On Wed, Feb 3, 2021 at 7:13 PM Nick Desaulniers [off-list ref] wrote:

On Wed, Feb 3, 2021 at 6:58 PM Andrii Nakryiko
[off-list ref] wrote:

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On Wed, Feb 3, 2021 at 5:31 PM Nick Desaulniers [off-list ref] wrote:

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On Sun, Jan 17, 2021 at 12:14 PM Arnaldo Carvalho de Melo
[off-list ref] wrote:

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Em Fri, Jan 15, 2021 at 03:43:06PM -0800, Yonghong Song escreveu:

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On 1/15/21 3:34 PM, Nick Desaulniers wrote:

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On Fri, Jan 15, 2021 at 3:24 PM Yonghong Song [off-list ref] wrote:

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On 1/15/21 1:53 PM, Sedat Dilek wrote:

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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?

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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 [off-list ref],
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 (local)
-O - | git am
$ wget https://lore.kernel.org/lkml/20210130004401.2528717-3-ndesaulniers@google.com/raw (local)
-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

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referenced by arch/x86/realmode/rm/header.o:(real_mode_header)

ld.lld: error: undefined symbol: pa_trampoline_header

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referenced by arch/x86/realmode/rm/header.o:(real_mode_header)

ld.lld: error: undefined symbol: pa_trampoline_pgd

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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

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referenced by arch/x86/realmode/rm/header.o:(real_mode_header)

ld.lld: error: undefined symbol: pa_wakeup_header

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referenced by arch/x86/realmode/rm/header.o:(real_mode_header)

ld.lld: error: undefined symbol: pa_machine_real_restart_asm

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referenced by arch/x86/realmode/rm/header.o:(real_mode_header)

ld.lld: error: undefined symbol: pa_startup_32

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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.

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(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