[PATCH v2 bpf-next 0/7] Trusted PTR_TO_BTF_ID arg support in global subprogs

[Andrii Nakryiko <andrii@kernel.org>]

This patch set follows recent changes that added btf_decl_tag-based argument
annotation support for global subprogs. This time we add ability to pass
PTR_TO_BTF_ID (BTF-aware kernel pointers) arguments into global subprograms.
We support explicitly trusted arguments only, for now.

First three patches are preparatory. Patches #1 and #3 does post-BPF token
code adjustments, to undo merge conflict avoidance measures. Patch #2 makes
PERF_EVENT type enforcement logic aligned with kernel-side logic.

Patch #4 adds logic for arg:trusted tag support on the verifier side. Default
semantic of such arguments is non-NULL, enforced on caller side. But patch #5
adds arg:maybe_null tag that can be combined with arg:trusted to make callee
explicitly do the NULL check, which helps implement "optional" PTR_TO_BTF_ID
arguments.

Patch #6 adds libbpf-side __arg_trusted and __arg_maybe_null macros. Patch #7
adds a bunch of tests validating __arg_trusted in combination with
__arg_maybe_null.

v1->v2:
  - added fix up to type enforcement changes, landed earlier;
  - dropped bpf_core_cast() changes, will post them separately, as they now
    are not used in added tests;
  - dropped arg:untrusted support (Alexei);
  - renamed arg:nullable to arg:maybe_null (Alexei);
  - and also added task_struct___local flavor tests (Alexei).

Andrii Nakryiko (7):
  libbpf: integrate __arg_ctx feature detector into kernel_supports()
  libbpf: fix __arg_ctx type enforcement for perf_event programs
  bpf: move arg:ctx type enforcement check inside the main logic loop
  bpf: add __arg_trusted global func arg tag
  bpf: add arg:maybe_null tag to be combined with trusted pointers
  libbpf: add __arg_trusted and __arg_maybe_null tag macros
  selftests/bpf: add trusted global subprog arg tests

 include/linux/bpf_verifier.h                  |   1 +
 kernel/bpf/btf.c                              | 130 +++++++++++----
 kernel/bpf/verifier.c                         |  24 +++
 tools/lib/bpf/bpf_helpers.h                   |   2 +
 tools/lib/bpf/features.c                      |  58 +++++++
 tools/lib/bpf/libbpf.c                        |  86 +++-------
 tools/lib/bpf/libbpf_internal.h               |   2 +
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 .../bpf/progs/verifier_global_ptr_args.c      | 156 ++++++++++++++++++
 9 files changed, 366 insertions(+), 95 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c

-- 
2.34.1