On Tue, Sep 14, 2021 at 3:30 PM Yonghong Song <yhs@xxxxxx> wrote:
>
> LLVM14 added support for a new C attribute ([1])
> __attribute__((btf_tag("arbitrary_str")))
> This attribute will be emitted to dwarf ([2]) and pahole
> will convert it to BTF. Or for bpf target, this
> attribute will be emitted to BTF directly ([3], [4]).
> The attribute is intended to provide additional
> information for
> - struct/union type or struct/union member
> - static/global variables
> - static/global function or function parameter.
>
> This new attribute can be used to add attributes
> to kernel codes, e.g., pre- or post- conditions,
> allow/deny info, or any other info in which only
> the kernel is interested. Such attributes will
> be processed by clang frontend and emitted to
> dwarf, converting to BTF by pahole. Ultimiately
> the verifier can use these information for
> verification purpose.
>
> The new attribute can also be used for bpf
> programs, e.g., tagging with __user attributes
> for function parameters, specifying global
> function preconditions, etc. Such information
> may help verifier to detect user program
> bugs.
>
> After this series, pahole dwarf->btf converter
> will be enhanced to support new llvm tag
> for btf_tag attribute. With pahole support,
> we will then try to add a few real use case,
> e.g., __user/__rcu tagging, allow/deny list,
> some kernel function precondition, etc,
> in the kernel.
>
> In the rest of the series, Patches 1-2 had
> kernel support. Patches 3-4 added
> libbpf support. Patch 5 added bpftool
> support. Patches 6-10 added various selftests.
> Patch 11 added documentation for the new kind.
>
> [1] https://reviews.llvm.org/D106614
> [2] https://reviews.llvm.org/D106621
> [3] https://reviews.llvm.org/D106622
> [4] https://reviews.llvm.org/D109560
>
> Changelog:
> v2 -> v3:
> - put NR_BTF_KINDS and BTF_KIND_MAX into enum as well
> - check component_idx earlier (check_meta stage) in kernel
> - add more tests
> - fix misc nits
> v1 -> v2:
> - BTF ELF format changed in llvm ([4] above),
> so cross-board change to use the new format.
> - Clarified in commit message that BTF_KIND_TAG
> is not emitted by bpftool btf dump format c.
> - Fix various comments from Andrii.
>
> Yonghong Song (11):
> btf: change BTF_KIND_* macros to enums
> bpf: support for new btf kind BTF_KIND_TAG
> libbpf: rename btf_{hash,equal}_int to btf_{hash,equal}_int_tag
> libbpf: add support for BTF_KIND_TAG
> bpftool: add support for BTF_KIND_TAG
> selftests/bpf: test libbpf API function btf__add_tag()
> selftests/bpf: change NAME_NTH/IS_NAME_NTH for BTF_KIND_TAG format
> selftests/bpf: add BTF_KIND_TAG unit tests
> selftests/bpf: test BTF_KIND_TAG for deduplication
> selftests/bpf: add a test with a bpf program with btf_tag attributes
> docs/bpf: add documentation for BTF_KIND_TAG
>
> Documentation/bpf/btf.rst | 29 +-
> include/uapi/linux/btf.h | 55 ++-
> kernel/bpf/btf.c | 128 +++++
> tools/bpf/bpftool/btf.c | 12 +
> tools/include/uapi/linux/btf.h | 55 ++-
> tools/lib/bpf/btf.c | 84 +++-
> tools/lib/bpf/btf.h | 15 +
> tools/lib/bpf/btf_dump.c | 3 +
> tools/lib/bpf/libbpf.c | 31 +-
> tools/lib/bpf/libbpf.map | 2 +
> tools/lib/bpf/libbpf_internal.h | 2 +
> tools/testing/selftests/bpf/btf_helpers.c | 7 +-
> tools/testing/selftests/bpf/prog_tests/btf.c | 441 +++++++++++++++++-
> .../selftests/bpf/prog_tests/btf_tag.c | 14 +
> .../selftests/bpf/prog_tests/btf_write.c | 21 +
> tools/testing/selftests/bpf/progs/tag.c | 39 ++
> tools/testing/selftests/bpf/test_btf.h | 3 +
> 17 files changed, 869 insertions(+), 72 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/btf_tag.c
> create mode 100644 tools/testing/selftests/bpf/progs/tag.c
>
> --
> 2.30.2
>
I've acked every individual patch, but just to make it more clear, for
the series:
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
