xous-core/services/test-spawn/spawn

Spawn a process

This crate represents an initial program that will run when a process starts up. It will listen on a Server and take orders from the parent process to finish setting itself up.

Initialization

The process starts with a stack and a text section but no heap, BSS, or data section. The entrypoint looks like this:

pub extern "C" init(a1: u32, a2: u32, a3: u32, a4: u32) -> ! {
    let sid = xous::SID::from_u32(a1, a2, a3, a4);
    loop {}
}

This process is responsible for performing its own bootstrapping (i.e. allocating/initializing .data and .bss), after which it should accept messages on the connection and copy data as necessary.

API

The following messages are supported:

Mnemonic	Opcode	Type	Description
WriteMemory	1	M	Write memory into an area of memory. The Offset field is used to determine where the block will start.
WriteArgs	2	M	Reserved
WriteEnvironment	3	M	Reserved
FinishSetup	255	*	Terminate the loop, shutdown the server, and start the program.