE, cache) == NULL) {
		printk(BIOS_ERR, "failed to read nvdata\n");
		return 1;
	}

	blob_offset = offset;

	return 0;
}

static int vbnv_flash_probe(void)
{
	if (!spi_flash) {
		spi_flash = spi_flash_probe(CONFIG_BOOT_MEDIA_SPI_BUS, 0);
		if (!spi_flash) {
			printk(BIOS_ERR, "failed to probe spi flash\n");
			return 1;
		}
	}
	return 0;
}

static int erase_nvram(void)
{
	if (vbnv_flash_probe())
		return 1;

	if (spi_flash->erase(spi_flash, nvram_region.offset_addr,
			     nvram_region.size)) {
		printk(BIOS_ERR, "failed to erase nvram\n");
		return 1;
	}

	printk(BIOS_INFO, "nvram is cleared\n");
	return 0;
}

void read_vbnv(uint8_t *vbnv_copy)
{
	if (!is_initialized())
		if (init_vbnv())
			return;  /* error */
	memcpy(vbnv_copy, cache, BLOB_SIZE);
}

void save_vbnv(const uint8_t *vbnv_copy)
{
	int new_offset = blob_offset;
	int i;

	if (!is_initialized())
		if (init_vbnv())
			return;  /* error */

	/* Bail out if there have been no changes. */
	if (!memcmp(vbnv_copy, cache, BLOB_SIZE))
		return;

	/* See if we can overwrite the current blob with the new one */
	for (i = 0; i < BLOB_SIZE; i++) {
		if (!can_overwrite(cache[i], vbnv_copy[i])) {
			/* unable to overwrite. need to use the next blob */
			new_offset += BLOB_SIZE;
			if (new_offset > nvram_region.size - BLOB_SIZE) {
				if (erase_nvram())
					return;  /* error */
				new_offset = 0;
			}
			break;
		}
	}

	if (vbnv_flash_probe())
		return;  /* error */

	if (spi_flash->write(spi_flash, new_offset,
			     BLOB_SIZE, vbnv_copy) != BLOB_SIZE) {
		printk(BIOS_ERR, "failed to write nvdata\n");
		return;  /* error */
	}

	/* write was successful. safely move pointer forward */
	blob_offset = new_offset;
	memcpy(cache, vbnv_copy, BLOB_SIZE);

	return;
}