Extend struct tpm_buf to support sized buffers (TPM2B)

This patch set extends struct tpm_buf to support TPM2 sized buffers, and adds reader functions for parsing more complex response data. It is implemented to support smooth landing of [2]. Sealing of the TPM2 trusted keys is updated to utilize the new functionality, and thus provides a legit test case for it.

TPM2 sized buffer, i.e. the buffers in TPM2 format, are defined in the section 10.4 of the TPM2 Structures [1] specification.

Here's the smoke test that I've run for TPM2:

/usr/lib/kselftests/run_kselftest.sh
tpm2_createprimary --hierarchy o -G rsa2048 -c key.ctxt tpm2_evictcontrol -c key.ctxt 0x81000001
keyctl add trusted kmk "new 32 keyhandle=0x81000001" @u keyctl add encrypted 1000100010001000 "new ecryptfs trusted:kmk 64" @u

[1] https://trustedcomputinggroup.org/resource/tpm-library-specification/
[2] https://lore.kernel.org/linux-integrity/[email protected]/

v6:
- 7/8: fixed off-by-one error in the boundary check
v5:
- Fixed glitch in tpm_buf_read() reported by James Bottomley to the v4. Was forgotten from v4.
- Remove a spurious memset() call introduced in v4.
- Allow command buffer tag to be initially set to zero (caused spurious warnings).
v4:
- Cleaned up the bit too spread code changes based on the v3 review.
- For testing instructions see the previous cover letter, and use linux-v6.6.y branch:
https://lore.kernel.org/linux-integrity/[email protected]/
v3:
- Resend with rebase to the latest upstream.

James Bottomley (1):
tpm: Move buffer handling from static inlines to real functions

Jarkko Sakkinen (7):
tpm: Remove unused tpm_buf_tag()
tpm: Remove tpm_send()
tpm: Update struct tpm_buf documentation comments
tpm: Store the length of the tpm_buf data separately.
tpm: TPM2B formatted buffers
tpm: Add tpm_buf_read_{u8,u16,u32}
KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers

 drivers/char/tpm/Makefile                 |   1 +
 drivers/char/tpm/tpm-buf.c                | 222 ++++++++++++++++++++++
 drivers/char/tpm/tpm-interface.c          |  26 +--
 include/keys/trusted_tpm.h                |   2 -
 include/linux/tpm.h                       | 112 +++--------
 security/keys/trusted-keys/trusted_tpm1.c |  23 ++-
 security/keys/trusted-keys/trusted_tpm2.c |  54 +++---
 7 files changed, 295 insertions(+), 145 deletions(-)
 create mode 100644 drivers/char/tpm/tpm-buf.c

2.43.0