linux-kernel - Re: [PATCH v2 0/2] fix failure of integration IMA with tpm_crb

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Message-ID: <aEqsX0hBKb7ZC1qZ@kernel.org>
Date: Thu, 12 Jun 2025 13:30:55 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: sudeep.holla@....com, peterhuewe@....de, jgg@...pe.ca,
	stuart.yoder@....com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-integrity@...r.kernel.org
Subject: Re: [PATCH v2 0/2] fix failure of integration IMA with tpm_crb_ffa

On Wed, Jun 11, 2025 at 06:36:02PM +0100, Yeoreum Yun wrote:
> Hi Jarkko,
> 
> > On Tue, Jun 10, 2025 at 04:22:04PM +0100, Yeoreum Yun wrote:
> > > > OK, if ffa_init() is leveled up in the initcall hierarchy, shouldn't
> > > > that be enough as long as ko's can be found from initramfs?
> > >
> > > As you mentioned, this is handled in Patch #1.
> > > However, although ffa_init() is called first,
> > > unless tpm_crb_ffa_init() is also invoked,
> > > crb_acpi_driver_init() will fail with -EPROBE_DEFER.
> > >
> > > Please note that IMA is always built-in and cannot be built as a module.
> >
> > Sure but if one needs IMA, then tpm_crb_ffa can be compiled as built-in
> > with zero code changes.
> 
> All of my describtion based on all things are built as "built-in".
> in case of ffa_init() changes the init level to root_initcall,
> so, the ffa_device will be produced first before the trial of TPM probe.
> 
> Note that tpm_crb_ffa_init() which is the "ffa_driver" is called in
> device_initcall level. I mean
> 
>     ffa_init() -> arm_ffa -> root_initcall
>     tpm_crb_ffa_init() -> device_initcall
>     crb_acpi_driver_init() -> device_initcall
> 
> therefore, "crb_acpi_driver_init()" can be call first before
> tpm_crb_ffa_init() since they're deployed in device_initcall.
> If this happen, "crb_acpi_driver_init()" failed with -EPROBE_DEFER.
> 
> That's why this patch is required to probe "tpm_crb_ffa" when
> crb_acpi_driver_init() called to complete the TPM device probe before
> IMA subsystem initailization.

Yep, and you sort it out by not compiling it as a module.

+	ret = ffa_register(&tpm_crb_ffa_driver);
+	BUG_ON(!ret && !tpm_crb_ffa);

These lines struck me in your patch. The commit message has nothing
about ffa_register().

Also, please remove BUG_ON(). That said, I don't think 2/2 is needed.

> 
> Thanks.
> 
> --
> Sincerely,
> Yeoreum Yun


BR, Jarkko