/*

   * trace event based perf event profiling/tracing

   *
   * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>

   * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com>

   */

  #include <linux/module.h>

  #include <linux/kprobes.h>

  #include "trace.h"

  static char __percpu *perf_trace_buf[PERF_NR_CONTEXTS];

  /*
   * Force it to be aligned to unsigned long to avoid misaligned accesses
   * suprises
   */
  typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)])
  	perf_trace_t;

  /* Count the events in use (per event id, not per instance) */

  static int	total_ref_count;

  static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
  				 struct perf_event *p_event)
  {
  	/* No tracing, just counting, so no obvious leak */
  	if (!(p_event->attr.sample_type & PERF_SAMPLE_RAW))
  		return 0;
  
  	/* Some events are ok to be traced by non-root users... */
  	if (p_event->attach_state == PERF_ATTACH_TASK) {
  		if (tp_event->flags & TRACE_EVENT_FL_CAP_ANY)
  			return 0;
  	}
  
  	/*
  	 * ...otherwise raw tracepoint data can be a severe data leak,
  	 * only allow root to have these.
  	 */
  	if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	return 0;
  }

  static int perf_trace_event_init(struct ftrace_event_call *tp_event,
  				 struct perf_event *p_event)

  {

  	struct hlist_head __percpu *list;

  	int ret;

  	int cpu;

  	ret = perf_trace_event_perm(tp_event, p_event);
  	if (ret)
  		return ret;

  	p_event->tp_event = tp_event;
  	if (tp_event->perf_refcount++ > 0)

  		return 0;

  	ret = -ENOMEM;

  	list = alloc_percpu(struct hlist_head);
  	if (!list)
  		goto fail;
  
  	for_each_possible_cpu(cpu)
  		INIT_HLIST_HEAD(per_cpu_ptr(list, cpu));

  	tp_event->perf_events = list;

  	if (!total_ref_count) {

  		char __percpu *buf;

  		int i;

  		for (i = 0; i < PERF_NR_CONTEXTS; i++) {

  			buf = (char __percpu *)alloc_percpu(perf_trace_t);

  			if (!buf)

  				goto fail;

  			perf_trace_buf[i] = buf;

  		}

  	}

  	ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER);

  	if (ret)
  		goto fail;

  	total_ref_count++;
  	return 0;
  
  fail:

  	if (!total_ref_count) {

  		int i;

  		for (i = 0; i < PERF_NR_CONTEXTS; i++) {

  			free_percpu(perf_trace_buf[i]);
  			perf_trace_buf[i] = NULL;
  		}

  	}

  
  	if (!--tp_event->perf_refcount) {
  		free_percpu(tp_event->perf_events);
  		tp_event->perf_events = NULL;

  	}

  
  	return ret;

  }

  int perf_trace_init(struct perf_event *p_event)

  {

  	struct ftrace_event_call *tp_event;
  	int event_id = p_event->attr.config;

  	int ret = -EINVAL;

  	mutex_lock(&event_mutex);

  	list_for_each_entry(tp_event, &ftrace_events, list) {

  		if (tp_event->event.type == event_id &&

  		    tp_event->class && tp_event->class->reg &&

  		    try_module_get(tp_event->mod)) {
  			ret = perf_trace_event_init(tp_event, p_event);

  			if (ret)
  				module_put(tp_event->mod);

  			break;
  		}

  	}

  	mutex_unlock(&event_mutex);

  	return ret;

  }

  int perf_trace_add(struct perf_event *p_event, int flags)

  {

  	struct ftrace_event_call *tp_event = p_event->tp_event;

  	struct hlist_head __percpu *pcpu_list;

  	struct hlist_head *list;

  	pcpu_list = tp_event->perf_events;
  	if (WARN_ON_ONCE(!pcpu_list))

  		return -EINVAL;

  	if (!(flags & PERF_EF_START))
  		p_event->hw.state = PERF_HES_STOPPED;

  	list = this_cpu_ptr(pcpu_list);

  	hlist_add_head_rcu(&p_event->hlist_entry, list);

  	return 0;
  }

  void perf_trace_del(struct perf_event *p_event, int flags)

  {
  	hlist_del_rcu(&p_event->hlist_entry);

  }

  void perf_trace_destroy(struct perf_event *p_event)

  {

  	struct ftrace_event_call *tp_event = p_event->tp_event;
  	int i;

  	mutex_lock(&event_mutex);

  	if (--tp_event->perf_refcount > 0)

  		goto out;

  	tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER);

  	/*

  	 * Ensure our callback won't be called anymore. The buffers
  	 * will be freed after that.

  	 */

  	tracepoint_synchronize_unregister();

  	free_percpu(tp_event->perf_events);
  	tp_event->perf_events = NULL;
  
  	if (!--total_ref_count) {

  		for (i = 0; i < PERF_NR_CONTEXTS; i++) {

  			free_percpu(perf_trace_buf[i]);
  			perf_trace_buf[i] = NULL;

  		}

  	}

  out:

  	module_put(tp_event->mod);

  	mutex_unlock(&event_mutex);

  }

  __kprobes void *perf_trace_buf_prepare(int size, unsigned short type,

  				       struct pt_regs *regs, int *rctxp)

  {
  	struct trace_entry *entry;

  	unsigned long flags;

  	char *raw_data;

  	int pc;

  	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));

  	pc = preempt_count();

  	*rctxp = perf_swevent_get_recursion_context();
  	if (*rctxp < 0)

  		return NULL;

  	raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]);

  
  	/* zero the dead bytes from align to not leak stack to user */

  	memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64));

  
  	entry = (struct trace_entry *)raw_data;

  	local_save_flags(flags);
  	tracing_generic_entry_update(entry, flags, pc);

  	entry->type = type;
  
  	return raw_data;

  }

  EXPORT_SYMBOL_GPL(perf_trace_buf_prepare);