Switch IPC

These are my personal notes that aid me in understand the IPC interface of the Nintendo Switch, which is further documented on SwitchBrew.

Overview

All system services on the Nintendo Switch are implemented in userland processes. These processes communicate with each other through IPC.

The following syscalls can be used to manage ports:

svcManageNamedPort register a named port on the kernel.
svcConnectToNamedPort returns a session handle that can be used to communicate with a specific port.

On the Switch, there exists only one named port: sm:. The sm: port is used by userland processes to register other services, and to establish a session with them for communication.

The following syscalls can be used to send IPC requests to other services:

svcSendSyncRequest
svcSendSyncRequestLight
svcSendSyncRequestWithUserBuffer
svcSendAsyncRequestWithUserBuffer

By default, the message is stored in thread local storage, although a user buffer can be provided as well.

Furthermore, the following syscalls can be used to receive IPC requests, and to send a reply:

svcReplyAndReceive
svcReplyAndReceiveLight
svcReplyAndReceiveWithUserBuffer