Merge tag 'tpmdd-next-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd

Pull TPM updates from Jarkko Sakkinen:
 "These are the changes for the TPM driver with a single major new
  feature: TPM bus encryption and integrity protection. The key pair on
  TPM side is generated from so called null random seed per power on of
  the machine [1]. This supports the TPM encryption of the hard drive by
  adding layer of protection against bus interposer attacks.

  Other than that, a few minor fixes and documentation for tpm_tis to
  clarify basics of TPM localities for future patch review discussions
  (will be extended and refined over times, just a seed)"

Link: https://lore.kernel.org/linux-integrity/20240429202811.13643-1-James.Bottomley@HansenPartnership.com/ [1]

* tag 'tpmdd-next-6.10-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd: (28 commits)
  Documentation: tpm: Add TPM security docs toctree entry
  tpm: disable the TPM if NULL name changes
  Documentation: add tpm-security.rst
  tpm: add the null key name as a sysfs export
  KEYS: trusted: Add session encryption protection to the seal/unseal path
  tpm: add session encryption protection to tpm2_get_random()
  tpm: add hmac checks to tpm2_pcr_extend()
  tpm: Add the rest of the session HMAC API
  tpm: Add HMAC session name/handle append
  tpm: Add HMAC session start and end functions
  tpm: Add TCG mandated Key Derivation Functions (KDFs)
  tpm: Add NULL primary creation
  tpm: export the context save and load commands
  tpm: add buffer function to point to returned parameters
  crypto: lib - implement library version of AES in CFB mode
  KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers
  tpm: Add tpm_buf_read_{u8,u16,u32}
  tpm: TPM2B formatted buffers
  tpm: Store the length of the tpm_buf data separately.
  tpm: Update struct tpm_buf documentation comments
  ...

1 files changed, 46 insertions, 0 deletions

diff --git a/Documentation/security/tpm/tpm_tis.rst b/Documentation/security/tpm/tpm_tis.rst
new file mode 100644
index 000000000000..b9637f295638
--- /dev/null
+++ b/Documentation/security/tpm/tpm_tis.rst
@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
+TPM FIFO interface driver
+=========================
+
+TCG PTP Specification defines two interface types: FIFO and CRB. The former is
+based on sequenced read and write operations,  and the latter is based on a
+buffer containing the full command or response.
+
+FIFO (First-In-First-Out) interface is used by the tpm_tis_core dependent
+drivers. Originally Linux had only a driver called tpm_tis, which covered
+memory mapped (aka MMIO) interface but it was later on extended to cover other
+physical interfaces supported by the TCG standard.
+
+For historical reasons above the original MMIO driver is called tpm_tis and the
+framework for FIFO drivers is named as tpm_tis_core. The postfix "tis" in
+tpm_tis comes from the TPM Interface Specification, which is the hardware
+interface specification for TPM 1.x chips.
+
+Communication is based on a 20 KiB buffer shared by the TPM chip through a
+hardware bus or memory map, depending on the physical wiring. The buffer is
+further split into five equal-size 4 KiB buffers, which provide equivalent
+sets of registers for communication between the CPU and TPM. These
+communication endpoints are called localities in the TCG terminology.
+
+When the kernel wants to send commands to the TPM chip, it first reserves
+locality 0 by setting the requestUse bit in the TPM_ACCESS register. The bit is
+cleared by the chip when the access is granted. Once it completes its
+communication, the kernel writes the TPM_ACCESS.activeLocality bit. This
+informs the chip that the locality has been relinquished.
+
+Pending localities are served in order by the chip in descending order, one at
+a time:
+
+- Locality 0 has the lowest priority.
+- Locality 5 has the highest priority.
+
+Further information on the purpose and meaning of the localities can be found
+in section 3.2 of the TCG PC Client Platform TPM Profile Specification.
+
+References
+==========
+
+TCG PC Client Platform TPM Profile (PTP) Specification
+https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/