[PATCH] kbuild: buildtar: add comments about inconsistent package generation

[Masahiro Yamada]

scripts/package/buildtar checks some kernel packages, and copies the
first image found. This may potentially produce an inconsistent (and
possibly wrong) package.

For instance, the for-loop for arm64 checks Image.{bz2,gz,lz4,lzma,lzo},
and vmlinuz.efi, then copies the first image found, which might be a
stale image.

When CONFIG_EFI_ZBOOT is enabled in the pristine source tree,
'make ARCH=arm64 tar-pkg' will build and copy vmlinuz.efi. This is the
expected behavior.

If you build the kernel with CONFIG_EFI_ZBOOT, Image.gz will be created,
which will remain in the build directory unless you clean it. Even if
CONFIG_EFI_ZBOOT is turned on later, 'make ARCH=arm64 tar-pkg' will copy
stale Image.gz instead of the latest vmlinuz.efi, as Image.gz takes
precedence over vmlinuz.efi.

In summary, the code "[ -f ... ] && cp" does not consistently produce
the desired outcome.

The other package scripts are deterministic; scripts/package/mkdebian,
for example, chooses a copied kernel image based on CONFIG options.

I removed [ -f ... ] checks from x86, alpha, parisc, and the default
because they have a single kernel image to copy. If it is missing, it
should be an error.

I did not modify the code for mips, arm64, riscv. Instead, I left some
comments. Eventually, someone may fix the code, or at the very least,
it may discourage the copy-pasting of incorrect code.

Signed-off-by: Masahiro Yamada <masahiroy at kernel.org>
---

 scripts/package/buildtar | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/scripts/package/buildtar b/scripts/package/buildtar
index 72c91a1b832f..ed8d9b496305 100755
--- a/scripts/package/buildtar
+++ b/scripts/package/buildtar
@@ -53,18 +53,24 @@ cp -v -- "${objtree}/vmlinux" "${tmpdir}/boot/vmlinux-${KERNELRELEASE}"
 #
 # Install arch-specific kernel image(s)
 #
+# Note:
+#   mips, arm64, and riscv copy the first image found. This may not produce
+#   the desired outcome because it may pick up a stale file remaining in the
+#   build tree.
+#
 case "${ARCH}" in
 	x86|i386|x86_64)
-		[ -f "${objtree}/arch/x86/boot/bzImage" ] && cp -v -- "${objtree}/arch/x86/boot/bzImage" "${tmpdir}/boot/vmlinuz-${KERNELRELEASE}"
+		cp -v -- "${objtree}/arch/x86/boot/bzImage" "${tmpdir}/boot/vmlinuz-${KERNELRELEASE}"
 		;;
 	alpha)
-		[ -f "${objtree}/arch/alpha/boot/vmlinux.gz" ] && cp -v -- "${objtree}/arch/alpha/boot/vmlinux.gz" "${tmpdir}/boot/vmlinuz-${KERNELRELEASE}"
+		cp -v -- "${objtree}/arch/alpha/boot/vmlinux.gz" "${tmpdir}/boot/vmlinuz-${KERNELRELEASE}"
 		;;
 	parisc*)
-		[ -f "${KBUILD_IMAGE}" ] && cp -v -- "${KBUILD_IMAGE}" "${tmpdir}/boot/vmlinux-${KERNELRELEASE}"
+		cp -v -- "${KBUILD_IMAGE}" "${tmpdir}/boot/vmlinux-${KERNELRELEASE}"
 		[ -f "${objtree}/lifimage" ] && cp -v -- "${objtree}/lifimage" "${tmpdir}/boot/lifimage-${KERNELRELEASE}"
 		;;
 	mips)
+		# Please note the following code may copy a stale file.
 		if [ -f "${objtree}/arch/mips/boot/compressed/vmlinux.bin" ]; then
 			cp -v -- "${objtree}/arch/mips/boot/compressed/vmlinux.bin" "${tmpdir}/boot/vmlinuz-${KERNELRELEASE}"
 		elif [ -f "${objtree}/arch/mips/boot/compressed/vmlinux.ecoff" ]; then
@@ -86,6 +92,7 @@ case "${ARCH}" in
 		fi
 		;;
 	arm64)
+		# Please note the following code may copy a stale file.
 		for i in Image.bz2 Image.gz Image.lz4 Image.lzma Image.lzo vmlinuz.efi ; do
 			if [ -f "${objtree}/arch/arm64/boot/${i}" ] ; then
 				cp -v -- "${objtree}/arch/arm64/boot/${i}" "${tmpdir}/boot/vmlinuz-${KERNELRELEASE}"
@@ -94,6 +101,7 @@ case "${ARCH}" in
 		done
 		;;
 	riscv)
+		# Please note the following code may copy a stale file.
 		for i in Image.bz2 Image.gz Image; do
 			if [ -f "${objtree}/arch/riscv/boot/${i}" ] ; then
 				cp -v -- "${objtree}/arch/riscv/boot/${i}" "${tmpdir}/boot/vmlinux-${KERNELRELEASE}"
@@ -102,7 +110,7 @@ case "${ARCH}" in
 		done
 		;;
 	*)
-		[ -f "${KBUILD_IMAGE}" ] && cp -v -- "${KBUILD_IMAGE}" "${tmpdir}/boot/vmlinux-kbuild-${KERNELRELEASE}"
+		cp -v -- "${KBUILD_IMAGE}" "${tmpdir}/boot/vmlinux-kbuild-${KERNELRELEASE}"
 		echo "" >&2
 		echo '** ** **  WARNING  ** ** **' >&2
 		echo "" >&2
-- 
2.40.1