kernel: channel: implement channel_read_msg and msg_read

syscall/msg.c

@@ -162,6 +162,29 @@ kern_status_t sys_port_disconnect(kern_handle_t port_handle)
 	return status;
 }
 
+static bool validate_iovec(
+	struct task *task,
+	const struct iovec *iov,
+	size_t count,
+	bool rw)
+{
+	for (size_t i = 0; i < count; i++) {
+		bool ok = false;
+		const struct iovec *vec = &iov[i];
+		if (rw) {
+			ok = validate_access_w(task, vec->io_base, vec->io_len);
+		} else {
+			ok = validate_access_r(task, vec->io_base, vec->io_len);
+		}
+
+		if (!ok) {
+			return false;
+		}
+	}
+
+	return true;
+}
+
 static bool validate_msg(struct task *task, const struct msg *msg, bool rw)
 {
 	if (!validate_access_r(task, msg, sizeof *msg)) {
@@ -184,18 +207,8 @@ static bool validate_msg(struct task *task, const struct msg *msg, bool rw)
 		return false;
 	}
 
-	for (size_t i = 0; i < msg->msg_data_count; i++) {
-		bool ok = false;
-		const struct iovec *iov = &msg->msg_data[i];
-		if (rw) {
-			ok = validate_access_w(task, iov->io_base, iov->io_len);
-		} else {
-			ok = validate_access_r(task, iov->io_base, iov->io_len);
-		}
-
-		if (!ok) {
-			return false;
-		}
+	if (!validate_iovec(task, msg->msg_data, msg->msg_data_count, rw)) {
+		return false;
 	}
 
 	for (size_t i = 0; i < msg->msg_handles_count; i++) {
@@ -368,13 +381,56 @@ kern_status_t sys_msg_reply(
 }
 
 kern_status_t sys_msg_read(
-	kern_handle_t channel,
+	kern_handle_t channel_handle,
 	msgid_t id,
 	size_t offset,
-	struct iovec *out,
-	size_t nr_out)
+	const struct iovec *iov,
+	size_t iov_count,
+	size_t *nr_read)
 {
-	return KERN_UNIMPLEMENTED;
+	struct task *self = current_task();
+
+	unsigned long flags;
+
+	task_lock_irqsave(self, &flags);
+
+	struct object *channel_obj = NULL;
+	handle_flags_t channel_handle_flags = 0;
+	kern_status_t status = task_resolve_handle(
+		self,
+		channel_handle,
+		&channel_obj,
+		&channel_handle_flags);
+	if (status != KERN_OK) {
+		return status;
+	}
+
+	/* add a reference to the port object to make sure it isn't deleted
+	 * while we're using it */
+	object_ref(channel_obj);
+	task_unlock_irqrestore(self, flags);
+
+	struct channel *channel = channel_cast(channel_obj);
+	if (!channel) {
+		object_unref(channel_obj);
+		return KERN_INVALID_ARGUMENT;
+	}
+
+	channel_lock_irqsave(channel, &flags);
+	vm_region_lock(self->t_address_space);
+	status = channel_read_msg(
+		channel,
+		id,
+		offset,
+		self->t_address_space,
+		iov,
+		iov_count,
+		nr_read);
+	vm_region_unlock(self->t_address_space);
+	channel_unlock_irqrestore(channel, flags);
+	object_unref(channel_obj);
+
+	return status;
 }
 
 kern_status_t sys_msg_read_handles(