modifying the BIOS of an Acer C720 from within FreeBSD CURRENT

[Matthias Apitz]

Hello,

This is with flashrom of FreeBSD CURRENT amd64.

The background: To be able to install and boot FreeBSD on an Acer C720
Chromebook, one must tweak some bits in the BIOS and enable a so called
LEGACY BIOS mode (after removing the hardware write protection of the
BIOS). To do so, there are some tools within ChromeOS which allow this
procedure, but after this you can not boot ChromeOS anymore (from the
saved SSD) and so you can't use these tools within ChromeOS to switch
the bits back.

The tools to use are simple:

# flashrom -p internal -i GBB -r bios.bin
# futility gbb -s --flags=$flags bios.bin
# flashrom -p host -i GBB --fast-verify -w bios.bin

Flashrom we have in the FreeBSD ports as sysutils/flashrom and it seems
to works:

$ flashrom -R
flashrom v0.9.9-r1955 on FreeBSD 12.0-CURRENT (amd64)
flashrom is free software, get the source code at https://flashrom.org

$ flashrom -L | egrep -i 'acer|720|chro'
Acer            V75-M                                   OK
Acer            EM61SM/EM61PM                           OK
GIGABYTE        GA-M720-US3                             OK
MSI             MS-7207 (K8NGM2-L)                      OK      (autodetected)
Acer       Aspire 1520         OK
Acer       Aspire One          BAD

$ flashrom -p internal -i GBB -r bios.bin
flashrom v0.9.9-r1955 on FreeBSD 12.0-CURRENT (amd64)
flashrom is free software, get the source code at https://flashrom.org

Region requested (with -i "GBB"), but no layout data is available.

What does this error message mean?

Thanks

matthias

[Stefan Tauner]

On Tue, 12 Sep 2017 13:44:31 +0200
Matthias Apitz  wrote:
> Hello,
>
> This is with flashrom of FreeBSD CURRENT amd64.
>
> The background: To be able to install and boot FreeBSD on an Acer C720
> Chromebook, one must tweak some bits in the BIOS and enable a so called
> LEGACY BIOS mode (after removing the hardware write protection of the
> BIOS). To do so, there are some tools within ChromeOS which allow this
> procedure, but after this you can not boot ChromeOS anymore (from the
> saved SSD) and so you can't use these tools within ChromeOS to switch
> the bits back.
>
> The tools to use are simple:
>
> # flashrom -p internal -i GBB -r bios.bin
> # futility gbb -s --flags=$flags bios.bin
> # flashrom -p host -i GBB --fast-verify -w bios.bin

According to these commands you want to use the chromiumos fork of
flashrom for this not the one provided by distributions or flashrom.org.
> Flashrom we have in the FreeBSD ports as sysutils/flashrom and it seems
> to works:
>
> $ flashrom -R
> flashrom v0.9.9-r1955 on FreeBSD 12.0-CURRENT (amd64)
> flashrom is free software, get the source code at https://flashrom.org
>
> $ flashrom -L | egrep -i 'acer|720|chro'
> Acer            V75-M                                   OK
> Acer            EM61SM/EM61PM                           OK
> GIGABYTE        GA-M720-US3                             OK
> MSI             MS-7207 (K8NGM2-L)                      OK      (autodetected)
> Acer       Aspire 1520         OK
> Acer       Aspire One          BAD
>
> $ flashrom -p internal -i GBB -r bios.bin
> flashrom v0.9.9-r1955 on FreeBSD 12.0-CURRENT (amd64)
> flashrom is free software, get the source code at https://flashrom.org
>
> Region requested (with -i "GBB"), but no layout data is available.
>
> What does this error message mean?

The vanilla flashrom expects a layout file to specify the address range.