linux-kernel - Re: [PATCH v4 1/2] fTPM: firmware TPM running in TEE

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Message-ID: <CAFA6WYMOjgHRw9RVrjherNo0ZNbTtEonPwSFFC0dT4CZO=A1NQ@mail.gmail.com>
Date:   Wed, 5 Jun 2019 16:39:36 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     peterhuewe@....de,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        jgg@...pe.ca, corbet@....net,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-doc@...r.kernel.org, linux-integrity@...r.kernel.org,
        Microsoft Linux Kernel List <linux-kernel@...rosoft.com>,
        Thirupathaiah Annapureddy <thiruan@...rosoft.com>,
        "Bryan Kelly (CSI)" <bryankel@...rosoft.com>,
        tee-dev@...ts.linaro.org
Subject: Re: [PATCH v4 1/2] fTPM: firmware TPM running in TEE

On Wed, 5 Jun 2019 at 01:39, Sasha Levin <sashal@...nel.org> wrote:
>
> On Tue, Jun 04, 2019 at 11:45:52AM +0530, Sumit Garg wrote:
> >On Thu, 30 May 2019 at 20:58, Sasha Levin <sashal@...nel.org> wrote:
> >> +       /* Open context with TEE driver */
> >> +       pvt_data->ctx = tee_client_open_context(NULL, ftpm_tee_match, NULL,
> >> +                                               NULL);
> >> +       if (IS_ERR(pvt_data->ctx)) {
> >> +               dev_err(dev, "%s:tee_client_open_context failed\n", __func__);
> >
> >Is this well tested? I see this misleading error multiple times as
> >follows although TEE driver works pretty well.
>
> Yes, this was all functionally tested.

Can you share your build instructions and testing approach?

>
> Why is this error message misleading? I'd be happy to fix it.

IIUC, here you are trying to resolve dependency with OP-TEE driver
using "-EPROBE_DEFER". So user shouldn't be prompted with error
messages until OP-TEE driver comes up.

BTW, for me this OP-TEE driver dependency seems not to work, boot is
simply stuck waiting for device. Probably the reason being this fTPM
driver is a platform driver and OP-TEE NOT a platform driver.

>
> >Module built with "CONFIG_TCG_FTPM_TEE=y"
> >
> >[    1.436878] ftpm-tee tpm@0: ftpm_tee_probe:tee_client_open_context failed
> >[    1.509471] ftpm-tee tpm@0: ftpm_tee_probe:tee_client_open_context failed
> >[    1.517268] ftpm-tee tpm@0: ftpm_tee_probe:tee_client_open_context failed
> >[    1.525596] ftpm-tee tpm@0: ftpm_tee_probe:tee_client_open_context failed
>
> Does the TEE have the fTPM implementation and such? Could you provide
> details about your testing environment (hardware, fTPM verions, etc)?
>

I just did a sanity check on my arm64 machine (Developerbox), just
adding following DT node and enabled CONFIG_TCG_FTPM_TEE=y:

+    tpm@0 {
+        compatible = "microsoft,ftpm";
+    };

Basically with no fTPM TA, I expected the driver to fail during
"tee_client_open_session()" call with TA not found error and boot
should continue. But it fails during "tee_client_open_context()" which
opens a context with OP-TEE driver and has nothing to do with fTPM TA.

-Sumit

> --
> Thanks,
> Sasha