This patch set adds verifier support for annotating user's global BPF subprog
arguments with few commonly requested annotations, to improve global subprog
verification experience.
These tags are:
- ability to annotate a special PTR_TO_CTX argument;
- ability to annotate a generic PTR_TO_MEM as non-null;
- ability to annotate special PTR_TO_PACKET, PTR_TO_PACKET_END, and
PTR_TO_PACKET_META pointers for networking programs;
- ability to annotate argument as CONST_PTR_TO_DYNPTR to pass generic
dynptrs into global subprogs, for use cases that deal with variable-sized
generic memory pointers.
We utilize btf_decl_tag attribute for this and provide few helper macros as
part of bpf_helpers.h in libbpf (patch #12).
Patches #1 and #2 are tiny improvements to verifier log, printing relevant
information for PTR_TO_MEM and dynptr. Those missing pieces came up during
development of this patch set.
Big chunk of the patch set (patches #3 through #9) are various refactorings to
make verifier internals around global subprog validation logic easier to
extend and support long term, eliminating BTF parsing logic duplication,
factoring out argument expectation definitions from BTF parsing, etc.
New functionality is added in patch #10 (ctx, non-null, pkt pointers) and
patch #11 (dynptr), extending global subprog checks with awareness for arg
tags.
Patch #12 adds simple macro helpers for arg tags to standardize their usage
across BPF code base.
Patch #13 adds simple tests validating each of the added tags.
Andrii Nakryiko (13):
bpf: log PTR_TO_MEM memory size in verifier log
bpf: emit more dynptr information in verifier log
bpf: tidy up exception callback management a bit
bpf: use bitfields for simple per-subprog bool flags
bpf: abstract away global subprog arg preparation logic from reg state
setup
bpf: remove unnecessary and (mostly) ignored BTF check for main
program
bpf: prepare btf_prepare_func_args() for handling static subprogs
bpf: move subprog call logic back to verifier.c
bpf: reuse subprog argument parsing logic for subprog call checks
bpf: support 'arg:xxx' btf_decl_tag-based hints for global subprog
args
bpf: add dynptr global subprog arg tag support
libbpf: add __arg_xxx macros for annotating global func args
selftests/bpf: add global subprog annotation tests
include/linux/bpf.h | 12 +-
include/linux/bpf_verifier.h | 41 ++-
kernel/bpf/btf.c | 291 +++++-------------
kernel/bpf/log.c | 29 +-
kernel/bpf/verifier.c | 221 +++++++++++--
tools/lib/bpf/bpf_helpers.h | 9 +
.../selftests/bpf/prog_tests/log_fixup.c | 4 +-
.../selftests/bpf/progs/cgrp_kfunc_failure.c | 2 +-
.../selftests/bpf/progs/task_kfunc_failure.c | 2 +-
.../selftests/bpf/progs/test_global_func5.c | 2 +-
.../bpf/progs/verifier_global_subprogs.c | 134 +++++++-
11 files changed, 459 insertions(+), 288 deletions(-)
--
2.34.1
