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Date:	Mon, 13 Mar 2000 16:56:11 +0100
From:	almesber@lrc.di.epfl.ch
To:	Linus Torvalds <torvalds@transmeta.com>
Subject: bootimg: 2.4 or later ?

[ Copied to linux-kernel ]

Hi Linus,

maybe you've already seen the bootimg system call and framework that
I've been working on recently. The idea is to let a Linux kernel load
another Linux kernel (and initrd, etc.), and then to boot it. My
latest version is on

ftp://icaftp.epfl.ch/pub/people/almesber/misc/bootimg-8.tar.gz

bootimg has the following uses:

 - allows booting from media hard to support using traditional boot
   loaders (e.g. RAID, NFS, disk disabled in BIOS, etc.)
 - for many "advanced" features, it provides a single point of
   implementation instead of once per boot loader over all
   architectures
 - allows people to implement fancy boot procedures (e.g. mpegs of
   dancing penguins, with voice recognition for kernel selection)
 - should be useful for projects that put Linux into (EP)ROM, e.g.
   linuxbios
 - makes reboot even faster ;-)

Of course there are also some drawbacks:

 - doesn't help people with very tight storage constraints
 - will trip over devices that don't do a full reset on initialization
   (1)
 - not ported beyond the i386 architecture yet (2)

(1) Right now, there is one known problem in the area: as of 2.3.48,
    SMP systems seem to reset interrupts only partially, so the system
    hangs after bootimg(2), waiting for interrupts that don't arrive.
    It also shows up occasionally on UP. (Of course, I only have UP,
    so I only see a problem every 10-50 reboots :-( )
(2) I'm confident that it will work well on ARM - half of the concept
    is adapted from the linux-7110 boot code)

Now my question is if I should work towards getting this ready for
inclusion in 2.4 ? There's a bit of cleanup left to do, and the
interrupts bug needs to be fixed. All this shouldn't take more than
0.5-2 weeks.

At the moment, the cases where people actually require bootimg to solve
a specific problem seem to be few. On the other hand, I see a tendency
towards more complex boot setups, so something like bootimg may become
necessary sooner than we like.

Please let me know what you think.

Cheers, Werner

-- 
  _________________________________________________________________________
 / Werner Almesberger, ICA, EPFL, CH       werner.almesberger@ica.epfl.ch /
/_IN_N_032__Tel_+41_21_693_6621__Fax_+41_21_693_6610_____________________/

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