/*
* 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_timeout_func(struct work_struct *dummy);
static DECLARE_DELAYED_WORK(fcopy_timeout_work, fcopy_timeout_func);
static u8 *recv_buffer;
static void fcopy_timeout_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);
/* In the case the user-space daemon crashes, hangs or is killed, we
* need to down the semaphore, otherwise, after the daemon starts next
* time, the obsolete data in fcopy_transaction.message or
* fcopy_transaction.fcopy_msg will be used immediately.
*
* NOTE: fcopy_read() happens to get the semaphore (very rare)? We're
* still OK, because we've reported the failure to the host.
*/
if (down_trylock(&fcopy_transaction.read_sema))
;
hv_poll_channel(fcopy_transaction.fcopy_context,
hv_fcopy_onchannelcallback);
}
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;
hv_poll_channel(fcopy_transaction.fcopy_context,
hv_fcopy_onchannelcallback);
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;
}
fcopy_transaction.fcopy_context = NULL;
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.
*/
schedule_delayed_work(&fcopy_timeout_work, 5*HZ);
fcopy_send_data();
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_timeout_work))
fcopy_respond_to_host(response);
hv_poll_channel(fcopy_transaction.fcopy_context,
hv_fcopy_onchannelcallback);
}
return sizeof(int);
}
static 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;
}
/* XXX: there are still some tricky corner cases, e.g.,
* 1) In a SMP guest, when fcopy_release() runs between
* schedule_delayed_work() and fcopy_send_data(), there is
* still a chance an obsolete message will be queued.
*
* 2) When the fcopy daemon is running, if we unload the driver,
* we'll notice a kernel oops when we kill the daemon later.
*/
static int fcopy_release(struct inode *inode, struct file *f)
{
/*
* The daemon has exited; reset the state.
*/
in_hand_shake = true;
opened = false;
if (cancel_delayed_work_sync(&fcopy_timeout_work)) {
/* We haven't up()-ed the semaphore(very rare)? */
if (down_trylock(&fcopy_transaction.read_sema))
;
fcopy_respond_to_host(HV_E_FAIL);
}
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_timeout_work);
fcopy_dev_deinit();
}
