@@ -43,4 +43,6 @@ struct trace_buffer_meta {
 	__u64	Reserved2;
 };
 
+#define TRACE_MMAP_IOCTL_GET_READER		_IO('T', 0x1)
+
 #endif /* _TRACE_MMAP_H_ */

@@ -1175,6 +1175,12 @@ static void tracing_snapshot_instance_cond(struct trace_array *tr,
 		return;
 	}
 
+	if (tr->mapped) {
+		trace_array_puts(tr, "*** BUFFER MEMORY MAPPED ***\n");
+		trace_array_puts(tr, "*** Can not use snapshot (sorry) ***\n");
+		return;
+	}
+
 	local_irq_save(flags);
 	update_max_tr(tr, current, smp_processor_id(), cond_data);
 	local_irq_restore(flags);

@@ -1307,7 +1313,7 @@ static int tracing_arm_snapshot_locked(struct trace_array *tr)
 	lockdep_assert_held(&trace_types_lock);
 
 	spin_lock(&tr->snapshot_trigger_lock);
-	if (tr->snapshot == UINT_MAX) {
+	if (tr->snapshot == UINT_MAX || tr->mapped) {
 		spin_unlock(&tr->snapshot_trigger_lock);
 		return -EBUSY;
 	}

@@ -6533,7 +6539,7 @@ static void tracing_set_nop(struct trace_array *tr)
 {
 	if (tr->current_trace == &nop_trace)
 		return;
-	
+
 	tr->current_trace->enabled--;
 
 	if (tr->current_trace->reset)

@@ -8652,15 +8658,31 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 	return ret;
 }
 
-/* An ioctl call with cmd 0 to the ring buffer file will wake up all waiters */
 static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
 	struct ftrace_buffer_info *info = file->private_data;
 	struct trace_iterator *iter = &info->iter;
+	int err;
+
+	if (cmd == TRACE_MMAP_IOCTL_GET_READER) {
+		if (!(file->f_flags & O_NONBLOCK)) {
+			err = ring_buffer_wait(iter->array_buffer->buffer,
+					       iter->cpu_file,
+					       iter->tr->buffer_percent);
+			if (err)
+				return err;
+		}
 
-	if (cmd)
-		return -ENOIOCTLCMD;
+		return ring_buffer_map_get_reader(iter->array_buffer->buffer,
+						  iter->cpu_file);
+	} else if (cmd) {
+		return -ENOTTY;
+	}
 
+	/*
+	 * An ioctl call with cmd 0 to the ring buffer file will wake up all
+	 * waiters
+	 */
 	mutex_lock(&trace_types_lock);
 
 	iter->wait_index++;

@@ -8673,6 +8695,97 @@ static long tracing_buffers_ioctl(struct file *file, unsigned int cmd, unsigned
 	return 0;
 }
 
+static vm_fault_t tracing_buffers_mmap_fault(struct vm_fault *vmf)
+{
+	struct ftrace_buffer_info *info = vmf->vma->vm_file->private_data;
+	struct trace_iterator *iter = &info->iter;
+	vm_fault_t ret = VM_FAULT_SIGBUS;
+	struct page *page;
+
+	page = ring_buffer_map_fault(iter->array_buffer->buffer, iter->cpu_file,
+				     vmf->pgoff);
+	if (!page)
+		return ret;
+
+	get_page(page);
+	vmf->page = page;
+	vmf->page->mapping = vmf->vma->vm_file->f_mapping;
+	vmf->page->index = vmf->pgoff;
+
+	return 0;
+}
+
+static void tracing_buffers_mmap_close(struct vm_area_struct *vma)
+{
+	struct ftrace_buffer_info *info = vma->vm_file->private_data;
+	struct trace_iterator *iter = &info->iter;
+	struct trace_array *tr = iter->tr;
+
+	ring_buffer_unmap(iter->array_buffer->buffer, iter->cpu_file);
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+	spin_lock(&tr->snapshot_trigger_lock);
+	if (!WARN_ON(!tr->mapped))
+		tr->mapped--;
+	spin_unlock(&tr->snapshot_trigger_lock);
+#endif
+}
+
+static void tracing_buffers_mmap_open(struct vm_area_struct *vma)
+{
+	struct ftrace_buffer_info *info = vma->vm_file->private_data;
+	struct trace_iterator *iter = &info->iter;
+
+	WARN_ON(ring_buffer_map(iter->array_buffer->buffer, iter->cpu_file));
+}
+
+static const struct vm_operations_struct tracing_buffers_vmops = {
+	.open		= tracing_buffers_mmap_open,
+	.close		= tracing_buffers_mmap_close,
+	.fault		= tracing_buffers_mmap_fault,
+};
+
+static int tracing_buffers_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct ftrace_buffer_info *info = filp->private_data;
+	struct trace_iterator *iter = &info->iter;
+	struct trace_array *tr = iter->tr;
+	int ret = 0;
+
+	if (vma->vm_flags & VM_WRITE)
+		return -EPERM;
+
+	vm_flags_mod(vma, VM_DONTCOPY | VM_DONTDUMP, VM_MAYWRITE);
+	vma->vm_ops = &tracing_buffers_vmops;
+
+#ifdef CONFIG_TRACER_MAX_TRACE
+	/*
+	 * We hold mmap_lock here. lockdep would be unhappy if we would now take
+	 * trace_types_lock. Instead use the specific snapshot_trigger_lock.
+	 */
+	spin_lock(&tr->snapshot_trigger_lock);
+	if (tr->snapshot || tr->mapped == UINT_MAX) {
+		spin_unlock(&tr->snapshot_trigger_lock);
+		return -EBUSY;
+	}
+	tr->mapped++;
+	spin_unlock(&tr->snapshot_trigger_lock);
+
+	/* Wait for update_max_tr() to observe iter->tr->mapped */
+	if (tr->mapped == 1)
+		synchronize_rcu();
+#endif
+	ret = ring_buffer_map(iter->array_buffer->buffer, iter->cpu_file);
+#ifdef CONFIG_TRACER_MAX_TRACE
+	if (ret) {
+		spin_lock(&tr->snapshot_trigger_lock);
+		iter->tr->mapped--;
+		spin_unlock(&tr->snapshot_trigger_lock);
+	}
+#endif
+	return ret;
+}
+
 static const struct file_operations tracing_buffers_fops = {
 	.open		= tracing_buffers_open,
 	.read		= tracing_buffers_read,

@@ -8681,6 +8794,7 @@ static const struct file_operations tracing_buffers_fops = {
 	.splice_read	= tracing_buffers_splice_read,
 	.unlocked_ioctl = tracing_buffers_ioctl,
 	.llseek		= no_llseek,
+	.mmap		= tracing_buffers_mmap,
 };
 
 static ssize_t

@@ -336,6 +336,7 @@ struct trace_array {
 	bool			allocated_snapshot;
 	spinlock_t		snapshot_trigger_lock;
 	unsigned int		snapshot;
+	unsigned int		mapped;
 	unsigned long		max_latency;
 #ifdef CONFIG_FSNOTIFY
 	struct dentry		*d_max_latency;