? about kernel size..

[Ian Lepore]

On Tue, 2016-03-08 at 14:32 -0700, Brad Walker wrote:
> On Tue, Mar 8, 2016 at 11:42 AM, Warner Losh <imp at bsdimp.com> wrote:
> 
> > 
> > 
> > On Tue, Mar 8, 2016 at 10:42 AM, Brad Walker <bwalker at musings.com>
> > wrote:
> > 
> > > I'm looking at working on a new project that will use the FreeBSD
> > > kernel.
> > > I
> > > would attempt to embed the kernel on a very small NXP Kinetis
> > > chip. I've
> > > previously done this using a Linux kernel but also had DDR memory
> > > attached
> > > to the chip. This project would not have a DDR chip attached.
> > > 
> > > So a couple of questions. 1 - What is the smallest size I could
> > > configure
> > > the FreeBSD kernel out of the box? Could I get the size to be
> > > less than
> > > 10MB, 5MB, 2MB, or etc.?
> > > 
> > 
> > I've managed to get this down to about 2MB or a bit smaller.
> > Compressed
> > this can be a little smaller. It takes a fair amount of work, but
> > it can be
> > done.
> > 
> > 
> 
> That's great.. Was this out of the box tuning?
> 
> 
> > 
> > I did a little bit of research on the PicoBSD and NanoBSD but that
> > still
> > > seem to be targeted to a little bit bigger chip than I have
> > > available.
> > > 
> > 
> > How big a chip do you have? NanoBSD currently needs at least
> > 64MB (and ideally 128MB) of storage. PicoBSD can be a bit smaller.
> > 
> 
> I have 2MB on-chip flash and 512KB of SRAM. There is an external
> flash that
> will be attached. What I'm currently thinking is that I would like to
> boot
> into BusyBox verses multi-user..
> 
> One question that I'm curious about. All the work that I do on this,
> or
> you've done in the past, how does it get integrated into the mainline
> build.

Wait a sec here... NXP Kinetis is ARM Cortex-M, and that means no MMU,
right?  No MMU means no freebsd running on it.

-- Ian