binder: BINDER_GET_FROZEN_INFO ioctl

User space needs to know if binder transactions occurred to frozen
processes. Introduce a new BINDER_GET_FROZEN ioctl and keep track of
transactions occurring to frozen proceses.

Signed-off-by: Marco Ballesio <balejs@google.com>
Signed-off-by: Li Li <dualli@google.com>
Acked-by: Todd Kjos <tkjos@google.com>
Link: https://lore.kernel.org/r/20210316011630.1121213-4-dualli@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -2360,6 +2360,10 @@ static int binder_proc_transaction(struct binder_transaction *t,
 	}
 
 	binder_inner_proc_lock(proc);
+	if (proc->is_frozen) {
+		proc->sync_recv |= !oneway;
+		proc->async_recv |= oneway;
+	}
 
 	if ((proc->is_frozen && !oneway) || proc->is_dead ||
 			(thread && thread->is_dead)) {
@@ -4634,6 +4638,8 @@ static int binder_ioctl_freeze(struct binder_freeze_info *info,
 
 	if (!info->enable) {
 		binder_inner_proc_lock(target_proc);
+		target_proc->sync_recv = false;
+		target_proc->async_recv = false;
 		target_proc->is_frozen = false;
 		binder_inner_proc_unlock(target_proc);
 		return 0;
@@ -4645,6 +4651,8 @@ static int binder_ioctl_freeze(struct binder_freeze_info *info,
 	 * for transactions to drain.
 	 */
 	binder_inner_proc_lock(target_proc);
+	target_proc->sync_recv = false;
+	target_proc->async_recv = false;
 	target_proc->is_frozen = true;
 	binder_inner_proc_unlock(target_proc);
 
@@ -4666,6 +4674,33 @@ static int binder_ioctl_freeze(struct binder_freeze_info *info,
 	return ret;
 }
 
+static int binder_ioctl_get_freezer_info(
+				struct binder_frozen_status_info *info)
+{
+	struct binder_proc *target_proc;
+	bool found = false;
+
+	info->sync_recv = 0;
+	info->async_recv = 0;
+
+	mutex_lock(&binder_procs_lock);
+	hlist_for_each_entry(target_proc, &binder_procs, proc_node) {
+		if (target_proc->pid == info->pid) {
+			found = true;
+			binder_inner_proc_lock(target_proc);
+			info->sync_recv |= target_proc->sync_recv;
+			info->async_recv |= target_proc->async_recv;
+			binder_inner_proc_unlock(target_proc);
+		}
+	}
+	mutex_unlock(&binder_procs_lock);
+
+	if (!found)
+		return -EINVAL;
+
+	return 0;
+}
+
 static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	int ret;
@@ -4844,6 +4879,24 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			goto err;
 		break;
 	}
+	case BINDER_GET_FROZEN_INFO: {
+		struct binder_frozen_status_info info;
+
+		if (copy_from_user(&info, ubuf, sizeof(info))) {
+			ret = -EFAULT;
+			goto err;
+		}
+
+		ret = binder_ioctl_get_freezer_info(&info);
+		if (ret < 0)
+			goto err;
+
+		if (copy_to_user(ubuf, &info, sizeof(info))) {
+			ret = -EFAULT;
+			goto err;
+		}
+		break;
+	}
 	default:
 		ret = -EINVAL;
 		goto err;
@@ -5154,6 +5207,8 @@ static void binder_deferred_release(struct binder_proc *proc)
 
 	proc->is_dead = true;
 	proc->is_frozen = false;
+	proc->sync_recv = false;
+	proc->async_recv = false;
 	threads = 0;
 	active_transactions = 0;
 	while ((n = rb_first(&proc->threads))) {

drivers/android/binder_internal.h

@@ -376,6 +376,10 @@ struct binder_ref {
  * @is_frozen:            process is frozen and unable to service
  *                        binder transactions
  *                        (protected by @inner_lock)
+ * @sync_recv:            process received sync transactions since last frozen
+ *                        (protected by @inner_lock)
+ * @async_recv:           process received async transactions since last frozen
+ *                        (protected by @inner_lock)
  * @freeze_wait:          waitqueue of processes waiting for all outstanding
  *                        transactions to be processed
  *                        (protected by @inner_lock)
@@ -422,6 +426,8 @@ struct binder_proc {
 	int outstanding_txns;
 	bool is_dead;
 	bool is_frozen;
+	bool sync_recv;
+	bool async_recv;
 	wait_queue_head_t freeze_wait;
 
 	struct list_head todo;

include/uapi/linux/android/binder.h

@@ -223,6 +223,12 @@ struct binder_freeze_info {
 	__u32            timeout_ms;
 };
 
+struct binder_frozen_status_info {
+	__u32            pid;
+	__u32            sync_recv;
+	__u32            async_recv;
+};
+
 #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)
@@ -234,6 +240,7 @@ struct binder_freeze_info {
 #define BINDER_GET_NODE_INFO_FOR_REF	_IOWR('b', 12, struct binder_node_info_for_ref)
 #define BINDER_SET_CONTEXT_MGR_EXT	_IOW('b', 13, struct flat_binder_object)
 #define BINDER_FREEZE			_IOW('b', 14, struct binder_freeze_info)
+#define BINDER_GET_FROZEN_INFO		_IOWR('b', 15, struct binder_frozen_status_info)
 
 /*
  * NOTE: Two special error codes you should check for when calling