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Everything was going just fine until I made a vendor_db with 17kB of
sha256 sums in it. And then the same source tree that had worked fine
without that threw errors and failed all over the place. I wrote some
code to diagnose the problem, and of course it was a failure in
mirroring MokList to MokListRT.
As Patrick noted in 741c61abba7, some systems have obnoxiously low
amounts of variable storage available:
mok.c:550:import_mok_state() BS+RT variable info:
MaximumVariableStorageSize:0x000000000000DFE4
RemainingVariableStorageSize:0x000000000000D21C
MaximumVariableSize:0x0000000000001FC4
The most annoying part is that on at least this edk2 build,
SetVariable() /does actually appear to set the variable/, but it returns
EFI_INVALID_PARAMETER. I'm not planning on relying on that behavior.
So... yeah, the largest *volatile* (i.e. RAM only) variable this edk2
build will let you create is less than two pages. It's only got 7.9G
free, so I guess it's feeling like space is a little tight.
We're also not quite preserving that return code well enough for his
workaround to work.
New plan. We try to create variables the normal way, but we don't
consider not having enough space to be fatal. In that case, we create
an EFI_SECURITY_LIST with one sha256sum in it, with a value of all 0,
and try to add that so we're sure there's /something/ there that's
innocuous. On systems where the first SetVariable() /
QueryVariableInfo() lied to us, the correct variable should be there,
otherwise the one with the zero-hash will be.
We then also build a config table to hold this info and install that.
The config table is a packed array of this struct:
struct mok_variable_config_entry {
CHAR8 name[256];
UINT64 data_size;
UINT8 data[];
};
There will be N+1 entries, and the last entry is all 0 for name and
data_size. The total allocation size will always be a multiple of 4096.
In the typical RHEL 7.9 case that means it'll be around 5 pages.
It's installed with this guid:
c451ed2b-9694-45d3-baba-ed9f8988a389
Anything that can go wrong will.
Signed-off-by: Peter Jones <pjones@redhat.com>
Upstream: not yet, I don't want people to read this before Wednesday.
Signed-off-by: Peter Jones <pjones@redhat.com>
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