netdev - Re: [PATCH bpf-next 02/11] bpf: always emit struct bpf_perf

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20220416174330.195496-1-alobakin@pm.me>
Date:   Sat, 16 Apr 2022 17:50:39 +0000
From:   Alexander Lobakin <alobakin@...me>
To:     Song Liu <song@...nel.org>
Cc:     Alexander Lobakin <alobakin@...me>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Björn Töpel <bjorn@...nel.org>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Dmitrii Dolgov <9erthalion6@...il.com>,
        Quentin Monnet <quentin@...valent.com>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Kumar Kartikeya Dwivedi <memxor@...il.com>,
        Chenbo Feng <fengc@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Thomas Graf <tgraf@...g.ch>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        linux-perf-users@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH bpf-next 02/11] bpf: always emit struct bpf_perf_link BTF

From: Song Liu <song@...nel.org>
Date: Fri, 15 Apr 2022 16:24:41 -0700

> On Thu, Apr 14, 2022 at 3:45 PM Alexander Lobakin <alobakin@...me> wrote:
> >
> > When building bpftool with !CONFIG_PERF_EVENTS:
> >
> > skeleton/pid_iter.bpf.c:47:14: error: incomplete definition of type 'struct bpf_perf_link'
> >         perf_link = container_of(link, struct bpf_perf_link, link);
> >                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:74:22: note: expanded from macro 'container_of'
> >                 ((type *)(__mptr - offsetof(type, member)));    \
> >                                    ^~~~~~~~~~~~~~~~~~~~~~
> > tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:68:60: note: expanded from macro 'offsetof'
> >  #define offsetof(TYPE, MEMBER)  ((unsigned long)&((TYPE *)0)->MEMBER)
> >                                                   ~~~~~~~~~~~^
> > skeleton/pid_iter.bpf.c:44:9: note: forward declaration of 'struct bpf_perf_link'
> >         struct bpf_perf_link *perf_link;
> >                ^
> >
> > &bpf_perf_link is being defined and used only under the ifdef.
> > Move it out of the block and explicitly emit a BTF to fix
> > compilation.
> >
> > Fixes: cbdaf71f7e65 ("bpftool: Add bpf_cookie to link output")
> > Signed-off-by: Alexander Lobakin <alobakin@...me>
>
> Similar to v1, this fix is weird to me. I hope we have can fix it in user
> space.

I've been thinking on this, but userspace is not provided with any
autoconf.h definitions (only selftests have them), so its code must
be sort of universal.
Both this and 01/11 are compile time and due to imcomplete and/or
absent BTF struct declarations. I'm not familiar with
bpf_core_field_exists(), and it might be that it's able to solve
01/11, but not this one. &bpf_perf_link must be present
unconditionally, otherwise it won't be defined in the generated
vmlinux.h at all.

Thanks,
Al