People reportedly want to compile the stub on i686 and AArch64
platforms for testing. Make compilation possible by providing proper
`make_instruction_cache_coherent` implementations on these platforms.
For x86 (just as x86_64), this is a no-op, because Intel made the
instruction cache coherent for compatibility with code that was written
before caches existed.
For AArch64, adapt the procedure from their manual to multiple
instructions.
Do not pass our own cmdline on to the kernel. It may have been set by a
malicious boot loader specification entry, and could instruct the
kernel to load an arbitrary unprotected initrd (or perform some other
fun stuff). Instead, always pass the command line built into the UKI,
which is properly authenticated.
When loading something with UEFI LoadImage, signature validation is
performed. However, we verify the kernel by its hash already, and don't
want to sign it. Hence, we have to load it on our own.
Alois Wohlschlager