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Date:   Tue, 1 Aug 2023 09:52:02 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Masahiro Yamada <masahiroy@kernel.org>
Cc:     linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
        Ben Hutchings <ben@decadent.org.uk>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>
Subject: Re: [PATCH v2 1/2] kbuild: deb-pkg: use Debian compliant shebang for
 debian/rules
Message-ID: <20230801165202.GA2472327@dev-arch.thelio-3990X>
References: <20230801121926.1677205-1-masahiroy@kernel.org>
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In-Reply-To: <20230801121926.1677205-1-masahiroy@kernel.org>
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On Tue, Aug 01, 2023 at 09:19:25PM +0900, Masahiro Yamada wrote:
> Debian Policy "4.9. Main building script: debian/rules" requires
> "debian/rules must start with the line #!/usr/bin/make -f". [1]
> 
> Currently, Kbuild does not follow this policy.
> 
> When Kbuild generates debian/rules, "#!$(command -v $MAKE) -f" is
> expanded by shell. The resuling string may not be "#!/usr/bin/make -f".
> 
> There was a reason to opt out the Debian policy.
> 
> If you run '/path/to/my/custom/make deb-pkg', debian/rules must also be
> invoked by the same Make program. If #!/usr/bin/make were hard-coded in
> debian/rules, the sub-make would be executed by a possibly different
> Make version.
> 
> This is problematic due to the MAKEFLAGS incompatibility, especially the
> job server flag. Old Make versions used --jobserver-fds to propagate job
> server file descriptors, but Make >= 4.2 uses --jobserver-auth. The flag
> disagreement between the parent/child Makes would result in a process
> fork explosion.
> 
> However, having a non-standard path in the shebang causes another issue;
> the generated source package is not portable as such a path does not
> exist in other build environments.
> 
> This commit solves those conflicting demands.
> 
> Hard-code '#!/usr/bin/make -f' in debian/rules to create a portable and
> Debian-compliant source package.
> 
> Pass '--rules-file=$(MAKE) -f debian/rules' when dpkg-buildpackage is
> invoked from Makefile so that debian/rules is executed by the same Make
> program as used to start Kbuild.
> 
> [1] https://www.debian.org/doc/debian-policy/ch-source.html#main-building-script-debian-rules
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Tested-by: Nathan Chancellor <nathan@kernel.org>

> ---
> 
> (no changes since v1)
> 
>  scripts/Makefile.package | 2 +-
>  scripts/package/mkdebian | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/Makefile.package b/scripts/Makefile.package
> index 85beab0363d7..f8a948ec2c6b 100644
> --- a/scripts/Makefile.package
> +++ b/scripts/Makefile.package
> @@ -148,7 +148,7 @@ deb-pkg srcdeb-pkg bindeb-pkg:
>  	$(if $(findstring source, $(build-type)), \
>  		--unsigned-source --compression=$(KDEB_SOURCE_COMPRESS)) \
>  	$(if $(findstring binary, $(build-type)), \
> -		-r$(KBUILD_PKG_ROOTCMD) -a$$(cat debian/arch), \
> +		--rules-file='$(MAKE) -f debian/rules' -r$(KBUILD_PKG_ROOTCMD) -a$$(cat debian/arch), \
>  		--no-check-builddeps) \
>  	$(DPKG_FLAGS))
>  
> diff --git a/scripts/package/mkdebian b/scripts/package/mkdebian
> index 9105abab9728..2829f5b8aea6 100755
> --- a/scripts/package/mkdebian
> +++ b/scripts/package/mkdebian
> @@ -264,7 +264,7 @@ EOF
>  fi
>  
>  cat <<EOF > debian/rules
> -#!$(command -v $MAKE) -f
> +#!/usr/bin/make -f
>  
>  srctree ?= .
>  KERNELRELEASE = ${KERNELRELEASE}
> -- 
> 2.39.2
>