Plasma/Mobile/Porting

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Current Architecture of Plasma Mobile

For ARM devices which requires Android binary blobs

  • Kernel, either provided by vendor or thirdparty with config options enabled to support LXC containers
  • AOSP/LineageOS base, built with core_tiny target, just base items
  • LXC container with Neon/Ubuntu rootfs containing KWin/Wayland and Plasma Mobile

Kernel

Kernel needs to support the various config options, you can use lxc-checkconfig script provided by lxc userspace tools to check if all required features are enabled, for example:

% CONFIG=arch/arm64/configs/bullhead_defconfig lxc-checkconfig
--- Namespaces ---
Namespaces: enabled
Utsname namespace: enabled
Ipc namespace: enabled
Pid namespace: enabled
User namespace: enabled
Network namespace: missing
Multiple /dev/pts instances: enabled

--- Control groups ---
Cgroup: enabled
Cgroup clone_children flag: enabled
Cgroup device: enabled
Cgroup sched: enabled
Cgroup cpu account: enabled
Cgroup memory controller: enabled
Cgroup cpuset: enabled

[..]

Below is the list of the config options,

CONFIG_CGROUP_DEVICE=y
CONFIG_CPUSETS=y
CONFIG_CGROUP_MEM_RES_CTLR=y
CONFIG_CGROUP_PERF=y
CONFIG_UTS_NS=y
CONFIG_IPC_NS=y
CONFIG_USER_NS=y
CONFIG_PID_NS=y
CONFIG_DEVPTS_MULTIPLE_INSTANCES=y

AOSP/LineageOS base

AOSP/LineageOS base should have all non-required things removed and some changes in base to accomodate needs of libhybris and container containing Linux system. Below is list of various changes,

Export PATH and LD_LIBRARY_PATH to point to lxc userspace tools

We use prebuilt lxc userspace tools from linux containers CI. Those are installed in /data partition which by default is not in the PATH android shell looks binaries into. Modify the system/core/rootdir/init.environ.rc file to include the path of LXC userspace tools in $PATH and export LD_LIBRARY_PATH.

project system/core/
diff --git a/rootdir/init.environ.rc.in b/rootdir/init.environ.rc.in
index c32337a..9d91d60 100644
--- a/rootdir/init.environ.rc.in
+++ b/rootdir/init.environ.rc.in
@@ -1,6 +1,6 @@
 # set up the global environment
 on init
-    export PATH /sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin
+    export PATH /data/lxc/lxc/bin:/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin
     export ANDROID_BOOTLOGO 1
     export ANDROID_ROOT /system
     export ANDROID_ASSETS /system/app
@@ -8,6 +8,7 @@ on init
     export ANDROID_STORAGE /storage
     export ASEC_MOUNTPOINT /mnt/asec
     export LOOP_MOUNTPOINT /mnt/obb
+    export LD_LIBRARY_PATH /data/lxc/lxc/lib
     export BOOTCLASSPATH %BOOTCLASSPATH%
     export SYSTEMSERVERCLASSPATH %SYSTEMSERVERCLASSPATH%
     export LD_PRELOAD libsigchain.so%TARGET_LDPRELOAD%

However, LD_LIBRARY_PATH doesn't work for AOSP based android image and needs investigation. See phabricator task for more details.

Disable enforced PIE executables in bionic

Disable SELinux

Remove the nosuid,nodev option from the data partition

Apply bionic patch to shift TLS slots

Fix Permission for backlight brightness file

For devices which don't require Android binary blobs

  • Normal Linux system with kernel and drivers supporting Wayland
  • KWin/Wayland and Plasma Mobile packages

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