Hi Alex,
how have you built the efi files for grub2? I tried to build them from master and from the commit you used in Genode [1]. If I run configure with --with-platform=efi some headers are missing for the build and if I configure without it grub-mkimage fails with error: no symbol table.
Regards,
JK
[1]: https://github.com/alex-ab/genode/commit/de98d57a85c3b1f5fd632f1dd14f2984867...