Re: [RFC PATCH 0/4] Alternative TPM patches for Trenchboot

["Jarkko Sakkinen" <jarkko@kernel.org>]

On Sat Nov 2, 2024 at 5:22 PM EET, Jarkko Sakkinen wrote:
> It is not really my problem but I'm also wondering how the
> initialization order is managed. What if e.g. IMA happens to
> initialize before slmodule?

The first obvious observation from Trenchboot implementation is that it
is 9/10 times worst idea ever to have splitted root of trust. Here it
is realized by an LKM for slmodule.

So based on that usually a literal and unquestionable truth, when it
comes to securing platforms, the next question is how to make a single
atomic root of trust for Trenchboot.

There is really only one answer I think of for this it to make slmodule
part of the tpm_tis_core and also init order will be sorted out.

I'll describe the steps forward.

Step 1: declare and refactor that module into
drivers/char/tpm/tpm_tis_slmodule.c and add this to the Makefile:

ifdef CONFIG_SECURE_LAUNCH
obj-$(CONFIG_TCG_TIS_CORE) += tpm_tis_slmodule.o
endif

Step 2: add 'int kernel_locality;' to struct tpm_tis_data.
Step 3: implement tpm_tis_set_locality() internal function.
Step 4: drop sysfs-patch completely (solution is not generic).

BR, Jarkko