bpf-lsm: Extend interoperability with IMA

Extend the interoperability with IMA, to give wider flexibility for the
implementation of integrity-focused LSMs based on eBPF.

Patch 1 fixes some style issues.

Patches 2-4 gives the ability to eBPF-based LSMs to take advantage of the
measurement capability of IMA without needing to setup a policy in IMA
(those LSMs might implement the policy capability themselves).

Patches 5-6 allows eBPF-based LSMs to evaluate files read by the kernel.

Changelog

v1:
- Modify ima_file_hash() only and allow the usage of the function with the
  modified behavior by eBPF-based LSMs through the new function
  bpf_ima_file_hash() (suggested by Mimi)
- Make bpf_lsm_kernel_read_file() sleepable so that bpf_ima_inode_hash()
  and bpf_ima_file_hash() can be called inside the implementation of
  eBPF-based LSMs for this hook

Roberto Sassu (6):
  ima: Fix documentation-related warnings in ima_main.c
  ima: Always return a file measurement in ima_file_hash()
  bpf-lsm: Introduce new helper bpf_ima_file_hash()
  selftests/bpf: Add test for bpf_ima_file_hash()
  bpf-lsm: Make bpf_lsm_kernel_read_file() as sleepable
  selftests/bpf: Add test for bpf_lsm_kernel_read_file()

 include/uapi/linux/bpf.h                      | 11 +++++
 kernel/bpf/bpf_lsm.c                          | 21 +++++++++
 security/integrity/ima/ima_main.c             | 47 ++++++++++++-------
 tools/include/uapi/linux/bpf.h                | 11 +++++
 tools/testing/selftests/bpf/ima_setup.sh      |  2 +
 .../selftests/bpf/prog_tests/test_ima.c       | 30 ++++++++++--
 tools/testing/selftests/bpf/progs/ima.c       | 34 ++++++++++++--
 7 files changed, 132 insertions(+), 24 deletions(-)

-- 
2.32.0