sysinit #

The sysinit program provided by Mercury initializes the system and provides critical low-level runtime services for drivers and other processes. It provides the following services:

Service Interface
Bootstrap filesystem fs
Device manager* devmgr
Device registry* devregistry
Driver loader* devloader
Physical memory manager* pmem
Process manager procmgr & process
Memory manager mmapper & munmapper

* Available to drivers via the services manifest

Process loader #

The process manager service may be used to query running processes or set up new ones. Calling procmgr::new with a provided argument vector will create a new process, and an ELF image may be loaded into this process via process::load. This will invoke the loader, which in addition to loading the ELF image will perform the following tasks:

  • Set up a System-V auxiliary vector and populate the argument vector
  • Allocate an IPC buffer and populate an auxv entry for it
  • Allocate a stack and set the stack pointer accordingly

For processes which are not loaded via the driver loader, additional steps are taken:

  • Install a copy of the process’s CSpace capability into the process’s CSpace
  • Allocate an I/O buffer pool

Driver loader #

The driver loader works in tandem with the process loader to provide additional functionality specific to drivers. The driver loader will fetch the driver manifest from the ELF file, via a special ELF section named .manifest, and load additional capabilities and services accordingly. See the manifest.ini documentation for more details.

Startup #

On startup, sysinit loads its services and runs /sbin/usrinit, which should continue with userspace initialization per system policy (e.g. loading drivers and starting the rest of the system).

sysinit provides the bootstrap filesystem service by loading a tarball from the first boot module provided by the kernel.

usrinit environment #

In addition to the standard process environment provided by process loader, the following services are installed in usrinit and enumerated in the auxiliary vector by default:

  • Bootstrap filesystem
  • Device manager
  • Device registry
  • Driver loader
  • Process manager