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 and untrusted arguments. Legacy semi-trusted variant is not supported. Patches #2 through #4 do preparatory refactorings to add support for multiple tags per argument. This is important for being able to use modifiers like __arg_nonnull together with trusted/untrusted arguments. Patch #5 is adding the actual __arg_trusted and __arg_untrusted support. It also raises a question about default nullable vs non-nullable semantics for PTR_TO_BTF_ID arguments. It feels like having both __arg_nonnull and __arg_nullable would provide the best kind of experience and flexibility, but for now we implement nullable by default semantics, as a more conservative behavior. Patch #7 adds bpf_core_cast() helper macro which is a wrapper around bpf_rdonly_cast() kfunc, but hides BTF ID manipulations behind more user-friendly type argument instead. We utilize this macro in selftests added in patch #8. Patch #8 adds a bunch of positive and negative tests to validate expected semantics for various trusted/untrusted + nullable/non-null variants. We also make sure that global subprog cannot destroy PTR_TO_BTF_ID, as that would wreak havoc in caller program that is not aware of this possibility. There were proposals to do kernel-side type enforcement for __arg_ctx, let's decide whether we should do that and for which program types, and I can accommodate the logic in future revisions. Cc: Dave Marchevsky <davemarchevsky@xxxxxxxx> Andrii Nakryiko (8): selftests/bpf: fix test_loader check message bpf: make sure scalar args don't accept __arg_nonnull tag bpf: prepare btf_prepare_func_args() for multiple tags per argument bpf: support multiple tags per argument bpf: add __arg_trusted and __arg_untrusted global func tags libbpf: add __arg_trusted and __arg_untrusted annotation macros libbpf: add bpf_core_cast() macro selftests/bpf: add trusted/untrusted global subprog arg tests include/linux/bpf.h | 2 + include/linux/bpf_verifier.h | 1 + kernel/bpf/btf.c | 228 +++++++++++++----- kernel/bpf/verifier.c | 32 ++- tools/lib/bpf/bpf_core_read.h | 13 + tools/lib/bpf/bpf_helpers.h | 2 + tools/testing/selftests/bpf/bpf_kfuncs.h | 2 +- .../selftests/bpf/prog_tests/verifier.c | 2 + .../bpf/progs/nested_trust_failure.c | 2 +- .../bpf/progs/sk_storage_omem_uncharge.c | 2 - tools/testing/selftests/bpf/progs/type_cast.c | 4 +- .../bpf/progs/verifier_global_ptr_args.c | 160 ++++++++++++ tools/testing/selftests/bpf/test_loader.c | 2 +- 13 files changed, 387 insertions(+), 65 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c -- 2.34.1
