[PATCH v2] tpm: Allow committing non-volatile data

[Simon Glass]

Hi Ilias,

On Tue, 21 Feb 2023 at 06:58, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Hi Simon,
>
> On Mon, Feb 20, 2023 at 09:31:24AM -0700, Simon Glass wrote:
> > Add an option to tell the TPM to commit non-volatile data immediately it
> > is changed, rather than waiting until later. This is needed in some
> > situations, since if the device reboots it may not write the data.
> >
> > Add definitions for the rest of the Cr50 commands while we are here.
>
> This defines a function that's unused. IIRC you said U-Boot doesn't use it,
> but some code that run for that laptop does right?

Yes it is used by ChromeOS code which is not upstream at present.

> In any case the function declaration doesn't belong to the TPMv2 library.
> I think we are better off adding it to the cr50 driver itself.  I also

We cannot call tpm_sendrecv_command() from a TPM driver..it is in lib/
and that would be a violation of the software layers. This is a TPM2
command, even if it is specific to cr50.

> assume you compile u-boot in a 'special' way so the linker doesn't get rid
> of the emitted code?  Does t hat mean we can define it as __unused as well?

Nothing special, but this allows the ChromeOS code to build correctly.
I could also add a command to use it, if that helps?

Regards,
Simon

>
> Thanks
> /Ilias
> >
> > Signed-off-by: Simon Glass <sjg at chromium.org>
> > ---
> > I am resending this as I think it got lost.
> >
> > Changes in v2:
> > - Rebase to master
> >
> >  include/tpm-v2.h | 14 ++++++++++++++
> >  lib/tpm-v2.c     | 20 ++++++++++++++++++++
> >  2 files changed, 34 insertions(+)
> >
> > diff --git a/include/tpm-v2.h b/include/tpm-v2.h
> > index 8e90a616220..0a03994740d 100644
> > --- a/include/tpm-v2.h
> > +++ b/include/tpm-v2.h
> > @@ -712,4 +712,18 @@ u32 tpm2_submit_command(struct udevice *dev, const u8 *sendbuf,
> >   */
> >  u32 tpm2_cr50_report_state(struct udevice *dev, u8 *recvbuf, size_t *recv_size);
> >
> > +/*
> > + * tpm2_cr50_enable_nvcommits() - Tell Cr50 to commit NV data immediately
> > + *
> > + * For Chromium OS verified boot, we may reboot or reset at different times,
> > + * possibly leaving non-volatile data unwritten by the TPM.
> > + *
> > + * This vendor command is used to indicate that non-volatile data should be
> > + * written to its store immediately.
> > + *
> > + * @dev              TPM device
> > + * Return: result of the operation
> > + */
> > +u32 tpm2_cr50_enable_nvcommits(struct udevice *dev);
> > +
> >  #endif /* __TPM_V2_H */
> > diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
> > index bdf019b0f93..5fcd3649b74 100644
> > --- a/lib/tpm-v2.c
> > +++ b/lib/tpm-v2.c
> > @@ -699,3 +699,23 @@ u32 tpm2_cr50_report_state(struct udevice *dev, u8 *recvbuf, size_t *recv_size)
> >
> >       return 0;
> >  }
> > +
> > +u32 tpm2_cr50_enable_nvcommits(struct udevice *dev)
> > +{
> > +     u8 command_v2[COMMAND_BUFFER_SIZE] = {
> > +             /* header 10 bytes */
> > +             tpm_u16(TPM2_ST_NO_SESSIONS),           /* TAG */
> > +             tpm_u32(10 + 2),                        /* Length */
> > +             tpm_u32(TPM2_CR50_VENDOR_COMMAND),      /* Command code */
> > +
> > +             tpm_u16(TPM2_CR50_SUB_CMD_NVMEM_ENABLE_COMMITS),
> > +     };
> > +     int ret;
> > +
> > +     ret = tpm_sendrecv_command(dev, command_v2, NULL, NULL);
> > +     log_debug("ret=%s, %x\n", dev->name, ret);
> > +     if (ret)
> > +             return ret;
> > +
> > +     return 0;
> > +}
> > --
> > 2.39.2.637.g21b0678d19-goog
> >