[coreboot-gerrit] Change in coreboot[master]: cpu/x86/smm: Add sinkhole mitigation to relocatable smmstub

[Arthur Heymans (Code Review)]

Hello Aaron Durbin, build bot (Jenkins), Patrick Georgi, Martin Roth,

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

https://review.coreboot.org/c/coreboot/+/37289

to look at the new patch set (#3).

Change subject: cpu/x86/smm: Add sinkhole mitigation to relocatable smmstub
......................................................................

cpu/x86/smm: Add sinkhole mitigation to relocatable smmstub

This adds a check for LAPIC base twice. There is a very early check
when the CPU is still executing in real mode checks if the LAPIC base
is inside the region [smmbase,smmbase + SMM_DEFAULT_SIZE). The CPU
cannot use anything but a hardcoded size since even accessing the
relocatable parameters is impossible in the state of the CPU.

The actual SMI handler is located above smmbase + SMM_DEFAULT_SIZE and
before jumping to it the LAPIC base is checked against the whole SMM
region. Given that we have a working stack at this point, this is done
in C code.

UNTESTED.

Change-Id: I49927c4f4218552b732bac8aae551d845ad7f079
Signed-off-by: Arthur Heymans 
---
M src/cpu/x86/smm/Makefile.inc
A src/cpu/x86/smm/sinkhole.c
M src/cpu/x86/smm/smm_stub.S
M src/include/cpu/x86/smm.h
4 files changed, 84 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/89/37289/3