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Re: On a Samsung ARM Chromebook, could nv-uboot easily boot to stock lin

From: Luke Kenneth Casson Leighton
Subject: Re: On a Samsung ARM Chromebook, could nv-uboot easily boot to stock linux kernels, by way of ARM-GRUB?
Date: Wed, 1 Jan 2014 17:09:27 +0000

subharo, hi,

basically you've been caught out by the use of treacherous computing,
and have purchased a product that you cannot and will not ever own.
the samsung processors have bootloader-signing actually built-in to
the ROM: once the e-fuses are fired and the private key installed in
EEPROM there is no way to gain control of the machine short of paying
someone tens of thousands of dollars to have the top taken off the
processor in a class 1 cleanroom and to use lasers to dig around, hunt
for and re-build the e-fuse.  and then put the plastic back.

actually, there *might* be a cheaper way: obtain a replacement
processor, pay for the treacherous one to be removed and have the
"stock" one soldered in its place (and then blow the e-fuse which
permanently disables treacherous computing).  as this would involve
heating up the board to around 200C and these SoCs have a hell of a
lot of pins it is not without risk.

but, without going down that insane route, you are along the right
kind of lines with loading a 2nd bootloader - one that can then load
an unsigned kernel.

there is potentially a simpler option: you might wish to look at the
kexec option.  this would allow you to continue to use the *existing*
kernel - unmodified - purely as a bootloader.  there is a userspace
program kicking around which allows selection of kernels (heck, you
could even try using grub in userspace).  modify /sbin/init (or other
method) to run that userspace "kernel-selector", then that userspace
kernel-selector-program will kexec the *actual* kernel that you
require, which can, of course, be anything you want.

regarding the custom-compiled packages: yep... tough.  that's how
things are in the ARM world.  i won't say "get used to it"... instead
i'll say "please *consider* getting used to it" :)  there is no BIOS:
*every* kernel is custom-compiled and hard-coded to match the
hardware... which, because there is no BIOS, and all the CPUs are
different *and* all the hardware is different.... you see how that
quickly becomes a complete nightmare?

so.... yeah, if someone's already done custom-compiled packages then
you are very, very lucky.


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