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

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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@xxxxxxxx>
> ---
>  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




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