Re: ANNOUNCE: pahole v1.24 (Faster BTF encoding, 64-bit BTF enum entries)

[Martin Reboredo <yakoyoku@gmail.com>]

On 8/24/22 11:38, Luna Jernberg wrote:
> https://forum.endeavouros.com/t/failed-to-start-load-kernel-modules-on-boot-after-system-update-nvidia/30584/17?u=sradjoker
> 
> On 8/24/22, Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> wrote:
>> Em Wed, Aug 24, 2022 at 04:36:18PM +0200, Luna Jernberg escreveu:
>>> The Nvidia driver breaks
>>
>> How? What are the messages?
>>
>> Here is a test on an Archlinux container:
>>
>> [perfbuilder@758097c04011 dwarves-1.24]$ pahole --version
>> v1.24
>> [perfbuilder@758097c04011 dwarves-1.24]$ cat /etc/os-release
>> NAME="Arch Linux"
>> PRETTY_NAME="Arch Linux"
>> ID=arch
>> BUILD_ID=rolling
>> VERSION_ID=TEMPLATE_VERSION_ID
>> ANSI_COLOR="38;2;23;147;209"
>> HOME_URL="https://archlinux.org/"
>> DOCUMENTATION_URL="https://wiki.archlinux.org/"
>> SUPPORT_URL="https://bbs.archlinux.org/"
>> BUG_REPORT_URL="https://bugs.archlinux.org/"
>> LOGO=archlinux-logo
>> [perfbuilder@758097c04011 dwarves-1.24]$ pahole list_head
>> struct list_head {
>> 	struct list_head *         next;                 /*     0     8 */
>> 	struct list_head *         prev;                 /*     8     8 */
>>
>> 	/* size: 16, cachelines: 1, members: 2 */
>> 	/* last cacheline: 16 bytes */
>> };
>> [perfbuilder@758097c04011 dwarves-1.24]$ pahole --sizes | sort -k2 -nr |
>> head
>> rcu_state	300608	7
>> cmp_data	290904	1
>> dec_data	274520	1
>> cpu_entry_area	241664	0
>> kvm	190016	6
>> pglist_data	173440	6
>> ZSTD_DCtx_s	161480	6
>> saved_cmdlines_buffer	131104	1
>> debug_store_buffers	131072	0
>> hid_parser	110848	1
>> [perfbuilder@758097c04011 dwarves-1.24]$
>>
>>> On 8/24/22, Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> wrote:
>>>> Em Wed, Aug 24, 2022 at 03:23:29PM +0200, Luna Jernberg escreveu:
>>>>> This package breaks on Arch Linux at the moment and if you are using
>>>>> Arch
>>>>> its recommended that you downgrade to 1.23
>>>>
>>>> Breaks in what sense? Can you please provide details?
>>>>
>>>> - Arnaldo
>>>>
>>>>> On Tue, Aug 23, 2022 at 1:59 AM Arnaldo Carvalho de Melo
>>>>> <acme@kernel.org>
>>>>> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>>         The v1.24 release of pahole and its friends is out, with
>>>>>> faster
>>>>>> BTF generation by parallelizing the encoding part in addition to the
>>>>>> previoulsy parallelized DWARF loading, support for 64-bit BTF
>>>>>> enumeration
>>>>>> entries, signed BTF encoding of 'char', exclude/select DWARF loading
>>>>>> based on the language that generated the objects, etc.
>>>>>>
>>>>>> Main git repo:
>>>>>>
>>>>>>    git://git.kernel.org/pub/scm/devel/pahole/pahole.git
>>>>>>
>>>>>> Mirror git repo:
>>>>>>
>>>>>>    https://github.com/acmel/dwarves.git
>>>>>>
>>>>>> tarball + gpg signature:
>>>>>>
>>>>>>    https://fedorapeople.org/~acme/dwarves/dwarves-1.24.tar.xz
>>>>>>    https://fedorapeople.org/~acme/dwarves/dwarves-1.24.tar.bz2
>>>>>>    https://fedorapeople.org/~acme/dwarves/dwarves-1.24.tar.sign
>>>>>>
>>>>>>         Thanks a lot to all the contributors and distro packagers,
>>>>>> you're
>>>>>> on the
>>>>>> CC list, I appreciate a lot the work you put into these tools,
>>>>>>
>>>>>> Best Regards,
>>>>>>
>>>>>> BTF encoder:
>>>>>>
>>>>>> - Add support to BTF_KIND_ENUM64 to represent enumeration entries
>>>>>> with
>>>>>>   more than 32 bits.
>>>>>>
>>>>>> - Support multithreaded encoding, in addition to DWARF multithreaded
>>>>>>   loading, speeding up the process.
>>>>>>
>>>>>>   Selected just like DWARF multithreaded loading, using the 'pahole
>>>>>> -j'
>>>>>>   option.
>>>>>>
>>>>>> - Encode 'char' type as signed.
>>>>>>
>>>>>> BTF Loader:
>>>>>>
>>>>>> - Add support to BTF_KIND_ENUM64.
>>>>>>
>>>>>> pahole:
>>>>>>
>>>>>> - Introduce --lang and --lang_exclude to specify the language the
>>>>>>   DWARF compile units were originated from to use or filter.
>>>>>>
>>>>>>   Use case is to exclude Rust compile units while aspects of the
>>>>>>   DWARF generated for it get sorted out in a way that the kernel
>>>>>>   BPF verifier don't refuse loading the BTF generated from them.
>>>>>>
>>>>>> - Introduce --compile to generate compilable code in a similar
>>>>>> fashion
>>>>>> to:
>>>>>>
>>>>>>    bpftool btf dump file vmlinux format c > vmlinux.h
>>>>>>
>>>>>>   As with 'bpftool', this will notice type shadowing, i.e. multiple
>>>>>> types
>>>>>>   with the same name and will disambiguate by adding a suffix.
>>>>>>
>>>>>> - Don't segfault when processing bogus files.
>>>>>>
>>>>
>>>> --
>>>>
>>>> - Arnaldo
>>>>
>>
>> --
>>
>> - Arnaldo
>>

Can you try a build of the kernel or the by passing the
--skip_encoding_btf_enum64 to scripts/pahole-flags.sh?

Here's a patch for either in tree scripts/pahole-flags.sh or
/usr/lib/modules/5.19.3-arch1-1/build/scripts/pahole-flags.sh

diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
index 0d99ef17e4a528..1f1f1d397c399a 100755
--- a/scripts/pahole-flags.sh
+++ b/scripts/pahole-flags.sh
@@ -19,5 +19,9 @@ fi
 if [ "${pahole_ver}" -ge "122" ]; then
 	extra_paholeopt="${extra_paholeopt} -j"
 fi
+if [ "${pahole_ver}" -ge "124" ]; then
+	# see PAHOLE_HAS_LANG_EXCLUDE
+	extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_enum64"
+fi

 echo ${extra_paholeopt}

- Martin Rodriguez Reboredo