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Date:      Tue, 18 Mar 1997 16:24:58 +1030 (CST)
From:      Michael Smith <msmith@atrad.adelaide.edu.au>
To:        thorpej@nas.nasa.gov
Cc:        msmith@atrad.adelaide.edu.au, hackers@freebsd.org
Subject:   Bootstrapping (was Re: wd driver questions)
Message-ID:  <199703180554.QAA15812@genesis.atrad.adelaide.edu.au>
In-Reply-To: <199703180543.VAA13412@lestat.nas.nasa.gov> from Jason Thorpe at "Mar 17, 97 09:43:21 pm"

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Jason Thorpe stands accused of saying:
>  > Thing wot uses simplistic file services to assemble from data on
>  > disk (kernel link instructions, object files) a kernel and runs it.
> 
> ...oh... I rather like just having A Kernel Image and loading it :-)

That's nice in it's own way, but it falls short on a few things, like
being able to page bits of the kernel, replace bits of it on the fly,
load and discard drivers etc.

> Basically, you're talking about two-stage there... but the only reason
> to use two-stage is space constraints (stupid limit on PCs, space until
> file system begins on SPARCs, etc.)

Yup.

> If you don't hardcode the block numbers of the secondary boot program
> into the primary, you have to include all the file system reading code,
> which sort of defeats "small".

Well, the current FreeBSD bootloader manages that in 7.5K along with a
reasonably healthy amount of cruft.

> installboot(8) deals with all of it anyhow, and since you currently
> have to run something to stash the primary bootstrap into the right
> sector, it's not that big of a deal :-)

It just grates that you're putting something into the filesystem and
then duplicating that information somewhere else.  If I throw a new
boot program in /boot, I don't necessarily want to have to hardcode
its location into the stage-1 bootstrap.  Or for that matter what if I
want to choose between several different boot programs?


-- 
]] Mike Smith, Software Engineer        msmith@gsoft.com.au             [[
]] Genesis Software                     genesis@gsoft.com.au            [[
]] High-speed data acquisition and      (GSM mobile)     0411-222-496   [[
]] realtime instrument control.         (ph)          +61-8-8267-3493   [[
]] Unix hardware collector.             "Where are your PEZ?" The Tick  [[



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