[coreboot] Rettungsboot

[Charlotte Plusplus]

Hello

On Sat, Nov 26, 2016 at 6:19 PM, Trammell Hudson <hudson at trmm.net> wrote:

> The 4MB flash in the older thinkpads is a little tight, but still
> sufficient for a text-based modern Linux kernel -- the biggest issue is
> the cryptsetup tool brings in quite a few dependencies right now,
> which complicates using it with a fully encrypted drive.
>

Using busybox, cryptsetup, dmsetup, blkid and the libraries, my inittrd.gz
is 2.6M
I didn't do any special optimization.

I suppose not using glibc but a smaller libc could make it smaller


> With 8-16 MB you can have a write-protected, interactive shell version
> that can mount a USB drive and run spiflash tools to recover from
> failures, and a second, read-write version that can be reflashed by the
> system's owner with all the fancy features.


In my ideal scenario, coreboot would have the 2 images (normal, fallback)
both starting the same payload (a minimal linux kernel) to save space.

/init would be a shell script using nvram to check whether it is running in
normal or in fallback.

In normal mode, the kernel would just kexec the kernel that is used
normally, using cmdline parameters found in the CBFS

In fallback mode, busybox, flashtools and diagnosis tools (cbmem, ectool,
inteltool, etc) would let the user at least mount a thumbdrive to reflash a
working image

This would make development for new boards simpler. FT232 and serial
consoles and ISP cables are nice, but I prefer to stay in software. Unless
I mess up big time, I don't see any good reason to not use normal/fallback
and flashrom straight on the board.

Charlotte
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