Re: [edk2-devel] measurement to command-line/initrd for loading kernel via -kernel option

["Lu, Ken" <ken.lu@intel.com>]

> >
> 
> Not fundamentally, no. But between the measurement of the image itself (which
> the firmware should do) and the measurement of the initrd and command line
> (which the EFI stub will do), I'm not sure there is that much left.


> In general, I think the combinatorial explosion of CC attestation protocols
> multiplied by the number of boot stages and loaders is going to be a concern.
> We really need some abstractions here.

[Lu, Ken]  I understand your now. It might looks reasonable if think 
- the LoadImage() is a common abstraction for all EFI application, so image itself should be measured by OVMF/BIOS.
- but kernel command and initrd stuff should belong to EFI stub, who has more knowledge of kernel booting than a general image loading.

> 
> > > However, there are corner cases that we would like to cover, such as
> > > booting Linux from the EFI shell.
> >
> > I remember Bottomley or someone mentioned to use CONFIG_CMDLINE and
> CONFIG_INITRAMFS_SOURCE, such as https://blog.decentriq.com/swiss-
> cheese-to-cheddar-securing-amd-sev-snp-early-boot-2/ for this corner case,
> especially for confidential container use case without grub.
> >
> > Or in general, any loader that
> > > knows how to load an image and pass a command line, but may not be
> > > aware of whether or which flavor of measured boot is being used by the
> platform.
> > >
> >
> > This is headache.... but if loader do not know, why kernel know? How to
> guarantee both loader and kernel know for consistent measurement results?
> >
> > > > In another side, "EFI stub" is bind to EFI boot protocol and "EFI
> > > > handover
> > > protocol" is deprecated in grub 2.06[2]. (CC to Daniel).
> > > >
> > >
> > > Apologies, I don't understand this sentence.
> >
> > May be I am wrong.  I mean whether "EFI stub" code is only valid for
> > "EFI handover protocol", or is it also valid for Linux 32bit/64bit
> > boot? See https://www.kernel.org/doc/html/latest/x86/boot.html
> > If it is only valid for "EFI handover protocol", then it is deprecated.
> 
> No it is not deprecated. The EFI handover protocol uses LoadImage() but not
> StartImage(). Instead, it jumps directly to an alternative entrypoint in the image
> which has a Linux/x86 specific prototype, and passes additional data.
> 
> > So "EFI stub" code for measurement will not work for Linux 32bit/64bit boot.
> 
> No you misunderstood. The EFI stub is an integral part of the boot flow. The
> only thing we deprecated is invoking it without going through StartImage().
[Lu, Ken] Thanks your clarification!