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 14:39:31 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Andrii Nakryiko <andriin@...com>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...com,
        daniel@...earbox.net, andrii.nakryiko@...il.com, kernel-team@...com
Subject: Re: [PATCH bpf-next 0/3] Add generic and raw BTF parsing APIs to
 libbpf

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;
        |         ~~~~~~~~~~~~~~~~~~~^~~~~

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