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

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Message-ID: <20250726151030.142548-1-mgorny@gentoo.org>
Date: Sat, 26 Jul 2025 17:10:30 +0200
From: Michał Górny <mgorny@...too.org>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>,
	Sam James <sam@...too.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Michał Górny <mgorny@...too.org>
Subject: [PATCH v3 kbuild-rebased] kheaders: make it possible to override TAR

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

diff --git a/Makefile b/Makefile
index ba0827a1fccd..081d494d037a 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 c64e5a00a3d9..59ec52f62c52 100755
--- a/kernel/gen_kheaders.sh
+++ b/kernel/gen_kheaders.sh
@@ -31,7 +31,7 @@ mkdir "${tmpdir}"
 
 # shellcheck disable=SC2154 # srctree is passed as an env variable
 sed "s:^${srctree}/::" "${srclist}" | tar -c -f - -C "${srctree}" -T - | tar -xf - -C "${tmpdir}"
-tar -c -f - -T "${objlist}" | tar -xf - -C "${tmpdir}"
+${TAR:-tar} -c -f - -T "${objlist}" | tar -xf - -C "${tmpdir}"
 
 # Remove comments except SDPX lines
 # Use a temporary file to store directory contents to prevent find/xargs from
@@ -43,7 +43,7 @@ xargs -0 -P8 -n1 \
 rm -f "${tmpdir}.contents.txt"
 
 # Create archive and try to normalize metadata for reproducibility.
-tar "${timestamp:+--mtime=$timestamp}" \
+${TAR:-tar} "${timestamp:+--mtime=$timestamp}" \
     --owner=0 --group=0 --sort=name --numeric-owner --mode=u=rw,go=r,a+X \
     -I "${XZ}" -cf "${tarfile}" -C "${tmpdir}/" . > /dev/null