/*
 * Copyright (c) 2015-2018, The Linux Foundation. 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 version 2 and
 * only version 2 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.
 */

/*
 * Per-File-Key (PFK) - f2fs
 *
 * This driver is used for working with EXT4/F2FS crypt extension
 *
 * The key information  is stored in node by EXT4/F2FS when file is first opened
 * and will be later accessed by Block Device Driver to actually load the key
 * to encryption hw.
 *
 * PFK exposes API's for loading and removing keys from encryption hw
 * and also API to determine whether 2 adjacent blocks can be agregated by
 * Block Layer in one request to encryption hw.
 *
 */


/* Uncomment the line below to enable debug messages */
#define DEBUG 1
#define pr_fmt(fmt)	"pfk_f2fs [%s]: " fmt, __func__

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/printk.h>

#include "fscrypt_ice.h"
#include "pfk_f2fs.h"

static bool pfk_f2fs_ready;

/*
 * pfk_f2fs_deinit() - Deinit function, should be invoked by upper PFK layer
 */
void pfk_f2fs_deinit(void)
{
	pfk_f2fs_ready = false;
}

/*
 * pfk_f2fs_init() - Init function, should be invoked by upper PFK layer
 */
int __init pfk_f2fs_init(void)
{
	pfk_f2fs_ready = true;
	pr_info("PFK F2FS inited successfully\n");

	return 0;
}

/**
 * pfk_f2fs_is_ready() - driver is initialized and ready.
 *
 * Return: true if the driver is ready.
 */
static inline bool pfk_f2fs_is_ready(void)
{
	return pfk_f2fs_ready;
}

/**
 * pfk_is_f2fs_type() - return true if inode belongs to ICE F2FS PFE
 * @inode: inode pointer
 */
bool pfk_is_f2fs_type(const struct inode *inode)
{
	if (!pfe_is_inode_filesystem_type(inode, "f2fs"))
		return false;

	return fscrypt_should_be_processed_by_ice(inode);
}

/**
 * pfk_f2fs_parse_cipher() - parse cipher from inode to enum
 * @inode: inode
 * @algo: pointer to store the output enum (can be null)
 *
 * return 0 in case of success, error otherwise (i.e not supported cipher)
 */
static int pfk_f2fs_parse_cipher(const struct inode *inode,
		enum ice_cryto_algo_mode *algo)
{
	/*
	 * currently only AES XTS algo is supported
	 * in the future, table with supported ciphers might
	 * be introduced
	 */
	if (!inode)
		return -EINVAL;

	if (!fscrypt_is_aes_xts_cipher(inode)) {
		pr_err("f2fs alghoritm is not supported by pfk\n");
		return -EINVAL;
	}

	if (algo)
		*algo = ICE_CRYPTO_ALGO_MODE_AES_XTS;

	return 0;
}


int pfk_f2fs_parse_inode(const struct bio *bio,
		const struct inode *inode,
		struct pfk_key_info *key_info,
		enum ice_cryto_algo_mode *algo,
		bool *is_pfe,
		const char *storage_type)
{
	int ret = 0;

	if (!is_pfe)
		return -EINVAL;

	/*
	 * only a few errors below can indicate that
	 * this function was not invoked within PFE context,
	 * otherwise we will consider it PFE
	 */
	*is_pfe = true;

	if (!pfk_f2fs_is_ready())
		return -ENODEV;

	if (!inode)
		return -EINVAL;

	if (!key_info)
		return -EINVAL;

	key_info->key = fscrypt_get_ice_encryption_key(inode);
	if (!key_info->key) {
		pr_err("could not parse key from f2fs\n");
		return -EINVAL;
	}

	key_info->key_size = fscrypt_get_ice_encryption_key_size(inode);
	if (!key_info->key_size) {
		pr_err("could not parse key size from f2fs\n");
		return -EINVAL;
	}

	key_info->salt = fscrypt_get_ice_encryption_salt(inode);
	if (!key_info->salt) {
		pr_err("could not parse salt from f2fs\n");
		return -EINVAL;
	}

	key_info->salt_size = fscrypt_get_ice_encryption_salt_size(inode);
	if (!key_info->salt_size) {
		pr_err("could not parse salt size from f2fs\n");
		return -EINVAL;
	}

	ret = pfk_f2fs_parse_cipher(inode, algo);
	if (ret != 0) {
		pr_err("not supported cipher\n");
		return ret;
	}

	return 0;
}

bool pfk_f2fs_allow_merge_bio(const struct bio *bio1,
		const struct bio *bio2, const struct inode *inode1,
		const struct inode *inode2)
{
	bool mergeable;

	/* if there is no f2fs pfk, don't disallow merging blocks */
	if (!pfk_f2fs_is_ready())
		return true;

	if (!inode1 || !inode2)
		return false;

	mergeable = fscrypt_is_ice_encryption_info_equal(inode1, inode2);
	if (!mergeable)
		return false;


	/* ICE allows only consecutive iv_key stream. */
	if (!bio_dun(bio1) && !bio_dun(bio2))
		return true;
	else if (!bio_dun(bio1) || !bio_dun(bio2))
		return false;

	return bio_end_dun(bio1) == bio_dun(bio2);
}