How to increase ukify PE header size?

[ragazenta]

I tried to add splash image to UKI with config file in mkosi.skeleton/etc/systemd/ukify.conf

[UKI]
Splash=/path/to/splash.bmp

Failed when make_uki:

# I've added some lines for debugging
Section: .osrel 712 + 40 vs 1024
Section: .cmdline 752 + 40 vs 1024
Section: .uname 792 + 40 vs 1024
Section: .splash 832 + 40 vs 1024
Section: .pcrpkey 872 + 40 vs 1024
Section: .initrd 912 + 40 vs 1024
Section: .sbat 952 + 40 vs 1024
Section: .pcrsig 952 + 40 vs 1024
Section: .linux 992 + 40 vs 1024
Traceback (most recent call last):
  File "/usr/bin/ukify", line 1669, in <module>
    main()
  File "/usr/bin/ukify", line 1658, in main
    make_uki(opts)
  File "/usr/bin/ukify", line 835, in make_uki
    pe_add_sections(uki, unsigned_output)
  File "/usr/bin/ukify", line 590, in pe_add_sections
    raise PEError(f'Not enough header space to add section {section.name}.')
PEError: Not enough header space to add section .linux.

[ragazenta]

I guess systemd efi stub version 252 is not compatible. It works fine in 254.