Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 1091 insertions, 0 deletions

diff --git a/drivers/tty/vcc.c b/drivers/tty/vcc.c
new file mode 100644
index 000000000..27a55465b
--- /dev/null
+++ b/drivers/tty/vcc.c
@@ -0,0 +1,1091 @@
+// SPDX-License-Identifier: GPL-2.0
+/* vcc.c: sun4v virtual channel concentrator
+ *
+ * Copyright (C) 2017 Oracle. All rights reserved.
+ */
+
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/termios_internal.h>
+#include <asm/vio.h>
+#include <asm/ldc.h>
+
+MODULE_DESCRIPTION("Sun LDOM virtual console concentrator driver");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.1");
+
+struct vcc_port {
+	struct vio_driver_state vio;
+
+	spinlock_t lock;
+	char *domain;
+	struct tty_struct *tty;	/* only populated while dev is open */
+	unsigned long index;	/* index into the vcc_table */
+
+	u64 refcnt;
+	bool excl_locked;
+
+	bool removed;
+
+	/* This buffer is required to support the tty write_room interface
+	 * and guarantee that any characters that the driver accepts will
+	 * be eventually sent, either immediately or later.
+	 */
+	size_t chars_in_buffer;
+	struct vio_vcc buffer;
+
+	struct timer_list rx_timer;
+	struct timer_list tx_timer;
+};
+
+/* Microseconds that thread will delay waiting for a vcc port ref */
+#define VCC_REF_DELAY		100
+
+#define VCC_MAX_PORTS		1024
+#define VCC_MINOR_START		0	/* must be zero */
+#define VCC_BUFF_LEN		VIO_VCC_MTU_SIZE
+
+#define VCC_CTL_BREAK		-1
+#define VCC_CTL_HUP		-2
+
+static struct tty_driver *vcc_tty_driver;
+
+static struct vcc_port *vcc_table[VCC_MAX_PORTS];
+static DEFINE_SPINLOCK(vcc_table_lock);
+
+static unsigned int vcc_dbg;
+static unsigned int vcc_dbg_ldc;
+static unsigned int vcc_dbg_vio;
+
+module_param(vcc_dbg, uint, 0664);
+module_param(vcc_dbg_ldc, uint, 0664);
+module_param(vcc_dbg_vio, uint, 0664);
+
+#define VCC_DBG_DRV	0x1
+#define VCC_DBG_LDC	0x2
+#define VCC_DBG_PKT	0x4
+
+#define vccdbg(f, a...)						\
+	do {							\
+		if (vcc_dbg & VCC_DBG_DRV)			\
+			pr_info(f, ## a);			\
+	} while (0)						\
+
+#define vccdbgl(l)						\
+	do {							\
+		if (vcc_dbg & VCC_DBG_LDC)			\
+			ldc_print(l);				\
+	} while (0)						\
+
+#define vccdbgp(pkt)						\
+	do {							\
+		if (vcc_dbg & VCC_DBG_PKT) {			\
+			int i;					\
+			for (i = 0; i < pkt.tag.stype; i++)	\
+				pr_info("[%c]", pkt.data[i]);	\
+		}						\
+	} while (0)						\
+
+/* Note: Be careful when adding flags to this line discipline.  Don't
+ * add anything that will cause echoing or we'll go into recursive
+ * loop echoing chars back and forth with the console drivers.
+ */
+static const struct ktermios vcc_tty_termios = {
+	.c_iflag = IGNBRK | IGNPAR,
+	.c_oflag = OPOST,
+	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
+	.c_cc = INIT_C_CC,
+	.c_ispeed = 38400,
+	.c_ospeed = 38400
+};
+
+/**
+ * vcc_table_add() - Add VCC port to the VCC table
+ * @port: pointer to the VCC port
+ *
+ * Return: index of the port in the VCC table on success,
+ *	   -1 on failure
+ */
+static int vcc_table_add(struct vcc_port *port)
+{
+	unsigned long flags;
+	int i;
+
+	spin_lock_irqsave(&vcc_table_lock, flags);
+	for (i = VCC_MINOR_START; i < VCC_MAX_PORTS; i++) {
+		if (!vcc_table[i]) {
+			vcc_table[i] = port;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&vcc_table_lock, flags);
+
+	if (i < VCC_MAX_PORTS)
+		return i;
+	else
+		return -1;
+}
+
+/**
+ * vcc_table_remove() - Removes a VCC port from the VCC table
+ * @index: Index into the VCC table
+ */
+static void vcc_table_remove(unsigned long index)
+{
+	unsigned long flags;
+
+	if (WARN_ON(index >= VCC_MAX_PORTS))
+		return;
+
+	spin_lock_irqsave(&vcc_table_lock, flags);
+	vcc_table[index] = NULL;
+	spin_unlock_irqrestore(&vcc_table_lock, flags);
+}
+
+/**
+ * vcc_get() - Gets a reference to VCC port
+ * @index: Index into the VCC table
+ * @excl: Indicates if an exclusive access is requested
+ *
+ * Return: reference to the VCC port, if found
+ *	   NULL, if port not found
+ */
+static struct vcc_port *vcc_get(unsigned long index, bool excl)
+{
+	struct vcc_port *port;
+	unsigned long flags;
+
+try_again:
+	spin_lock_irqsave(&vcc_table_lock, flags);
+
+	port = vcc_table[index];
+	if (!port) {
+		spin_unlock_irqrestore(&vcc_table_lock, flags);
+		return NULL;
+	}
+
+	if (!excl) {
+		if (port->excl_locked) {
+			spin_unlock_irqrestore(&vcc_table_lock, flags);
+			udelay(VCC_REF_DELAY);
+			goto try_again;
+		}
+		port->refcnt++;
+		spin_unlock_irqrestore(&vcc_table_lock, flags);
+		return port;
+	}
+
+	if (port->refcnt) {
+		spin_unlock_irqrestore(&vcc_table_lock, flags);
+		/* Threads wanting exclusive access will wait half the time,
+		 * probably giving them higher priority in the case of
+		 * multiple waiters.
+		 */
+		udelay(VCC_REF_DELAY/2);
+		goto try_again;
+	}
+
+	port->refcnt++;
+	port->excl_locked = true;
+	spin_unlock_irqrestore(&vcc_table_lock, flags);
+
+	return port;
+}
+
+/**
+ * vcc_put() - Returns a reference to VCC port
+ * @port: pointer to VCC port
+ * @excl: Indicates if the returned reference is an exclusive reference
+ *
+ * Note: It's the caller's responsibility to ensure the correct value
+ *	 for the excl flag
+ */
+static void vcc_put(struct vcc_port *port, bool excl)
+{
+	unsigned long flags;
+
+	if (!port)
+		return;
+
+	spin_lock_irqsave(&vcc_table_lock, flags);
+
+	/* check if caller attempted to put with the wrong flags */
+	if (WARN_ON((excl && !port->excl_locked) ||
+		    (!excl && port->excl_locked)))
+		goto done;
+
+	port->refcnt--;
+
+	if (excl)
+		port->excl_locked = false;
+
+done:
+	spin_unlock_irqrestore(&vcc_table_lock, flags);
+}
+
+/**
+ * vcc_get_ne() - Get a non-exclusive reference to VCC port
+ * @index: Index into the VCC table
+ *
+ * Gets a non-exclusive reference to VCC port, if it's not removed
+ *
+ * Return: pointer to the VCC port, if found
+ *	   NULL, if port not found
+ */
+static struct vcc_port *vcc_get_ne(unsigned long index)
+{
+	struct vcc_port *port;
+
+	port = vcc_get(index, false);
+
+	if (port && port->removed) {
+		vcc_put(port, false);
+		return NULL;
+	}
+
+	return port;
+}
+
+static void vcc_kick_rx(struct vcc_port *port)
+{
+	struct vio_driver_state *vio = &port->vio;
+
+	assert_spin_locked(&port->lock);
+
+	if (!timer_pending(&port->rx_timer) && !port->removed) {
+		disable_irq_nosync(vio->vdev->rx_irq);
+		port->rx_timer.expires = (jiffies + 1);
+		add_timer(&port->rx_timer);
+	}
+}
+
+static void vcc_kick_tx(struct vcc_port *port)
+{
+	assert_spin_locked(&port->lock);
+
+	if (!timer_pending(&port->tx_timer) && !port->removed) {
+		port->tx_timer.expires = (jiffies + 1);
+		add_timer(&port->tx_timer);
+	}
+}
+
+static int vcc_rx_check(struct tty_struct *tty, int size)
+{
+	if (WARN_ON(!tty || !tty->port))
+		return 1;
+
+	/* tty_buffer_request_room won't sleep because it uses
+	 * GFP_ATOMIC flag to allocate buffer
+	 */
+	if (test_bit(TTY_THROTTLED, &tty->flags) ||
+	    (tty_buffer_request_room(tty->port, VCC_BUFF_LEN) < VCC_BUFF_LEN))
+		return 0;
+
+	return 1;
+}
+
+static int vcc_rx(struct tty_struct *tty, char *buf, int size)
+{
+	int len = 0;
+
+	if (WARN_ON(!tty || !tty->port))
+		return len;
+
+	len = tty_insert_flip_string(tty->port, buf, size);
+	if (len)
+		tty_flip_buffer_push(tty->port);
+
+	return len;
+}
+
+static int vcc_ldc_read(struct vcc_port *port)
+{
+	struct vio_driver_state *vio = &port->vio;
+	struct tty_struct *tty;
+	struct vio_vcc pkt;
+	int rv = 0;
+
+	tty = port->tty;
+	if (!tty) {
+		rv = ldc_rx_reset(vio->lp);
+		vccdbg("VCC: reset rx q: rv=%d\n", rv);
+		goto done;
+	}
+
+	/* Read as long as LDC has incoming data. */
+	while (1) {
+		if (!vcc_rx_check(tty, VIO_VCC_MTU_SIZE)) {
+			vcc_kick_rx(port);
+			break;
+		}
+
+		vccdbgl(vio->lp);
+
+		rv = ldc_read(vio->lp, &pkt, sizeof(pkt));
+		if (rv <= 0)
+			break;
+
+		vccdbg("VCC: ldc_read()=%d\n", rv);
+		vccdbg("TAG [%02x:%02x:%04x:%08x]\n",
+		       pkt.tag.type, pkt.tag.stype,
+		       pkt.tag.stype_env, pkt.tag.sid);
+
+		if (pkt.tag.type == VIO_TYPE_DATA) {
+			vccdbgp(pkt);
+			/* vcc_rx_check ensures memory availability */
+			vcc_rx(tty, pkt.data, pkt.tag.stype);
+		} else {
+			pr_err("VCC: unknown msg [%02x:%02x:%04x:%08x]\n",
+			       pkt.tag.type, pkt.tag.stype,
+			       pkt.tag.stype_env, pkt.tag.sid);
+			rv = -ECONNRESET;
+			break;
+		}
+
+		WARN_ON(rv != LDC_PACKET_SIZE);
+	}
+
+done:
+	return rv;
+}
+
+static void vcc_rx_timer(struct timer_list *t)
+{
+	struct vcc_port *port = timer_container_of(port, t, rx_timer);
+	struct vio_driver_state *vio;
+	unsigned long flags;
+	int rv;
+
+	spin_lock_irqsave(&port->lock, flags);
+	port->rx_timer.expires = 0;
+
+	vio = &port->vio;
+
+	enable_irq(vio->vdev->rx_irq);
+
+	if (!port->tty || port->removed)
+		goto done;
+
+	rv = vcc_ldc_read(port);
+	if (rv == -ECONNRESET)
+		vio_conn_reset(vio);
+
+done:
+	spin_unlock_irqrestore(&port->lock, flags);
+	vcc_put(port, false);
+}
+
+static void vcc_tx_timer(struct timer_list *t)
+{
+	struct vcc_port *port = timer_container_of(port, t, tx_timer);
+	struct vio_vcc *pkt;
+	unsigned long flags;
+	size_t tosend = 0;
+	int rv;
+
+	spin_lock_irqsave(&port->lock, flags);
+	port->tx_timer.expires = 0;
+
+	if (!port->tty || port->removed)
+		goto done;
+
+	tosend = min(VCC_BUFF_LEN, port->chars_in_buffer);
+	if (!tosend)
+		goto done;
+
+	pkt = &port->buffer;
+	pkt->tag.type = VIO_TYPE_DATA;
+	pkt->tag.stype = tosend;
+	vccdbgl(port->vio.lp);
+
+	rv = ldc_write(port->vio.lp, pkt, (VIO_TAG_SIZE + tosend));
+	WARN_ON(!rv);
+
+	if (rv < 0) {
+		vccdbg("VCC: ldc_write()=%d\n", rv);
+		vcc_kick_tx(port);
+	} else {
+		struct tty_struct *tty = port->tty;
+
+		port->chars_in_buffer = 0;
+		if (tty)
+			tty_wakeup(tty);
+	}
+
+done:
+	spin_unlock_irqrestore(&port->lock, flags);
+	vcc_put(port, false);
+}
+
+/**
+ * vcc_event() - LDC event processing engine
+ * @arg: VCC private data
+ * @event: LDC event
+ *
+ * Handles LDC events for VCC
+ */
+static void vcc_event(void *arg, int event)
+{
+	struct vio_driver_state *vio;
+	struct vcc_port *port;
+	unsigned long flags;
+	int rv;
+
+	port = arg;
+	vio = &port->vio;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	switch (event) {
+	case LDC_EVENT_RESET:
+	case LDC_EVENT_UP:
+		vio_link_state_change(vio, event);
+		break;
+
+	case LDC_EVENT_DATA_READY:
+		rv = vcc_ldc_read(port);
+		if (rv == -ECONNRESET)
+			vio_conn_reset(vio);
+		break;
+
+	default:
+		pr_err("VCC: unexpected LDC event(%d)\n", event);
+	}
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static struct ldc_channel_config vcc_ldc_cfg = {
+	.event		= vcc_event,
+	.mtu		= VIO_VCC_MTU_SIZE,
+	.mode		= LDC_MODE_RAW,
+	.debug		= 0,
+};
+
+/* Ordered from largest major to lowest */
+static struct vio_version vcc_versions[] = {
+	{ .major = 1, .minor = 0 },
+};
+
+static struct tty_port_operations vcc_port_ops = { 0 };
+
+static ssize_t domain_show(struct device *dev,
+			   struct device_attribute *attr,
+			   char *buf)
+{
+	struct vcc_port *port;
+	int rv;
+
+	port = dev_get_drvdata(dev);
+	if (!port)
+		return -ENODEV;
+
+	rv = scnprintf(buf, PAGE_SIZE, "%s\n", port->domain);
+
+	return rv;
+}
+
+static int vcc_send_ctl(struct vcc_port *port, int ctl)
+{
+	struct vio_vcc pkt;
+	int rv;
+
+	pkt.tag.type = VIO_TYPE_CTRL;
+	pkt.tag.sid = ctl;
+	pkt.tag.stype = 0;
+
+	rv = ldc_write(port->vio.lp, &pkt, sizeof(pkt.tag));
+	WARN_ON(!rv);
+	vccdbg("VCC: ldc_write(%ld)=%d\n", sizeof(pkt.tag), rv);
+
+	return rv;
+}
+
+static ssize_t break_store(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t count)
+{
+	struct vcc_port *port;
+	unsigned long flags;
+	int rv = count;
+	int brk;
+
+	port = dev_get_drvdata(dev);
+	if (!port)
+		return -ENODEV;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (sscanf(buf, "%ud", &brk) != 1 || brk != 1)
+		rv = -EINVAL;
+	else if (vcc_send_ctl(port, VCC_CTL_BREAK) < 0)
+		vcc_kick_tx(port);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	return rv;
+}
+
+static DEVICE_ATTR_ADMIN_RO(domain);
+static DEVICE_ATTR_WO(break);
+
+static struct attribute *vcc_sysfs_entries[] = {
+	&dev_attr_domain.attr,
+	&dev_attr_break.attr,
+	NULL
+};
+
+static struct attribute_group vcc_attribute_group = {
+	.name = NULL,
+	.attrs = vcc_sysfs_entries,
+};
+
+/**
+ * vcc_probe() - Initialize VCC port
+ * @vdev: Pointer to VIO device of the new VCC port
+ * @id: VIO device ID
+ *
+ * Initializes a VCC port to receive serial console data from
+ * the guest domain. Sets up a TTY end point on the control
+ * domain. Sets up VIO/LDC link between the guest & control
+ * domain endpoints.
+ *
+ * Return: status of the probe
+ */
+static int vcc_probe(struct vio_dev *vdev, const struct vio_device_id *id)
+{
+	struct mdesc_handle *hp;
+	struct vcc_port *port;
+	struct device *dev;
+	const char *domain;
+	char *name;
+	u64 node;
+	int rv;
+
+	vccdbg("VCC: name=%s\n", dev_name(&vdev->dev));
+
+	if (!vcc_tty_driver) {
+		pr_err("VCC: TTY driver not registered\n");
+		return -ENODEV;
+	}
+
+	port = kzalloc_obj(struct vcc_port);
+	if (!port)
+		return -ENOMEM;
+
+	name = kstrdup(dev_name(&vdev->dev), GFP_KERNEL);
+	if (!name) {
+		rv = -ENOMEM;
+		goto free_port;
+	}
+
+	rv = vio_driver_init(&port->vio, vdev, VDEV_CONSOLE_CON, vcc_versions,
+			     ARRAY_SIZE(vcc_versions), NULL, name);
+	if (rv)
+		goto free_name;
+
+	port->vio.debug = vcc_dbg_vio;
+	vcc_ldc_cfg.debug = vcc_dbg_ldc;
+
+	rv = vio_ldc_alloc(&port->vio, &vcc_ldc_cfg, port);
+	if (rv)
+		goto free_name;
+
+	spin_lock_init(&port->lock);
+
+	port->index = vcc_table_add(port);
+	if (port->index == -1) {
+		pr_err("VCC: no more TTY indices left for allocation\n");
+		rv = -ENOMEM;
+		goto free_ldc;
+	}
+
+	/* Register the device using VCC table index as TTY index */
+	dev = tty_register_device(vcc_tty_driver, port->index, &vdev->dev);
+	if (IS_ERR(dev)) {
+		rv = PTR_ERR(dev);
+		goto free_table;
+	}
+
+	hp = mdesc_grab();
+
+	node = vio_vdev_node(hp, vdev);
+	if (node == MDESC_NODE_NULL) {
+		rv = -ENXIO;
+		mdesc_release(hp);
+		goto unreg_tty;
+	}
+
+	domain = mdesc_get_property(hp, node, "vcc-domain-name", NULL);
+	if (!domain) {
+		rv = -ENXIO;
+		mdesc_release(hp);
+		goto unreg_tty;
+	}
+	port->domain = kstrdup(domain, GFP_KERNEL);
+	if (!port->domain) {
+		rv = -ENOMEM;
+		goto unreg_tty;
+	}
+
+
+	mdesc_release(hp);
+
+	rv = sysfs_create_group(&vdev->dev.kobj, &vcc_attribute_group);
+	if (rv)
+		goto free_domain;
+
+	timer_setup(&port->rx_timer, vcc_rx_timer, 0);
+	timer_setup(&port->tx_timer, vcc_tx_timer, 0);
+
+	dev_set_drvdata(&vdev->dev, port);
+
+	/* It's possible to receive IRQs in the middle of vio_port_up. Disable
+	 * IRQs until the port is up.
+	 */
+	disable_irq_nosync(vdev->rx_irq);
+	vio_port_up(&port->vio);
+	enable_irq(vdev->rx_irq);
+
+	return 0;
+
+free_domain:
+	kfree(port->domain);
+unreg_tty:
+	tty_unregister_device(vcc_tty_driver, port->index);
+free_table:
+	vcc_table_remove(port->index);
+free_ldc:
+	vio_ldc_free(&port->vio);
+free_name:
+	kfree(name);
+free_port:
+	kfree(port);
+
+	return rv;
+}
+
+/**
+ * vcc_remove() - Terminate a VCC port
+ * @vdev: Pointer to VIO device of the VCC port
+ *
+ * Terminates a VCC port. Sets up the teardown of TTY and
+ * VIO/LDC link between guest and primary domains.
+ *
+ * Return: status of removal
+ */
+static void vcc_remove(struct vio_dev *vdev)
+{
+	struct vcc_port *port = dev_get_drvdata(&vdev->dev);
+
+	timer_delete_sync(&port->rx_timer);
+	timer_delete_sync(&port->tx_timer);
+
+	/* If there's a process with the device open, do a synchronous
+	 * hangup of the TTY. This *may* cause the process to call close
+	 * asynchronously, but it's not guaranteed.
+	 */
+	if (port->tty)
+		tty_vhangup(port->tty);
+
+	/* Get exclusive reference to VCC, ensures that there are no other
+	 * clients to this port. This cannot fail.
+	 */
+	vcc_get(port->index, true);
+
+	tty_unregister_device(vcc_tty_driver, port->index);
+
+	timer_delete_sync(&port->vio.timer);
+	vio_ldc_free(&port->vio);
+	sysfs_remove_group(&vdev->dev.kobj, &vcc_attribute_group);
+	dev_set_drvdata(&vdev->dev, NULL);
+	if (port->tty) {
+		port->removed = true;
+		vcc_put(port, true);
+	} else {
+		vcc_table_remove(port->index);
+
+		kfree(port->vio.name);
+		kfree(port->domain);
+		kfree(port);
+	}
+}
+
+static const struct vio_device_id vcc_match[] = {
+	{
+		.type = "vcc-port",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(vio, vcc_match);
+
+static struct vio_driver vcc_driver = {
+	.id_table	= vcc_match,
+	.probe		= vcc_probe,
+	.remove		= vcc_remove,
+	.name		= "vcc",
+};
+
+static int vcc_open(struct tty_struct *tty, struct file *vcc_file)
+{
+	struct vcc_port *port;
+
+	if (tty->count > 1)
+		return -EBUSY;
+
+	port = vcc_get_ne(tty->index);
+	if (unlikely(!port)) {
+		pr_err("VCC: open: Failed to find VCC port\n");
+		return -ENODEV;
+	}
+
+	if (unlikely(!port->vio.lp)) {
+		pr_err("VCC: open: LDC channel not configured\n");
+		vcc_put(port, false);
+		return -EPIPE;
+	}
+	vccdbgl(port->vio.lp);
+
+	vcc_put(port, false);
+
+	if (unlikely(!tty->port)) {
+		pr_err("VCC: open: TTY port not found\n");
+		return -ENXIO;
+	}
+
+	if (unlikely(!tty->port->ops)) {
+		pr_err("VCC: open: TTY ops not defined\n");
+		return -ENXIO;
+	}
+
+	return tty_port_open(tty->port, tty, vcc_file);
+}
+
+static void vcc_close(struct tty_struct *tty, struct file *vcc_file)
+{
+	if (unlikely(tty->count > 1))
+		return;
+
+	if (unlikely(!tty->port)) {
+		pr_err("VCC: close: TTY port not found\n");
+		return;
+	}
+
+	tty_port_close(tty->port, tty, vcc_file);
+}
+
+static void vcc_ldc_hup(struct vcc_port *port)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (vcc_send_ctl(port, VCC_CTL_HUP) < 0)
+		vcc_kick_tx(port);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static void vcc_hangup(struct tty_struct *tty)
+{
+	struct vcc_port *port;
+
+	port = vcc_get_ne(tty->index);
+	if (unlikely(!port)) {
+		pr_err("VCC: hangup: Failed to find VCC port\n");
+		return;
+	}
+
+	if (unlikely(!tty->port)) {
+		pr_err("VCC: hangup: TTY port not found\n");
+		vcc_put(port, false);
+		return;
+	}
+
+	vcc_ldc_hup(port);
+
+	vcc_put(port, false);
+
+	tty_port_hangup(tty->port);
+}
+
+static ssize_t vcc_write(struct tty_struct *tty, const u8 *buf, size_t count)
+{
+	struct vcc_port *port;
+	struct vio_vcc *pkt;
+	unsigned long flags;
+	size_t total_sent = 0;
+	size_t tosend = 0;
+	int rv = -EINVAL;
+
+	port = vcc_get_ne(tty->index);
+	if (unlikely(!port)) {
+		pr_err("VCC: write: Failed to find VCC port");
+		return -ENODEV;
+	}
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	pkt = &port->buffer;
+	pkt->tag.type = VIO_TYPE_DATA;
+
+	while (count > 0) {
+		/* Minimum of data to write and space available */
+		tosend = min_t(size_t, count,
+			       (VCC_BUFF_LEN - port->chars_in_buffer));
+
+		if (!tosend)
+			break;
+
+		memcpy(&pkt->data[port->chars_in_buffer], &buf[total_sent],
+		       tosend);
+		port->chars_in_buffer += tosend;
+		pkt->tag.stype = tosend;
+
+		vccdbg("TAG [%02x:%02x:%04x:%08x]\n", pkt->tag.type,
+		       pkt->tag.stype, pkt->tag.stype_env, pkt->tag.sid);
+		vccdbg("DATA [%s]\n", pkt->data);
+		vccdbgl(port->vio.lp);
+
+		/* Since we know we have enough room in VCC buffer for tosend
+		 * we record that it was sent regardless of whether the
+		 * hypervisor actually took it because we have it buffered.
+		 */
+		rv = ldc_write(port->vio.lp, pkt, (VIO_TAG_SIZE + tosend));
+		vccdbg("VCC: write: ldc_write(%zu)=%d\n",
+		       (VIO_TAG_SIZE + tosend), rv);
+
+		total_sent += tosend;
+		count -= tosend;
+		if (rv < 0) {
+			vcc_kick_tx(port);
+			break;
+		}
+
+		port->chars_in_buffer = 0;
+	}
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	vcc_put(port, false);
+
+	vccdbg("VCC: write: total=%zu rv=%d", total_sent, rv);
+
+	return total_sent ? total_sent : rv;
+}
+
+static unsigned int vcc_write_room(struct tty_struct *tty)
+{
+	struct vcc_port *port;
+	unsigned int num;
+
+	port = vcc_get_ne(tty->index);
+	if (unlikely(!port)) {
+		pr_err("VCC: write_room: Failed to find VCC port\n");
+		return 0;
+	}
+
+	num = VCC_BUFF_LEN - port->chars_in_buffer;
+
+	vcc_put(port, false);
+
+	return num;
+}
+
+static unsigned int vcc_chars_in_buffer(struct tty_struct *tty)
+{
+	struct vcc_port *port;
+	unsigned int num;
+
+	port = vcc_get_ne(tty->index);
+	if (unlikely(!port)) {
+		pr_err("VCC: chars_in_buffer: Failed to find VCC port\n");
+		return 0;
+	}
+
+	num = port->chars_in_buffer;
+
+	vcc_put(port, false);
+
+	return num;
+}
+
+static int vcc_break_ctl(struct tty_struct *tty, int state)
+{
+	struct vcc_port *port;
+	unsigned long flags;
+
+	port = vcc_get_ne(tty->index);
+	if (unlikely(!port)) {
+		pr_err("VCC: break_ctl: Failed to find VCC port\n");
+		return -ENODEV;
+	}
+
+	/* Turn off break */
+	if (state == 0) {
+		vcc_put(port, false);
+		return 0;
+	}
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (vcc_send_ctl(port, VCC_CTL_BREAK) < 0)
+		vcc_kick_tx(port);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	vcc_put(port, false);
+
+	return 0;
+}
+
+static int vcc_install(struct tty_driver *driver, struct tty_struct *tty)
+{
+	struct vcc_port *port_vcc;
+	struct tty_port *port_tty;
+	int ret;
+
+	if (tty->index >= VCC_MAX_PORTS)
+		return -EINVAL;
+
+	ret = tty_standard_install(driver, tty);
+	if (ret)
+		return ret;
+
+	port_tty = kzalloc_obj(struct tty_port);
+	if (!port_tty)
+		return -ENOMEM;
+
+	port_vcc = vcc_get(tty->index, true);
+	if (!port_vcc) {
+		pr_err("VCC: install: Failed to find VCC port\n");
+		tty->port = NULL;
+		kfree(port_tty);
+		return -ENODEV;
+	}
+
+	tty_port_init(port_tty);
+	port_tty->ops = &vcc_port_ops;
+	tty->port = port_tty;
+
+	port_vcc->tty = tty;
+
+	vcc_put(port_vcc, true);
+
+	return 0;
+}
+
+static void vcc_cleanup(struct tty_struct *tty)
+{
+	struct vcc_port *port;
+
+	port = vcc_get(tty->index, true);
+	if (port) {
+		port->tty = NULL;
+
+		if (port->removed) {
+			vcc_table_remove(tty->index);
+			kfree(port->vio.name);
+			kfree(port->domain);
+			kfree(port);
+		} else {
+			vcc_put(port, true);
+		}
+	}
+
+	tty_port_destroy(tty->port);
+	kfree(tty->port);
+	tty->port = NULL;
+}
+
+static const struct tty_operations vcc_ops = {
+	.open			= vcc_open,
+	.close			= vcc_close,
+	.hangup			= vcc_hangup,
+	.write			= vcc_write,
+	.write_room		= vcc_write_room,
+	.chars_in_buffer	= vcc_chars_in_buffer,
+	.break_ctl		= vcc_break_ctl,
+	.install		= vcc_install,
+	.cleanup		= vcc_cleanup,
+};
+
+#define VCC_TTY_FLAGS   (TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_REAL_RAW)
+
+static int vcc_tty_init(void)
+{
+	int rv;
+
+	vcc_tty_driver = tty_alloc_driver(VCC_MAX_PORTS, VCC_TTY_FLAGS);
+	if (IS_ERR(vcc_tty_driver)) {
+		pr_err("VCC: TTY driver alloc failed\n");
+		return PTR_ERR(vcc_tty_driver);
+	}
+
+	vcc_tty_driver->driver_name = "vcc";
+	vcc_tty_driver->name = "vcc";
+
+	vcc_tty_driver->minor_start = VCC_MINOR_START;
+	vcc_tty_driver->type = TTY_DRIVER_TYPE_SYSTEM;
+	vcc_tty_driver->init_termios = vcc_tty_termios;
+
+	tty_set_operations(vcc_tty_driver, &vcc_ops);
+
+	rv = tty_register_driver(vcc_tty_driver);
+	if (rv) {
+		pr_err("VCC: TTY driver registration failed\n");
+		tty_driver_kref_put(vcc_tty_driver);
+		vcc_tty_driver = NULL;
+		return rv;
+	}
+
+	vccdbg("VCC: TTY driver registered\n");
+
+	return 0;
+}
+
+static void vcc_tty_exit(void)
+{
+	tty_unregister_driver(vcc_tty_driver);
+	tty_driver_kref_put(vcc_tty_driver);
+	vccdbg("VCC: TTY driver unregistered\n");
+
+	vcc_tty_driver = NULL;
+}
+
+static int __init vcc_init(void)
+{
+	int rv;
+
+	rv = vcc_tty_init();
+	if (rv) {
+		pr_err("VCC: TTY init failed\n");
+		return rv;
+	}
+
+	rv = vio_register_driver(&vcc_driver);
+	if (rv) {
+		pr_err("VCC: VIO driver registration failed\n");
+		vcc_tty_exit();
+	} else {
+		vccdbg("VCC: VIO driver registered successfully\n");
+	}
+
+	return rv;
+}
+
+static void __exit vcc_exit(void)
+{
+	vio_unregister_driver(&vcc_driver);
+	vccdbg("VCC: VIO driver unregistered\n");
+	vcc_tty_exit();
+	vccdbg("VCC: TTY driver unregistered\n");
+}
+
+module_init(vcc_init);
+module_exit(vcc_exit);