/*

   * trace event based perf event profiling/tracing

   *

   * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra

   * 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 trace_event_call *tp_event,

  				 struct perf_event *p_event)
  {

  	if (tp_event->perf_perm) {
  		int ret = tp_event->perf_perm(tp_event, p_event);
  		if (ret)
  			return ret;
  	}

  	/*
  	 * We checked and allowed to create parent,
  	 * allow children without checking.
  	 */
  	if (p_event->parent)
  		return 0;
  
  	/*
  	 * It's ok to check current process (owner) permissions in here,
  	 * because code below is called only via perf_event_open syscall.
  	 */

  	/* The ftrace function trace is allowed only for root. */

  	if (ftrace_event_is_function(tp_event)) {
  		if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
  			return -EPERM;

  		if (!is_sampling_event(p_event))
  			return 0;

  		/*
  		 * We don't allow user space callchains for  function trace
  		 * event, due to issues with page faults while tracing page
  		 * fault handler and its overall trickiness nature.
  		 */
  		if (!p_event->attr.exclude_callchain_user)
  			return -EINVAL;

  
  		/*
  		 * Same reason to disable user stack dump as for user space
  		 * callchains above.
  		 */
  		if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
  			return -EINVAL;

  	}

  	/* 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_reg(struct trace_event_call *tp_event,

  				struct perf_event *p_event)

  {

  	struct hlist_head __percpu *list;

  	int ret = -ENOMEM;

  	int cpu;

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

  		return 0;

  	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, NULL);

  	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;

  }

  static void perf_trace_event_unreg(struct perf_event *p_event)
  {

  	struct trace_event_call *tp_event = p_event->tp_event;

  	int i;
  
  	if (--tp_event->perf_refcount > 0)
  		goto out;
  
  	tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL);
  
  	/*
  	 * 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);
  }
  
  static int perf_trace_event_open(struct perf_event *p_event)
  {

  	struct trace_event_call *tp_event = p_event->tp_event;

  	return tp_event->class->reg(tp_event, TRACE_REG_PERF_OPEN, p_event);
  }
  
  static void perf_trace_event_close(struct perf_event *p_event)
  {

  	struct trace_event_call *tp_event = p_event->tp_event;

  	tp_event->class->reg(tp_event, TRACE_REG_PERF_CLOSE, p_event);
  }

  static int perf_trace_event_init(struct trace_event_call *tp_event,

  				 struct perf_event *p_event)
  {
  	int ret;
  
  	ret = perf_trace_event_perm(tp_event, p_event);
  	if (ret)
  		return ret;
  
  	ret = perf_trace_event_reg(tp_event, p_event);
  	if (ret)
  		return ret;
  
  	ret = perf_trace_event_open(p_event);
  	if (ret) {
  		perf_trace_event_unreg(p_event);
  		return ret;
  	}
  
  	return 0;
  }

  int perf_trace_init(struct perf_event *p_event)

  {

  	struct trace_event_call *tp_event;

  	u64 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;

  }

  void perf_trace_destroy(struct perf_event *p_event)
  {
  	mutex_lock(&event_mutex);
  	perf_trace_event_close(p_event);
  	perf_trace_event_unreg(p_event);
  	mutex_unlock(&event_mutex);
  }

  int perf_trace_add(struct perf_event *p_event, int flags)

  {

  	struct trace_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 tp_event->class->reg(tp_event, TRACE_REG_PERF_ADD, p_event);

  }

  void perf_trace_del(struct perf_event *p_event, int flags)

  {

  	struct trace_event_call *tp_event = p_event->tp_event;

  	hlist_del_rcu(&p_event->hlist_entry);

  	tp_event->class->reg(tp_event, TRACE_REG_PERF_DEL, p_event);

  }

  void *perf_trace_buf_alloc(int size, struct pt_regs **regs, int *rctxp)

  {

  	char *raw_data;

  	int rctx;

  	BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long));

  	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,

  		      "perf buffer not large enough"))

  		return NULL;

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

  		return NULL;

  	if (regs)

  		*regs = this_cpu_ptr(&__perf_regs[rctx]);
  	raw_data = this_cpu_ptr(perf_trace_buf[rctx]);

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

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

  	return raw_data;
  }
  EXPORT_SYMBOL_GPL(perf_trace_buf_alloc);
  NOKPROBE_SYMBOL(perf_trace_buf_alloc);
  
  void perf_trace_buf_update(void *record, u16 type)
  {
  	struct trace_entry *entry = record;
  	int pc = preempt_count();
  	unsigned long flags;

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

  	entry->type = type;

  }

  NOKPROBE_SYMBOL(perf_trace_buf_update);

  
  #ifdef CONFIG_FUNCTION_TRACER
  static void

  perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,

  			  struct ftrace_ops *ops, struct pt_regs *pt_regs)

  {

  	struct perf_event *event;

  	struct ftrace_entry *entry;
  	struct hlist_head *head;
  	struct pt_regs regs;
  	int rctx;

  	head = this_cpu_ptr(event_function.perf_events);
  	if (hlist_empty(head))
  		return;

  #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
  		    sizeof(u64)) - sizeof(u32))
  
  	BUILD_BUG_ON(ENTRY_SIZE > PERF_MAX_TRACE_SIZE);

  	memset(&regs, 0, sizeof(regs));

  	perf_fetch_caller_regs(&regs);

  	entry = perf_trace_buf_alloc(ENTRY_SIZE, NULL, &rctx);

  	if (!entry)
  		return;
  
  	entry->ip = ip;
  	entry->parent_ip = parent_ip;

  	event = container_of(ops, struct perf_event, ftrace_ops);

  	perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, TRACE_FN,

  			      1, &regs, head, NULL, event);

  
  #undef ENTRY_SIZE
  }
  
  static int perf_ftrace_function_register(struct perf_event *event)
  {
  	struct ftrace_ops *ops = &event->ftrace_ops;

  	ops->flags |= FTRACE_OPS_FL_PER_CPU | FTRACE_OPS_FL_RCU;

  	ops->func = perf_ftrace_function_call;
  	return register_ftrace_function(ops);
  }
  
  static int perf_ftrace_function_unregister(struct perf_event *event)
  {
  	struct ftrace_ops *ops = &event->ftrace_ops;

  	int ret = unregister_ftrace_function(ops);
  	ftrace_free_filter(ops);
  	return ret;

  }
  
  static void perf_ftrace_function_enable(struct perf_event *event)
  {
  	ftrace_function_local_enable(&event->ftrace_ops);
  }
  
  static void perf_ftrace_function_disable(struct perf_event *event)
  {
  	ftrace_function_local_disable(&event->ftrace_ops);
  }

  int perf_ftrace_event_register(struct trace_event_call *call,

  			       enum trace_reg type, void *data)
  {
  	switch (type) {
  	case TRACE_REG_REGISTER:
  	case TRACE_REG_UNREGISTER:
  		break;
  	case TRACE_REG_PERF_REGISTER:
  	case TRACE_REG_PERF_UNREGISTER:
  		return 0;
  	case TRACE_REG_PERF_OPEN:
  		return perf_ftrace_function_register(data);
  	case TRACE_REG_PERF_CLOSE:
  		return perf_ftrace_function_unregister(data);
  	case TRACE_REG_PERF_ADD:
  		perf_ftrace_function_enable(data);
  		return 0;
  	case TRACE_REG_PERF_DEL:
  		perf_ftrace_function_disable(data);
  		return 0;
  	}
  
  	return -EINVAL;
  }
  #endif /* CONFIG_FUNCTION_TRACER */