Oftentimes knowing the class of exception is not enough and full ESR
value is needed to decode the specifics. Add code to print ESR as a
part of excpetion traceback to provide that information.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Data aborts can be masked using the data_abort_mask() function.
Add the missing pieces for functionality on aarch64 so that the
'md' command is safe to call even with faulting addresses.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

On a sync exception more useful information can be printed than we
currently do. Pass the ESR and FAR value to do_sync and print the
reason for the exception along with the address that actually faulted.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The Exception Syndrome Register (ESR) holds information over an
exception. This adds the strings necessary to dispatch this information.
Based on Linux code.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Implement stacktraces as a great debugging aid. On aarch64 this is cheap
enough to be enabled unconditionally. Unwinding code is taken from the
Kernel.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Do something useful in an exception and at least print the current
register contents.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The vectors are currently configured in arm_cpu_lowlevel_init(). This
shall be callable from PBL, but here the vectors are not available so
calling it from PBL will result in a linker error.
Move the vector setup to an initcall.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

The exception support for arm32 and aarch64 does not have much in
common. Move aarch64 exception support to a separate file to avoid
more ifdeffery.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>