ULIX: Literate Unix
A diary documenting the implementation of ULIX-i386
Welcome to the ULIX blog.
Ulix (Literate Unix) is a Unix-like operating system developed at
University of Erlangen-Nürnberg.
I use D. E. Knuth's concept of
for the implementation and documentation. The goal was a fully working system which can be
used in operating system courses to show students how OS concepts (such as paging and scheduling)
can be implemented. Literate programs are very accessible because they can be read like a book;
the order of presentation is not enforced by program logic or compiler restrictions, but instead
is guided by the implementer's creative process.
Ulix is written in C and assembler for the Intel architecture. The literate programming
part is handled by noweb.
On this page I document my progress with the implementation.
|v0.07: Scheduling, fork(), exit(), and waitpid() are working (05.04.2013) |
It's taken some time, but I finally got the context switch working,
and so Ulix can now launch new processes and have them all run in
parallel by the (simple round-robin) scheduler. The problem was in the
function which changes the address space (by modifying the CR3 register
which points to the page directory). For some time I thought it should
be sufficient to make that function an inline function, but now I found
that it must not be a function at all (there's still parameter-passing
involved in calling inline functions, and these parameters are lost
when changing the page directory). So now it's not a function call anymore,
instead the scheduler directly switches the page directory,
and everything works.
The first two Bachelor theses (on Ulix-Filesystem/RAM disk and the ELF binary
loader) are completed, so after I've included the code in Ulix, it will be
able to start programs from disk properly. The third student who is working
on a priority-based scheduler is also about to complete his work in the next
[ Path: | persistent link ]
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