1 files changed, 794 insertions, 0 deletions

diff --git a/arch/tile/kernel/hardwall.c b/arch/tile/kernel/hardwall.c
new file mode 100644
index 000000000000..7bf0627b733d
--- /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);