Hi Marvin,
Your understanding of SecMigrationPei is correct. It is not ideal as
it's an unfamiliar pattern that could give the false impression that it
is a universal SEC migration solution, which it is not. But if platforms
understand that any additional data published in SecCore must be
explicitly migrated (potentially via library extension to
SecMigrationPei), it can be used to serve the SEC post-memory migration
role.
I assumed it was related to the reset vector due to the 16-bit
alignment. I think it would be great to have SecCore aligned properly if
possible.
Thanks,
Michael
On 8/14/2021 8:29 AM, Marvin Häuser wrote:
Hey Michael,
Thank you for your response! It was actually quicker than I imagined. :)
I think I understand, but please let me try to get this absolutely
right. Can I think of "SecMigrationPei" as a sort of "SecCorePostMem",
which either is loaded into permanent RAM directly or is shadowed
because it is a PEIM unlike SecCore - and it republishes all public
data, most especially PPIs, such that the entire PEI stage no longer
has any references to the original SecCore at all, and the SecCore
module basically just sits there in the ROM, and its exposed data is
either discarded or orphaned? Is that about right?
I think I hit the alignment issue of SecCore too, but only for X64
builds (likely just because the size happens to be lucky for IA32) of
OVMF. Pretty much sure it's just ResetVector positioning. What would
be the issue with moving the ResetVector into a separate component,
with its fixed position in FD (this is actually how UefiCpuPkg/VTF0
works), and having SecCore aligned correctly? Not specifically to
restore MigrateSecModulesInFv(), but as future-proofing to ensure
expected outputs. In fact, I noticed because my new PE loader code was
upset about the unaligned XIP load address.
Also thanks for your patch!
Best regards,
Marvin
On 13/08/2021 18:51, Michael Kubacki wrote:
Hi Marvin,
I apologize for the delayed response, I missed this message earlier.
The function was called from EvacuateTempRam() in the initial set of
patches:
[PATCH 1/6] MdeModulePkg/PeiCore: Enable T-RAM evacuation in PeiCore
(CVE-2019-11098) (groups.io)
<https://edk2.groups.io/g/devel/message/61823>
I was not involved in the patch series on the mailing list (job role
change at the time) but as a comment in that patch notes, there was
an inconsistency observed in PE32 section alignment in SEC modules. I
don't see where this was resolved other than the calls being removed
later in the series. SecCore migration would not occur implicitly in
the PeiCore flow but there is functionality for SEC data migration in
UefiCpuPkg/SecMigrationPei.
Based on what I see now, I'd be happy to send a patch to remove
MigrateSecModulesInFv().
Thanks,
Michael
On 8/7/2021 2:54 PM, Marvin Häuser wrote:
Good day everyone,
Good day Michael,
The commit that introduced T-RAM evacuation [1] also introduced the
function "MigrateSecModulesInFv()". It also is explicitly mentioned
as part of the control flow in the commit message. As far as I can
see, since then till today this function has never been called
anywhere. Was this some draft function that accidentally made it
into the patch, or did the caller get lost somewhere? The
description makes sense to me and I'm not experienced enough with
the PeiCore control flow to tell whether the PEIM migration somehow
covers SecCore implicitly. Also I noticed it only supports SecCore
in a PE/COFF section, not a TE section. Is there a rationale for that?
Thank you for your time!
Best regards,
Marvin
[1]
https://github.com/tianocore/edk2/commit/9bedaec05b7b8ba9aee248361bb61a85a26726cb
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