arch/tile: Add driver to enable access to the user dynamic network.

This network (the "UDN") connects all the cpus on the chip in a
wormhole-routed dynamic network.  Subrectangles of the chip can
be allocated by a "create" ioctl on /dev/hardwall, and then to access the
UDN in that rectangle, tasks must perform an "activate" ioctl on that
same file object after affinitizing themselves to a single cpu in
the region.  Sending a wormhole-routed message that tries to leave
that subrectangle causes all activated tasks to receive a SIGILL
(just as they would if they tried to access the UDN without first
activating themselves to a hardwall rectangle).

The original submission of this code to LKML had the driver
instantiated under /proc/tile/hardwall.  Now we just use a character
device for this, conventionally /dev/hardwall.  Some futures planning
for the TILE-Gx chip suggests that we may want to have other types of
devices that share the general model of "bind a task to a cpu, then
'activate' a file descriptor on a pseudo-device that gives access to
some hardware resource".  As such, we are using a device rather
than, for example, a syscall, to set up and activate this code.

As part of this change, the compat_ptr() declaration was fixed and used
to pass the compat_ioctl argument to the normal ioctl.  So far we limit
compat code to 2GB, so the difference between zero-extend and sign-extend
(the latter being correct, eventually) had been overlooked.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

3 files changed, 799 insertions, 2 deletions

diff --git a/arch/tile/kernel/Makefile b/arch/tile/kernel/Makefile
index 756e6ec452d..112b1e248f0 100644
--- a/arch/tile/kernel/Makefile
+++ b/arch/tile/kernel/Makefile
@@ -8,6 +8,7 @@ obj-y := backtrace.o entry.o init_task.o irq.o messaging.o \
 	setup.o signal.o single_step.o stack.o sys.o time.o traps.o \
 	intvec_$(BITS).o regs_$(BITS).o tile-desc_$(BITS).o
 
+obj-$(CONFIG_HARDWALL)		+= hardwall.o
 obj-$(CONFIG_TILEGX)		+= futex_64.o
 obj-$(CONFIG_COMPAT)		+= compat.o compat_signal.o
 obj-$(CONFIG_SMP)		+= smpboot.o smp.o tlb.o
diff --git a/arch/tile/kernel/hardwall.c b/arch/tile/kernel/hardwall.c
new file mode 100644
index 00000000000..7bf0627b733
--- /dev/null
+++ b/arch/tile/kernel/hardwall.c
@@ -0,0 +1,794 @@
+/*
+ * Copyright 2010 Tilera Corporation. 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
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   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.
+ */
+
+#include <linux/fs.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/rwsem.h>
+#include <linux/kprobes.h>
+#include <linux/sched.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/smp.h>
+#include <linux/cdev.h>
+#include <linux/compat.h>
+#include <asm/hardwall.h>
+#include <asm/traps.h>
+#include <asm/siginfo.h>
+#include <asm/irq_regs.h>
+
+#include <arch/interrupts.h>
+#include <arch/spr_def.h>
+
+
+/*
+ * This data structure tracks the rectangle data, etc., associated
+ * one-to-one with a "struct file *" from opening HARDWALL_FILE.
+ * Note that the file's private data points back to this structure.
+ */
+struct hardwall_info {
+	struct list_head list;             /* "rectangles" list */
+	struct list_head task_head;        /* head of tasks in this hardwall */
+	int ulhc_x;                        /* upper left hand corner x coord */
+	int ulhc_y;                        /* upper left hand corner y coord */
+	int width;                         /* rectangle width */
+	int height;                        /* rectangle height */
+	int teardown_in_progress;          /* are we tearing this one down? */
+};
+
+/* Currently allocated hardwall rectangles */
+static LIST_HEAD(rectangles);
+
+/*
+ * Guard changes to the hardwall data structures.
+ * This could be finer grained (e.g. one lock for the list of hardwall
+ * rectangles, then separate embedded locks for each one's list of tasks),
+ * but there are subtle correctness issues when trying to start with
+ * a task's "hardwall" pointer and lock the correct rectangle's embedded
+ * lock in the presence of a simultaneous deactivation, so it seems
+ * easier to have a single lock, given that none of these data
+ * structures are touched very frequently during normal operation.
+ */
+static DEFINE_SPINLOCK(hardwall_lock);
+
+/* Allow disabling UDN access. */
+static int udn_disabled;
+static int __init noudn(char *str)
+{
+	pr_info("User-space UDN access is disabled\n");
+	udn_disabled = 1;
+	return 0;
+}
+early_param("noudn", noudn);
+
+
+/*
+ * Low-level primitives
+ */
+
+/* Set a CPU bit if the CPU is online. */
+#define cpu_online_set(cpu, dst) do { \
+	if (cpu_online(cpu))          \
+		cpumask_set_cpu(cpu, dst);    \
+} while (0)
+
+
+/* Does the given rectangle contain the given x,y coordinate? */
+static int contains(struct hardwall_info *r, int x, int y)
+{
+	return (x >= r->ulhc_x && x < r->ulhc_x + r->width) &&
+		(y >= r->ulhc_y && y < r->ulhc_y + r->height);
+}
+
+/* Compute the rectangle parameters and validate the cpumask. */
+static int setup_rectangle(struct hardwall_info *r, struct cpumask *mask)
+{
+	int x, y, cpu, ulhc, lrhc;
+
+	/* The first cpu is the ULHC, the last the LRHC. */
+	ulhc = find_first_bit(cpumask_bits(mask), nr_cpumask_bits);
+	lrhc = find_last_bit(cpumask_bits(mask), nr_cpumask_bits);
+
+	/* Compute the rectangle attributes from the cpus. */
+	r->ulhc_x = cpu_x(ulhc);
+	r->ulhc_y = cpu_y(ulhc);
+	r->width = cpu_x(lrhc) - r->ulhc_x + 1;
+	r->height = cpu_y(lrhc) - r->ulhc_y + 1;
+
+	/* Width and height must be positive */
+	if (r->width <= 0 || r->height <= 0)
+		return -EINVAL;
+
+	/* Confirm that the cpumask is exactly the rectangle. */
+	for (y = 0, cpu = 0; y < smp_height; ++y)
+		for (x = 0; x < smp_width; ++x, ++cpu)
+			if (cpumask_test_cpu(cpu, mask) != contains(r, x, y))
+				return -EINVAL;
+
+	/*
+	 * Note that offline cpus can't be drained when this UDN
+	 * rectangle eventually closes.  We used to detect this
+	 * situation and print a warning, but it annoyed users and
+	 * they ignored it anyway, so now we just return without a
+	 * warning.
+	 */
+	return 0;
+}
+
+/* Do the two given rectangles overlap on any cpu? */
+static int overlaps(struct hardwall_info *a, struct hardwall_info *b)
+{
+	return a->ulhc_x + a->width > b->ulhc_x &&    /* A not to the left */
+		b->ulhc_x + b->width > a->ulhc_x &&   /* B not to the left */
+		a->ulhc_y + a->height > b->ulhc_y &&  /* A not above */
+		b->ulhc_y + b->height > a->ulhc_y;    /* B not above */
+}
+
+
+/*
+ * Hardware management of hardwall setup, teardown, trapping,
+ * and enabling/disabling PL0 access to the networks.
+ */
+
+/* Bit field values to mask together for writes to SPR_XDN_DIRECTION_PROTECT */
+enum direction_protect {
+	N_PROTECT = (1 << 0),
+	E_PROTECT = (1 << 1),
+	S_PROTECT = (1 << 2),
+	W_PROTECT = (1 << 3)
+};
+
+static void enable_firewall_interrupts(void)
+{
+	raw_local_irq_unmask_now(INT_UDN_FIREWALL);
+}
+
+static void disable_firewall_interrupts(void)
+{
+	raw_local_irq_mask_now(INT_UDN_FIREWALL);
+}
+
+/* Set up hardwall on this cpu based on the passed hardwall_info. */
+static void hardwall_setup_ipi_func(void *info)
+{
+	struct hardwall_info *r = info;
+	int cpu = smp_processor_id();
+	int x = cpu % smp_width;
+	int y = cpu / smp_width;
+	int bits = 0;
+	if (x == r->ulhc_x)
+		bits |= W_PROTECT;
+	if (x == r->ulhc_x + r->width - 1)
+		bits |= E_PROTECT;
+	if (y == r->ulhc_y)
+		bits |= N_PROTECT;
+	if (y == r->ulhc_y + r->height - 1)
+		bits |= S_PROTECT;
+	BUG_ON(bits == 0);
+	__insn_mtspr(SPR_UDN_DIRECTION_PROTECT, bits);
+	enable_firewall_interrupts();
+
+}
+
+/* Set up all cpus on edge of rectangle to enable/disable hardwall SPRs. */
+static void hardwall_setup(struct hardwall_info *r)
+{
+	int x, y, cpu, delta;
+	struct cpumask rect_cpus;
+
+	cpumask_clear(&rect_cpus);
+
+	/* First include the top and bottom edges */
+	cpu = r->ulhc_y * smp_width + r->ulhc_x;
+	delta = (r->height - 1) * smp_width;
+	for (x = 0; x < r->width; ++x, ++cpu) {
+		cpu_online_set(cpu, &rect_cpus);
+		cpu_online_set(cpu + delta, &rect_cpus);
+	}
+
+	/* Then the left and right edges */
+	cpu -= r->width;
+	delta = r->width - 1;
+	for (y = 0; y < r->height; ++y, cpu += smp_width) {
+		cpu_online_set(cpu, &rect_cpus);
+		cpu_online_set(cpu + delta, &rect_cpus);
+	}
+
+	/* Then tell all the cpus to set up their protection SPR */
+	on_each_cpu_mask(&rect_cpus, hardwall_setup_ipi_func, r, 1);
+}
+
+void __kprobes do_hardwall_trap(struct pt_regs* regs, int fault_num)
+{
+	struct hardwall_info *rect;
+	struct task_struct *p;
+	struct siginfo info;
+	int x, y;
+	int cpu = smp_processor_id();
+	int found_processes;
+	unsigned long flags;
+
+	struct pt_regs *old_regs = set_irq_regs(regs);
+	irq_enter();
+
+	/* This tile trapped a network access; find the rectangle. */
+	x = cpu % smp_width;
+	y = cpu / smp_width;
+	spin_lock_irqsave(&hardwall_lock, flags);
+	list_for_each_entry(rect, &rectangles, list) {
+		if (contains(rect, x, y))
+			break;
+	}
+
+	/*
+	 * It shouldn't be possible not to find this cpu on the
+	 * rectangle list, since only cpus in rectangles get hardwalled.
+	 * The hardwall is only removed after the UDN is drained.
+	 */
+	BUG_ON(&rect->list == &rectangles);
+
+	/*
+	 * If we already started teardown on this hardwall, don't worry;
+	 * the abort signal has been sent and we are just waiting for things
+	 * to quiesce.
+	 */
+	if (rect->teardown_in_progress) {
+		pr_notice("cpu %d: detected hardwall violation %#lx"
+		       " while teardown already in progress\n",
+		       cpu, (long) __insn_mfspr(SPR_UDN_DIRECTION_PROTECT));
+		goto done;
+	}
+
+	/*
+	 * Kill off any process that is activated in this rectangle.
+	 * We bypass security to deliver the signal, since it must be
+	 * one of the activated processes that generated the UDN
+	 * message that caused this trap, and all the activated
+	 * processes shared a single open file so are pretty tightly
+	 * bound together from a security point of view to begin with.
+	 */
+	rect->teardown_in_progress = 1;
+	wmb(); /* Ensure visibility of rectangle before notifying processes. */
+	pr_notice("cpu %d: detected hardwall violation %#lx...\n",
+	       cpu, (long) __insn_mfspr(SPR_UDN_DIRECTION_PROTECT));
+	info.si_signo = SIGILL;
+	info.si_errno = 0;
+	info.si_code = ILL_HARDWALL;
+	found_processes = 0;
+	list_for_each_entry(p, &rect->task_head, thread.hardwall_list) {
+		BUG_ON(p->thread.hardwall != rect);
+		if (p->sighand) {
+			found_processes = 1;
+			pr_notice("hardwall: killing %d\n", p->pid);
+			spin_lock(&p->sighand->siglock);
+			__group_send_sig_info(info.si_signo, &info, p);
+			spin_unlock(&p->sighand->siglock);
+		}
+	}
+	if (!found_processes)
+		pr_notice("hardwall: no associated processes!\n");
+
+ done:
+	spin_unlock_irqrestore(&hardwall_lock, flags);
+
+	/*
+	 * We have to disable firewall interrupts now, or else when we
+	 * return from this handler, we will simply re-interrupt back to
+	 * it.  However, we can't clear the protection bits, since we
+	 * haven't yet drained the network, and that would allow packets
+	 * to cross out of the hardwall region.
+	 */
+	disable_firewall_interrupts();
+
+	irq_exit();
+	set_irq_regs(old_regs);
+}
+
+/* Allow access from user space to the UDN. */
+void grant_network_mpls(void)
+{
+	__insn_mtspr(SPR_MPL_UDN_ACCESS_SET_0, 1);
+	__insn_mtspr(SPR_MPL_UDN_AVAIL_SET_0, 1);
+	__insn_mtspr(SPR_MPL_UDN_COMPLETE_SET_0, 1);
+	__insn_mtspr(SPR_MPL_UDN_TIMER_SET_0, 1);
+#if !CHIP_HAS_REV1_XDN()
+	__insn_mtspr(SPR_MPL_UDN_REFILL_SET_0, 1);
+	__insn_mtspr(SPR_MPL_UDN_CA_SET_0, 1);
+#endif
+}
+
+/* Deny access from user space to the UDN. */
+void restrict_network_mpls(void)
+{
+	__insn_mtspr(SPR_MPL_UDN_ACCESS_SET_1, 1);
+	__insn_mtspr(SPR_MPL_UDN_AVAIL_SET_1, 1);
+	__insn_mtspr(SPR_MPL_UDN_COMPLETE_SET_1, 1);
+	__insn_mtspr(SPR_MPL_UDN_TIMER_SET_1, 1);
+#if !CHIP_HAS_REV1_XDN()
+	__insn_mtspr(SPR_MPL_UDN_REFILL_SET_1, 1);
+	__insn_mtspr(SPR_MPL_UDN_CA_SET_1, 1);
+#endif
+}
+
+
+/*
+ * Code to create, activate, deactivate, and destroy hardwall rectangles.
+ */
+
+/* Create a hardwall for the given rectangle */
+static struct hardwall_info *hardwall_create(
+	size_t size, const unsigned char __user *bits)
+{
+	struct hardwall_info *iter, *rect;
+	struct cpumask mask;
+	unsigned long flags;
+	int rc;
+
+	/* Reject crazy sizes out of hand, a la sys_mbind(). */
+	if (size > PAGE_SIZE)
+		return ERR_PTR(-EINVAL);
+
+	/* Copy whatever fits into a cpumask. */
+	if (copy_from_user(&mask, bits, min(sizeof(struct cpumask), size)))
+		return ERR_PTR(-EFAULT);
+
+	/*
+	 * If the size was short, clear the rest of the mask;
+	 * otherwise validate that the rest of the user mask was zero
+	 * (we don't try hard to be efficient when validating huge masks).
+	 */
+	if (size < sizeof(struct cpumask)) {
+		memset((char *)&mask + size, 0, sizeof(struct cpumask) - size);
+	} else if (size > sizeof(struct cpumask)) {
+		size_t i;
+		for (i = sizeof(struct cpumask); i < size; ++i) {
+			char c;
+			if (get_user(c, &bits[i]))
+				return ERR_PTR(-EFAULT);
+			if (c)
+				return ERR_PTR(-EINVAL);
+		}
+	}
+
+	/* Allocate a new rectangle optimistically. */
+	rect = kmalloc(sizeof(struct hardwall_info),
+			GFP_KERNEL | __GFP_ZERO);
+	INIT_LIST_HEAD(&rect->task_head);
+
+	/* Compute the rectangle size and validate that it's plausible. */
+	rc = setup_rectangle(rect, &mask);
+	if (rc != 0) {
+		kfree(rect);
+		return ERR_PTR(rc);
+	}
+
+	/* Confirm it doesn't overlap and add it to the list. */
+	spin_lock_irqsave(&hardwall_lock, flags);
+	list_for_each_entry(iter, &rectangles, list) {
+		if (overlaps(iter, rect)) {
+			spin_unlock_irqrestore(&hardwall_lock, flags);
+			kfree(rect);
+			return ERR_PTR(-EBUSY);
+		}
+	}
+	list_add_tail(&rect->list, &rectangles);
+	spin_unlock_irqrestore(&hardwall_lock, flags);
+
+	/* Set up appropriate hardwalling on all affected cpus. */
+	hardwall_setup(rect);
+
+	return rect;
+}
+
+/* Activate a given hardwall on this cpu for this process. */
+static int hardwall_activate(struct hardwall_info *rect)
+{
+	int cpu, x, y;
+	unsigned long flags;
+	struct task_struct *p = current;
+	struct thread_struct *ts = &p->thread;
+
+	/* Require a rectangle. */
+	if (rect == NULL)
+		return -ENODATA;
+
+	/* Not allowed to activate a rectangle that is being torn down. */
+	if (rect->teardown_in_progress)
+		return -EINVAL;
+
+	/*
+	 * Get our affinity; if we're not bound to this tile uniquely,
+	 * we can't access the network registers.
+	 */
+	if (cpumask_weight(&p->cpus_allowed) != 1)
+		return -EPERM;
+
+	/* Make sure we are bound to a cpu in this rectangle. */
+	cpu = smp_processor_id();
+	BUG_ON(cpumask_first(&p->cpus_allowed) != cpu);
+	x = cpu_x(cpu);
+	y = cpu_y(cpu);
+	if (!contains(rect, x, y))
+		return -EINVAL;
+
+	/* If we are already bound to this hardwall, it's a no-op. */
+	if (ts->hardwall) {
+		BUG_ON(ts->hardwall != rect);
+		return 0;
+	}
+
+	/* Success!  This process gets to use the user networks on this cpu. */
+	ts->hardwall = rect;
+	spin_lock_irqsave(&hardwall_lock, flags);
+	list_add(&ts->hardwall_list, &rect->task_head);
+	spin_unlock_irqrestore(&hardwall_lock, flags);
+	grant_network_mpls();
+	printk(KERN_DEBUG "Pid %d (%s) activated for hardwall: cpu %d\n",
+	       p->pid, p->comm, cpu);
+	return 0;
+}
+
+/*
+ * Deactivate a task's hardwall.  Must hold hardwall_lock.
+ * This method may be called from free_task(), so we don't want to
+ * rely on too many fields of struct task_struct still being valid.
+ * We assume the cpus_allowed, pid, and comm fields are still valid.
+ */
+static void _hardwall_deactivate(struct task_struct *task)
+{
+	struct thread_struct *ts = &task->thread;
+
+	if (cpumask_weight(&task->cpus_allowed) != 1) {
+		pr_err("pid %d (%s) releasing networks with"
+		       " an affinity mask containing %d cpus!\n",
+		       task->pid, task->comm,
+		       cpumask_weight(&task->cpus_allowed));
+		BUG();
+	}
+
+	BUG_ON(ts->hardwall == NULL);
+	ts->hardwall = NULL;
+	list_del(&ts->hardwall_list);
+	if (task == current)
+		restrict_network_mpls();
+}
+
+/* Deactivate a task's hardwall. */
+int hardwall_deactivate(struct task_struct *task)
+{
+	unsigned long flags;
+	int activated;
+
+	spin_lock_irqsave(&hardwall_lock, flags);
+	activated = (task->thread.hardwall != NULL);
+	if (activated)
+		_hardwall_deactivate(task);
+	spin_unlock_irqrestore(&hardwall_lock, flags);
+
+	if (!activated)
+		return -EINVAL;
+
+	printk(KERN_DEBUG "Pid %d (%s) deactivated for hardwall: cpu %d\n",
+	       task->pid, task->comm, smp_processor_id());
+	return 0;
+}
+
+/* Stop a UDN switch before draining the network. */
+static void stop_udn_switch(void *ignored)
+{
+#if !CHIP_HAS_REV1_XDN()
+	/* Freeze the switch and the demux. */
+	__insn_mtspr(SPR_UDN_SP_FREEZE,
+		     SPR_UDN_SP_FREEZE__SP_FRZ_MASK |
+		     SPR_UDN_SP_FREEZE__DEMUX_FRZ_MASK |
+		     SPR_UDN_SP_FREEZE__NON_DEST_EXT_MASK);
+#endif
+}
+
+/* Drain all the state from a stopped switch. */
+static void drain_udn_switch(void *ignored)
+{
+#if !CHIP_HAS_REV1_XDN()
+	int i;
+	int from_tile_words, ca_count;
+
+	/* Empty out the 5 switch point fifos. */
+	for (i = 0; i < 5; i++) {
+		int words, j;
+		__insn_mtspr(SPR_UDN_SP_FIFO_SEL, i);
+		words = __insn_mfspr(SPR_UDN_SP_STATE) & 0xF;
+		for (j = 0; j < words; j++)
+			(void) __insn_mfspr(SPR_UDN_SP_FIFO_DATA);
+		BUG_ON((__insn_mfspr(SPR_UDN_SP_STATE) & 0xF) != 0);
+	}
+
+	/* Dump out the 3 word fifo at top. */
+	from_tile_words = (__insn_mfspr(SPR_UDN_DEMUX_STATUS) >> 10) & 0x3;
+	for (i = 0; i < from_tile_words; i++)
+		(void) __insn_mfspr(SPR_UDN_DEMUX_WRITE_FIFO);
+
+	/* Empty out demuxes. */
+	while (__insn_mfspr(SPR_UDN_DATA_AVAIL) & (1 << 0))
+		(void) __tile_udn0_receive();
+	while (__insn_mfspr(SPR_UDN_DATA_AVAIL) & (1 << 1))
+		(void) __tile_udn1_receive();
+	while (__insn_mfspr(SPR_UDN_DATA_AVAIL) & (1 << 2))
+		(void) __tile_udn2_receive();
+	while (__insn_mfspr(SPR_UDN_DATA_AVAIL) & (1 << 3))
+		(void) __tile_udn3_receive();
+	BUG_ON((__insn_mfspr(SPR_UDN_DATA_AVAIL) & 0xF) != 0);
+
+	/* Empty out catch all. */
+	ca_count = __insn_mfspr(SPR_UDN_DEMUX_CA_COUNT);
+	for (i = 0; i < ca_count; i++)
+		(void) __insn_mfspr(SPR_UDN_CA_DATA);
+	BUG_ON(__insn_mfspr(SPR_UDN_DEMUX_CA_COUNT) != 0);
+
+	/* Clear demux logic. */
+	__insn_mtspr(SPR_UDN_DEMUX_CTL, 1);
+
+	/*
+	 * Write switch state; experimentation indicates that 0xc3000
+	 * is an idle switch point.
+	 */
+	for (i = 0; i < 5; i++) {
+		__insn_mtspr(SPR_UDN_SP_FIFO_SEL, i);
+		__insn_mtspr(SPR_UDN_SP_STATE, 0xc3000);
+	}
+#endif
+}
+
+/* Reset random UDN state registers at boot up and during hardwall teardown. */
+void reset_network_state(void)
+{
+#if !CHIP_HAS_REV1_XDN()
+	/* Reset UDN coordinates to their standard value */
+	unsigned int cpu = smp_processor_id();
+	unsigned int x = cpu % smp_width;
+	unsigned int y = cpu / smp_width;
+#endif
+
+	if (udn_disabled)
+		return;
+
+#if !CHIP_HAS_REV1_XDN()
+	__insn_mtspr(SPR_UDN_TILE_COORD, (x << 18) | (y << 7));
+
+	/* Set demux tags to predefined values and enable them. */
+	__insn_mtspr(SPR_UDN_TAG_VALID, 0xf);
+	__insn_mtspr(SPR_UDN_TAG_0, (1 << 0));
+	__insn_mtspr(SPR_UDN_TAG_1, (1 << 1));
+	__insn_mtspr(SPR_UDN_TAG_2, (1 << 2));
+	__insn_mtspr(SPR_UDN_TAG_3, (1 << 3));
+#endif
+
+	/* Clear out other random registers so we have a clean slate. */
+	__insn_mtspr(SPR_UDN_AVAIL_EN, 0);
+	__insn_mtspr(SPR_UDN_DEADLOCK_TIMEOUT, 0);
+#if !CHIP_HAS_REV1_XDN()
+	__insn_mtspr(SPR_UDN_REFILL_EN, 0);
+	__insn_mtspr(SPR_UDN_DEMUX_QUEUE_SEL, 0);
+	__insn_mtspr(SPR_UDN_SP_FIFO_SEL, 0);
+#endif
+
+	/* Start the switch and demux. */
+#if !CHIP_HAS_REV1_XDN()
+	__insn_mtspr(SPR_UDN_SP_FREEZE, 0);
+#endif
+}
+
+/* Restart a UDN switch after draining. */
+static void restart_udn_switch(void *ignored)
+{
+	reset_network_state();
+
+	/* Disable firewall interrupts. */
+	__insn_mtspr(SPR_UDN_DIRECTION_PROTECT, 0);
+	disable_firewall_interrupts();
+}
+
+/* Build a struct cpumask containing all valid tiles in bounding rectangle. */
+static void fill_mask(struct hardwall_info *r, struct cpumask *result)
+{
+	int x, y, cpu;
+
+	cpumask_clear(result);
+
+	cpu = r->ulhc_y * smp_width + r->ulhc_x;
+	for (y = 0; y < r->height; ++y, cpu += smp_width - r->width) {
+		for (x = 0; x < r->width; ++x, ++cpu)
+			cpu_online_set(cpu, result);
+	}
+}
+
+/* Last reference to a hardwall is gone, so clear the network. */
+static void hardwall_destroy(struct hardwall_info *rect)
+{
+	struct task_struct *task;
+	unsigned long flags;
+	struct cpumask mask;
+
+	/* Make sure this file actually represents a rectangle. */
+	if (rect == NULL)
+		return;
+
+	/*
+	 * Deactivate any remaining tasks.  It's possible to race with
+	 * some other thread that is exiting and hasn't yet called
+	 * deactivate (when freeing its thread_info), so we carefully
+	 * deactivate any remaining tasks before freeing the
+	 * hardwall_info object itself.
+	 */
+	spin_lock_irqsave(&hardwall_lock, flags);
+	list_for_each_entry(task, &rect->task_head, thread.hardwall_list)
+		_hardwall_deactivate(task);
+	spin_unlock_irqrestore(&hardwall_lock, flags);
+
+	/* Drain the UDN. */
+	printk(KERN_DEBUG "Clearing hardwall rectangle %dx%d %d,%d\n",
+	       rect->width, rect->height, rect->ulhc_x, rect->ulhc_y);
+	fill_mask(rect, &mask);
+	on_each_cpu_mask(&mask, stop_udn_switch, NULL, 1);
+	on_each_cpu_mask(&mask, drain_udn_switch, NULL, 1);
+
+	/* Restart switch and disable firewall. */
+	on_each_cpu_mask(&mask, restart_udn_switch, NULL, 1);
+
+	/* Now free the rectangle from the list. */
+	spin_lock_irqsave(&hardwall_lock, flags);
+	BUG_ON(!list_empty(&rect->task_head));
+	list_del(&rect->list);
+	spin_unlock_irqrestore(&hardwall_lock, flags);
+	kfree(rect);
+}
+
+
+/*
+ * Dump hardwall state via /proc; initialized in arch/tile/sys/proc.c.
+ */
+int proc_tile_hardwall_show(struct seq_file *sf, void *v)
+{
+	struct hardwall_info *r;
+
+	if (udn_disabled) {
+		seq_printf(sf, "%dx%d 0,0 pids:\n", smp_width, smp_height);
+		return 0;
+	}
+
+	spin_lock_irq(&hardwall_lock);
+	list_for_each_entry(r, &rectangles, list) {
+		struct task_struct *p;
+		seq_printf(sf, "%dx%d %d,%d pids:",
+			   r->width, r->height, r->ulhc_x, r->ulhc_y);
+		list_for_each_entry(p, &r->task_head, thread.hardwall_list) {
+			unsigned int cpu = cpumask_first(&p->cpus_allowed);
+			unsigned int x = cpu % smp_width;
+			unsigned int y = cpu / smp_width;
+			seq_printf(sf, " %d@%d,%d", p->pid, x, y);
+		}
+		seq_printf(sf, "\n");
+	}
+	spin_unlock_irq(&hardwall_lock);
+	return 0;
+}
+
+
+/*
+ * Character device support via ioctl/close.
+ */
+
+static long hardwall_ioctl(struct file *file, unsigned int a, unsigned long b)
+{
+	struct hardwall_info *rect = file->private_data;
+
+	if (_IOC_TYPE(a) != HARDWALL_IOCTL_BASE)
+		return -EINVAL;
+
+	switch (_IOC_NR(a)) {
+	case _HARDWALL_CREATE:
+		if (udn_disabled)
+			return -ENOSYS;
+		if (rect != NULL)
+			return -EALREADY;
+		rect = hardwall_create(_IOC_SIZE(a),
+					(const unsigned char __user *)b);
+		if (IS_ERR(rect))
+			return PTR_ERR(rect);
+		file->private_data = rect;
+		return 0;
+
+	case _HARDWALL_ACTIVATE:
+		return hardwall_activate(rect);
+
+	case _HARDWALL_DEACTIVATE:
+		if (current->thread.hardwall != rect)
+			return -EINVAL;
+		return hardwall_deactivate(current);
+
+	default:
+		return -EINVAL;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static long hardwall_compat_ioctl(struct file *file,
+				  unsigned int a, unsigned long b)
+{
+	/* Sign-extend the argument so it can be used as a pointer. */
+	return hardwall_ioctl(file, a, (unsigned long)compat_ptr(b));
+}
+#endif
+
+/* The user process closed the file; revoke access to user networks. */
+static int hardwall_flush(struct file *file, fl_owner_t owner)
+{
+	struct hardwall_info *rect = file->private_data;
+	struct task_struct *task, *tmp;
+	unsigned long flags;
+
+	if (rect) {
+		/*
+		 * NOTE: if multiple threads are activated on this hardwall
+		 * file, the other threads will continue having access to the
+		 * UDN until they are context-switched out and back in again.
+		 *
+		 * NOTE: A NULL files pointer means the task is being torn
+		 * down, so in that case we also deactivate it.
+		 */
+		spin_lock_irqsave(&hardwall_lock, flags);
+		list_for_each_entry_safe(task, tmp, &rect->task_head,
+					 thread.hardwall_list) {
+			if (task->files == owner || task->files == NULL)
+				_hardwall_deactivate(task);
+		}
+		spin_unlock_irqrestore(&hardwall_lock, flags);
+	}
+
+	return 0;
+}
+
+/* This hardwall is gone, so destroy it. */
+static int hardwall_release(struct inode *inode, struct file *file)
+{
+	hardwall_destroy(file->private_data);
+	return 0;
+}
+
+static const struct file_operations dev_hardwall_fops = {
+	.unlocked_ioctl = hardwall_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = hardwall_compat_ioctl,
+#endif
+	.flush          = hardwall_flush,
+	.release        = hardwall_release,
+};
+
+static struct cdev hardwall_dev;
+
+static int __init dev_hardwall_init(void)
+{
+	int rc;
+	dev_t dev;
+
+	rc = alloc_chrdev_region(&dev, 0, 1, "hardwall");
+	if (rc < 0)
+		return rc;
+	cdev_init(&hardwall_dev, &dev_hardwall_fops);
+	rc = cdev_add(&hardwall_dev, dev, 1);
+	if (rc < 0)
+		return rc;
+
+	return 0;
+}
+late_initcall(dev_hardwall_init);
diff --git a/arch/tile/kernel/intvec_32.S b/arch/tile/kernel/intvec_32.S
index 207271f0cce..3404c75f8e6 100644
--- a/arch/tile/kernel/intvec_32.S
+++ b/arch/tile/kernel/intvec_32.S
@@ -17,9 +17,9 @@
 #include <linux/linkage.h>
 #include <linux/errno.h>
 #include <linux/init.h>
+#include <linux/unistd.h>
 #include <asm/ptrace.h>
 #include <asm/thread_info.h>
-#include <asm/unistd.h>
 #include <asm/irqflags.h>
 #include <asm/atomic.h>
 #include <asm/asm-offsets.h>
@@ -32,7 +32,7 @@
 # error "No support for kernel preemption currently"
 #endif
 
-#if INT_INTCTRL_1 < 32 || INT_INTCTL_1 >= 48
+#if INT_INTCTRL_1 < 32 || INT_INTCTRL_1 >= 48
 # error INT_INTCTRL_1 coded to set high interrupt mask
 #endif
 
@@ -1941,7 +1941,9 @@ int_unalign:
 #define op_handle_perf_interrupt bad_intr
 #define op_handle_aux_perf_interrupt bad_intr
 
+#ifndef CONFIG_HARDWALL
 #define do_hardwall_trap bad_intr
+#endif
 
 	int_hand     INT_ITLB_MISS, ITLB_MISS, \
 		     do_page_fault, handle_interrupt_no_single_step