With the changes proposed by rust-vmm/linux-loader#29, the test_badnote.bin and test_elfnote.bin binaries must be modified to use the correct name of "Xen" for the note header, as the PVH ABI specifies. I'm uploading the source files and the resulting binaries here. Built with:
gcc elfnote.S -s -nostdlib -o test_elfnote.bin
gcc badnote.S -s -nostdlib -o test_badnote.bin