/*
 * SCSI Block Commands (SBC) parsing and emulation.
 *
 * (c) Copyright 2002-2012 RisingTide Systems LLC.
 *
 * Nicholas A. Bellinger <nab@kernel.org>
 *
 * 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; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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 <linux/kernel.h>
#include <linux/module.h>
#include <linux/ratelimit.h>
#include <asm/unaligned.h>
#include <scsi/scsi.h>

#include <target/target_core_base.h>
#include <target/target_core_backend.h>
#include <target/target_core_fabric.h>

#include "target_core_internal.h"
#include "target_core_ua.h"


static sense_reason_t
sbc_emulate_readcapacity(struct se_cmd *cmd)
{
	struct se_device *dev = cmd->se_dev;
	unsigned long long blocks_long = dev->transport->get_blocks(dev);
	unsigned char *rbuf;
	unsigned char buf[8];
	u32 blocks;

	if (blocks_long >= 0x00000000ffffffff)
		blocks = 0xffffffff;
	else
		blocks = (u32)blocks_long;

	buf[0] = (blocks >> 24) & 0xff;
	buf[1] = (blocks >> 16) & 0xff;
	buf[2] = (blocks >> 8) & 0xff;
	buf[3] = blocks & 0xff;
	buf[4] = (dev->dev_attrib.block_size >> 24) & 0xff;
	buf[5] = (dev->dev_attrib.block_size >> 16) & 0xff;
	buf[6] = (dev->dev_attrib.block_size >> 8) & 0xff;
	buf[7] = dev->dev_attrib.block_size & 0xff;

	rbuf = transport_kmap_data_sg(cmd);
	if (!rbuf)
		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	memcpy(rbuf, buf, min_t(u32, sizeof(buf), cmd->data_length));
	transport_kunmap_data_sg(cmd);

	target_complete_cmd(cmd, GOOD);
	return 0;
}

static sense_reason_t
sbc_emulate_readcapacity_16(struct se_cmd *cmd)
{
	struct se_device *dev = cmd->se_dev;
	unsigned char *rbuf;
	unsigned char buf[32];
	unsigned long long blocks = dev->transport->get_blocks(dev);

	memset(buf, 0, sizeof(buf));
	buf[0] = (blocks >> 56) & 0xff;
	buf[1] = (blocks >> 48) & 0xff;
	buf[2] = (blocks >> 40) & 0xff;
	buf[3] = (blocks >> 32) & 0xff;
	buf[4] = (blocks >> 24) & 0xff;
	buf[5] = (blocks >> 16) & 0xff;
	buf[6] = (blocks >> 8) & 0xff;
	buf[7] = blocks & 0xff;
	buf[8] = (dev->dev_attrib.block_size >> 24) & 0xff;
	buf[9] = (dev->dev_attrib.block_size >> 16) & 0xff;
	buf[10] = (dev->dev_attrib.block_size >> 8) & 0xff;
	buf[11] = dev->dev_attrib.block_size & 0xff;
	/*
	 * Set Thin Provisioning Enable bit following sbc3r22 in section
	 * READ CAPACITY (16) byte 14 if emulate_tpu or emulate_tpws is enabled.
	 */
	if (dev->dev_attrib.emulate_tpu || dev->dev_attrib.emulate_tpws)
		buf[14] = 0x80;

	rbuf = transport_kmap_data_sg(cmd);
	if (!rbuf)
		return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;

	memcpy(rbuf, buf, min_t(u32, sizeof(buf), cmd->data_length));
	transport_kunmap_data_sg(cmd);

	target_complete_cmd(cmd, GOOD);
	return 0;
}

sector_t spc_get_write_same_sectors(struct se_cmd *cmd)
{
	u32 num_blocks;

	if (cmd->t_task_cdb[0] == WRITE_SAME)
		num_blocks = get_unaligned_be16(&cmd->t_task_cdb[7]);
	else if (cmd->t_task_cdb[0] == WRITE_SAME_16)
		num_blocks = get_unaligned_be32(&cmd->t_task_cdb[10]);
	else /* WRITE_SAME_32 via VARIABLE_LENGTH_CMD */
		num_blocks = get_unaligned_be32(&cmd->t_task_cdb[28]);

	/*
	 * Use the explicit range when non zero is supplied, otherwise calculate
	 * the remaining range based on ->get_blocks() - starting LBA.
	 */
	if (num_blocks)
		return num_blocks;

	return cmd->se_dev->transport->get_blocks(cmd->se_dev) -
		cmd->t_task_lba + 1;
}
EXPORT_SYMBOL(spc_get_write_same_sectors);

static sense_reason_t
sbc_emulate_noop(struct se_cmd *cmd)
{
	target_complete_cmd(cmd, GOOD);
	return 0;
}

static inline u32 sbc_get_size(struct se_cmd *cmd, u32 sectors)
{
	return cmd->se_dev->dev_attrib.block_size * sectors;
}

static int sbc_check_valid_sectors(struct se_cmd *cmd)
{
	struct se_device *dev = cmd->se_dev;
	unsigned long long end_lba;
	u32 sectors;

	sectors = cmd->data_length / dev->dev_attrib.block_size;
	end_lba = dev->transport->get_blocks(dev) + 1;

	if (cmd->t_task_lba + sectors > end_lba) {
		pr_err("target: lba %llu, sectors %u exceeds end lba %llu\n",
			cmd->t_task_lba, sectors, end_lba);
		return -EINVAL;
	}

	return 0;
}

static inline u32 transport_get_sectors_6(unsigned char *cdb)
{
	/*
	 * Use 8-bit sector value.  SBC-3 says:
	 *
	 *   A TRANSFER LENGTH field set to zero specifies that 256
	 *   logical blocks shall be written.  Any other value
	 *   specifies the number of logical blocks that shall be
	 *   written.
	 */
	return cdb[4] ? : 256;
}

static inline u32 transport_get_sectors_10(unsigned char *cdb)
{
	return (u32)(cdb[7] << 8) + cdb[8];
}

static inline u32 transport_get_sectors_12(unsigned char *cdb)
{
	return (u32)(cdb[6] << 24) + (cdb[7] << 16) + (cdb[8] << 8) + cdb[9];
}

static inline u32 transport_get_sectors_16(unsigned char *cdb)
{
	return (u32)(cdb[10] << 24) + (cdb[11] << 16) +
		    (cdb[12] << 8) + cdb[13];
}

/*
 * Used for VARIABLE_LENGTH_CDB WRITE_32 and READ_32 variants
 */
static inline u32 transport_get_sectors_32(unsigned char *cdb)
{
	return (u32)(cdb[28] << 24) + (cdb[29] << 16) +
		    (cdb[30] << 8) + cdb[31];

}

static inline u32 transport_lba_21(unsigned char *cdb)
{
	return ((cdb[1] & 0x1f) << 16) | (cdb[2] << 8) | cdb[3];
}

static inline u32 transport_lba_32(unsigned char *cdb)
{
	return (cdb[2] << 24) | (cdb[3] << 16) | (cdb[4] << 8) | cdb[5];
}

static inline unsigned long long transport_lba_64(unsigned char *cdb)
{
	unsigned int __v1, __v2;

	__v1 = (cdb[2] << 24) | (cdb[3] << 16) | (cdb[4] << 8) | cdb[5];
	__v2 = (cdb[6] << 24) | (cdb[7] << 16) | (cdb[8] << 8) | cdb[9];

	return ((unsigned long long)__v2) | (unsigned long long)__v1 << 32;
}

/*
 * For VARIABLE_LENGTH_CDB w/ 32 byte extended CDBs
 */
static inline unsigned long long transport_lba_64_ext(unsigned char *cdb)
{
	unsigned int __v1, __v2;

	__v1 = (cdb[12] << 24) | (cdb[13] << 16) | (cdb[14] << 8) | cdb[15];
	__v2 = (cdb[16] << 24) | (cdb[17] << 16) | (cdb[18] << 8) | cdb[19];

	return ((unsigned long long)__v2) | (unsigned long long)__v1 << 32;
}

static sense_reason_t
sbc_setup_write_same(struct se_cmd *cmd, unsigned char *flags, struct sbc_ops *ops)
{
	unsigned int sectors = spc_get_write_same_sectors(cmd);

	if ((flags[0] & 0x04) || (flags[0] & 0x02)) {
		pr_err("WRITE_SAME PBDATA and LBDATA"
			" bits not supported for Block Discard"
			" Emulation\n");
		return TCM_UNSUPPORTED_SCSI_OPCODE;
	}
	if (sectors > cmd->se_dev->dev_attrib.max_write_same_len) {
		pr_warn("WRITE_SAME sectors: %u exceeds max_write_same_len: %u\n",
			sectors, cmd->se_dev->dev_attrib.max_write_same_len);
		return TCM_INVALID_CDB_FIELD;
	}
	/*
	 * Special case for WRITE_SAME w/ UNMAP=1 that ends up getting
	 * translated into block discard requests within backend code.
	 */
	if (flags[0] & 0x08) {
		if (!ops->execute_write_same_unmap)
			return TCM_UNSUPPORTED_SCSI_OPCODE;

		cmd->execute_cmd = ops->execute_write_same_unmap;
		return 0;
	}
	if (!ops->execute_write_same)
		return TCM_UNSUPPORTED_SCSI_OPCODE;

	cmd->execute_cmd = ops->execute_write_same;
	return 0;
}

static void xdreadwrite_callback(struct se_cmd *cmd)
{
	unsigned char *buf, *addr;
	struct scatterlist *sg;
	unsigned int offset;
	int i;
	int count;
	/*
	 * From sbc3r22.pdf section 5.48 XDWRITEREAD (10) command
	 *
	 * 1) read the specified logical block(s);
	 * 2) transfer logical blocks from the data-out buffer;
	 * 3) XOR the logical blocks transferred from the data-out buffer with
	 *    the logical blocks read, storing the resulting XOR data in a buffer;
	 * 4) if the DISABLE WRITE bit is set to zero, then write the logical
	 *    blocks transferred from the data-out buffer; and
	 * 5) transfer the resulting XOR data to the data-in buffer.
	 */
	buf = kmalloc(cmd->data_length, GFP_KERNEL);
	if (!buf) {
		pr_err("Unable to allocate xor_callback buf\n");
		return;
	}
	/*
	 * Copy the scatterlist WRITE buffer located at cmd->t_data_sg
	 * into the locally allocated *buf
	 */
	sg_copy_to_buffer(cmd->t_data_sg,
			  cmd->t_data_nents,
			  buf,
			  cmd->data_length);

	/*
	 * Now perform the XOR against the BIDI read memory located at
	 * cmd->t_mem_bidi_list
	 */

	offset = 0;
	for_each_sg(cmd->t_bidi_data_sg, sg, cmd->t_bidi_data_nents, count) {
		addr = kmap_atomic(sg_page(sg));
		if (!addr)
			goto out;

		for (i = 0; i < sg->length; i++)
			*(addr + sg->offset + i) ^= *(buf + offset + i);

		offset += sg->length;
		kunmap_atomic(addr);
	}

out:
	kfree(buf);
}

sense_reason_t
sbc_parse_cdb(struct se_cmd *cmd, struct sbc_ops *ops)
{
	struct se_device *dev = cmd->se_dev;
	unsigned char *cdb = cmd->t_task_cdb;
	unsigned int size;
	u32 sectors = 0;
	sense_reason_t ret;

	switch (cdb[0]) {
	case READ_6:
		sectors = transport_get_sectors_6(cdb);
		cmd->t_task_lba = transport_lba_21(cdb);
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case READ_10:
		sectors = transport_get_sectors_10(cdb);
		cmd->t_task_lba = transport_lba_32(cdb);
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case READ_12:
		sectors = transport_get_sectors_12(cdb);
		cmd->t_task_lba = transport_lba_32(cdb);
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case READ_16:
		sectors = transport_get_sectors_16(cdb);
		cmd->t_task_lba = transport_lba_64(cdb);
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case WRITE_6:
		sectors = transport_get_sectors_6(cdb);
		cmd->t_task_lba = transport_lba_21(cdb);
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case WRITE_10:
	case WRITE_VERIFY:
		sectors = transport_get_sectors_10(cdb);
		cmd->t_task_lba = transport_lba_32(cdb);
		if (cdb[1] & 0x8)
			cmd->se_cmd_flags |= SCF_FUA;
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case WRITE_12:
		sectors = transport_get_sectors_12(cdb);
		cmd->t_task_lba = transport_lba_32(cdb);
		if (cdb[1] & 0x8)
			cmd->se_cmd_flags |= SCF_FUA;
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case WRITE_16:
		sectors = transport_get_sectors_16(cdb);
		cmd->t_task_lba = transport_lba_64(cdb);
		if (cdb[1] & 0x8)
			cmd->se_cmd_flags |= SCF_FUA;
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;
		cmd->execute_cmd = ops->execute_rw;
		break;
	case XDWRITEREAD_10:
		if (cmd->data_direction != DMA_TO_DEVICE ||
		    !(cmd->se_cmd_flags & SCF_BIDI))
			return TCM_INVALID_CDB_FIELD;
		sectors = transport_get_sectors_10(cdb);

		cmd->t_task_lba = transport_lba_32(cdb);
		cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;

		/*
		 * Setup BIDI XOR callback to be run after I/O completion.
		 */
		cmd->execute_cmd = ops->execute_rw;
		cmd->transport_complete_callback = &xdreadwrite_callback;
		if (cdb[1] & 0x8)
			cmd->se_cmd_flags |= SCF_FUA;
		break;
	case VARIABLE_LENGTH_CMD:
	{
		u16 service_action = get_unaligned_be16(&cdb[8]);
		switch (service_action) {
		case XDWRITEREAD_32:
			sectors = transport_get_sectors_32(cdb);

			/*
			 * Use WRITE_32 and READ_32 opcodes for the emulated
			 * XDWRITE_READ_32 logic.
			 */
			cmd->t_task_lba = transport_lba_64_ext(cdb);
			cmd->se_cmd_flags |= SCF_SCSI_DATA_CDB;

			/*
			 * Setup BIDI XOR callback to be run during after I/O
			 * completion.
			 */
			cmd->execute_cmd = ops->execute_rw;
			cmd->transport_complete_callback = &xdreadwrite_callback;
			if (cdb[1] & 0x8)
				cmd->se_cmd_flags |= SCF_FUA;
			break;
		case WRITE_SAME_32:
			sectors = transport_get_sectors_32(cdb);
			if (!sectors) {
				pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not"
				       " supported\n");
				return TCM_INVALID_CDB_FIELD;
			}

			size = sbc_get_size(cmd, 1);
			cmd->t_task_lba = get_unaligned_be64(&cdb[12]);

			ret = sbc_setup_write_same(cmd, &cdb[10], ops);
			if (ret)
				return ret;
			break;
		default:
			pr_err("VARIABLE_LENGTH_CMD service action"
				" 0x%04x not supported\n", service_action);
			return TCM_UNSUPPORTED_SCSI_OPCODE;
		}
		break;
	}
	case READ_CAPACITY:
		size = READ_CAP_LEN;
		cmd->execute_cmd = sbc_emulate_readcapacity;
		break;
	case SERVICE_ACTION_IN:
		switch (cmd->t_task_cdb[1] & 0x1f) {
		case SAI_READ_CAPACITY_16:
			cmd->execute_cmd = sbc_emulate_readcapacity_16;
			break;
		default:
			pr_err("Unsupported SA: 0x%02x\n",
				cmd->t_task_cdb[1] & 0x1f);
			return TCM_INVALID_CDB_FIELD;
		}
		size = (cdb[10] << 24) | (cdb[11] << 16) |
		       (cdb[12] << 8) | cdb[13];
		break;
	case SYNCHRONIZE_CACHE:
	case SYNCHRONIZE_CACHE_16:
		if (!ops->execute_sync_cache)
			return TCM_UNSUPPORTED_SCSI_OPCODE;

		/*
		 * Extract LBA and range to be flushed for emulated SYNCHRONIZE_CACHE
		 */
		if (cdb[0] == SYNCHRONIZE_CACHE) {
			sectors = transport_get_sectors_10(cdb);
			cmd->t_task_lba = transport_lba_32(cdb);
		} else {
			sectors = transport_get_sectors_16(cdb);
			cmd->t_task_lba = transport_lba_64(cdb);
		}

		size = sbc_get_size(cmd, sectors);

		/*
		 * Check to ensure that LBA + Range does not exceed past end of
		 * device for IBLOCK and FILEIO ->do_sync_cache() backend calls
		 */
		if (cmd->t_task_lba || sectors) {
			if (sbc_check_valid_sectors(cmd) < 0)
				return TCM_INVALID_CDB_FIELD;
		}
		cmd->execute_cmd = ops->execute_sync_cache;
		break;
	case UNMAP:
		if (!ops->execute_unmap)
			return TCM_UNSUPPORTED_SCSI_OPCODE;

		size = get_unaligned_be16(&cdb[7]);
		cmd->execute_cmd = ops->execute_unmap;
		break;
	case WRITE_SAME_16:
		sectors = transport_get_sectors_16(cdb);
		if (!sectors) {
			pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not supported\n");
			return TCM_INVALID_CDB_FIELD;
		}

		size = sbc_get_size(cmd, 1);
		cmd->t_task_lba = get_unaligned_be64(&cdb[2]);

		ret = sbc_setup_write_same(cmd, &cdb[1], ops);
		if (ret)
			return ret;
		break;
	case WRITE_SAME:
		sectors = transport_get_sectors_10(cdb);
		if (!sectors) {
			pr_err("WSNZ=1, WRITE_SAME w/sectors=0 not supported\n");
			return TCM_INVALID_CDB_FIELD;
		}

		size = sbc_get_size(cmd, 1);
		cmd->t_task_lba = get_unaligned_be32(&cdb[2]);

		/*
		 * Follow sbcr26 with WRITE_SAME (10) and check for the existence
		 * of byte 1 bit 3 UNMAP instead of original reserved field
		 */
		ret = sbc_setup_write_same(cmd, &cdb[1], ops);
		if (ret)
			return ret;
		break;
	case VERIFY:
		size = 0;
		cmd->execute_cmd = sbc_emulate_noop;
		break;
	case REZERO_UNIT:
	case SEEK_6:
	case SEEK_10:
		/*
		 * There are still clients out there which use these old SCSI-2
		 * commands. This mainly happens when running VMs with legacy
		 * guest systems, connected via SCSI command pass-through to
		 * iSCSI targets. Make them happy and return status GOOD.
		 */
		size = 0;
		cmd->execute_cmd = sbc_emulate_noop;
		break;
	default:
		ret = spc_parse_cdb(cmd, &size);
		if (ret)
			return ret;
	}

	/* reject any command that we don't have a handler for */
	if (!(cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) && !cmd->execute_cmd)
		return TCM_UNSUPPORTED_SCSI_OPCODE;

	if (cmd->se_cmd_flags & SCF_SCSI_DATA_CDB) {
		unsigned long long end_lba;

		if (sectors > dev->dev_attrib.fabric_max_sectors) {
			printk_ratelimited(KERN_ERR "SCSI OP %02xh with too"
				" big sectors %u exceeds fabric_max_sectors:"
				" %u\n", cdb[0], sectors,
				dev->dev_attrib.fabric_max_sectors);
			return TCM_INVALID_CDB_FIELD;
		}
		if (sectors > dev->dev_attrib.hw_max_sectors) {
			printk_ratelimited(KERN_ERR "SCSI OP %02xh with too"
				" big sectors %u exceeds backend hw_max_sectors:"
				" %u\n", cdb[0], sectors,
				dev->dev_attrib.hw_max_sectors);
			return TCM_INVALID_CDB_FIELD;
		}

		end_lba = dev->transport->get_blocks(dev) + 1;
		if (cmd->t_task_lba + sectors > end_lba) {
			pr_err("cmd exceeds last lba %llu "
				"(lba %llu, sectors %u)\n",
				end_lba, cmd->t_task_lba, sectors);
			return TCM_INVALID_CDB_FIELD;
		}

		size = sbc_get_size(cmd, sectors);
	}

	return target_cmd_size_check(cmd, size);
}
EXPORT_SYMBOL(sbc_parse_cdb);

u32 sbc_get_device_type(struct se_device *dev)
{
	return TYPE_DISK;
}
EXPORT_SYMBOL(sbc_get_device_type);