[PATCH v3 bpf-next 0/4] 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.

Patch #1 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 #2
adds arg:nullable 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 #3 adds libbpf-side __arg_trusted and __arg_nullable macros.

Patch #4 adds a bunch of tests validating __arg_trusted in combination with
__arg_nullable.

v2->v3:
  - went back to arg:nullable and __arg_nullable naming;
  - rebased on latest bpf-next after prepartory patches landed;
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 (4):
  bpf: add __arg_trusted global func arg tag
  bpf: add arg:nullable tag to be combined with trusted pointers
  libbpf: add __arg_trusted and __arg_nullable tag macros
  selftests/bpf: add trusted global subprog arg tests

 include/linux/bpf_verifier.h                  |   1 +
 kernel/bpf/btf.c                              | 109 ++++++++++--
 kernel/bpf/verifier.c                         |  24 +++
 tools/lib/bpf/bpf_helpers.h                   |   2 +
 .../selftests/bpf/prog_tests/verifier.c       |   2 +
 .../bpf/progs/verifier_global_ptr_args.c      | 156 ++++++++++++++++++
 6 files changed, 281 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c

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2.34.1