classes: Update overlayfs classes to use new bitbake functionality

OverlayFS classes belong to a recipe scope

(From OE-Core rev: 7afa7739e82220729566ccabe2675a8991f9485a)

Signed-off-by: Vyacheslav Yurkov <v.yurkov@precitec.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 137 insertions, 0 deletions

diff --git a/meta/classes-recipe/overlayfs.bbclass b/meta/classes-recipe/overlayfs.bbclass
new file mode 100644
index 0000000000..bdc6dd9d57
--- /dev/null
+++ b/meta/classes-recipe/overlayfs.bbclass
@@ -0,0 +1,137 @@
+#
+# Copyright OpenEmbedded Contributors
+#
+# SPDX-License-Identifier: MIT
+#
+
+# Class for generation of overlayfs mount units
+#
+# It's often desired in Embedded System design to have a read-only rootfs.
+# But a lot of different applications might want to have a read-write access to
+# some parts of a filesystem. It can be especially useful when your update mechanism
+# overwrites the whole rootfs, but you want your application data to be preserved
+# between updates. This class provides a way to achieve that by means
+# of overlayfs and at the same time keeping the base rootfs read-only.
+#
+# Usage example.
+#
+# Set a mount point for a partition overlayfs is going to use as upper layer
+# in your machine configuration. Underlying file system can be anything that
+# is supported by overlayfs. This has to be done in your machine configuration.
+# QA check fails to catch file existence if you redefine this variable in your recipe!
+#
+#   OVERLAYFS_MOUNT_POINT[data] ?= "/data"
+#
+# Per default the class assumes you have a corresponding fstab entry or systemd
+# mount unit (data.mount in this case) for this mount point installed on the
+# image, for instance via a wks script or the systemd-machine-units recipe.
+#
+# If the mount point is handled somewhere else, e.g. custom boot or preinit
+# scripts or in a initramfs, then this QA check can be skipped by adding
+# mount-configured to the related OVERLAYFS_QA_SKIP flag:
+#
+#   OVERLAYFS_QA_SKIP[data] = "mount-configured"
+#
+# To use the overlayfs, you just have to specify writable directories inside
+# their recipe:
+#
+#   OVERLAYFS_WRITABLE_PATHS[data] = "/usr/share/my-custom-application"
+#
+# To support several mount points you can use a different variable flag. Assume we
+# want to have a writable location on the file system, but not interested where the data
+# survive a reboot. Then we could have a mnt-overlay.mount unit for a tmpfs file system:
+#
+#   OVERLAYFS_MOUNT_POINT[mnt-overlay] = "/mnt/overlay"
+#   OVERLAYFS_WRITABLE_PATHS[mnt-overlay] = "/usr/share/another-application"
+#
+# If your recipe deploys a systemd service, then it should require and be
+# started after the ${PN}-overlays.service to make sure that all overlays are
+# mounted beforehand.
+#
+# Note: the class does not support /etc directory itself, because systemd depends on it
+# For /etc directory use overlayfs-etc class
+
+REQUIRED_DISTRO_FEATURES += "systemd overlayfs"
+
+inherit systemd features_check
+
+OVERLAYFS_CREATE_DIRS_TEMPLATE ??= "${COREBASE}/meta/files/overlayfs-create-dirs.service.in"
+OVERLAYFS_MOUNT_UNIT_TEMPLATE ??= "${COREBASE}/meta/files/overlayfs-unit.mount.in"
+OVERLAYFS_ALL_OVERLAYS_TEMPLATE ??= "${COREBASE}/meta/files/overlayfs-all-overlays.service.in"
+
+python do_create_overlayfs_units() {
+    from oe.overlayfs import mountUnitName
+
+    with open(d.getVar("OVERLAYFS_CREATE_DIRS_TEMPLATE"), "r") as f:
+        CreateDirsUnitTemplate = f.read()
+    with open(d.getVar("OVERLAYFS_MOUNT_UNIT_TEMPLATE"), "r") as f:
+        MountUnitTemplate = f.read()
+    with open(d.getVar("OVERLAYFS_ALL_OVERLAYS_TEMPLATE"), "r") as f:
+        AllOverlaysTemplate = f.read()
+
+    def prepareUnits(data, lower):
+        from oe.overlayfs import helperUnitName
+
+        args = {
+            'DATA_MOUNT_POINT': data,
+            'DATA_MOUNT_UNIT': mountUnitName(data),
+            'CREATE_DIRS_SERVICE': helperUnitName(lower),
+            'LOWERDIR': lower,
+        }
+
+        bb.debug(1, "Generate systemd unit %s" % mountUnitName(lower))
+        with open(os.path.join(d.getVar('WORKDIR'), mountUnitName(lower)), 'w') as f:
+            f.write(MountUnitTemplate.format(**args))
+
+        bb.debug(1, "Generate helper systemd unit %s" % helperUnitName(lower))
+        with open(os.path.join(d.getVar('WORKDIR'), helperUnitName(lower)), 'w') as f:
+            f.write(CreateDirsUnitTemplate.format(**args))
+
+    def prepareGlobalUnit(dependentUnits):
+        from oe.overlayfs import allOverlaysUnitName
+        args = {
+            'ALL_OVERLAYFS_UNITS': " ".join(dependentUnits),
+            'PN': d.getVar('PN')
+        }
+
+        bb.debug(1, "Generate systemd unit with all overlays %s" % allOverlaysUnitName(d))
+        with open(os.path.join(d.getVar('WORKDIR'), allOverlaysUnitName(d)), 'w') as f:
+            f.write(AllOverlaysTemplate.format(**args))
+
+    mountUnitList = []
+    overlayMountPoints = d.getVarFlags("OVERLAYFS_MOUNT_POINT")
+    for mountPoint in overlayMountPoints:
+        bb.debug(1, "Process variable flag %s" % mountPoint)
+        for lower in d.getVarFlag('OVERLAYFS_WRITABLE_PATHS', mountPoint).split():
+            bb.debug(1, "Prepare mount unit for %s with data mount point %s" %
+                     (lower, d.getVarFlag('OVERLAYFS_MOUNT_POINT', mountPoint)))
+            prepareUnits(d.getVarFlag('OVERLAYFS_MOUNT_POINT', mountPoint), lower)
+            mountUnitList.append(mountUnitName(lower))
+
+    # set up one unit, which depends on all mount units, so users can set
+    # only one dependency in their units to make sure software starts
+    # when all overlays are mounted
+    prepareGlobalUnit(mountUnitList)
+}
+
+# we need to generate file names early during parsing stage
+python () {
+    from oe.overlayfs import strForBash, unitFileList
+
+    unitList = unitFileList(d)
+    for unit in unitList:
+        d.appendVar('SYSTEMD_SERVICE:' + d.getVar('PN'), ' ' + unit)
+        d.appendVar('FILES:' + d.getVar('PN'), ' ' +
+                d.getVar('systemd_system_unitdir') + '/' + strForBash(unit))
+
+    d.setVar('OVERLAYFS_UNIT_LIST', ' '.join([strForBash(s) for s in unitList]))
+}
+
+do_install:append() {
+    install -d ${D}${systemd_system_unitdir}
+    for unit in ${OVERLAYFS_UNIT_LIST}; do
+        install -m 0444 ${WORKDIR}/${unit} ${D}${systemd_system_unitdir}
+    done
+}
+
+addtask create_overlayfs_units before do_install