[0/1] add sysfs exports for TPM 2 PCR registers

Message

James Bottomley July 20, 2020, 3 p.m. UTC

At last year's plumbers conference it was agreed in principle to
export TPM 2 PCRs via sysfs.  We also agreed we should conform to
sysfs rules of one value per file, which rules out the "pcrs" file
format of TPM 1.2 which has every PCR value in the same file.

I added these files using device groups, so one group per bank hash of
the TPM.  Using an emulator which supports a variety of hashes, you
can see the structure of the group files:

root@testdeb:~# ls -F /sys/class/tpm/tpm0/
dev      pcr-sha1/    pcr-sha384/  power/      tpm_version_major
device@  pcr-sha256/  pcr-sha512/  subsystem@  uevent

As a future enhancement, we could use the group is_visible function to
remove files corresponding to PCRs which don't exist.  The reason this
isn't present is that so far I've never seen a TPM with a missing PCR.

James

---

James Bottomley (1):
  tpm: add sysfs exports for all banks of PCR registers

 drivers/char/tpm/tpm-sysfs.c | 178 +++++++++++++++++++++++++++++++++++
 include/linux/tpm.h          |   8 +-
 2 files changed, 185 insertions(+), 1 deletion(-)