Running pieces of PEI from binary UEFI images

[Stefano Cristalli <stefanocristalli@gmail.com>]

Hello everyone,

I'm interested in experimenting with the PEI phase using EmulatorPkg,
OVMF and other EDKII parts that could be useful.
In particular, I'm interested in the possibility of integrating parts
of an existing pre-built binary UEFI image with such environments. If
the image was developed based on EDKII, would I expect things to work?
I'm not looking for complete emulation, I just think it would be
interesting to be able to single-step code inside PEIMs or even the
PeiCore from random images, leveraging the already existing EDKII
infrastructures (rather than switching to other debugging/emulation
projects).

I thought that the task might be feasible, since the layout of the
memory at the beginning of PEI and even the arguments passed to the
PeiCore are standardized... I should at least be able to begin
execution.

What do you think? Am I missing something?

Additionally, I would ask for technical help, as it's not clear to me
how exactly I would be able to load such modules. I saw that there is
the possibility of loading binaries inside an EDKII image build (cfr.
INF_Spec_1_25 section 2.7), but I don't understand how would I do this
for PEI binaries and if I could expect things to work (as in with only
the pointer to the image, without any additional information
specified).

I'd really appreciate if someone could give me some explanations to
clear my ideas about this. Some pointers to documentation would be
just fine, for it's quite complicated to figure out completely as an
EDKII beginner. "Dude, it's completely unfeasible" is also fine and
helpful as a response, if that's the case for some reason.

Thanks in advance.
Best regards.

Stefano Cristalli