Messages in this thread | | | Date | Sun, 14 Dec 2014 11:09:18 -0500 | From | Stefan Berger <> | Subject | Re: [PATCH v10 8/8] tpm: TPM 2.0 FIFO Interface |
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On 12/14/2014 10:40 AM, Jarkko Sakkinen wrote: > On Sun, Dec 14, 2014 at 09:48:26AM -0500, Stefan Berger wrote: >> On 12/12/2014 02:46 PM, Jarkko Sakkinen wrote: >>> Detect TPM 2.0 by sending idempotent TPM 2.x command. Ordinals for >>> TPM 2.0 are higher than TPM 1.x commands so this should be fail-safe. >>> Using STS3 is unreliable because some chips just report 0xff and not >>> what the spec says. >> TPM TIS 1.2 can report either 0xff or 0x00 for sts3 since that part of >> register was not defined for this version but only for a later version. So, >> unless the TIS 1.3 for TPM 2.0 is broken, it should report a bit _pattern_ >> (not plain 0x00 or 0xff) that you could apply the suggested mask to and >> check then. > I propose this: lets keep the bit ugly but approach for now and when > there are TPM2 FIFOs available in the market move to your workaround. > I think that would be the most reasonable middle road here.
You are now calling tpm2_gen_interrupt and are looking at the rc, which is the rc from tpm_transmit_cmd, which seems to make sure that the sending of the command went alright and the reception of the response. Is this good enough to distinguish between a TPM 2 and a TPM 1.2? If you send a valid TPM 2 command to a TPM 1.2 this will at least transmit the data ok, but the TPM will respond with a TPM 1.2 tag in the response. The way I understand the code, the rc does not include whether the response packet is a valid TPM 2 response packet and lets you conclude to a TPM2. I do something similar in upcoming QEMU patches where I send a valid TPM2 command for probing and if the tag(!) in the response is a TPM2 tag (0x8001 = TPM_ST_NO_SESSIONS), then it's a TPM 2, otherwise a TPM 1.2.
Did you test this with a TPM 1.2 ?
Stefan
> >> Stefan > /Jarkko >
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