ARM: Make it possible to use a custom bootblock implementation.

Tegra needs to use a custom bootblock implementation because it starts on a
coprocessor which uses ARMv4. It doesn't have the same control registers,
caches, etc., and the regular bootblock gets exceptions and dies.

TEST=Built for pit. With this and other changes, built and booted on nyan and
verified that it got into the bootblock.

Change-Id: Id197db2939bc840ad64244d6e2017fc5c89e0cbd
Signed-off-by: Gabe Black <>
Reviewed-by: Ronald Minnich <>
Commit-Queue: Gabe Black <>
Tested-by: Gabe Black <>
2 files changed