kernel: channel: implement channel_read_msg and msg_read

include/kernel/channel.h

@@ -38,15 +38,17 @@ extern kern_status_t channel_read_msg(
 	struct channel *channel,
 	msgid_t msg,
 	size_t offset,
-	void *buf,
-	size_t len,
+	struct vm_region *dest_region,
+	const struct iovec *dest_iov,
+	size_t dest_iov_count,
 	size_t *nr_read);
 extern kern_status_t channel_write_msg(
 	struct channel *channel,
 	msgid_t msg,
 	size_t offset,
-	const void *buf,
-	size_t len,
+	struct vm_region *src_region,
+	const struct iovec *src_iov,
+	size_t src_iov_count,
 	size_t *nr_written);
 
 DEFINE_OBJECT_LOCK_FUNCTION(channel, c_base)

include/kernel/syscall.h

@@ -158,11 +158,12 @@ extern kern_status_t sys_msg_reply(
 	const struct msg *reply);
 
 extern 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);
 extern kern_status_t sys_msg_read_handles(
 	kern_handle_t channel,
 	msgid_t id,