linux-kernel - Re: [PATCH] selftests/bpf: ignore pointer types check with clang

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Date:   Sat, 15 Apr 2023 10:31:13 +0200
From:   Andrea Righi <andrea.righi@...onical.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Ilya Leoshkevich <iii@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>,
        Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>,
        Shuah Khan <shuah@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Paolo Pisati <paolo.pisati@...onical.com>,
        bpf <bpf@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        clang-built-linux <llvm@...ts.linux.dev>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selftests/bpf: ignore pointer types check with clang

On Fri, Apr 14, 2023 at 06:15:41PM -0700, Alexei Starovoitov wrote:
> On Fri, Apr 14, 2023 at 9:28 AM Andrea Righi <andrea.righi@...onical.com> wrote:
> >
> > On Fri, Apr 14, 2023 at 06:15:38PM +0200, Ilya Leoshkevich wrote:
> > > On Fri, Apr 14, 2023 at 08:15:03AM +0200, Andrea Righi wrote:
> > > > On Thu, Apr 13, 2023 at 09:56:00PM -0700, Alexei Starovoitov wrote:
> > > > > On Wed, Apr 12, 2023 at 2:59 AM Andrea Righi <andrea.righi@...onical.com> wrote:
> > > > > >
> > > > > > Building bpf selftests with clang can trigger errors like the following:
> > > > > >
> > > > > >   CLNG-BPF [test_maps] bpf_iter_netlink.bpf.o
> > > > > > progs/bpf_iter_netlink.c:32:4: error: incompatible pointer types assigning to 'struct sock *' from 'struct sock___17 *' [-Werror,-Wincompatible-pointer-types]
> > > > > >         s = &nlk->sk;
> > > > > >           ^ ~~~~~~~~
> > > > > > 1 error generated.
> > > > >
> > > > > I cannot reproduce this and BPF CI doesn't complain about it either.
> > > > > What kind of clang do you use?
> > > > > Some special version and build flags?
> > > >
> > > > I'm using Ubuntu clang version 15.0.7 (Ubuntu 23.04), no special build
> > > > flag (unless Ubuntu enables some different default flags, but it
> > > > shouldn't be the case... I'll double check).
> > > >
> > > > -Andrea
> > >
> > > Hi,
> > >
> > > FWIW, I see similar errors when I don't use recent pahole.
> >
> > I'm using pahole v1.24.
> 
> I believe Ilya is correct.
> 
> struct sock___17 is likely coming from vmlinux.h
> Which means that there were errors due vmlinux build which
> caused multiple structs to be present in BTF
> and therefore bpftool generated such broken vmlinux.h
> 
> The BTF section in such vmlinux is likely much larger than normal.
> Let's get to the bottom of it instead of masking build error.
> 
> Please try pahole 1.25.

Yay! Success. Everything is working fine with pahole 1.25. Please ignore
my patch, the fix is to simply upgrade pahole.

Thanks!
-Andrea