Re: Learning kernel programming with netbsd

[David Holland <dholland+netbsd%eecs.harvard.edu@localhost>]

On Sat, Jun 28, 2008 at 12:48:36PM -0700, Michael Litchard wrote:
 > The end goal here is to start making contributions to -current.
 > Here's where I am at now.
 > I have done some x86,RISC (using SPIM) and AVR assembler programming.
 > I know C, and how to construct the data structures typically discussed
 > in a first data structures class.
 > so, given that, would anyone be willing to give me a series of tasks
 > that will prepare me to meet my goal?

I would say the first step is to learn a bit about how kernels are set
up; an OS textbook or the daemon book might help. (You can find this
all out by reading code, but there's a lot of code, and the high-level
organization isn't always that easy to see.)

Learn how userland interfaces to the kernel; read some of the more
obscure section 2 man pages and write a program that uses one or two
low-level features. For a few of the less obscure system calls (e.g.,
read, lseek) read the code in the kernel to see how the implementation
works and where things go.

Add some hacks to the kernel just for practice - e.g. add a new system
call that causes the kernel to print "hello" to the console. Or
something like that. You'll never commit this but it'll get you some
practice building and running test kernels.

Then pick some reasonably small project (from the projects list on the
web site, or something of your own; historically a lot of people begin
by writing a device driver for some piece of hardware) and sit down to
get that working. And don't be afraid to ask for help.

When we teach students this stuff we give them a toy OS with key
pieces missing or half-written and have them write those pieces. You
can't do that with NetBSD (the pieces are all already there) so you
have to pick projects from less fundamental parts of the system.

You could also do the toy OS thing yourself first and then move across
to NetBSD.

-- 
   - David A. Holland / dholland+netbsd%eecs.harvard.edu@localhost