NACK/Cmnt: [SRU JAMMY] [PATCH] UBUNTU: SAUCE: scripts/pahole-flags.sh: Add --skip_encoding_btf_enum64 for pahole versions >= 124

[Stefan Bader]

On 26.01.24 19:54, mitchell.augustin at canonical.com wrote:
> From: Mitchell Augustin <mitchell.augustin at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/2051376
> 
> UpstreamStatus: Merged with 5.15.148
> 
> This patch will not go upstream since 6.7-rc1 converts this script into a makefile snippet, and since this patch is already present
> in upstream 5.15.148 and the master branch for Noble.
> 
> New pahole (version 1.24) generates by default new BTF_KIND_ENUM64 BTF tag,
> which is not supported by stable kernel.
> 
> As a result the kernel with CONFIG_DEBUG_INFO_BTF option will fail to
> compile with following error:
> 
>    BTFIDS  vmlinux
> FAILED: load BTF from vmlinux: Invalid argument
> 
> New pahole provides --skip_encoding_btf_enum64 option to skip BTF_KIND_ENUM64
> generation and produce BTF supported by stable kernel.
> 
> (cherry picked from commit b775fbf532dc01ae53a6fc56168fd30cb4b0c658 in 5.15.148 tree)
> 
> Signed-off-by: Mitchell Augustin <mitchell.augustin at canonical.com>
> ---

Rejected for the following reasons:
Ok, so this patch is taken from the upstream stable repository. In which 
case the proper provenance (including commit message) needs to be 
preserved. That is if there is a need for speed. Eventually all 
linux-5.15.y will be picked into Jammy, we just lag a bit behind 
(currently we have 5.15.143 committed).
So what the patch should look like is:

 From b775fbf532dc01ae53a6fc56168fd30cb4b0c658 Mon Sep 17 00:00:00 2001
From: Martin Rodriguez Reboredo <yakoyoku at gmail.com>
Date: Sun, 4 Sep 2022 15:19:01 +0200
Subject: [PATCH] kbuild: Add skip_encoding_btf_enum64 option to pahole

BugLink: https://bugs.launchpad.net/bugs/2051376

New pahole (version 1.24) generates by default new BTF_KIND_ENUM64 BTF tag,
which is not supported by stable kernel.

As a result the kernel with CONFIG_DEBUG_INFO_BTF option will fail to
compile with following error:

   BTFIDS  vmlinux
FAILED: load BTF from vmlinux: Invalid argument

New pahole provides --skip_encoding_btf_enum64 option to skip 
BTF_KIND_ENUM64
generation and produce BTF supported by stable kernel.

Adding this option to scripts/pahole-flags.sh.

This change does not have equivalent commit in linus tree, because linus 
tree
has support for BTF_KIND_ENUM64 tag, so it does not need to be disabled.

Signed-off-by: Martin Rodriguez Reboredo <yakoyoku at gmail.com>
Signed-off-by: Jiri Olsa <jolsa at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

(cherry picked from commit b775fbf532dc01ae53a6fc56168fd30cb4b0c658 
linux-5.15.y)
Signed-off-by: Mitchell Augustin <mitchell.augustin at canonical.com>
---
  scripts/pahole-flags.sh | 4 ++++
  1 file changed, 4 insertions(+)

...

The second question I had in previous replies was whether we also need 
to do something for HWE kernels. Jammy (5.15) fails to compile when 
pahole >= 1.24 is available. This must be a configuration other than 
what we use by default for the distro, otherwise we should have seen 
this. But we also have HWE kernels (now 6.5, at some point 6.8). I 
currently do not see something adjusted in the 6.5 kernel. That might 
mean in Mantic there is a pahole version which does not have the 
problem. Or it is the kernel Makefiles which got adjusted, so this is no 
longer necessary.

-Stefan
>   scripts/pahole-flags.sh | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
> index ac8b23787427..d38fa6d84d62 100755
> --- a/scripts/pahole-flags.sh
> +++ b/scripts/pahole-flags.sh
> @@ -4,7 +4,7 @@
>   extra_paholeopt=
>   
>   if ! [ -x "$(command -v ${PAHOLE})" ]; then
> -	return
> +	exit 0
>   fi
>   
>   pahole_ver=$($(dirname $0)/pahole-version.sh ${PAHOLE})
> @@ -17,4 +17,8 @@ if [ "${pahole_ver}" -ge "121" ]; then
>   	extra_paholeopt="${extra_paholeopt} --btf_gen_floats"
>   fi
>   
> +if [ "${pahole_ver}" -ge "124" ]; then
> +	extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_enum64"
> +fi
> +
>   echo ${extra_paholeopt}

-- 
- Stefan

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