Change in coreboot[master]: cpu/x86/smm_module_load: Rewrite setup_stub

[Arthur Heymans (Code Review)]

Attention is currently required from: Arthur Heymans.
Hello build bot (Jenkins), Jonathan Zhang, Angel Pons,

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

https://review.coreboot.org/c/coreboot/+/63478

to look at the new patch set (#5).

Change subject: cpu/x86/smm_module_load: Rewrite setup_stub
......................................................................

cpu/x86/smm_module_load: Rewrite setup_stub

This code was hard to read as it did too much and had a lot of state
to keep track of.

It also looks like the staggered entry points were first copied and
only later the parameters of the first stub w ere filled in. This
means that only the BSP stub is actually jumping to the permanent
smihandler. On the APs the stub would jump to wherever c_handler
happens to point to, which is likely 0. This effectively means that on
APs it's likely easy to have arbitrary code execution in SMM which is a
security problem.

Change-Id: I42ef9d6a30f3039f25e2cde975086a1365ca4182
Signed-off-by: Arthur Heymans 
---
M src/cpu/x86/smm/smm_module_loader.c
1 file changed, 21 insertions(+), 71 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/78/63478/5