ANDROID: binder: Add BINDER_GET_NODE_DEBUG_INFO ioctl

The BINDER_GET_NODE_DEBUG_INFO ioctl will return debug info on
a node.  Each successive call reusing the previous return value
will return the next node.  The data will be used by
libmemunreachable to mark the pointers with kernel references
as reachable.
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Martijn Coenen <maco@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -4389,6 +4389,31 @@ static int binder_ioctl_set_ctx_mgr(struct file *filp)
 	return ret;
 }
 
+static int binder_ioctl_get_node_debug_info(struct binder_proc *proc,
+				struct binder_node_debug_info *info)
+{
+	struct rb_node *n;
+	binder_uintptr_t ptr = info->ptr;
+
+	memset(info, 0, sizeof(*info));
+
+	binder_inner_proc_lock(proc);
+	for (n = rb_first(&proc->nodes); n != NULL; n = rb_next(n)) {
+		struct binder_node *node = rb_entry(n, struct binder_node,
+						    rb_node);
+		if (node->ptr > ptr) {
+			info->ptr = node->ptr;
+			info->cookie = node->cookie;
+			info->has_strong_ref = node->has_strong_ref;
+			info->has_weak_ref = node->has_weak_ref;
+			break;
+		}
+	}
+	binder_inner_proc_unlock(proc);
+
+	return 0;
+}
+
 static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	int ret;
@@ -4458,6 +4483,24 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		}
 		break;
 	}
+	case BINDER_GET_NODE_DEBUG_INFO: {
+		struct binder_node_debug_info info;
+
+		if (copy_from_user(&info, ubuf, sizeof(info))) {
+			ret = -EFAULT;
+			goto err;
+		}
+
+		ret = binder_ioctl_get_node_debug_info(proc, &info);
+		if (ret < 0)
+			goto err;
+
+		if (copy_to_user(ubuf, &info, sizeof(info))) {
+			ret = -EFAULT;
+			goto err;
+		}
+		break;
+	}
 	default:
 		ret = -EINVAL;
 		goto err;

include/uapi/linux/android/binder.h

@@ -186,6 +186,19 @@ struct binder_version {
 #define BINDER_CURRENT_PROTOCOL_VERSION 8
 #endif
 
+/*
+ * Use with BINDER_GET_NODE_DEBUG_INFO, driver reads ptr, writes to all fields.
+ * Set ptr to NULL for the first call to get the info for the first node, and
+ * then repeat the call passing the previously returned value to get the next
+ * nodes.  ptr will be 0 when there are no more nodes.
+ */
+struct binder_node_debug_info {
+	binder_uintptr_t ptr;
+	binder_uintptr_t cookie;
+	__u32            has_strong_ref;
+	__u32            has_weak_ref;
+};
+
 #define BINDER_WRITE_READ		_IOWR('b', 1, struct binder_write_read)
 #define BINDER_SET_IDLE_TIMEOUT		_IOW('b', 3, __s64)
 #define BINDER_SET_MAX_THREADS		_IOW('b', 5, __u32)
@@ -193,6 +206,7 @@ struct binder_version {
 #define BINDER_SET_CONTEXT_MGR		_IOW('b', 7, __s32)
 #define BINDER_THREAD_EXIT		_IOW('b', 8, __s32)
 #define BINDER_VERSION			_IOWR('b', 9, struct binder_version)
+#define BINDER_GET_NODE_DEBUG_INFO	_IOWR('b', 11, struct binder_node_debug_info)
 
 /*
  * NOTE: Two special error codes you should check for when calling