Re: [tpm2] [tpm2-driver] Error at boot : A TPM error (256) occurred continue selftest

[Tricca, Philip B <philip.b.tricca at intel.com>]

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A bit more data on the "why": if the TPM receives a startup command when it is not required (TPM has *already* completed startup) then it will return TPM_RC_INITIALIZE (you can test this using the tpm2_startup command from tpm2-tools). By the time the kernel takes over the platform firmware should have already initialized the TPM. The kernel sends a startup command regardless since we have no guarantee that the firmware did what it was supposed to do. So in the common case the kernel will receive this RC in response to the Startup command.

Reporting this as an error is inaccurate but harmless. I'm not seeing this on my 4.19 kernel so this may have already been addressed upstream. Might be worth an email to the drivers maintainers if you can repro on a newer kernel.

Philip

-----Original Message-----
From: tpm2 [mailto:tpm2-bounces(a)lists.01.org] On Behalf Of Roberts, William C
Sent: 23 August, 2019 10:22
To: Gael GUEGAN <Gael.Guegan(a)non.se.com>; tpm2(a)lists.01.org; javierm(a)redhat.com
Subject: Re: [tpm2] [tpm2-driver] Error at boot : A TPM error (256) occurred continue selftest

You should be able to ignore that. But I am unsure of what is leading you to that state. Is someone Sending a selftest command before a startup command? The startup command, when not in field upgrade Mode, should be startup. So when the tpm initializes, it expects one of the first commands as described In the spec:
https://trustedcomputinggroup.org/wp-content/uploads/TPM-Rev-2.0-Part-1-Architecture-01.38.pdf

The first command sent to the tpm should be a startup command..... you can see that in Figure 5 on page 57 Of the spec above and described in detail in section 12.2.2

Bill

> -----Original Message-----
> From: tpm2 [mailto:tpm2-bounces(a)lists.01.org] On Behalf Of Gael GUEGAN
> Sent: Thursday, August 8, 2019 3:35 AM
> To: tpm2(a)lists.01.org; javierm(a)redhat.com
> Subject: [tpm2] [tpm2-driver] Error at boot : A TPM error (256) 
> occurred continue selftest
> 
> Hello all,
> 
> 
> 
> I am working with the linux kernel version 4.9 on an embedded target.
> 
> And I am having the following error message from the TPM driver at boot :
> 
> 
> 
> > $  dmesg | grep TPM
> 
> [    2.946137] tpm_tis_spi spi32766.0: 2.0 TPM (device-id 0x0, rev-id 78)
> 
> [    2.975824] tpm tpm0: A TPM error (256) occurred continue selftest
> 
> 
> 
> So I have seen that this error 256 correspond to TPM2_RC_INITIALIZE = 
> 0x0100, and that it is thrown  from this function
> <https://github.com/torvalds/linux/blob/v4.9/drivers/char/tpm/tpm-
> interface.c#L422>  (be32_to_cpu() when executing a tpm_transmit_cmd()).
> 
> 
> 
> However can someone explain why I am having this error ? Is it 
> possible that it is because I am trying to access to the TPM during 
> its initialization phase / selftest phase ?
> 
> Can I ignore this error without worry ?
> 
> 
> 
> 
> 
> Thank for your help,
> 
> 
> 
> 
> 
> Gael GUEGAN

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