[PATCH] tpm: Add upgrade/reduced mode support for TPM1.2 modules

Stefan Mahnke-Hartmann
2022-06-01T08:35:38Z

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_MODE 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_MODE flag. This patch simply follows
the same rationale as TPM2 in field upgrade mode.

Signed-off-by: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@infineon.com>
---
If you have any better suggestions, please let me know.

drivers/char/tpm/tpm1-cmd.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index f7dc986fa4a0..7a42d74c450c 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -710,8 +710,10 @@ int tpm1_auto_startup(struct tpm_chip *chip)
goto out;
rc = tpm1_do_selftest(chip);
if (rc) {
- dev_err(&chip->dev, "TPM self test failed\n");
- goto out;
+ 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;
+ rc = 0;
}

return rc;
--
2.25.1