It is possible to install GNU Boot on I945 Thinkpads without opening
the computer even if the nonfree bios sets the bootblock region (the
last 64K of the flash chip) read-only.
The flash chip looks like that:
+----- -----+---------------------------+-------------------------+
| ... | Secondary bootblock (64k) | Primary bootblock (64k) |
+----- -----+---------------------------+-------------------------+
0 0x1e0000 2MiB
To bypass the read-only restriction we use an utility (bucts) that
tells the hardware to swap the primary bootblock with the secondary
one for the next boot. We then have to disable that swap and reflash
again.
CONFIG_INTEL_ADD_TOP_SWAP_BOOTBLOCK generates the two bootblocks
directly in coreboot so we don't need to use special commands to do
that anymore.
In addition the MacBook 1.1 and 2.1 are known not to have such
read-only restrictions so they don't need to have
CONFIG_INTEL_ADD_TOP_SWAP_BOOTBLOCK enabled.
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
Acked-by: Adrien 'neox' Bourmault <neox@gnu.org>
Denis 'GNUtoo' Carikli
585f4d359a
