1 files changed, 453 insertions, 0 deletions
diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
new file mode 100644
index 0000000..dbcbf6a
--- /dev/null
+++ b/kernel/hw_breakpoint.c
@@ -0,0 +1,453 @@
+/*
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) 2007 Alan Stern
+ * Copyright (C) IBM Corporation, 2009
+ * Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Thanks to Ingo Molnar for his many suggestions.
+ *
+ * Authors: Alan Stern <stern@rowland.harvard.edu>
+ *          K.Prasad <prasad@linux.vnet.ibm.com>
+ *          Frederic Weisbecker <fweisbec@gmail.com>
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ * This file contains the arch-independent routines.
+ */
+
+#include <linux/irqflags.h>
+#include <linux/kallsyms.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+
+#include <linux/hw_breakpoint.h>
+
+/*
+ * Constraints data
+ */
+
+/* Number of pinned cpu breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned);
+
+/* Number of pinned task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_task_bp_pinned[HBP_NUM]);
+
+/* Number of non-pinned cpu/task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_bp_flexible);
+
+/* Gather the number of total pinned and un-pinned bp in a cpuset */
+struct bp_busy_slots {
+	unsigned int pinned;
+	unsigned int flexible;
+};
+
+/* Serialize accesses to the above constraints */
+static DEFINE_MUTEX(nr_bp_mutex);
+
+/*
+ * Report the maximum number of pinned breakpoints a task
+ * have in this cpu
+ */
+static unsigned int max_task_bp_pinned(int cpu)
+{
+	int i;
+	unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned, cpu);
+
+	for (i = HBP_NUM -1; i >= 0; i--) {
+		if (tsk_pinned[i] > 0)
+			return i + 1;
+	}
+
+	return 0;
+}
+
+static int task_bp_pinned(struct task_struct *tsk)
+{
+	struct perf_event_context *ctx = tsk->perf_event_ctxp;
+	struct list_head *list;
+	struct perf_event *bp;
+	unsigned long flags;
+	int count = 0;
+
+	if (WARN_ONCE(!ctx, "No perf context for this task"))
+		return 0;
+
+	list = &ctx->event_list;
+
+	raw_spin_lock_irqsave(&ctx->lock, flags);
+
+	/*
+	 * The current breakpoint counter is not included in the list
+	 * at the open() callback time
+	 */
+	list_for_each_entry(bp, list, event_entry) {
+		if (bp->attr.type == PERF_TYPE_BREAKPOINT)
+			count++;
+	}
+
+	raw_spin_unlock_irqrestore(&ctx->lock, flags);
+
+	return count;
+}
+
+/*
+ * Report the number of pinned/un-pinned breakpoints we have in
+ * a given cpu (cpu > -1) or in all of them (cpu = -1).
+ */
+static void
+fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp)
+{
+	int cpu = bp->cpu;
+	struct task_struct *tsk = bp->ctx->task;
+
+	if (cpu >= 0) {
+		slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
+		if (!tsk)
+			slots->pinned += max_task_bp_pinned(cpu);
+		else
+			slots->pinned += task_bp_pinned(tsk);
+		slots->flexible = per_cpu(nr_bp_flexible, cpu);
+
+		return;
+	}
+
+	for_each_online_cpu(cpu) {
+		unsigned int nr;
+
+		nr = per_cpu(nr_cpu_bp_pinned, cpu);
+		if (!tsk)
+			nr += max_task_bp_pinned(cpu);
+		else
+			nr += task_bp_pinned(tsk);
+
+		if (nr > slots->pinned)
+			slots->pinned = nr;
+
+		nr = per_cpu(nr_bp_flexible, cpu);
+
+		if (nr > slots->flexible)
+			slots->flexible = nr;
+	}
+}
+
+/*
+ * Add a pinned breakpoint for the given task in our constraint table
+ */
+static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
+{
+	unsigned int *tsk_pinned;
+	int count = 0;
+
+	count = task_bp_pinned(tsk);
+
+	tsk_pinned = per_cpu(nr_task_bp_pinned, cpu);
+	if (enable) {
+		tsk_pinned[count]++;
+		if (count > 0)
+			tsk_pinned[count-1]--;
+	} else {
+		tsk_pinned[count]--;
+		if (count > 0)
+			tsk_pinned[count-1]++;
+	}
+}
+
+/*
+ * Add/remove the given breakpoint in our constraint table
+ */
+static void toggle_bp_slot(struct perf_event *bp, bool enable)
+{
+	int cpu = bp->cpu;
+	struct task_struct *tsk = bp->ctx->task;
+
+	/* Pinned counter task profiling */
+	if (tsk) {
+		if (cpu >= 0) {
+			toggle_bp_task_slot(tsk, cpu, enable);
+			return;
+		}
+
+		for_each_online_cpu(cpu)
+			toggle_bp_task_slot(tsk, cpu, enable);
+		return;
+	}
+
+	/* Pinned counter cpu profiling */
+	if (enable)
+		per_cpu(nr_cpu_bp_pinned, bp->cpu)++;
+	else
+		per_cpu(nr_cpu_bp_pinned, bp->cpu)--;
+}
+
+/*
+ * Contraints to check before allowing this new breakpoint counter:
+ *
+ *  == Non-pinned counter == (Considered as pinned for now)
+ *
+ *   - If attached to a single cpu, check:
+ *
+ *       (per_cpu(nr_bp_flexible, cpu) || (per_cpu(nr_cpu_bp_pinned, cpu)
+ *           + max(per_cpu(nr_task_bp_pinned, cpu)))) < HBP_NUM
+ *
+ *       -> If there are already non-pinned counters in this cpu, it means
+ *          there is already a free slot for them.
+ *          Otherwise, we check that the maximum number of per task
+ *          breakpoints (for this cpu) plus the number of per cpu breakpoint
+ *          (for this cpu) doesn't cover every registers.
+ *
+ *   - If attached to every cpus, check:
+ *
+ *       (per_cpu(nr_bp_flexible, *) || (max(per_cpu(nr_cpu_bp_pinned, *))
+ *           + max(per_cpu(nr_task_bp_pinned, *)))) < HBP_NUM
+ *
+ *       -> This is roughly the same, except we check the number of per cpu
+ *          bp for every cpu and we keep the max one. Same for the per tasks
+ *          breakpoints.
+ *
+ *
+ * == Pinned counter ==
+ *
+ *   - If attached to a single cpu, check:
+ *
+ *       ((per_cpu(nr_bp_flexible, cpu) > 1) + per_cpu(nr_cpu_bp_pinned, cpu)
+ *            + max(per_cpu(nr_task_bp_pinned, cpu))) < HBP_NUM
+ *
+ *       -> Same checks as before. But now the nr_bp_flexible, if any, must keep
+ *          one register at least (or they will never be fed).
+ *
+ *   - If attached to every cpus, check:
+ *
+ *       ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
+ *            + max(per_cpu(nr_task_bp_pinned, *))) < HBP_NUM
+ */
+int reserve_bp_slot(struct perf_event *bp)
+{
+	struct bp_busy_slots slots = {0};
+	int ret = 0;
+
+	mutex_lock(&nr_bp_mutex);
+
+	fetch_bp_busy_slots(&slots, bp);
+
+	/* Flexible counters need to keep at least one slot */
+	if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
+		ret = -ENOSPC;
+		goto end;
+	}
+
+	toggle_bp_slot(bp, true);
+
+end:
+	mutex_unlock(&nr_bp_mutex);
+
+	return ret;
+}
+
+void release_bp_slot(struct perf_event *bp)
+{
+	mutex_lock(&nr_bp_mutex);
+
+	toggle_bp_slot(bp, false);
+
+	mutex_unlock(&nr_bp_mutex);
+}
+
+
+int register_perf_hw_breakpoint(struct perf_event *bp)
+{
+	int ret;
+
+	ret = reserve_bp_slot(bp);
+	if (ret)
+		return ret;
+
+	/*
+	 * Ptrace breakpoints can be temporary perf events only
+	 * meant to reserve a slot. In this case, it is created disabled and
+	 * we don't want to check the params right now (as we put a null addr)
+	 * But perf tools create events as disabled and we want to check
+	 * the params for them.
+	 * This is a quick hack that will be removed soon, once we remove
+	 * the tmp breakpoints from ptrace
+	 */
+	if (!bp->attr.disabled || !bp->overflow_handler)
+		ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
+
+	return ret;
+}
+
+/**
+ * register_user_hw_breakpoint - register a hardware breakpoint for user space
+ * @attr: breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ */
+struct perf_event *
+register_user_hw_breakpoint(struct perf_event_attr *attr,
+			    perf_overflow_handler_t triggered,
+			    struct task_struct *tsk)
+{
+	return perf_event_create_kernel_counter(attr, -1, tsk->pid, triggered);
+}
+EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
+
+/**
+ * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
+ * @bp: the breakpoint structure to modify
+ * @attr: new breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ */
+int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
+{
+	u64 old_addr = bp->attr.bp_addr;
+	int old_type = bp->attr.bp_type;
+	int old_len = bp->attr.bp_len;
+	int err = 0;
+
+	perf_event_disable(bp);
+
+	bp->attr.bp_addr = attr->bp_addr;
+	bp->attr.bp_type = attr->bp_type;
+	bp->attr.bp_len = attr->bp_len;
+
+	if (attr->disabled)
+		goto end;
+
+	err = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
+	if (!err)
+		perf_event_enable(bp);
+
+	if (err) {
+		bp->attr.bp_addr = old_addr;
+		bp->attr.bp_type = old_type;
+		bp->attr.bp_len = old_len;
+		if (!bp->attr.disabled)
+			perf_event_enable(bp);
+
+		return err;
+	}
+
+end:
+	bp->attr.disabled = attr->disabled;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
+
+/**
+ * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
+ * @bp: the breakpoint structure to unregister
+ */
+void unregister_hw_breakpoint(struct perf_event *bp)
+{
+	if (!bp)
+		return;
+	perf_event_release_kernel(bp);
+}
+EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
+
+/**
+ * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
+ * @attr: breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ *
+ * @return a set of per_cpu pointers to perf events
+ */
+struct perf_event **
+register_wide_hw_breakpoint(struct perf_event_attr *attr,
+			    perf_overflow_handler_t triggered)
+{
+	struct perf_event **cpu_events, **pevent, *bp;
+	long err;
+	int cpu;
+
+	cpu_events = alloc_percpu(typeof(*cpu_events));
+	if (!cpu_events)
+		return ERR_PTR(-ENOMEM);
+
+	for_each_possible_cpu(cpu) {
+		pevent = per_cpu_ptr(cpu_events, cpu);
+		bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
+
+		*pevent = bp;
+
+		if (IS_ERR(bp)) {
+			err = PTR_ERR(bp);
+			goto fail;
+		}
+	}
+
+	return cpu_events;
+
+fail:
+	for_each_possible_cpu(cpu) {
+		pevent = per_cpu_ptr(cpu_events, cpu);
+		if (IS_ERR(*pevent))
+			break;
+		unregister_hw_breakpoint(*pevent);
+	}
+	free_percpu(cpu_events);
+	/* return the error if any */
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
+
+/**
+ * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
+ * @cpu_events: the per cpu set of events to unregister
+ */
+void unregister_wide_hw_breakpoint(struct perf_event **cpu_events)
+{
+	int cpu;
+	struct perf_event **pevent;
+
+	for_each_possible_cpu(cpu) {
+		pevent = per_cpu_ptr(cpu_events, cpu);
+		unregister_hw_breakpoint(*pevent);
+	}
+	free_percpu(cpu_events);
+}
+EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
+
+static struct notifier_block hw_breakpoint_exceptions_nb = {
+	.notifier_call = hw_breakpoint_exceptions_notify,
+	/* we need to be notified first */
+	.priority = 0x7fffffff
+};
+
+static int __init init_hw_breakpoint(void)
+{
+	return register_die_notifier(&hw_breakpoint_exceptions_nb);
+}
+core_initcall(init_hw_breakpoint);
+
+
+struct pmu perf_ops_bp = {
+	.enable		= arch_install_hw_breakpoint,
+	.disable	= arch_uninstall_hw_breakpoint,
+	.read		= hw_breakpoint_pmu_read,
+	.unthrottle	= hw_breakpoint_pmu_unthrottle
+};