Re: [PATCH v4 1/1] tpm: add sysfs exports for all banks of PCR registers

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Aug 19, 2020 at 09:27:33AM -0400, Mimi Zohar wrote:
> On Wed, 2020-08-19 at 09:02 -0300, Jason Gunthorpe wrote:
> > On Tue, Aug 18, 2020 at 02:55:50PM -0400, Mimi Zohar wrote:
> > 
> > > The problem is that there isn't just one single userspace library or
> > > application for reading PCRs.  So now not only is there the kernel
> > > "boot_aggregate" regression testing, but regression testing of the tool
> > > itself to support multiple methods of reading the PCRs.
> > 
> > I was thinking just open code 
> >   open("/dev/tpm")
> >   write(read_pcrs_cmd)
> >   read(read_pcrs_cmd)
> >  
> > It isn't particularly hard to retrive the PCRs, don't really need to
> > depend on a library.
> 
> Ok, do you want to contribute it to ima-evm-utils?  While you're at it,
> do you also have code to parse the TPM 2.0 event log that you could
> contribute?
> 
> Seriously, we shouldn't be (re-)writing code to do this.

The kernel should not be used a dumping ground to work around a
dysfunctional userspace either. :(

You've basicaly said you can't rely on a sane userspace library
because *reasons* so we need to dump stuff in the kernel instead.

It is not a good justification to add new uAPI.

James seems to have the same basic conclusion too, unfortunately.

Jason