/*
   * Performance events ring-buffer code:
   *
   *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
   *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
   *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>

   *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>

   *
   * For licensing details see kernel-base/COPYING
   */
  
  #include <linux/perf_event.h>
  #include <linux/vmalloc.h>
  #include <linux/slab.h>
  
  #include "internal.h"
  
  static bool perf_output_space(struct ring_buffer *rb, unsigned long tail,
  			      unsigned long offset, unsigned long head)
  {

  	unsigned long sz = perf_data_size(rb);
  	unsigned long mask = sz - 1;

  	/*
  	 * check if user-writable
  	 * overwrite : over-write its own tail
  	 * !overwrite: buffer possibly drops events.
  	 */
  	if (rb->overwrite)

  		return true;

  	/*
  	 * verify that payload is not bigger than buffer
  	 * otherwise masking logic may fail to detect
  	 * the "not enough space" condition
  	 */
  	if ((head - offset) > sz)
  		return false;

  
  	offset = (offset - tail) & mask;
  	head   = (head   - tail) & mask;
  
  	if ((int)(head - offset) < 0)
  		return false;
  
  	return true;
  }
  
  static void perf_output_wakeup(struct perf_output_handle *handle)
  {
  	atomic_set(&handle->rb->poll, POLL_IN);

  	handle->event->pending_wakeup = 1;
  	irq_work_queue(&handle->event->pending);

  }
  
  /*
   * We need to ensure a later event_id doesn't publish a head when a former
   * event isn't done writing. However since we need to deal with NMIs we
   * cannot fully serialize things.
   *
   * We only publish the head (and generate a wakeup) when the outer-most
   * event completes.
   */
  static void perf_output_get_handle(struct perf_output_handle *handle)
  {
  	struct ring_buffer *rb = handle->rb;
  
  	preempt_disable();
  	local_inc(&rb->nest);
  	handle->wakeup = local_read(&rb->wakeup);
  }
  
  static void perf_output_put_handle(struct perf_output_handle *handle)
  {
  	struct ring_buffer *rb = handle->rb;
  	unsigned long head;
  
  again:
  	head = local_read(&rb->head);
  
  	/*
  	 * IRQ/NMI can happen here, which means we can miss a head update.
  	 */
  
  	if (!local_dec_and_test(&rb->nest))
  		goto out;
  
  	/*
  	 * Publish the known good head. Rely on the full barrier implied
  	 * by atomic_dec_and_test() order the rb->head read and this
  	 * write.
  	 */
  	rb->user_page->data_head = head;
  
  	/*
  	 * Now check if we missed an update, rely on the (compiler)
  	 * barrier in atomic_dec_and_test() to re-read rb->head.
  	 */
  	if (unlikely(head != local_read(&rb->head))) {
  		local_inc(&rb->nest);
  		goto again;
  	}
  
  	if (handle->wakeup != local_read(&rb->wakeup))
  		perf_output_wakeup(handle);
  
  out:
  	preempt_enable();
  }
  
  int perf_output_begin(struct perf_output_handle *handle,

  		      struct perf_event *event, unsigned int size)

  {
  	struct ring_buffer *rb;
  	unsigned long tail, offset, head;
  	int have_lost;
  	struct perf_sample_data sample_data;
  	struct {
  		struct perf_event_header header;
  		u64			 id;
  		u64			 lost;
  	} lost_event;
  
  	rcu_read_lock();
  	/*
  	 * For inherited events we send all the output towards the parent.
  	 */
  	if (event->parent)
  		event = event->parent;
  
  	rb = rcu_dereference(event->rb);
  	if (!rb)
  		goto out;
  
  	handle->rb	= rb;
  	handle->event	= event;

  
  	if (!rb->nr_pages)
  		goto out;
  
  	have_lost = local_read(&rb->lost);
  	if (have_lost) {
  		lost_event.header.size = sizeof(lost_event);
  		perf_event_header__init_id(&lost_event.header, &sample_data,
  					   event);
  		size += lost_event.header.size;
  	}
  
  	perf_output_get_handle(handle);
  
  	do {
  		/*
  		 * Userspace could choose to issue a mb() before updating the
  		 * tail pointer. So that all reads will be completed before the
  		 * write is issued.
  		 */
  		tail = ACCESS_ONCE(rb->user_page->data_tail);
  		smp_rmb();
  		offset = head = local_read(&rb->head);
  		head += size;
  		if (unlikely(!perf_output_space(rb, tail, offset, head)))
  			goto fail;
  	} while (local_cmpxchg(&rb->head, offset, head) != offset);
  
  	if (head - local_read(&rb->wakeup) > rb->watermark)
  		local_add(rb->watermark, &rb->wakeup);
  
  	handle->page = offset >> (PAGE_SHIFT + page_order(rb));
  	handle->page &= rb->nr_pages - 1;
  	handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
  	handle->addr = rb->data_pages[handle->page];
  	handle->addr += handle->size;
  	handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;
  
  	if (have_lost) {
  		lost_event.header.type = PERF_RECORD_LOST;
  		lost_event.header.misc = 0;
  		lost_event.id          = event->id;
  		lost_event.lost        = local_xchg(&rb->lost, 0);
  
  		perf_output_put(handle, lost_event);
  		perf_event__output_id_sample(event, handle, &sample_data);
  	}
  
  	return 0;
  
  fail:
  	local_inc(&rb->lost);
  	perf_output_put_handle(handle);
  out:
  	rcu_read_unlock();
  
  	return -ENOSPC;
  }

  unsigned int perf_output_copy(struct perf_output_handle *handle,

  		      const void *buf, unsigned int len)
  {

  	return __output_copy(handle, buf, len);

  }

  unsigned int perf_output_skip(struct perf_output_handle *handle,
  			      unsigned int len)
  {
  	return __output_skip(handle, NULL, len);
  }

  void perf_output_end(struct perf_output_handle *handle)
  {

  	perf_output_put_handle(handle);
  	rcu_read_unlock();
  }
  
  static void
  ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
  {
  	long max_size = perf_data_size(rb);
  
  	if (watermark)
  		rb->watermark = min(max_size, watermark);
  
  	if (!rb->watermark)
  		rb->watermark = max_size / 2;
  
  	if (flags & RING_BUFFER_WRITABLE)

  		rb->overwrite = 0;
  	else
  		rb->overwrite = 1;

  
  	atomic_set(&rb->refcount, 1);

  
  	INIT_LIST_HEAD(&rb->event_list);
  	spin_lock_init(&rb->event_lock);

  }
  
  #ifndef CONFIG_PERF_USE_VMALLOC
  
  /*
   * Back perf_mmap() with regular GFP_KERNEL-0 pages.
   */
  
  struct page *
  perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
  {
  	if (pgoff > rb->nr_pages)
  		return NULL;
  
  	if (pgoff == 0)
  		return virt_to_page(rb->user_page);
  
  	return virt_to_page(rb->data_pages[pgoff - 1]);
  }
  
  static void *perf_mmap_alloc_page(int cpu)
  {
  	struct page *page;
  	int node;
  
  	node = (cpu == -1) ? cpu : cpu_to_node(cpu);
  	page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
  	if (!page)
  		return NULL;
  
  	return page_address(page);
  }
  
  struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
  {
  	struct ring_buffer *rb;
  	unsigned long size;
  	int i;
  
  	size = sizeof(struct ring_buffer);
  	size += nr_pages * sizeof(void *);
  
  	rb = kzalloc(size, GFP_KERNEL);
  	if (!rb)
  		goto fail;
  
  	rb->user_page = perf_mmap_alloc_page(cpu);
  	if (!rb->user_page)
  		goto fail_user_page;
  
  	for (i = 0; i < nr_pages; i++) {
  		rb->data_pages[i] = perf_mmap_alloc_page(cpu);
  		if (!rb->data_pages[i])
  			goto fail_data_pages;
  	}
  
  	rb->nr_pages = nr_pages;
  
  	ring_buffer_init(rb, watermark, flags);
  
  	return rb;
  
  fail_data_pages:
  	for (i--; i >= 0; i--)
  		free_page((unsigned long)rb->data_pages[i]);
  
  	free_page((unsigned long)rb->user_page);
  
  fail_user_page:
  	kfree(rb);
  
  fail:
  	return NULL;
  }
  
  static void perf_mmap_free_page(unsigned long addr)
  {
  	struct page *page = virt_to_page((void *)addr);
  
  	page->mapping = NULL;
  	__free_page(page);
  }
  
  void rb_free(struct ring_buffer *rb)
  {
  	int i;
  
  	perf_mmap_free_page((unsigned long)rb->user_page);
  	for (i = 0; i < rb->nr_pages; i++)
  		perf_mmap_free_page((unsigned long)rb->data_pages[i]);
  	kfree(rb);
  }
  
  #else

  static int data_page_nr(struct ring_buffer *rb)
  {
  	return rb->nr_pages << page_order(rb);
  }

  
  struct page *
  perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
  {

  	/* The '>' counts in the user page. */
  	if (pgoff > data_page_nr(rb))

  		return NULL;
  
  	return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
  }
  
  static void perf_mmap_unmark_page(void *addr)
  {
  	struct page *page = vmalloc_to_page(addr);
  
  	page->mapping = NULL;
  }
  
  static void rb_free_work(struct work_struct *work)
  {
  	struct ring_buffer *rb;
  	void *base;
  	int i, nr;
  
  	rb = container_of(work, struct ring_buffer, work);

  	nr = data_page_nr(rb);

  
  	base = rb->user_page;

  	/* The '<=' counts in the user page. */
  	for (i = 0; i <= nr; i++)

  		perf_mmap_unmark_page(base + (i * PAGE_SIZE));
  
  	vfree(base);
  	kfree(rb);
  }
  
  void rb_free(struct ring_buffer *rb)
  {
  	schedule_work(&rb->work);
  }
  
  struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
  {
  	struct ring_buffer *rb;
  	unsigned long size;
  	void *all_buf;
  
  	size = sizeof(struct ring_buffer);
  	size += sizeof(void *);
  
  	rb = kzalloc(size, GFP_KERNEL);
  	if (!rb)
  		goto fail;
  
  	INIT_WORK(&rb->work, rb_free_work);
  
  	all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
  	if (!all_buf)
  		goto fail_all_buf;
  
  	rb->user_page = all_buf;
  	rb->data_pages[0] = all_buf + PAGE_SIZE;
  	rb->page_order = ilog2(nr_pages);

  	rb->nr_pages = !!nr_pages;

  
  	ring_buffer_init(rb, watermark, flags);
  
  	return rb;
  
  fail_all_buf:
  	kfree(rb);
  
  fail:
  	return NULL;
  }
  
  #endif