/*
   * 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/slab.h>

  #include <linux/list.h>

  #include <linux/cpu.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[TYPE_MAX]);

  
  /* Number of pinned task breakpoints in a cpu */

  static DEFINE_PER_CPU(unsigned int *, nr_task_bp_pinned[TYPE_MAX]);

  
  /* Number of non-pinned cpu/task breakpoints in a cpu */

  static DEFINE_PER_CPU(unsigned int, nr_bp_flexible[TYPE_MAX]);

  static int nr_slots[TYPE_MAX];

  /* Keep track of the breakpoints attached to tasks */
  static LIST_HEAD(bp_task_head);

  static int constraints_initialized;

  /* 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);

  __weak int hw_breakpoint_weight(struct perf_event *bp)
  {
  	return 1;
  }

  static inline enum bp_type_idx find_slot_idx(struct perf_event *bp)
  {
  	if (bp->attr.bp_type & HW_BREAKPOINT_RW)
  		return TYPE_DATA;
  
  	return TYPE_INST;
  }

  /*
   * Report the maximum number of pinned breakpoints a task
   * have in this cpu
   */

  static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)

  {

  	int i;

  	unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);

  	for (i = nr_slots[type] - 1; i >= 0; i--) {

  		if (tsk_pinned[i] > 0)
  			return i + 1;

  	}

  	return 0;

  }

  /*
   * Count the number of breakpoints of the same type and same task.
   * The given event must be not on the list.
   */
  static int task_bp_pinned(struct perf_event *bp, enum bp_type_idx type)

  {

  	struct task_struct *tsk = bp->hw.bp_target;

  	struct perf_event *iter;

  	int count = 0;

  	list_for_each_entry(iter, &bp_task_head, hw.bp_list) {

  		if (iter->hw.bp_target == tsk && find_slot_idx(iter) == type)

  			count += hw_breakpoint_weight(iter);

  	}

  	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,
  		    enum bp_type_idx type)

  {

  	int cpu = bp->cpu;

  	struct task_struct *tsk = bp->hw.bp_target;

  	if (cpu >= 0) {

  		slots->pinned = per_cpu(nr_cpu_bp_pinned[type], cpu);

  		if (!tsk)

  			slots->pinned += max_task_bp_pinned(cpu, type);

  		else

  			slots->pinned += task_bp_pinned(bp, type);

  		slots->flexible = per_cpu(nr_bp_flexible[type], cpu);

  
  		return;
  	}
  
  	for_each_online_cpu(cpu) {
  		unsigned int nr;

  		nr = per_cpu(nr_cpu_bp_pinned[type], cpu);

  		if (!tsk)

  			nr += max_task_bp_pinned(cpu, type);

  		else

  			nr += task_bp_pinned(bp, type);

  
  		if (nr > slots->pinned)
  			slots->pinned = nr;

  		nr = per_cpu(nr_bp_flexible[type], cpu);

  
  		if (nr > slots->flexible)
  			slots->flexible = nr;
  	}
  }
  
  /*

   * For now, continue to consider flexible as pinned, until we can
   * ensure no flexible event can ever be scheduled before a pinned event
   * in a same cpu.
   */
  static void
  fetch_this_slot(struct bp_busy_slots *slots, int weight)
  {
  	slots->pinned += weight;
  }
  
  /*

   * Add a pinned breakpoint for the given task in our constraint table
   */

  static void toggle_bp_task_slot(struct perf_event *bp, int cpu, bool enable,

  				enum bp_type_idx type, int weight)

  {

  	unsigned int *tsk_pinned;

  	int old_count = 0;
  	int old_idx = 0;
  	int idx = 0;

  	old_count = task_bp_pinned(bp, type);

  	old_idx = old_count - 1;
  	idx = old_idx + weight;

  	/* tsk_pinned[n] is the number of tasks having n breakpoints */

  	tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);

  	if (enable) {

  		tsk_pinned[idx]++;
  		if (old_count > 0)
  			tsk_pinned[old_idx]--;

  	} else {

  		tsk_pinned[idx]--;
  		if (old_count > 0)
  			tsk_pinned[old_idx]++;

  	}
  }
  
  /*
   * Add/remove the given breakpoint in our constraint table
   */

  static void

  toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
  	       int weight)

  {
  	int cpu = bp->cpu;

  	struct task_struct *tsk = bp->hw.bp_target;

  	/* Pinned counter cpu profiling */
  	if (!tsk) {
  
  		if (enable)
  			per_cpu(nr_cpu_bp_pinned[type], bp->cpu) += weight;
  		else
  			per_cpu(nr_cpu_bp_pinned[type], bp->cpu) -= weight;
  		return;
  	}

  	/* Pinned counter task profiling */

  	if (!enable)
  		list_del(&bp->hw.bp_list);
  
  	if (cpu >= 0) {
  		toggle_bp_task_slot(bp, cpu, enable, type, weight);
  	} else {

  		for_each_online_cpu(cpu)

  			toggle_bp_task_slot(bp, cpu, enable, type, weight);

  	}

  	if (enable)

  		list_add_tail(&bp->hw.bp_list, &bp_task_head);

  }
  
  /*

   * Function to perform processor-specific cleanup during unregistration
   */
  __weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
  {
  	/*
  	 * A weak stub function here for those archs that don't define
  	 * it inside arch/.../kernel/hw_breakpoint.c
  	 */
  }
  
  /*

   * 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

   */

  static int __reserve_bp_slot(struct perf_event *bp)

  {
  	struct bp_busy_slots slots = {0};

  	enum bp_type_idx type;

  	int weight;

  	/* We couldn't initialize breakpoint constraints on boot */
  	if (!constraints_initialized)
  		return -ENOMEM;

  	/* Basic checks */
  	if (bp->attr.bp_type == HW_BREAKPOINT_EMPTY ||
  	    bp->attr.bp_type == HW_BREAKPOINT_INVALID)
  		return -EINVAL;
  
  	type = find_slot_idx(bp);

  	weight = hw_breakpoint_weight(bp);

  	fetch_bp_busy_slots(&slots, bp, type);

  	/*
  	 * Simulate the addition of this breakpoint to the constraints
  	 * and see the result.
  	 */

  	fetch_this_slot(&slots, weight);

  
  	/* Flexible counters need to keep at least one slot */

  	if (slots.pinned + (!!slots.flexible) > nr_slots[type])

  		return -ENOSPC;

  	toggle_bp_slot(bp, true, type, weight);

  	return 0;
  }
  
  int reserve_bp_slot(struct perf_event *bp)
  {
  	int ret;
  
  	mutex_lock(&nr_bp_mutex);
  
  	ret = __reserve_bp_slot(bp);

  	mutex_unlock(&nr_bp_mutex);
  
  	return ret;
  }

  static void __release_bp_slot(struct perf_event *bp)
  {

  	enum bp_type_idx type;

  	int weight;

  
  	type = find_slot_idx(bp);

  	weight = hw_breakpoint_weight(bp);
  	toggle_bp_slot(bp, false, type, weight);

  }

  void release_bp_slot(struct perf_event *bp)

  {

  	mutex_lock(&nr_bp_mutex);

  	arch_unregister_hw_breakpoint(bp);

  	__release_bp_slot(bp);

  
  	mutex_unlock(&nr_bp_mutex);

  }

  /*
   * Allow the kernel debugger to reserve breakpoint slots without
   * taking a lock using the dbg_* variant of for the reserve and
   * release breakpoint slots.
   */
  int dbg_reserve_bp_slot(struct perf_event *bp)
  {
  	if (mutex_is_locked(&nr_bp_mutex))
  		return -1;
  
  	return __reserve_bp_slot(bp);
  }
  
  int dbg_release_bp_slot(struct perf_event *bp)
  {
  	if (mutex_is_locked(&nr_bp_mutex))
  		return -1;
  
  	__release_bp_slot(bp);
  
  	return 0;
  }

  static int validate_hw_breakpoint(struct perf_event *bp)
  {
  	int ret;
  
  	ret = arch_validate_hwbkpt_settings(bp);
  	if (ret)
  		return ret;
  
  	if (arch_check_bp_in_kernelspace(bp)) {
  		if (bp->attr.exclude_kernel)
  			return -EINVAL;
  		/*
  		 * Don't let unprivileged users set a breakpoint in the trap
  		 * path to avoid trap recursion attacks.
  		 */
  		if (!capable(CAP_SYS_ADMIN))
  			return -EPERM;
  	}
  
  	return 0;
  }

  int register_perf_hw_breakpoint(struct perf_event *bp)

  {

  	int ret;

  	ret = reserve_bp_slot(bp);
  	if (ret)
  		return ret;

  	ret = validate_hw_breakpoint(bp);

  	/* if arch_validate_hwbkpt_settings() fails then release bp slot */
  	if (ret)
  		release_bp_slot(bp);

  	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,

  			    void *context,

  			    struct task_struct *tsk)

  {

  	return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
  						context);

  }
  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;

  	u64 old_len = bp->attr.bp_len;

  	int old_type = bp->attr.bp_type;

  	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 = validate_hw_breakpoint(bp);

  	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 * __percpu *

  register_wide_hw_breakpoint(struct perf_event_attr *attr,

  			    perf_overflow_handler_t triggered,
  			    void *context)

  {

  	struct perf_event * __percpu *cpu_events, **pevent, *bp;

  	long err;
  	int cpu;
  
  	cpu_events = alloc_percpu(typeof(*cpu_events));
  	if (!cpu_events)

  		return (void __percpu __force *)ERR_PTR(-ENOMEM);

  	get_online_cpus();
  	for_each_online_cpu(cpu) {

  		pevent = per_cpu_ptr(cpu_events, cpu);

  		bp = perf_event_create_kernel_counter(attr, cpu, NULL,
  						      triggered, context);

  		*pevent = bp;

  		if (IS_ERR(bp)) {

  			err = PTR_ERR(bp);
  			goto fail;
  		}

  	}

  	put_online_cpus();

  	return cpu_events;
  
  fail:

  	for_each_online_cpu(cpu) {

  		pevent = per_cpu_ptr(cpu_events, cpu);

  		if (IS_ERR(*pevent))

  			break;
  		unregister_hw_breakpoint(*pevent);
  	}

  	put_online_cpus();

  	free_percpu(cpu_events);

  	return (void __percpu __force *)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 * __percpu *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 void bp_perf_event_destroy(struct perf_event *event)
  {
  	release_bp_slot(event);
  }
  
  static int hw_breakpoint_event_init(struct perf_event *bp)
  {
  	int err;
  
  	if (bp->attr.type != PERF_TYPE_BREAKPOINT)
  		return -ENOENT;
  
  	err = register_perf_hw_breakpoint(bp);
  	if (err)
  		return err;
  
  	bp->destroy = bp_perf_event_destroy;
  
  	return 0;
  }

  static int hw_breakpoint_add(struct perf_event *bp, int flags)
  {
  	if (!(flags & PERF_EF_START))
  		bp->hw.state = PERF_HES_STOPPED;
  
  	return arch_install_hw_breakpoint(bp);
  }
  
  static void hw_breakpoint_del(struct perf_event *bp, int flags)
  {
  	arch_uninstall_hw_breakpoint(bp);
  }
  
  static void hw_breakpoint_start(struct perf_event *bp, int flags)
  {
  	bp->hw.state = 0;
  }
  
  static void hw_breakpoint_stop(struct perf_event *bp, int flags)
  {
  	bp->hw.state = PERF_HES_STOPPED;
  }

  static struct pmu perf_breakpoint = {

  	.task_ctx_nr	= perf_sw_context, /* could eventually get its own */

  	.event_init	= hw_breakpoint_event_init,

  	.add		= hw_breakpoint_add,
  	.del		= hw_breakpoint_del,
  	.start		= hw_breakpoint_start,
  	.stop		= hw_breakpoint_stop,

  	.read		= hw_breakpoint_pmu_read,
  };

  int __init init_hw_breakpoint(void)

  {

  	unsigned int **task_bp_pinned;
  	int cpu, err_cpu;
  	int i;
  
  	for (i = 0; i < TYPE_MAX; i++)
  		nr_slots[i] = hw_breakpoint_slots(i);
  
  	for_each_possible_cpu(cpu) {
  		for (i = 0; i < TYPE_MAX; i++) {
  			task_bp_pinned = &per_cpu(nr_task_bp_pinned[i], cpu);
  			*task_bp_pinned = kzalloc(sizeof(int) * nr_slots[i],
  						  GFP_KERNEL);
  			if (!*task_bp_pinned)
  				goto err_alloc;
  		}
  	}
  
  	constraints_initialized = 1;

  	perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);

  	return register_die_notifier(&hw_breakpoint_exceptions_nb);

  
   err_alloc:
  	for_each_possible_cpu(err_cpu) {
  		if (err_cpu == cpu)
  			break;
  		for (i = 0; i < TYPE_MAX; i++)
  			kfree(per_cpu(nr_task_bp_pinned[i], cpu));
  	}
  
  	return -ENOMEM;

  }