On 07.06.23 10:25, Ilias Apalodimas wrote: > Hi Sumit, > > On Wed, 7 Jun 2023 at 10:25, Sumit Garg <sumit.garg@xxxxxxxxxx> wrote: >> >> Hi Ilias, >> >> On Wed, 7 Jun 2023 at 12:05, Ilias Apalodimas >> <ilias.apalodimas@xxxxxxxxxx> wrote: >>> >>> Hi Jan, >>> >>> [...] >>> >>>>>>>> >>>>> ... >>>>>>> >>>>>>> I think we have a probe ordering issue with this driver: >>>>>>> efivarfs_fill_super() may be called before the TEE bus was probed, thus >>>>>>> with the default efivar ops still registered. And that means >>>>>>> efivar_supports_writes() will return false, and the fs declares itself >>>>>>> as readonly. I've seen systemd mounting it r/o initialling, and you need >>>>>>> to remount the fs to enable writability. >>>>>>> >>>>>>> Is there anything that could be done to re-order things reliably, probe >>>>>>> the tee bus earlier etc.? >>>>>> >>>>>> This driver has a dependency on user-space daemon: tee-supplicant to >>>>>> be running for RPMB access. So once you start that daemon the >>>>>> corresponding device will be enumerated on the TEE bus and this driver >>>>>> probe will be invoked. So I would suggest you to load this daemon very >>>>>> early in the boot process or better to make it a part of initramfs. >>>>>> >>>>> >>>>> That is not the point, really. >>>>> >>>>> If this dependency exists, the code should be aware of that, and made >>>>> to work correctly in spite of it. Requiring a module to be part of >>>>> initramfs is not a reasonable fix. >>>> >>>> In fact, I've tested a non-modularized build as well, just to exclude >>>> that issue. The daemon dependency is more likely the problem here. >>>> >>>>> >>>>> IIUC, this also means that the efivar ops are updated while there is >>>>> already a client. This seems less than ideal as well >>> >>> As Sumit pointed out, the 'device' won't be available from OP-TEE >>> until the supplicant is up and running and as a result, the module >>> _probe() function won't run. Unfortunately, this isn't something we >>> can avoid since the supplicant is responsible for the RPMB writes. >>> The only thing I can think of is moving parts of the supplicant to the >>> kernel and wiring up the RPC calls for reading/writing data to the >>> eMMC subsystem. There was another discussion here [0] requesting the >>> same thing for different reasons. But unless I am missing something >>> this won't solve the problem completely either. You still have a >>> timing dependency of "when did the RT callbacks change" -- "when was >>> my efivarfs mounted". >> >> With the RPMB writes wired through the kernel [1], the only dependency >> left is when do you load the tee-stmm-efi driver to have real EFI >> runtime variables support. IMO, tee-stmm-efi driver should be built-in >> to support systems without initramfs. The distro installers may choose >> to bundle it in initramfs. Do you still see a timing dependency with >> this approach? > > No I don't, this will work reliably without the need to remount the efivarfs. > As you point out you will still have this dependency if you end up > building them as modules and you manage to mount the efivarfs before > those get inserted. Does anyone see a reasonable workaround? > Deceiving the kernel and making the bootloader set the RT property bit > to force the filesystem being mounted as rw is a nasty hack that we > should avoid. Maybe adding a kernel command line parameter that says > "Ignore the RTPROP I know what I am doing"? I don't particularly love > this either, but it's not unreasonable. In the context of https://github.com/OP-TEE/optee_os/issues/6094, basically this issue mapped on reboot/shutdown, I would really love to see the unhandy tee-supplicant daemon to be overcome. Jan -- Siemens AG, Technology Competence Center Embedded Linux
