[PATCH v3] kbuild: add script and target to generate pacman package

[Thomas Weißschuh]

pacman is the package manager used by Arch Linux and its derivates.
Creating native packages from the kernel tree has multiple advantages:

* The package triggers the correct hooks for initramfs generation and
  bootloader configuration
* Uninstallation is complete and also invokes the relevant hooks
* New UAPI headers can be installed without any manual bookkeeping

The PKGBUILD file is a simplified version of the one used for the
downstream Arch Linux "linux" package.
Extra steps that should not be necessary for a development kernel have
been removed and an UAPI header package has been added.

Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Tested-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
Changes in v3:
- Enforce matching architectures for installation
- Add Reviewed-by and Tested-by from Nathan
- Link to v2: https://lore.kernel.org/r/20240706-kbuild-pacman-pkg-v2-1-613422a03a7a@xxxxxxxxxxxxxx

Changes in v2:
- Replace ${MAKE} with $MAKE for consistency with other variables
- Use $MAKE for "-s image_name"
- Avoid permission warnings from build directory
- Clarify reason for /build symlink removal
- Install System.map and config
- Install dtbs where available
- Allow cross-build through arch=any
- Sort Contributor/Maintainer chronologically
- Disable some unneeded makepkg options
- Use DEPMOD=true for consistency with rpm-package
- Link to v1: https://lore.kernel.org/r/20240704-kbuild-pacman-pkg-v1-1-ac2f63f5fa7b@xxxxxxxxxxxxxx
---
 .gitignore               |  6 ++++
 scripts/Makefile.package | 16 ++++++++++
 scripts/package/PKGBUILD | 83 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 105 insertions(+)

diff --git a/.gitignore b/.gitignore
index c59dc60ba62e..7902adf4f7f1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -92,6 +92,12 @@ modules.order
 #
 /tar-install/
 
+#
+# pacman files (make pacman-pkg)
+#
+/PKGBUILD
+/pacman/
+
 #
 # We don't want to ignore the following even if they are dot-files
 #
diff --git a/scripts/Makefile.package b/scripts/Makefile.package
index bf016af8bf8a..a5b5b899d90c 100644
--- a/scripts/Makefile.package
+++ b/scripts/Makefile.package
@@ -141,6 +141,21 @@ snap-pkg:
 	cd $(objtree)/snap && \
 	snapcraft --target-arch=$(UTS_MACHINE)
 
+# pacman-pkg
+# ---------------------------------------------------------------------------
+
+PHONY += pacman-pkg
+pacman-pkg:
+	@ln -srf $(srctree)/scripts/package/PKGBUILD $(objtree)/PKGBUILD
+	cd $(objtree) && \
+		srctree="$(realpath $(srctree))" \
+		objtree="$(realpath $(objtree))" \
+		BUILDDIR="$(realpath $(objtree))/pacman" \
+		CARCH="$(UTS_MACHINE)" \
+		KBUILD_MAKEFLAGS="$(MAKEFLAGS)" \
+		KBUILD_REVISION="$(shell $(srctree)/init/build-version)" \
+		makepkg
+
 # dir-pkg tar*-pkg - tarball targets
 # ---------------------------------------------------------------------------
 
@@ -221,6 +236,7 @@ help:
 	@echo '  bindeb-pkg          - Build only the binary kernel deb package'
 	@echo '  snap-pkg            - Build only the binary kernel snap package'
 	@echo '                        (will connect to external hosts)'
+	@echo '  pacman-pkg          - Build only the binary kernel pacman package'
 	@echo '  dir-pkg             - Build the kernel as a plain directory structure'
 	@echo '  tar-pkg             - Build the kernel as an uncompressed tarball'
 	@echo '  targz-pkg           - Build the kernel as a gzip compressed tarball'
diff --git a/scripts/package/PKGBUILD b/scripts/package/PKGBUILD
new file mode 100644
index 000000000000..ee4b77526b5f
--- /dev/null
+++ b/scripts/package/PKGBUILD
@@ -0,0 +1,83 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Maintainer: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
+# Contributor: Jan Alexander Steffens (heftig) <heftig@xxxxxxxxxxxxx>
+
+pkgbase=linux-upstream
+pkgname=("$pkgbase" "$pkgbase-headers" "$pkgbase-api-headers")
+pkgver="${KERNELRELEASE//-/_}"
+pkgrel="$KBUILD_REVISION"
+pkgdesc='Linux'
+url='https://www.kernel.org/'
+arch=($CARCH)
+options=(!debug !strip !buildflags !makeflags)
+license=(GPL-2.0-only)
+
+build() {
+  export MAKEFLAGS="${KBUILD_MAKEFLAGS}"
+  cd "$objtree"
+
+  # makepkg does a "chmod a-srw", triggering warnings during kbuild
+  chmod 0755 "$pkgdirbase" || true
+
+  $MAKE -f "${srctree}/Makefile"
+}
+
+package_linux-upstream() {
+  pkgdesc="The $pkgdesc kernel and modules"
+
+  export MAKEFLAGS="${KBUILD_MAKEFLAGS}"
+  cd "$objtree"
+  local modulesdir="$pkgdir/usr/$MODLIB"
+
+  echo "Installing boot image..."
+  # systemd expects to find the kernel here to allow hibernation
+  # https://github.com/systemd/systemd/commit/edda44605f06a41fb86b7ab8128dcf99161d2344
+  install -Dm644 "$($MAKE -s image_name)" "$modulesdir/vmlinuz"
+
+  # Used by mkinitcpio to name the kernel
+  echo "$pkgbase" | install -Dm644 /dev/stdin "$modulesdir/pkgbase"
+
+  echo "Installing modules..."
+  $MAKE INSTALL_MOD_PATH="$pkgdir/usr" INSTALL_MOD_STRIP=1 \
+    DEPMOD=true modules_install
+
+  if $MAKE run-command KBUILD_RUN_COMMAND='test -d ${srctree}/arch/${SRCARCH}/boot/dts' 2>/dev/null; then
+    echo "Installing dtbs..."
+    $MAKE INSTALL_DTBS_PATH="$modulesdir/dtb" dtbs_install
+  fi
+
+  # remove build link, will be part of -headers package
+  rm -f "$modulesdir/build"
+}
+
+package_linux-upstream-headers() {
+  pkgdesc="Headers and scripts for building modules for the $pkgdesc kernel"
+
+  export MAKEFLAGS="${KBUILD_MAKEFLAGS}"
+  cd "$objtree"
+  local builddir="$pkgdir/usr/$MODLIB/build"
+
+  echo "Installing build files..."
+  "$srctree/scripts/package/install-extmod-build" "$builddir"
+
+  echo "Installing System.map and config..."
+  cp System.map "$builddir/System.map"
+  cp .config "$builddir/.config"
+
+  echo "Adding symlink..."
+  mkdir -p "$pkgdir/usr/src"
+  ln -sr "$builddir" "$pkgdir/usr/src/$pkgbase"
+}
+
+package_linux-upstream-api-headers() {
+  pkgdesc="Kernel headers sanitized for use in userspace"
+  provides=(linux-api-headers)
+  conflicts=(linux-api-headers)
+
+  export MAKEFLAGS="${KBUILD_MAKEFLAGS}"
+  cd "$objtree"
+
+  $MAKE headers_install INSTALL_HDR_PATH="$pkgdir/usr"
+}
+
+# vim:set ts=8 sts=2 sw=2 et:

---
base-commit: 256abd8e550ce977b728be79a74e1729438b4948
change-id: 20240625-kbuild-pacman-pkg-b4f87e19d036

Best regards,
-- 
Thomas Weißschuh <linux@xxxxxxxxxxxxxx>