Services

Services are an abstraction of ports and are the commonly used way of inter-process communication outside of the kernel. While handles of regular ports are retrieved from svcConnectToPort, service handles are retrieved through the port srv: (“service manager”).

When a service is registered, svcCreatePort is used without a port-name. This means that the port is inaccessible via the port SVCs outside of sm-module. See below for getting a session handle for sending commands to services.

Processes with PID less than or equal to the number of NATIVE_FIRM built-in modules (fs, sm, pm, pxi, ldr) have access to all services. This value is obtained from svcGetSystemInfo. Other processes are limited to access services listed in their service access control list, as passed to SRVPM:RegisterProcess.

Attempting to use GetServiceHandle with a service that the process has access to when that service isn’t registered will block until it is registered.

It appears these “port” commands can be used for transferring arbitrary handles, however GetPort still uses the same service-access-control validation as GetServiceHandle. Despite this fact, it appears that a “port” and a service with the same name can coexist independently.

Prior to to 7.0.0-13, the commands listed for “srv:” were also accessible under this port with the same command-headers. Starting with 7.0.0-13, the “srv:pm” port was changed to a service. With this change, commandIDs for these commands were changed. “srv:pm” was originally vulnerable, this was fixed with 7.0.0-13, see here. Originally any process could use “srv:pm”, however starting with 7.0.0-13 only the built-in NATIVE_FIRM sysmodules have access to it. The only system title which uses “srv:pm” is the Process Manager.