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Date:   Mon, 9 Nov 2020 14:31:52 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Jiri Olsa <jolsa@redhat.com>
Cc:     Ming Lei <tom.leiming@gmail.com>, Amy Parker <enbyamy@gmail.com>,
        linux-kbuild@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        masahiroy@kernel.org, michal.lkml@markovi.net,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>
Subject: Re: 5.10 tree fails to build
Message-ID: <20201109173152.GB340169@kernel.org>
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 <20201109103213.GA324561@krava>
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Em Mon, Nov 09, 2020 at 11:32:13AM +0100, Jiri Olsa escreveu:
> On Mon, Nov 09, 2020 at 05:57:37PM +0800, Ming Lei wrote:
> > On Thu, Nov 5, 2020 at 12:58 PM Amy Parker <enbyamy@gmail.com> wrote:
> > >
> > > On all attempts to build the 5.10 tree (from either release candidate,
> > > Linus's tree, Greg's tree, etc), the build crashes on the BTFID vmlinux
> > > stage. I've tested this on several different devices with completely
> > > different hardware and kernel configs. The symbol for vfs_getattr
> > > appears to be missing. Compiles for all of these work on any compile
> > > on any 5.9 tree. I've tested all 4 5.9 dot-releases as well as the first
> > > two and last two release candidates and Greg's staging tree.

> > > The specific error is:
> > >   BTFIDS  vmlinux
> > > FAILED unresolved symbol vfs_getattr
> > > make: *** [Makefile:1164: vmlinux] Error 255

> > > Any thoughts as to what's causing this? The main machine I'm
> > > compiling with is running kernel 5.8.17 with dwarves 1.17. My
> > > kernel config is attached as `kernel_config`.

> > Turns out the issue is introduced in the following commit:

> > commit 6e22ab9da79343532cd3cde39df25e5a5478c692
> > Author: Jiri Olsa <jolsa@kernel.org>
> > Date:   Tue Aug 25 21:21:20 2020 +0200

> >     bpf: Add d_path helper

> > The issue can be observed reliably when building kernel in Fedora 33 with
> > F33's kernel config.

> > GCC: gcc version 10.2.1 20200826 (Red Hat 10.2.1-3) (GCC)
 
> hi,
> it's gcc dwarf issue tracked in here:
>   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97060
 
> it's introduced by the gcc version 10.2.1 and we
> were told it will take some time to fix
 
> so we took steps to workaround that, the patchset
> just got acked and it's on its way to get merged:
 
>   https://lore.kernel.org/bpf/20201106222512.52454-1-jolsa@kernel.org/
 
> it's change for both dwarves/pahole and kernel
 
> the quick workaround is to disable CONFIG_DEBUG_INFO_BTF
> option

I've applied the series and I'm now testing it, will tag v1.19 then.

- Arnaldo