In case a TPM in failure mode is detected, the TPM should be accessible
through a transparent communication channel for analysing purposes (e.g.
TPM_GetTestResult) or a field upgrade. Since a TPM in failure mode has
similar reduced functionality as in field upgrade mode, the flag
TPM_CHIP_FLAG_FIRMWARE_UPGRADE is also valid.
As described in TCG TPM Main Part1 Design Principles, Revision 116,
chapter 9.2.1. the TPM also allows an update function in case a TPM is
in failure mode.
If the TPM in failure mode is detected, the function tpm1_auto_startup()
sets TPM_CHIP_FLAG_FIRMWARE_UPGRADE flag, which is used later during
driver initialization/deinitialization to disable functionality which
makes no sense or will fail in the current TPM state. The following
functionality is affected:
* Do not register TPM as a hwrng
* Do not get pcr allocation
* Do not register sysfs entries which provide information impossible to
obtain in limited mode
Signed-off-by: Stefan Mahnke-Hartmann <[email protected]>
---
Changelog:
* v2:
* Commit message updated.
* Error handling for failed self test and other errors seperated.
.
drivers/char/tpm/tpm.h | 1 +
drivers/char/tpm/tpm1-cmd.c | 9 +++++++--
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 2163c6ee0d36..c0778498bc41 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -56,6 +56,7 @@ enum tpm_addr {
#define TPM_ERR_DEACTIVATED 0x6
#define TPM_ERR_DISABLED 0x7
#define TPM_ERR_INVALID_POSTINIT 38
+#define TPM_ERR_FAILEDSELFTEST 0x1C
#define TPM_TAG_RQU_COMMAND 193
diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index f7dc986fa4a0..fe21679ba0b6 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -709,8 +709,13 @@ int tpm1_auto_startup(struct tpm_chip *chip)
if (rc)
goto out;
rc = tpm1_do_selftest(chip);
- if (rc) {
- dev_err(&chip->dev, "TPM self test failed\n");
+ if (rc == TPM_ERR_FAILEDSELFTEST) {
+ dev_err(&chip->dev, "TPM self test failed, so the TPM has limited functionality\n");
+ /* A TPM in this state possibly allows or needs a firmware upgrade */
+ chip->flags |= TPM_CHIP_FLAG_FIRMWARE_UPGRADE;
+ return 0;
+ } else if (rc) {
+ dev_err(&chip->dev, "TPM self test not successful\n");
goto out;
}
--
2.25.1
On Thu, Jun 02, 2022 at 06:13:01PM +0200, Stefan Mahnke-Hartmann wrote:
> In case a TPM in failure mode is detected, the TPM should be accessible
> through a transparent communication channel for analysing purposes (e.g.
> TPM_GetTestResult) or a field upgrade. Since a TPM in failure mode has
> similar reduced functionality as in field upgrade mode, the flag
> TPM_CHIP_FLAG_FIRMWARE_UPGRADE is also valid.
>
> As described in TCG TPM Main Part1 Design Principles, Revision 116,
> chapter 9.2.1. the TPM also allows an update function in case a TPM is
> in failure mode.
>
> If the TPM in failure mode is detected, the function tpm1_auto_startup()
> sets TPM_CHIP_FLAG_FIRMWARE_UPGRADE flag, which is used later during
> driver initialization/deinitialization to disable functionality which
> makes no sense or will fail in the current TPM state. The following
> functionality is affected:
> * Do not register TPM as a hwrng
> * Do not get pcr allocation
> * Do not register sysfs entries which provide information impossible to
> obtain in limited mode
>
> Signed-off-by: Stefan Mahnke-Hartmann <[email protected]>
> ---
> Changelog:
> * v2:
> * Commit message updated.
> * Error handling for failed self test and other errors seperated.
> .
> drivers/char/tpm/tpm.h | 1 +
> drivers/char/tpm/tpm1-cmd.c | 9 +++++++--
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 2163c6ee0d36..c0778498bc41 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -56,6 +56,7 @@ enum tpm_addr {
> #define TPM_ERR_DEACTIVATED 0x6
> #define TPM_ERR_DISABLED 0x7
> #define TPM_ERR_INVALID_POSTINIT 38
> +#define TPM_ERR_FAILEDSELFTEST 0x1C
>
> #define TPM_TAG_RQU_COMMAND 193
>
> diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> index f7dc986fa4a0..fe21679ba0b6 100644
> --- a/drivers/char/tpm/tpm1-cmd.c
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -709,8 +709,13 @@ int tpm1_auto_startup(struct tpm_chip *chip)
> if (rc)
> goto out;
> rc = tpm1_do_selftest(chip);
> - if (rc) {
> - dev_err(&chip->dev, "TPM self test failed\n");
> + if (rc == TPM_ERR_FAILEDSELFTEST) {
> + dev_err(&chip->dev, "TPM self test failed, so the TPM has limited functionality\n");
Given that returning to a legit state, as far as driver is concerned,
i.e. firmware upgrade mode, I would use the following warn here instead:
dev_warn(&chip->dev, "TPM self test failed, switching to the firmware upgrade mode\n");
It's a success state because you are returning zero.
> + /* A TPM in this state possibly allows or needs a firmware upgrade */
> + chip->flags |= TPM_CHIP_FLAG_FIRMWARE_UPGRADE;
> + return 0;
> + } else if (rc) {
> + dev_err(&chip->dev, "TPM self test not successful\n");
Why did you change the error message?
> goto out;
> }
>
> --
> 2.25.1
>
BR, Jarkko