Re: [PATCH v7 0/3] Add support for TPM devices over I2C bus

[Joel Stanley]

On Mon, 27 Mar 2023 at 11:11, Stefan Berger <stefanb@linux.ibm.com> wrote:
>
>
>
> On 3/26/23 21:05, Joel Stanley wrote:
> > Hi Ninad,
> >
> > On Sun, 26 Mar 2023 at 22:44, Ninad Palsule <ninad@linux.ibm.com> wrote:
> >>
> >> Hello,
> >>
> >> I have incorporated review comments from Stefan. Please review.
> >>
> >> This drop adds support for the TPM devices attached to the I2C bus. It
> >> only supports the TPM2 protocol. You need to run it with the external
> >> TPM emulator like swtpm. I have tested it with swtpm.
> >
> > Nice work. I tested these stop cedric's aspeed-8.0 qemu tree, using
> > the rainier machine and the openbmc dev-6.1 kernel.
> >
> > We get this message when booting from a kernel:
> >
> > [    0.582699] tpm_tis_i2c 12-002e: 2.0 TPM (device-id 0x1, rev-id 1)
> > [    0.586361] tpm tpm0: A TPM error (256) occurred attempting the self test
> > [    0.586623] tpm tpm0: starting up the TPM manually
> >
> > Do we understand why the error appears?
>
> The firmware did not initialize the TPM 2.

Which firmware are we talking about here?

In the case of these systems, we (u-boot+linux) are what would
traditionally be referred to as firmware.

> > # grep -r . /sys/class/tpm/tpm0/pcr-sha256/ | sort -n -k 7 -t /
> > /sys/class/tpm/tpm0/pcr-sha256/0:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/1:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/2:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/3:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/4:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/5:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/6:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/7:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/8:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/9:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/10:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/11:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/12:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/13:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/14:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/15:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/16:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/17:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/18:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/19:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/20:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/21:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/22:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/23:0000000000000000000000000000000000000000000000000000000000000000
> >
> > If I boot through the openbmc u-boot for the p10bmc machine, which
> > measures things into the PCRs:
> >
> > [    0.556713] tpm_tis_i2c 12-002e: 2.0 TPM (device-id 0x1, rev-id 1)
>
> In this case the firmware started up the TPM 2. Also the PCRs have been 
> touched by the firmware in this case.
>
> >
> > / # grep -r . /sys/class/tpm/tpm0/pcr-sha256/ | sort -n -k 7 -t /
> > /sys/class/tpm/tpm0/pcr-sha256/0:AFA13691EFC7BC6E189E92347F20676FB4523302CB957DA9A65C3430C45E8BCC
> > /sys/class/tpm/tpm0/pcr-sha256/1:37F0F710A5502FAE6DB7433B36001FEE1CBF15BA2A7D6923207FF56888584714
> > /sys/class/tpm/tpm0/pcr-sha256/2:E21B703EE69C77476BCCB43EC0336A9A1B2914B378944F7B00A10214CA8FEA93
> > /sys/class/tpm/tpm0/pcr-sha256/3:E21B703EE69C77476BCCB43EC0336A9A1B2914B378944F7B00A10214CA8FEA93
> > /sys/class/tpm/tpm0/pcr-sha256/4:E21B703EE69C77476BCCB43EC0336A9A1B2914B378944F7B00A10214CA8FEA93
> > /sys/class/tpm/tpm0/pcr-sha256/5:E21B703EE69C77476BCCB43EC0336A9A1B2914B378944F7B00A10214CA8FEA93
> > /sys/class/tpm/tpm0/pcr-sha256/6:E21B703EE69C77476BCCB43EC0336A9A1B2914B378944F7B00A10214CA8FEA93
> > /sys/class/tpm/tpm0/pcr-sha256/7:E21B703EE69C77476BCCB43EC0336A9A1B2914B378944F7B00A10214CA8FEA93
> > /sys/class/tpm/tpm0/pcr-sha256/8:AE67485BD01E8D6FE0208C46C473940173F66E9C6F43C75ABB404375787E9705
> > /sys/class/tpm/tpm0/pcr-sha256/9:DB99D92EADBB446894CB0C062AEB673F60DDAFBC62BC2A9CA561A13B31E5357C
> > /sys/class/tpm/tpm0/pcr-sha256/10:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/11:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/12:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/13:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/14:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/15:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/16:0000000000000000000000000000000000000000000000000000000000000000
> > /sys/class/tpm/tpm0/pcr-sha256/17:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/18:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/19:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/20:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/21:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/22:FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
> > /sys/class/tpm/tpm0/pcr-sha256/23:0000000000000000000000000000000000000000000000000000000000000000

> > However on a clean boot into the TPM, the u-boot tpm commands fail:
> >
> > ast# tpm info
> > tpm@2e v2.0: VendorID 0x1014, DeviceID 0x0001, RevisionID 0x01 [closed]
> > ast# tpINTERRUPT>
>
> Is this normal output? Is it an indication of some sort of IRQ?

Ignore that line, that was me using ctrl+c to cancel the input. I
should have trimmed it from the email before sending.

>
> > ast# tpm init
> > ast# tpm info
> > tpm@2e v2.0: VendorID 0x1014, DeviceID 0x0001, RevisionID 0x01 [open]
> > ast# tpm pcr_read 0 0x81000000
> > Error: 256
> > ast# md.l 0x81000000 16
> > 81000000: 00000000 00000000 00000000 00000000    ................
> > 81000010: 00000000 00000000 00000000 00000000    ................
> > 81000020: 00000000 00000000 00000000 00000000    ................
> > 81000030: 00000000 00000000 00000000 00000000    ................
> > 81000040: 00000000 00000000 00000000 00000000    ................
> > 81000050: 00000000 00000000                      ........
> >
> > This doesn't need to block merging into qemu, as the model works fine
> > for pcr measurement and accessing under Linux. However it would be
> > good to work though these issues in case there's a modelling
> > discrepancy.
>
>
> It reads the didvid and rid registers just fine and per the touched PCRs it 
> knows how to talk to the TPM 2 to extend the PCRs.

It hasn't done so in this case; the boot step that extends the PCRs
hasn't been executed.

> So this is strange. What is the 0x81000000 parameter in this command? Is it 
> some memory location?

Yes, it's an arbitrary DRAM location that we've asked u-boot to place
the contents of the PCR.

Cheers,

Joel