arm64: Print a char to UART early in exception handler

Over time our printk() seems to acquire more and more features... which
is nice, but it also makes it a little less robust when something goes
wrong. If the wrong global is trampled by some buffer overflow, it
suddenly doesn't print anymore. It would be nice to have at least some
way to tell that we triggered a real exception in that case.

With this patch, arm64 exceptions will print a '!' straight to the UART
before trying any of the more fancy printk() stuff. It's not much but it
should tell the difference between an exception and a hang and hopefully
help someone dig in the right direction sooner. This violates loglevels
(which is part of the point), but presumably when you have a fatal
exception you shouldn't care about that anymore.

Change-Id: I3b08ab86beaee55263786011caa5588d93bbc720
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37465
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

0 files changed, 0 insertions, 0 deletions