linux-kernel - [PATCH v3] kheaders: make it possible to override TAR

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Message-ID: <277557da458c5fa07eba7d785b4f527cc37a023f.1752938644.git.sam@gentoo.org>
Date: Sat, 19 Jul 2025 16:24:05 +0100
From: Sam James <sam@...too.org>
To: Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>
Cc: linux-kbuild@...r.kernel.org,
	Michał Górny <mgorny@...too.org>,
	Sam James <sam@...too.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3] kheaders: make it possible to override TAR

From: Michał Górny <mgorny@...too.org>

Commit 86cdd2fdc4e39c388d39c7ba2396d1a9dfd66226 ("kheaders: make headers
archive reproducible") introduced a number of options specific to GNU
tar to the `tar` invocation in `gen_kheaders.sh` script.  This causes
the script to fail to work on systems where `tar` is not GNU tar.  This
can occur e.g. on recent Gentoo Linux installations that support using
bsdtar from libarchive instead.

Add a `TAR` make variable to make it possible to override the tar
executable used, e.g. by specifying:

  make TAR=gtar

Link: https://bugs.gentoo.org/884061
Reported-by: Sam James <sam@...too.org>
Tested-by: Sam James <sam@...too.org>
Co-developed-by: Masahiro Yamada <masahiroy@...nel.org>
Signed-off-by: Michał Górny <mgorny@...too.org>
Signed-off-by: Sam James <sam@...too.org>
---
v3: Rebase, cover more tar instances.

 Makefile               | 3 ++-
 kernel/gen_kheaders.sh | 6 +++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index c09766beb7eff..22d6037d738fe 100644
--- a/Makefile
+++ b/Makefile
@@ -543,6 +543,7 @@ LZMA		= lzma
 LZ4		= lz4
 XZ		= xz
 ZSTD		= zstd
+TAR		= tar
 
 CHECKFLAGS     := -D__linux__ -Dlinux -D__STDC__ -Dunix -D__unix__ \
 		  -Wbitwise -Wno-return-void -Wno-unknown-attribute $(CF)
@@ -622,7 +623,7 @@ export RUSTC RUSTDOC RUSTFMT RUSTC_OR_CLIPPY_QUIET RUSTC_OR_CLIPPY BINDGEN
 export HOSTRUSTC KBUILD_HOSTRUSTFLAGS
 export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
 export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
-export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
+export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD TAR
 export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS KBUILD_PROCMACROLDFLAGS LDFLAGS_MODULE
 export KBUILD_USERCFLAGS KBUILD_USERLDFLAGS
 
diff --git a/kernel/gen_kheaders.sh b/kernel/gen_kheaders.sh
index c9e5dc068e854..bb609a9ed72b4 100755
--- a/kernel/gen_kheaders.sh
+++ b/kernel/gen_kheaders.sh
@@ -66,13 +66,13 @@ if [ "$building_out_of_srctree" ]; then
 		cd $srctree
 		for f in $dir_list
 			do find "$f" -name "*.h";
-		done | tar -c -f - -T - | tar -xf - -C "${tmpdir}"
+		done | ${TAR:-tar} -c -f - -T - | ${TAR:-tar} -xf - -C "${tmpdir}"
 	)
 fi
 
 for f in $dir_list;
 	do find "$f" -name "*.h";
-done | tar -c -f - -T - | tar -xf - -C "${tmpdir}"
+done | ${TAR:-tar} -c -f - -T - | ${TAR:-tar} -xf - -C "${tmpdir}"
 
 # Always exclude include/generated/utsversion.h
 # Otherwise, the contents of the tarball may vary depending on the build steps.
@@ -88,7 +88,7 @@ xargs -0 -P8 -n1 \
 rm -f "${tmpdir}.contents.txt"
 
 # Create archive and try to normalize metadata for reproducibility.
-tar "${KBUILD_BUILD_TIMESTAMP:+--mtime=$KBUILD_BUILD_TIMESTAMP}" \
+${TAR:-tar} "${KBUILD_BUILD_TIMESTAMP:+--mtime=$KBUILD_BUILD_TIMESTAMP}" \
     --owner=0 --group=0 --sort=name --numeric-owner --mode=u=rw,go=r,a+X \
     -I $XZ -cf $tarfile -C "${tmpdir}/" . > /dev/null
 
-- 
2.50.1