arm/arm64: Generalize bootblock C entry point

When we first added ARM support to coreboot, it was clear that the
bootblock would need to do vastly different tasks than on x86, so we
moved its main logic under arch/. Now that we have several more
architectures, it turns out (as with so many things lately) that x86 is
really the odd one out, and all the others are trying to do pretty much
the same thing. This has already caused maintenance issues as the ARM32
bootblock developed and less-mature architectures were left behind with
old cruft.

This patch tries to address that problem by centralizing that logic
under lib/ for use by all architectures/SoCs that don't explicitly
opt-out (with the slightly adapted existing BOOTBLOCK_CUSTOM option).
This works great out of the box for ARM32 and ARM64. It could probably
be easily applied to MIPS and RISCV as well, but I don't have any of
those boards to test so I'll mark them as BOOTBLOCK_CUSTOM for now and
leave that for later cleanup.

TEST=Built Jerry and Falco, booted Oak.

Change-Id: Ibbf727ad93651e388aef20e76f03f5567f9860cb
Signed-off-by: Julius Werner <>
Reviewed-by: Aaron Durbin <>
Tested-by: build bot (Jenkins)
27 files changed