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

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Message-ID: <aEhNnAxlToRMteA2@e129823.arm.com>
Date: Tue, 10 Jun 2025 16:22:04 +0100
From: Yeoreum Yun <yeoreum.yun@....com>
To: Jarkko Sakkinen <jarkko@...nel.org>
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

Hi Jarkko,

> > Unfortunately, when these components are built as built-in drivers,
> > the functions ffa_init(), tpm_crb_ffa_init(), and crb_acpi_driver_init() are
> > all executed during the device_initcall phase.
> > As a result, if crb_acpi_driver_init() is called before the ffa_device exists or
> > has been probed, it returns -EPROBE_DEFER,
>
> Please mention exactly this in the commit explicitly and then it should
> be in detail enough.

Okay. I'll add this in the next round in cover letter.

>
> > causing the probe to be deferred and retried later
> > during the deferred_probe_initcall phase.
>
> 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.
To generate boot_aggregate with TPM PCR values from 0 to 7,
the TPM-related modules must also be built-in and
properly initialized before init_ima(), which internally calls ima_init().

To ensure this, Patch #2 adds a routine to probe
the ffa_device() in tpm_crb_ffa_init().
This allows crb_acpi_driver_init() to successfully complete even if
it is called first, because tpm_crb_ffa_init() triggers
probing of the ffa_device via ffa_register() beforehand.

Thanks.
--
Sincerely,
Yeoreum Yun