Drivers: hv: Implement the file copy service

Implement the file copy service for Linux guests on Hyper-V. This permits the
host to copy a file (over VMBUS) into the guest. This facility is part of
"guest integration services" supported on the Windows platform.
Here is a link that provides additional details on this functionality:

http://technet.microsoft.com/en-us/library/dn464282.aspx

In V1 version of the patch I have addressed comments from
Olaf Hering <olaf@aepfle.de> and Dan Carpenter <dan.carpenter@oracle.com>

In V2 version of this patch I did some minor cleanup (making some globals
static). In V4 version of the patch I have addressed all of Olaf's
most recent set of comments/concerns.

In V5 version of the patch I had addressed Greg's most recent comments.
I would like to thank Greg for suggesting that I use misc device; it has
significantly simplified the code.

In V6 version of the patch I have cleaned up error message based on Olaf's
comments. I have also rebased the patch based on the current tip.

In this version of the patch, I have addressed the latest comments from Greg.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 414 insertions, 0 deletions

diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
new file mode 100644
index 000000000000..285b5e210a09
--- /dev/null
+++ b/drivers/hv/hv_fcopy.c
@@ -0,0 +1,414 @@
+/*
+ * An implementation of file copy service.
+ *
+ * Copyright (C) 2014, Microsoft, Inc.
+ *
+ * Author : K. Y. Srinivasan <ksrinivasan@novell.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License 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, GOOD TITLE or
+ * NON INFRINGEMENT.  See the GNU General Public License for more
+ * details.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/semaphore.h>
+#include <linux/fs.h>
+#include <linux/nls.h>
+#include <linux/workqueue.h>
+#include <linux/cdev.h>
+#include <linux/hyperv.h>
+#include <linux/sched.h>
+#include <linux/uaccess.h>
+#include <linux/miscdevice.h>
+
+#include "hyperv_vmbus.h"
+
+#define WIN8_SRV_MAJOR		1
+#define WIN8_SRV_MINOR		1
+#define WIN8_SRV_VERSION	(WIN8_SRV_MAJOR << 16 | WIN8_SRV_MINOR)
+
+/*
+ * Global state maintained for transaction that is being processed.
+ * For a class of integration services, including the "file copy service",
+ * the specified protocol is a "request/response" protocol which means that
+ * there can only be single outstanding transaction from the host at any
+ * given point in time. We use this to simplify memory management in this
+ * driver - we cache and process only one message at a time.
+ *
+ * While the request/response protocol is guaranteed by the host, we further
+ * ensure this by serializing packet processing in this driver - we do not
+ * read additional packets from the VMBUs until the current packet is fully
+ * handled.
+ *
+ * The transaction "active" state is set when we receive a request from the
+ * host and we cleanup this state when the transaction is completed - when we
+ * respond to the host with our response. When the transaction active state is
+ * set, we defer handling incoming packets.
+ */
+
+static struct {
+	bool active; /* transaction status - active or not */
+	int recv_len; /* number of bytes received. */
+	struct hv_fcopy_hdr  *fcopy_msg; /* current message */
+	struct hv_start_fcopy  message; /*  sent to daemon */
+	struct vmbus_channel *recv_channel; /* chn we got the request */
+	u64 recv_req_id; /* request ID. */
+	void *fcopy_context; /* for the channel callback */
+	struct semaphore read_sema;
+} fcopy_transaction;
+
+static bool opened; /* currently device opened */
+
+/*
+ * Before we can accept copy messages from the host, we need
+ * to handshake with the user level daemon. This state tracks
+ * if we are in the handshake phase.
+ */
+static bool in_hand_shake = true;
+static void fcopy_send_data(void);
+static void fcopy_respond_to_host(int error);
+static void fcopy_work_func(struct work_struct *dummy);
+static DECLARE_DELAYED_WORK(fcopy_work, fcopy_work_func);
+static u8 *recv_buffer;
+
+static void fcopy_work_func(struct work_struct *dummy)
+{
+	/*
+	 * If the timer fires, the user-mode component has not responded;
+	 * process the pending transaction.
+	 */
+	fcopy_respond_to_host(HV_E_FAIL);
+}
+
+static int fcopy_handle_handshake(u32 version)
+{
+	switch (version) {
+	case FCOPY_CURRENT_VERSION:
+		break;
+	default:
+		/*
+		 * For now we will fail the registration.
+		 * If and when we have multiple versions to
+		 * deal with, we will be backward compatible.
+		 * We will add this code when needed.
+		 */
+		return -EINVAL;
+	}
+	pr_info("FCP: user-mode registering done. Daemon version: %d\n",
+		version);
+	fcopy_transaction.active = false;
+	if (fcopy_transaction.fcopy_context)
+		hv_fcopy_onchannelcallback(fcopy_transaction.fcopy_context);
+	in_hand_shake = false;
+	return 0;
+}
+
+static void fcopy_send_data(void)
+{
+	struct hv_start_fcopy *smsg_out = &fcopy_transaction.message;
+	int operation = fcopy_transaction.fcopy_msg->operation;
+	struct hv_start_fcopy *smsg_in;
+
+	/*
+	 * The  strings sent from the host are encoded in
+	 * in utf16; convert it to utf8 strings.
+	 * The host assures us that the utf16 strings will not exceed
+	 * the max lengths specified. We will however, reserve room
+	 * for the string terminating character - in the utf16s_utf8s()
+	 * function we limit the size of the buffer where the converted
+	 * string is placed to W_MAX_PATH -1 to guarantee
+	 * that the strings can be properly terminated!
+	 */
+
+	switch (operation) {
+	case START_FILE_COPY:
+		memset(smsg_out, 0, sizeof(struct hv_start_fcopy));
+		smsg_out->hdr.operation = operation;
+		smsg_in = (struct hv_start_fcopy *)fcopy_transaction.fcopy_msg;
+
+		utf16s_to_utf8s((wchar_t *)smsg_in->file_name, W_MAX_PATH,
+				UTF16_LITTLE_ENDIAN,
+				(__u8 *)smsg_out->file_name, W_MAX_PATH - 1);
+
+		utf16s_to_utf8s((wchar_t *)smsg_in->path_name, W_MAX_PATH,
+				UTF16_LITTLE_ENDIAN,
+				(__u8 *)smsg_out->path_name, W_MAX_PATH - 1);
+
+		smsg_out->copy_flags = smsg_in->copy_flags;
+		smsg_out->file_size = smsg_in->file_size;
+		break;
+
+	default:
+		break;
+	}
+	up(&fcopy_transaction.read_sema);
+	return;
+}
+
+/*
+ * Send a response back to the host.
+ */
+
+static void
+fcopy_respond_to_host(int error)
+{
+	struct icmsg_hdr *icmsghdr;
+	u32 buf_len;
+	struct vmbus_channel *channel;
+	u64 req_id;
+
+	/*
+	 * Copy the global state for completing the transaction. Note that
+	 * only one transaction can be active at a time. This is guaranteed
+	 * by the file copy protocol implemented by the host. Furthermore,
+	 * the "transaction active" state we maintain ensures that there can
+	 * only be one active transaction at a time.
+	 */
+
+	buf_len = fcopy_transaction.recv_len;
+	channel = fcopy_transaction.recv_channel;
+	req_id = fcopy_transaction.recv_req_id;
+
+	fcopy_transaction.active = false;
+
+	icmsghdr = (struct icmsg_hdr *)
+			&recv_buffer[sizeof(struct vmbuspipe_hdr)];
+
+	if (channel->onchannel_callback == NULL)
+		/*
+		 * We have raced with util driver being unloaded;
+		 * silently return.
+		 */
+		return;
+
+	icmsghdr->status = error;
+	icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
+	vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
+				VM_PKT_DATA_INBAND, 0);
+}
+
+void hv_fcopy_onchannelcallback(void *context)
+{
+	struct vmbus_channel *channel = context;
+	u32 recvlen;
+	u64 requestid;
+	struct hv_fcopy_hdr *fcopy_msg;
+	struct icmsg_hdr *icmsghdr;
+	struct icmsg_negotiate *negop = NULL;
+	int util_fw_version;
+	int fcopy_srv_version;
+
+	if (fcopy_transaction.active) {
+		/*
+		 * We will defer processing this callback once
+		 * the current transaction is complete.
+		 */
+		fcopy_transaction.fcopy_context = context;
+		return;
+	}
+
+	vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
+			 &requestid);
+	if (recvlen <= 0)
+		return;
+
+	icmsghdr = (struct icmsg_hdr *)&recv_buffer[
+			sizeof(struct vmbuspipe_hdr)];
+	if (icmsghdr->icmsgtype == ICMSGTYPE_NEGOTIATE) {
+		util_fw_version = UTIL_FW_VERSION;
+		fcopy_srv_version = WIN8_SRV_VERSION;
+		vmbus_prep_negotiate_resp(icmsghdr, negop, recv_buffer,
+				util_fw_version, fcopy_srv_version);
+	} else {
+		fcopy_msg = (struct hv_fcopy_hdr *)&recv_buffer[
+				sizeof(struct vmbuspipe_hdr) +
+				sizeof(struct icmsg_hdr)];
+
+		/*
+		 * Stash away this global state for completing the
+		 * transaction; note transactions are serialized.
+		 */
+
+		fcopy_transaction.active = true;
+		fcopy_transaction.recv_len = recvlen;
+		fcopy_transaction.recv_channel = channel;
+		fcopy_transaction.recv_req_id = requestid;
+		fcopy_transaction.fcopy_msg = fcopy_msg;
+
+		/*
+		 * Send the information to the user-level daemon.
+		 */
+		fcopy_send_data();
+		schedule_delayed_work(&fcopy_work, 5*HZ);
+		return;
+	}
+	icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
+	vmbus_sendpacket(channel, recv_buffer, recvlen, requestid,
+			VM_PKT_DATA_INBAND, 0);
+}
+
+/*
+ * Create a char device that can support read/write for passing
+ * the payload.
+ */
+
+static ssize_t fcopy_read(struct file *file, char __user *buf,
+		size_t count, loff_t *ppos)
+{
+	void *src;
+	size_t copy_size;
+	int operation;
+
+	/*
+	 * Wait until there is something to be read.
+	 */
+	if (down_interruptible(&fcopy_transaction.read_sema))
+		return -EINTR;
+
+	/*
+	 * The channel may be rescinded and in this case, we will wakeup the
+	 * the thread blocked on the semaphore and we will use the opened
+	 * state to correctly handle this case.
+	 */
+	if (!opened)
+		return -ENODEV;
+
+	operation = fcopy_transaction.fcopy_msg->operation;
+
+	if (operation == START_FILE_COPY) {
+		src = &fcopy_transaction.message;
+		copy_size = sizeof(struct hv_start_fcopy);
+		if (count < copy_size)
+			return 0;
+	} else {
+		src = fcopy_transaction.fcopy_msg;
+		copy_size = sizeof(struct hv_do_fcopy);
+		if (count < copy_size)
+			return 0;
+	}
+	if (copy_to_user(buf, src, copy_size))
+		return -EFAULT;
+
+	return copy_size;
+}
+
+static ssize_t fcopy_write(struct file *file, const char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	int response = 0;
+
+	if (count != sizeof(int))
+		return -EINVAL;
+
+	if (copy_from_user(&response, buf, sizeof(int)))
+		return -EFAULT;
+
+	if (in_hand_shake) {
+		if (fcopy_handle_handshake(response))
+			return -EINVAL;
+		return sizeof(int);
+	}
+
+	/*
+	 * Complete the transaction by forwarding the result
+	 * to the host. But first, cancel the timeout.
+	 */
+	if (cancel_delayed_work_sync(&fcopy_work))
+		fcopy_respond_to_host(response);
+
+	return sizeof(int);
+}
+
+int fcopy_open(struct inode *inode, struct file *f)
+{
+	/*
+	 * The user level daemon that will open this device is
+	 * really an extension of this driver. We can have only
+	 * active open at a time.
+	 */
+	if (opened)
+		return -EBUSY;
+
+	/*
+	 * The daemon is alive; setup the state.
+	 */
+	opened = true;
+	return 0;
+}
+
+int fcopy_release(struct inode *inode, struct file *f)
+{
+	/*
+	 * The daemon has exited; reset the state.
+	 */
+	in_hand_shake = true;
+	opened = false;
+	return 0;
+}
+
+
+static const struct file_operations fcopy_fops = {
+	.read           = fcopy_read,
+	.write          = fcopy_write,
+	.release	= fcopy_release,
+	.open		= fcopy_open,
+};
+
+static struct miscdevice fcopy_misc = {
+	.minor          = MISC_DYNAMIC_MINOR,
+	.name           = "vmbus/hv_fcopy",
+	.fops           = &fcopy_fops,
+};
+
+static int fcopy_dev_init(void)
+{
+	return misc_register(&fcopy_misc);
+}
+
+static void fcopy_dev_deinit(void)
+{
+
+	/*
+	 * The device is going away - perhaps because the
+	 * host has rescinded the channel. Setup state so that
+	 * user level daemon can gracefully exit if it is blocked
+	 * on the read semaphore.
+	 */
+	opened = false;
+	/*
+	 * Signal the semaphore as the device is
+	 * going away.
+	 */
+	up(&fcopy_transaction.read_sema);
+	misc_deregister(&fcopy_misc);
+}
+
+int hv_fcopy_init(struct hv_util_service *srv)
+{
+	recv_buffer = srv->recv_buffer;
+
+	/*
+	 * When this driver loads, the user level daemon that
+	 * processes the host requests may not yet be running.
+	 * Defer processing channel callbacks until the daemon
+	 * has registered.
+	 */
+	fcopy_transaction.active = true;
+	sema_init(&fcopy_transaction.read_sema, 0);
+
+	return fcopy_dev_init();
+}
+
+void hv_fcopy_deinit(void)
+{
+	cancel_delayed_work_sync(&fcopy_work);
+	fcopy_dev_deinit();
+}