Advanced Operating Systems
M3: System call interface
The aim of this milestone is to design the RPC protocol for the
system call interface. You should implement both the client and
system side of this interface. This client side system call
interface must conform to the interface provided in include/sos.h handy.
You should create a
At this stage you will not actually be able to implement most
of the system calls, however you should be able to partially
Other system call should output
When a program opens the file
Reading the console is a blocking operation. If a process reads from the console and there is no data available it should block until data becomes available.
Be careful not to implement the console device as a 'hack'. You should think about being able to support multiple serial ports and other stream devices in your design (although not necessarily implement them).
You may once again find the documentation on libserial handy.
Changing your SConstruct
You will need to create a new library and to change your toplevel
To add a new library you should create a new directory in the
from: milestone = 0 to: milestone = 3
Once you have your libs/sos library set up, it should like like this:
libs/sos libs/sos/SConstruct libs/sos/src/ libs/sos/include/ libs/sos/include/sos.h
You should copy the contents of tty_test/ttyout.c to libs/sos/src. You can consider this new file as the acorn from which the entire grand tree of -lsos will flourish.
At this stage of the project you will need to decide whether you want to have a simple single-threaded server, or to multi-thread it. A multi-threaded design could be advantageous to deal with the inherent concurrency your system will have (e.g. between paging, system calls, asynchronous I/O and clock interrupts), but it will require careful design of synchronisation in order to avoid race conditions and deadlocks. A single threaded model will require extra attention to ensure liveness.
Another design descision is how to transfer data between the kernel and user processes. Some options you have are:
Whatever you do, remember the basic engineering rule: keep it simple, stupid!(KISS).
Update: A new sosh.c is available.
This milestone is larger than previous ones, and it is advisable that you split the workload between the group.
For this assessment you should be able to demonstrate
As always you should be able to explain both the design and your implementation.
Last modified: 27 Jul 2007.