netdev - Re: [PATCH v6 bpf-next 0/9] bpf: Add d_path helper

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Date:   Fri, 10 Jul 2020 13:46:02 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v6 bpf-next 0/9] bpf: Add d_path helper - preparation changes

On Fri, Jul 10, 2020 at 12:38 PM Jiri Olsa <jolsa@...nel.org> wrote:
>
> hi,
> this patchset does preparation work for adding d_path helper,
> which still needs more work, but the initial set of patches
> is ready and useful to have.
>
> This patchset adds:
>   - support to generate BTF ID lists that are resolved during
>     kernel linking and usable within kernel code with following
>     macros:
>
>       BTF_ID_LIST(bpf_skb_output_btf_ids)
>       BTF_ID(struct, sk_buff)
>
>     and access it in kernel code via:
>       extern u32 bpf_skb_output_btf_ids[];
>
>   - resolve_btfids tool that scans elf object for .BTF_ids
>     section and resolves its symbols with BTF ID values
>   - resolving of bpf_ctx_convert struct and several other
>     objects with BTF_ID_LIST
>
> v6 changes:
>   - added acks
>   - added general make rule to resolve_btfids Build [Andrii]
>   - renamed .BTF.ids to .BTF_ids [Andrii]
>   - added --no-fail option to resolve_btfids [Andrii]
>   - changed resolve_btfids test to work over BTF from object
>     file, so we don't depend on vmlinux BTF [Andrii]
>   - fixed few typos [Andrii]
>   - fixed the out of tree build [Andrii]
>
> Also available at:
>   https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
>   bpf/d_path
>
> thanks,
> jirka
>
>
> ---

You've missed fixing bpf_get_task_stack_proto with your
BTF_IDS_LIST/BTF_ID macro. It's currently failing in subtests. With
BTF_IDS_LIST/BTF_ID trivial fix it works again. Please fix that before
this can be applied.

btf_data.c could also use some name-conflicting entries, just to make
sure that kind (struct vs typedef) is taken into account. Maybe just
add some dummy `typedef int S;` or something?

So with the above, please add for the next revision:

Acked-by: Andrii Nakryiko <andriin@...com>
Tested-by: Andrii Nakryiko <andriin@...com>

> Jiri Olsa (9):
>       bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object
>       bpf: Compile resolve_btfids tool at kernel compilation start
>       bpf: Add BTF_ID_LIST/BTF_ID/BTF_ID_UNUSED macros
>       bpf: Resolve BTF IDs in vmlinux image
>       bpf: Remove btf_id helpers resolving
>       bpf: Use BTF_ID to resolve bpf_ctx_convert struct
>       bpf: Add info about .BTF_ids section to btf.rst
>       tools headers: Adopt verbatim copy of btf_ids.h from kernel sources
>       selftests/bpf: Add test for resolve_btfids
>
>  Documentation/bpf/btf.rst                               |  36 +++++
>  Makefile                                                |  25 +++-
>  include/asm-generic/vmlinux.lds.h                       |   4 +
>  include/linux/btf_ids.h                                 |  87 ++++++++++++
>  kernel/bpf/btf.c                                        | 103 ++------------
>  kernel/trace/bpf_trace.c                                |   9 +-
>  net/core/filter.c                                       |   9 +-
>  scripts/link-vmlinux.sh                                 |   6 +
>  tools/Makefile                                          |   3 +
>  tools/bpf/Makefile                                      |   9 +-
>  tools/bpf/resolve_btfids/Build                          |  10 ++
>  tools/bpf/resolve_btfids/Makefile                       |  77 +++++++++++
>  tools/bpf/resolve_btfids/main.c                         | 721 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tools/include/linux/btf_ids.h                           |  87 ++++++++++++
>  tools/include/linux/compiler.h                          |   4 +
>  tools/testing/selftests/bpf/Makefile                    |  14 +-
>  tools/testing/selftests/bpf/prog_tests/resolve_btfids.c | 107 ++++++++++++++
>  tools/testing/selftests/bpf/progs/btf_data.c            |  26 ++++
>  18 files changed, 1234 insertions(+), 103 deletions(-)
>  create mode 100644 include/linux/btf_ids.h
>  create mode 100644 tools/bpf/resolve_btfids/Build
>  create mode 100644 tools/bpf/resolve_btfids/Makefile
>  create mode 100644 tools/bpf/resolve_btfids/main.c
>  create mode 100644 tools/include/linux/btf_ids.h
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
>  create mode 100644 tools/testing/selftests/bpf/progs/btf_data.c
>