/* * 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 <linux/circ_buf.h>#include <linux/poll.h> #include "internal.h" static void perf_output_wakeup(struct perf_output_handle *handle){	atomic_set(&handle->rb->poll, POLLIN); 	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; 	/*	 * Since the mmap() consumer (userspace) can run on a different CPU:	 *	 *   kernel				user	 *	 *   if (LOAD ->data_tail) {		LOAD ->data_head	 *			(A)		smp_rmb()	(C)	 *	STORE $data			LOAD $data	 *	smp_wmb()	(B)		smp_mb()	(D)	 *	STORE ->data_head		STORE ->data_tail	 *   }	 *	 * Where A pairs with D, and B pairs with C.	 *	 * In our case (A) is a control dependency that separates the load of	 * the ->data_tail and the stores of $data. In case ->data_tail	 * indicates there is no room in the buffer to store $data we do not.	 *	 * D needs to be a full barrier since it separates the data READ	 * from the tail WRITE.	 *	 * For B a WMB is sufficient since it separates two WRITEs, and for C	 * an RMB is sufficient since it separates two READs.	 *	 * See perf_output_begin().	 */	smp_wmb(); /* B, matches C */	rb->user_page->data_head = head; 	/*	 * Now check if we missed an update -- rely on previous implied	 * compiler barriers to force a re-read.	 */	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, page_shift;	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 (unlikely(!rb))		goto out; 	if (unlikely(!rb->nr_pages))		goto out; 	handle->rb    = rb;	handle->event = event; 	have_lost = local_read(&rb->lost);	if (unlikely(have_lost)) {		size += sizeof(lost_event);		if (event->attr.sample_id_all)			size += event->id_header_size;	} 	perf_output_get_handle(handle); 	do {		tail = ACCESS_ONCE(rb->user_page->data_tail);		offset = head = local_read(&rb->head);		if (!rb->overwrite &&		    unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size))			goto fail; 		/*		 * The above forms a control dependency barrier separating the		 * @tail load above from the data stores below. Since the @tail		 * load is required to compute the branch to fail below.		 *		 * A, matches D; the full memory barrier userspace SHOULD issue		 * after reading the data and before storing the new tail		 * position.		 *		 * See perf_output_put_handle().		 */ 		head += size;	} while (local_cmpxchg(&rb->head, offset, head) != offset); 	/*	 * We rely on the implied barrier() by local_cmpxchg() to ensure	 * none of the data stores below can be lifted up by the compiler.	 */ 	if (unlikely(head - local_read(&rb->wakeup) > rb->watermark))		local_add(rb->watermark, &rb->wakeup); 	page_shift = PAGE_SHIFT + page_order(rb); 	handle->page = (offset >> page_shift) & (rb->nr_pages - 1);	offset &= (1UL << page_shift) - 1;	handle->addr = rb->data_pages[handle->page] + offset;	handle->size = (1UL << page_shift) - offset; 	if (unlikely(have_lost)) {		struct perf_sample_data sample_data; 		lost_event.header.size = sizeof(lost_event);		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_event_header__init_id(&lost_event.header,					   &sample_data, event);		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 voidring_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);} #elsestatic 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