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 were 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 <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63478
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>

0 files changed, 0 insertions, 0 deletions