/* * 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 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);} #else struct page *perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff){	if (pgoff > (1UL << page_order(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 = 1 << page_order(rb); 	base = rb->user_page;	for (i = 0; i < nr + 1; 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 = 1; 	ring_buffer_init(rb, watermark, flags); 	return rb; fail_all_buf:	kfree(rb); fail:	return NULL;} #endif