On Mon, 4 Nov 2024 at 12:52, Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx> wrote: > > On 11/4/24 06:27, Ard Biesheuvel wrote: > > On Mon, 4 Nov 2024 at 12:18, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: > >> > >> On Mon Nov 4, 2024 at 12:57 PM EET, Daniel P. Smith wrote: > >>> On 11/2/24 14:00, Jarkko Sakkinen wrote: > >>>> On Sat Nov 2, 2024 at 5:22 PM EET, Jarkko Sakkinen wrote: > >>>>> It is not really my problem but I'm also wondering how the > >>>>> initialization order is managed. What if e.g. IMA happens to > >>>>> initialize before slmodule? > >>>> > >>>> The first obvious observation from Trenchboot implementation is that it > >>>> is 9/10 times worst idea ever to have splitted root of trust. Here it > >>>> is realized by an LKM for slmodule. > >>> > >>> First, there is no conflict between IMA and slmodule. With your change > >>> to make locality switching a one shot, the only issue would be if IMA > >>> were to run first and issue a locality switch to Locality 0, thus > >>> blocking slmodule from switching to Locality 2. As for PCR usage, IMA > >>> uses the SRTM PCRs, which are completely accessible under Locality 2. > >> > >> Just pointing out a possible problem (e.g. with TPM2_PolicyLocality). > >> > >>> Honestly, a better path forward would be to revisit the issue that is > >>> driving most of that logic existing, which is the lack of a TPM > >>> interface code in the setup kernel. As a reminder, this issue is due to > >>> the TPM maintainers position that the only TPM code in the kernel can be > >>> the mainline driver. Which, unless something has changed, is impossible > >>> to compile into the setup kernel due to its use of mainline kernel > >>> constructs not present in the setup kernel. > >> > >> I don't categorically reject adding some code to early setup. We have > >> some shared code EFI stub but you have to explain your changes > >> proeprly. Getting rejection in some early version to some approach, > >> and being still pissed about that years forward is not really way > >> to go IMHO. > >> > > > > Daniel has been nothing but courteous and patient, and you've waited > > 11 revision to come up with some bikeshedding patches that don't > > materially improve anything. > > > > So commenting on Daniel's approach here is uncalled for. > > > > Can we please converge on this? > > > > Daniel - if no component can be built as a module, there should be no > > reason for the set_default_locality() hook to be exported to modules > > right? And do we even need a sysfs node to expose this information? > > Hi Ard, > > The only reason off the top of my head of why it was exported was to > support the fact that the tpm module itself could be built as a module, > not that we were looking for it to be done so. > But the inclusion of the secure launch module will force the TPM module to be builtin too, surely. > As to sysfs, there is the TXT register content that we would like to > have exposed, and they should be readonly. For context to contrast with, > tboot user space utility txt-stat worked by trying to read the TXT > register address space via /dev/mem, think enough is said there. The > other purpose we used sysfs was management of the DRTM log. We used it > to provide a means to ensure the DRTM eventlog is extended when > measurements are sent to the DRTM PCRs and then to be able to retrieve > the final log. > I was referring specifically to the read-write sysfs node that permits user space to update the default TPM locality. Does it need to be writable? And does it need to exist at all?
