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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Thu, 4 Feb 2021 16:04:40 -0800
Message-ID: <CAKwvOdk-4_Pt=DKFokDpG8L58xj4J-=PPrgSLEZnYs7VJu1jZA@mail.gmail.com>
Subject: Re: [PATCH v5 0/3] Kbuild: DWARF v5 support
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Nathan Chancellor <natechancellor@gmail.com>,
        Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
        Fangrui Song <maskray@google.com>, bpf <bpf@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Moving a bunch of folks + lists to BCC.

On Thu, Feb 4, 2021 at 3:54 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Wed, Feb 3, 2021 at 7:13 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
> >
> > On Wed, Feb 3, 2021 at 6:58 PM Andrii Nakryiko
> > <andrii.nakryiko@gmail.com> wrote:
> > >
> > > On Wed, Feb 3, 2021 at 5:31 PM Nick Desaulniers <ndesaulniers@google.com> wrote:
> > > >
> > > > On Sun, Jan 17, 2021 at 12:14 PM Arnaldo Carvalho de Melo
> > > > <acme@kernel.org> wrote:
> > > > >
> > > > > Em Fri, Jan 15, 2021 at 03:43:06PM -0800, Yonghong Song escreveu:
> > > > > >
> > > > > >
> > > > > > On 1/15/21 3:34 PM, Nick Desaulniers wrote:
> > > > > > > On Fri, Jan 15, 2021 at 3:24 PM Yonghong Song <yhs@fb.com> wrote:
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > On 1/15/21 1:53 PM, Sedat Dilek wrote:
> > > > > > > > > En plus, I encountered breakage with GCC v10.2.1 and LLVM=1 and
> > > > > > > > > CONFIG_DEBUG_INFO_DWARF4.
> > > > > > > > > So might be good to add a "depends on !DEBUG_INFO_BTF" in this combination.
> > > > > > >
> > > > > > > Can you privately send me your configs that repro? Maybe I can isolate
> > > > > > > it to a set of configs?
> > > > > > >
> > > > > > > >
> > > > > > > > I suggested not to add !DEBUG_INFO_BTF to CONFIG_DEBUG_INFO_DWARF4.
> > > > > > > > It is not there before and adding this may suddenly break some users.
> > > > > > > >
> > > > > > > > If certain combination of gcc/llvm does not work for
> > > > > > > > CONFIG_DEBUG_INFO_DWARF4 with pahole, this is a bug bpf community
> > > > > > > > should fix.
> > > > > > >
> > > > > > > Is there a place I should report bugs?
> > > > > >
> > > > > > You can send bug report to Arnaldo Carvalho de Melo <acme@kernel.org>,
> > > > > > dwarves@vger.kernel.org and bpf@vger.kernel.org.
> > > > >
> > > > > I'm coming back from vacation, will try to read the messages and see if
> > > > > I can fix this.
> > > >
> > > > IDK about DWARF v4; that seems to work for me.  I was previously observing
> > > > https://bugzilla.redhat.com/show_bug.cgi?id=1922698
> > > > with DWARF v5.  I just re-pulled the latest pahole, rebuilt, and no
> > > > longer see that warning.
> > > >
> > > > I now observe a different set.  I plan on attending "BPF office hours
> > > > tomorrow morning," but if anyone wants a sneak peak of the errors and
> > > > how to reproduce:
> > > > https://gist.github.com/nickdesaulniers/ae8c9efbe4da69b1cf0dce138c1d2781
> > > >
> > >
> > > Is there another (easy) way to get your patch set without the b4 tool?
> > > Is your patch set present in some patchworks instance, so that I can
> > > download it in mbox format, for example?
> >
> > $ wget https://lore.kernel.org/lkml/20210130004401.2528717-2-ndesaulniers@google.com/raw
> > -O - | git am
> > $ wget https://lore.kernel.org/lkml/20210130004401.2528717-3-ndesaulniers@google.com/raw
> > -O - | git am
> >
> > If you haven't tried b4 yet, it's quite nice.  Hard to go back.  Lore
> > also has mbox.gz links.  Not sure about patchwork.
> >
>
> Ok, I managed to apply that on linux-next, but I can't get past this:
>
> ld.lld: error: undefined symbol: pa_trampoline_start
> >>> referenced by arch/x86/realmode/rm/header.o:(real_mode_header)

Thanks for testing and the report. Do you have a .config you can send
me to reproduce?

>
> ld.lld: error: undefined symbol: pa_trampoline_header
> >>> referenced by arch/x86/realmode/rm/header.o:(real_mode_header)
>
> ld.lld: error: undefined symbol: pa_trampoline_pgd
> >>> referenced by arch/x86/realmode/rm/header.o:(real_mode_header)
> >>> referenced by trampoline_64.S:142 (/data/users/andriin/linux/arch/x86/realmode/rm/trampoline_64.S:142)
> >>>               arch/x86/realmode/rm/trampoline_64.o:(startup_32)
>
> ld.lld: error: undefined symbol: pa_wakeup_start
> >>> referenced by arch/x86/realmode/rm/header.o:(real_mode_header)
>
> ld.lld: error: undefined symbol: pa_wakeup_header
> >>> referenced by arch/x86/realmode/rm/header.o:(real_mode_header)
>
> ld.lld: error: undefined symbol: pa_machine_real_restart_asm
> >>> referenced by arch/x86/realmode/rm/header.o:(real_mode_header)
>
> ld.lld: error: undefined symbol: pa_startup_32
> >>> referenced by trampoline_64.S:77 (/data/users/andriin/linux/arch/x86/realmode/rm/trampoline_64.S:77)
> >>>               arch/x86/realmode/rm/trampoline_64.o:(trampoline_start)
>
> ld.lld: error: undefined symbol: pa_tr_flags
> >>> referenced by trampoline_64.S:124 (/data/users/andriin/linux/arch/x86/realmode/rm/trampoline_64.S:124)
> >>>               arch/x86/realmode/rm/trampoline_64.o:(startup_32)
>
> ld.lld: error: undefined symbol: pa_tr_cr4
> >>> referenced by trampoline_64.S:138 (/data/users/andriin/linux/arch/x86/realmode/rm/trampoline_64.S:138)
> >>>               arch/x86/realmode/rm/trampoline_64.o:(startup_32)
>
> ld.lld: error: undefined symbol: pa_tr_efer
> >>> referenced by trampoline_64.S:146 (/data/users/andriin/linux/arch/x86/realmode/rm/trampoline_64.S:146)
> >>>               arch/x86/realmode/rm/trampoline_64.o:(startup_32)
> >>> referenced by trampoline_64.S:147 (/data/users/andriin/linux/arch/x86/realmode/rm/trampoline_64.S:147)
> >>>               arch/x86/realmode/rm/trampoline_64.o:(startup_32)
>
> ld.lld: error: undefined symbol: pa_startup_64
> >>> referenced by trampoline_64.S:161 (/data/users/andriin/linux/arch/x86/realmode/rm/trampoline_64.S:161)
> >>>               arch/x86/realmode/rm/trampoline_64.o:(startup_32)
>
> ld.lld: error: undefined symbol: pa_tr_gdt
> >>> referenced by arch/x86/realmode/rm/trampoline_64.o:(tr_gdt)
> >>> referenced by reboot.S:28 (/data/users/andriin/linux/arch/x86/realmode/rm/reboot.S:28)
> >>>               arch/x86/realmode/rm/reboot.o:(machine_real_restart_asm)
>
> ld.lld: error: undefined symbol: pa_machine_real_restart_paging_off
> >>> referenced by reboot.S:34 (/data/users/andriin/linux/arch/x86/realmode/rm/reboot.S:34)
> >>>               arch/x86/realmode/rm/reboot.o:(machine_real_restart_asm)
>
> ld.lld: error: undefined symbol: pa_machine_real_restart_idt
> >>> referenced by reboot.S:47 (/data/users/andriin/linux/arch/x86/realmode/rm/reboot.S:47)
> >>>               arch/x86/realmode/rm/reboot.o:(machine_real_restart_asm)
>
> ld.lld: error: undefined symbol: pa_machine_real_restart_gdt
> >>> referenced by reboot.S:54 (/data/users/andriin/linux/arch/x86/realmode/rm/reboot.S:54)
> >>>               arch/x86/realmode/rm/reboot.o:(machine_real_restart_asm)
> >>> referenced by arch/x86/realmode/rm/reboot.o:(machine_real_restart_gdt)
>
> ld.lld: error: undefined symbol: pa_wakeup_gdt
> >>> referenced by arch/x86/realmode/rm/wakeup_asm.o:(wakeup_gdt)
>   CC      arch/x86/mm/numa_64.o
>   CC      arch/x86/mm/amdtopology.o
>   HOSTCC  arch/x86/entry/vdso/vdso2c
> make[4]: *** [arch/x86/realmode/rm/realmode.elf] Error 1
> make[3]: *** [arch/x86/realmode/rm/realmode.bin] Error 2
> make[2]: *** [arch/x86/realmode] Error 2
> make[2]: *** Waiting for unfinished jobs....
>
>
> Hopefully Arnaldo will have better luck.
>
>
>
> > >
> > > >
> > > > (FWIW: some other folks are hitting issues now with kernel's lack of
> > > > DWARF v5 support: https://bugzilla.redhat.com/show_bug.cgi?id=1922707)
> >
> >
> > --
> > Thanks,
> > ~Nick Desaulniers


-- 
Thanks,
~Nick Desaulniers