netdev - Re: [PATCH bpf-next 0/3] Add generic and raw BTF parsing APIs to libbpf

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Date:   Thu, 6 Aug 2020 10:49:59 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next 0/3] Add generic and raw BTF parsing APIs to libbpf

On Thu, Aug 6, 2020 at 10:39 AM Arnaldo Carvalho de Melo
<arnaldo.melo@...il.com> wrote:
>
> Em Sat, Aug 01, 2020 at 06:32:16PM -0700, Andrii Nakryiko escreveu:
> > It's pretty common for applications to want to parse raw (binary) BTF data
> > from file, as opposed to parsing it from ELF sections. It's also pretty common
> > for tools to not care whether given file is ELF or raw BTF format. This patch
> > series exposes internal raw BTF parsing API and adds generic variant of BTF
> > parsing, which will efficiently determine the format of a given fail and will
> > parse BTF appropriately.
> >
> > Patches #2 and #3 removes re-implementations of such APIs from bpftool and
> > resolve_btfids tools.
> >
> > Andrii Nakryiko (3):
> >   libbpf: add btf__parse_raw() and generic btf__parse() APIs
> >   tools/bpftool: use libbpf's btf__parse() API for parsing BTF from file
> >   tools/resolve_btfids: use libbpf's btf__parse() API
>
> I haven't checked which of the patches, or some in other series caused
> this on Clear Linux:
>
>   21 clearlinux:latest             : FAIL gcc (Clear Linux OS for Intel Architecture) 10.2.1 20200723 releases/gcc-10.2.0-3-g677b80db41, clang ver
> sion 10.0.1
>
>   gcc (Clear Linux OS for Intel Architecture) 10.2.1 20200723 releases/gcc-10.2.0-3-g677b80db41
>
>   btf.c: In function 'btf__parse_raw':
>   btf.c:625:28: error: 'btf' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>     625 |  return err ? ERR_PTR(err) : btf;
>         |         ~~~~~~~~~~~~~~~~~~~^~~~~
>

Yeah, fixed in https://patchwork.ozlabs.org/project/netdev/patch/20200805223359.32109-1-danieltimlee@gmail.com/

> This is what I have:
>
> [acme@...co perf]$ git log -10 --oneline tools/lib/bpf
> 94a1fedd63ed libbpf: Add btf__parse_raw() and generic btf__parse() APIs
> 2e49527e5248 libbpf: Add bpf_link detach APIs
> 1acf8f90ea7e libbpf: Fix register in PT_REGS MIPS macros
> 50450fc716c1 libbpf: Make destructors more robust by handling ERR_PTR(err) cases
> dc8698cac7aa libbpf: Add support for BPF XDP link
> d4b4dd6ce770 libbpf: Print hint when PERF_EVENT_IOC_SET_BPF returns -EPROTO
> cd31039a7347 tools/libbpf: Add support for bpf map element iterator
> da7a35062bcc libbpf bpf_helpers: Use __builtin_offsetof for offsetof
> 499dd29d90bb libbpf: Add support for SK_LOOKUP program type
> 4be556cf5aef libbpf: Add SEC name for xdp programs attached to CPUMAP
> [acme@...co perf]$
>
> >  tools/bpf/bpftool/btf.c             |  54 +------------
> >  tools/bpf/resolve_btfids/.gitignore |   4 +
> >  tools/bpf/resolve_btfids/main.c     |  58 +-------------
> >  tools/lib/bpf/btf.c                 | 114 +++++++++++++++++++---------
> >  tools/lib/bpf/btf.h                 |   5 +-
> >  tools/lib/bpf/libbpf.map            |   2 +
> >  6 files changed, 89 insertions(+), 148 deletions(-)
> >  create mode 100644 tools/bpf/resolve_btfids/.gitignore
> >
> > --
> > 2.24.1
> >
>
> --
>
> - Arnaldo