IDEA: Linux kernel and pcbios compatibility...

Eric W. Biederman ebiederman at lnxi.com
Fri Dec 19 19:06:01 CET 2003


Joshua Wise <joshua at joshuawise.com> writes:

> On Friday 19 December 2003 4:04 pm, Eric W. Biederman wrote:
> > ron minnich <rminnich at lanl.gov> writes:
> > > On 19 Dec 2003, Eric W. Biederman wrote:
> > > > The observation has been that any sufficiently general firmware
> > > > bootloader tends to become an OS, so why not use a real OS.
> > >
> > > ah ha! we've come full circle :-)
> > >
> > > good to hear.
> >
> > I have never disagreed.  Now that we have something that works for
> > the low end limited ROM solutions I can revisit some of the more
> > interesting ideas.
> 
> *jumps up and down like a hyperactive two-year-old* LAB can do that stuff!
> 
> I would definately like to see LAB used on more than just ARM.

Yes we are reaching the point where we can converge on some of these things.
LAB might be the right framework.  And if it is something good it will
save me the trouble of starting my own project.   But it takes more
than a hyper active 2 year old to convince me.  It might take a hyperactive
2 year old to remind me about interesting ideas though.

> > > > So the things I actually care about are: booting over myrinet,
> > > > booting over inifinband, booting over quadrics, booting over a pair of
> > > > bonded nics.  Having a good tg3 driver.   Getting Lustre as my root
> > > > filesystem.  Unless size issues kill it again I am going to use the
> > > > linux kernel as my bootloader to do this.
> If you can have it in the kernel you can have it in LAB. LAB's command line 
> API is really easy - I've ported userland apps (mtderase) to LAB in sub-10 
> minutes.

By and large I don't want a command line interface.  I don't want a hardware
monitor.  I want a configurable but non-interactive boot.

> As to size issues, we're at a 512k zImage. We do not have bzImages on ARM, so 
> I could not tell you the size with it.  

Compression wise there is not a difference between bzImage and zImage.  zImage
on x86 has a 640K limit because it loads below 1MB.  bzImage breaks that
ancient barrier.

> 512k is with a few ARM-specific drivers, and jffs2. It does not have
> networking. This is with kernel 2.6.

Hmm.  I am pretty certain I have gotten 2.6 down some smaller.  Our
practical limit with LinuxBIOS etc is in the neighborhood of 384KB.


> > > yah, this is why we still put linux in flash here at LANL.
> 
> Oh and did I say LAB had MTD support? :)

Well I think I have run finally convinced to use the MTD drivers...
Mostly I prefer to flash from a production kernel rather than a
bootloader, there are more recover options but anyway.

> > Now if you had more than a proof of concept implementation of most
> > of the pieces I would not be happier, but anyway...
> *jumps up and down* I do I do!!

I will see.  Does LAB restrict it's kernel to a very small subset of
memory?  Or do you use something like kexec?

Eric



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