It appears that xorriso 1.2.6 may produce a hybrid image[1] that exhibits weird behaviour during an attempt to boot it with UEFI firmware (both OVMF within kvm and 2.3.1/2.0 within hardware).

The lesser problems would look like partially missing refind icons; the worse ones would result in shim not showing up at all (the 0.4 build which emits at least some messages in any case).

It was found out that 32 Mb limit seems to be lurking somewhere as 32604160 bytes long image would boot fine but 33554432 bytes long one would hang.

Inspecting these with /sbin/fsck.vfat -n -l[2] shows the directory/file order which looks like explanatory for the phenomenon that some builds would have EFI/BOOT directory appear empty (as in "totally empty", not even . and ..) when in fallback EFI shell inside OVMF, and some would have that directory contents appear OK but trying to run a binary by hand would result in "Error Reported: Not Found" message (slightly depends on dosfstools version used, 3.0.23/3.0.11/3.0.24 have been tested).

xorriso-1.3.4 (or rather libisofs-1.3.4) appears to fix this kind of problem, or at least avoiding the worst case so far.

This is a "note" kind of bug posted while the information is not forgotten.

[1] http://git.altlinux.org/people/mike/packages/?p=mkimage.git;a=blob;f=tools/mki-pack-isoboot;h=85ca988c6aab94e3c44e64519baf2231e39d8d24;hb=HEAD#l77
[2] http://fly.osdn.org.ua/~mike/tmp/efiboot/