[RFC] Expose HII package list via C variables

["Marvin Häuser" <mhaeuser@posteo.de>]

Good day everyone,

Currently, the HII package list is stored in a PE/COFF resource section 
[1]. I propose to store it in a C variable (byte array with a pointer to 
it and its size exposed) instead. DxeCore would have a guard to toggle 
the deprecated support for the automatic protocol installation. This has 
the following advantages:

1. Fixes BZ (incl. future toolchains): 
https://bugzilla.tianocore.org/show_bug.cgi?id=557
2. Universal method across all toolchains and output file formats
3. Saves error-prone parsing work
4. Saves protocol install/locate work, the data is available right away
5. The omission of a dedicated section can save space
6. Terse file formats can support this and remain terse :)
7. Removes a dependency on the PE/COFF format specifically

A *very rough* PoC diff can be found here: 
https://github.com/mhaeuser/edk2/compare/master...wip_hii_cvar
If the feedback is positive, I will clean it up of course. OVMF boots 
with everything working fine.

I'd explicitly like feedback on the following:
A. Is this an acceptable solution to BZ 557 (Andrew?)?
B. Is this an acceptable solution for the "HII workflow" (MdeModule 
maintainers?)?
C. Is it acceptable to make support UEFI-side support for the old 
mechanism optional (Stewards?)?
D. Can an acceptable alternative be found for the removed ShellPkg code 
(Shell maintainers?)?

As you can see the BaseTools part also is rough, but that is more a 
question of "how" rather than "whether", so I'll postpone asking about it.

Thanks for your time and feedback!

Best regards,
Marvin


[1] "Once the image is loaded, LoadImage() installs 
EFI_HII_PACKAGE_LIST_PROTOCOL on the handle if
the image contains a custom PE/COFF resource with the type 'HII'."
- UEFI 2.9, 7.4, "EFI_BOOT_SERVICES.LoadImage()"