Linux on mobile devices Jozef Mlích Department of Computer Graphics and Multimedia Brno University of Technology, Faculty of Information Technology Božetěchova 2, 612 66 Brno, Czech Republic [email protected] http://www.fit.vutbr.cz/~imlich/ Application Development for Mobile DevicesTAM 2020 8.12.2020 | 1 / 32 Outline Motivation Alternative operating systems Where to get hardware Architecture of mobile operating system Development http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 2 / 32 Motivation Motivation Do it your self – learn something Special needs – Create new concept / add some extra feature / very special hardware Security – how we can trust to Chinese/Russian/US/* product? Longevity – security updates are available ~ 2 – 6 years depending on vendor Vendor lock-in – US Export laws http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 4 / 32 Software Distributions postmarketOS Nemo Mobile Ubuntu Touch KDE Neon Mobian NixOS Maemo Leste LuneOS SailfishOS Sxmo PureOS openSUSE Fedora AVMultiPhone Arch Linux ARM GloDroid Manjaro ARM Gentoo AsteroidOS Tizen LineageOS http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 6 / 32 Desktop Environment xfce4 Maemo Nemo Plasma Mobile Phosh Android http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 7 / 32 Hardware Hardware Librem 5 PinePhone F(x)tec Pro Dragonbox Pyra Motorola Droid 4, Nokia N900 Raspberry Pi And others Find your device at https://wiki.postmarketos.org/wiki/All_devices http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 9 / 32 Architecture Architecture depends on your needs http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 11 / 32 Hardware http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 12 / 32 Architecture I Bootloader Kernel – Drivers (+libhybris) – AOSP – Not sure what API is the right one for given task – /proc or GPSD or dbus GUI – Framebuffer, XOrg, Wayland – On-screen keyboard http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 13 / 32 Architecture II Modem / Networking – oFono, Network Manager, AT+?, QMI Audio – PulseAudio profiles Userspace applications http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 14 / 32 Bootloader http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 15 / 32 Boot FSBL (hardware ROM) Bootstrapping Bootloader – chicken or the egg problem – u-boot (blob, bootldr, redboot, – Limited resources able, etc.) Kernel Requirements Device tree / EFI – Keyboard vs. Volume keys vs Initramfs Touch screen only – charging Rootfs + Systemd (SYS V init) http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 16 / 32 Multimedia http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 17 / 32 Development Development (Cross) Compilation Remote debugging Profiling Security End user apps http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 19 / 32 Compilation export CC=/usr/local/bin/arm-linux-gnueabi-gcc export CFLAGS=-I /usr/local/arm_root/include make qmake myproject.pro -r -spec linux-g++-maemo http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 20 / 32 Remote debugging http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 21 / 32 Profiling Monitor – CPU load – Memory consumption – Network traffic (change of IM timeout added +1h) – Number of waking up and suspends (C-states) – Frequency of CPU – Interrupts (IRQs) (or NAPI) Pro-tip: try to use “heartbeat” or gproof, powertop, and much more Qt::VeryCoarseTimer to spare some CPU ticks. (perf cheat sheet) Android AlarmManager.setInexactRepeating(..) http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 22 / 32 Profiling http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 23 / 32 Performance cheat sheet ( 1 of 8 ) http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 24 / 32 Security Hardware security – Intel Management Engine – Baseband UEFI Posix permission, ACLs SELinux Chroots, Cgroup, Containers Flatpak portals http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 25 / 32 End user apps Anbox – android machine on linux – Google services are allowed only in Android Packaging – *.deb, *.rpm, *.apk – depends on distro – Flatpak, snap, appimage Monetization http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 26 / 32 Questions? Questions How does embedded hardware (phones) boots? What Linux distributions do we have? Are there some alternative Android distribution? Which indicators should be observed when developing mobile applications? How we can observe them? How we can reduce power consumption? How is the security designed on mobile linux distributions? http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 28 / 32 References Performance cheat sheet http://www.brendangregg.com/linuxperf.html CCC Chaos Communication Congress https://fahrplan.events.ccc.de/congress/2016/Fahrplan/events.html http://elinux.org/ Hoque, M.A., M. Siekkinen, and J.K. Nurminen. “On the Energy Efficiency of Proxy-based Traffic Shaping for Mobile Audio Streaming.” In 2011 IEEE Consumer Communications and Networking Conference (CCNC), 891 –895, 2011. Alternative Androids – https://copperhead.co/ https://lineageos.org/ https://www.replicant.us/ http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 29 / 32 Do we have time yet? PostmarketOS Based on Alpine Linux https://postmarketos.org/ /etc/deviceinfo Cross-compile all armhf- packages Effective caching out of the box (ccache) Flasher abstraction – Fastboot – heimdall UI (Phosh, Plasma, hildon, LuneOS ui, XFCE4, weston) http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 31 / 32 Motivation Baseband exploitation – AT+QCMD=uname -a http://www.fit.vutbr.cz/~imlich/ TAM 2020 | 32 / 32.