[PATCH] KEYS: trusted: Fix trusted key backends when building as module

[Jarkko Sakkinen]

On Mon, Jul 19, 2021 at 09:10:01AM +0200, Ahmad Fatoum wrote:
> Hello Andreas,
> 
> On 16.07.21 10:17, Andreas Rammhold wrote:
> > Before this commit the kernel could end up with no trusted key sources
> > even thought both of the currently supported backends (tpm & tee) were
> > compoiled as modules. This manifested in the trusted key type not being
> > registered at all.
> 
> I assume (TPM) trusted key module use worked before the TEE rework? If so,
> 
> an appropriate Fixes: Tag would then be in order.
> 
> > When checking if a CONFIG_… preprocessor variable is defined we only
> > test for the builtin (=y) case and not the module (=m) case. By using
> > the IS_ENABLE(…) macro we to test for both cases.
> 
> It looks to me like you could now provoke a link error if TEE is a module
> and built-in trusted key core tries to link against trusted_key_tee_ops.
> 
> One solution for that IS_REACHABLE(). Another is to address the root cause,
> which is the inflexible trusted keys Kconfig description:
> 
> - Trusted keys despite TEE support can still only be built when TCG_TPM is enabled
> - There is no support to have TEE or TPM enabled without using those for
>   enabled trusted keys as well
> - As you noticed, module build of the backend has issues
> 
> I addressed these three issues in a patch[1], a month ago, but have yet to
> receive feedback.

Which of the patches is the bug fix?

/Jarkko