Change in coreboot[master]: arch/x86: Add support for catching null dereferences through debug regs

[Robert Zieba (Code Review)]

Attention is currently required from: Robert Zieba, Raul Rangel, Nico Huber, Tim Wawrzynczak, Paul Menzel, Arthur Heymans, Kyösti Mälkki, Karthik Ramasubramanian.
Hello build bot (Jenkins), Nico Huber, Raul Rangel, Angel Pons, Arthur Heymans, Tim Wawrzynczak, Kyösti Mälkki, Karthik Ramasubramanian,

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/63657

to look at the new patch set (#10).

Change subject: arch/x86: Add support for catching null dereferences through debug regs
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arch/x86: Add support for catching null dereferences through debug regs

This commit adds support for catching null dereferences and execution
through x86's debug registers. This is particularly useful when running
32-bit coreboot as paging is not enabled to catch these through page
faults. This commit adds three new configs to support this feature:
DEBUG_HW_BREAKPOINTS, DEBUG_NULL_DEREF_BREAKPOINTS and
DEBUG_NULL_DEREF_HALT.

BUG=b:223902046
TEST=Ran on nipperkin device, verifying that HW breakpoints work as
expected.

Change-Id: I113590689046a13c2a552741bbfe7668a834354a
Signed-off-by: Robert Zieba 
---
M src/arch/x86/Kconfig
M src/arch/x86/Makefile.inc
A src/arch/x86/breakpoint.c
M src/arch/x86/exception.c
A src/arch/x86/include/arch/breakpoint.h
A src/arch/x86/include/arch/null_breakpoint.h
A src/arch/x86/null_breakpoint.c
7 files changed, 454 insertions(+), 1 deletion(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/57/63657/10