IPC basics in KasperskyOS
In KasperskyOS, the only means of interprocess communication (IPC) is exchange of messages.
Types of messages and roles of entities
Messaging in KasperskyOS is built on a client-server model.
When two entities interact, one of them is the client (client entity), and the other is the server (server entity). The client initiates the interaction by sending a request message (or simply "request"). The server receives the request and responds by sending a response message (or simply "response") to the client.
IPC channels
To enable two entities to exchange messages, an IPC channel, also referred to as "channel" or "connection", must be established between them. Each entity can have multiple connections, acting as a client for some entities while acting as a server for others.
System calls
KasperskyOS provides three system calls for IPC message exchange: Call, Recv and Reply. The corresponding functions are declared in the syscalls.h file:
Call()is used by the client to send a request and receive a response. It receives an IPC handle, buffer containing the request, and buffer for the response.Recv()is used by the server to receive a request. It receives an IPC handle and buffer for the request.Reply()is used by the server to send a response. It receives an IPC handle and buffer for the response.
The Call(), Recv() and Reply() functions return rcOk or an error code.
The Call() and Recv() system calls are locking calls, meaning that messages are exchanged according to the rendezvous principle:
- The server thread that executes the
Recv()call remains locked until a request is received. - The client thread that executes the
Call()call remains locked until a response is received from the server.
System calls are rarely used in entity code. It is recommended that you instead use more convenient NK-generated methods that execute system calls.