Re: [PATCH] tpm: Add Upgrade/Reduced mode support for TPM2 modules

[Borys Movchan <borysmn@axis.com>]

On 7/27/21 4:58 AM, Jarkko Sakkinen wrote:
> On Mon, Jul 19, 2021 at 03:37:17PM +0200, Borys Movchan wrote:
> > On some systems, especially embedded, TPM might start in
> > Upgrade/Reduced mode due to the previous failure of a firmware
> > upgrade process. Allow the TPM driver to handle such situations
> > properly. Enables a possibility for userspace application to
> > finalize TPM upgrade or recovery if required.
>
>
> Please add short explanation what you mean by upgrade/reduced mode.
>
> Maybe for clarity speak about upgrade mode.

I have send v2 patch with updated commit message and some notes.

Hope that would be more clear.

>
> >
> > Signed-off-by: Borys Movchan <borysmn@axis.com>
> > ---
> >  drivers/char/tpm/tpm-chip.c | 23 +++++++++++++++--------
> >  drivers/char/tpm/tpm2-cmd.c | 12 ++++++++++--
> >  include/linux/tpm.h         |  1 +
> >  3 files changed, 26 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index ddaeceb7e109..ff2367c447fb 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -574,20 +574,25 @@ static int tpm_get_pcr_allocation(struct 
> tpm_chip *chip)
> >  int tpm_chip_register(struct tpm_chip *chip)
> >  {
> >        int rc;
> > +     bool limited_mode = false;
> >
> >        rc = tpm_chip_start(chip);
> >        if (rc)
> >                return rc;
> >        rc = tpm_auto_startup(chip);
> > -     if (rc) {
> > +     if (rc == -EIO) {
> > +             limited_mode = true;
> > +     } else if (rc) {
> >                tpm_chip_stop(chip);
> >                return rc;
> >        }
> >
> > -     rc = tpm_get_pcr_allocation(chip);
> > -     tpm_chip_stop(chip);
> > -     if (rc)
> > -             return rc;
> > +     if (!limited_mode) {
> > +             rc = tpm_get_pcr_allocation(chip);
> > +             tpm_chip_stop(chip);
> > +             if (rc)
> > +                     return rc;
> > +     }
> >
> >        tpm_sysfs_add_device(chip);
> >
> > @@ -595,9 +600,11 @@ int tpm_chip_register(struct tpm_chip *chip)
> >
> >        tpm_add_ppi(chip);
> >
> > -     rc = tpm_add_hwrng(chip);
> > -     if (rc)
> > -             goto out_ppi;
> > +     if (!limited_mode) {
> > +             rc = tpm_add_hwrng(chip);
> > +             if (rc)
> > +                     goto out_ppi;
> > +     }
> >
> >        rc = tpm_add_char_device(chip);
> >        if (rc)
> > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> > index a25815a6f625..7468353ed67d 100644
> > --- a/drivers/char/tpm/tpm2-cmd.c
> > +++ b/drivers/char/tpm/tpm2-cmd.c
> > @@ -718,7 +718,8 @@ static int tpm2_startup(struct tpm_chip *chip)
> >   *                     sequence
> >   * @chip: TPM chip to use
> >   *
> > - * Returns 0 on success, < 0 in case of fatal error.
> > + * Returns 0 on success, -ENODEV in case of fatal error,
> > + *       -EIO in case of Reduced/Upgrade mode
> >   */
> >  int tpm2_auto_startup(struct tpm_chip *chip)
> >  {
> > @@ -729,7 +730,10 @@ int tpm2_auto_startup(struct tpm_chip *chip)
> >                goto out;
> >
> >        rc = tpm2_do_selftest(chip);
> > -     if (rc && rc != TPM2_RC_INITIALIZE)
> > +     if (rc == TPM2_RC_UPGRADE) {
> > +             rc = -EIO;
> > +             goto out;
> > +     } else if (rc && rc != TPM2_RC_INITIALIZE)
> >                goto out;
> >
> >        if (rc == TPM2_RC_INITIALIZE) {
> > @@ -743,6 +747,10 @@ int tpm2_auto_startup(struct tpm_chip *chip)
> >        }
> >
> >        rc = tpm2_get_cc_attrs_tbl(chip);
> > +     if (rc) { /* Succeeded until here, but failed -> reduced mode */
> > +             rc = -EIO;
> > +             goto out;
> > +     }
> >
> >  out:
> >        if (rc > 0)
> > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > index aa11fe323c56..e873c42907f0 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -207,6 +207,7 @@ enum tpm2_return_codes {
> >        TPM2_RC_INITIALIZE      = 0x0100, /* RC_VER1 */
> >        TPM2_RC_FAILURE         = 0x0101,
> >        TPM2_RC_DISABLED        = 0x0120,
> > +     TPM2_RC_UPGRADE         = 0x012D,
> >        TPM2_RC_COMMAND_CODE    = 0x0143,
> >        TPM2_RC_TESTING         = 0x090A, /* RC_WARN */
> >        TPM2_RC_REFERENCE_H0    = 0x0910,
> > --
> > 2.20.1
> >
> >
>
> /Jarkko

Kind regards,

Borys