Embedded Software Lab. @ SKKU 43 1 Tizen Bootup. Embedded Software Lab. @ SKKU 43 2 Bootloader...

Embedded Software Lab. @ SKKU

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Tizen Bootup


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• Bootloader overview• Tizen U-boot• Tizen Systemd• Platform bootup

Contents


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Bootloader


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• Bootloader– Pass Machine ID and the boot arguments to

kernel

Tizen bootup overview

ROM codePower onBooting device

Bootloader

Kernel

Platform


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• What is boot loader ?– A boot loader is the first program which

executes (before the main program i.e. kernel ) whenever a system is initialized

– A boot loader is a computer program that loads the main program (i.e. operating system, kernel ) for the board after completion of the self-tests

• Why boot loader is needed ?– Gives a development environment– Saves cost of flash writers– Give flexibility to load any operating system

What is bootloader


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• What are different types of boot loaders ?– Boot-ROM ( or Pre-Boot Loader)

• Small code which loads First stage boot loader

– First Stage Boot Loader• Small Piece of code that initialize the NAND/MMC &

DRAM controller.

– Second Stage Boot Loader• Primary function of the second-stage boot loader is to

Loading the kernel into RAM or jumping directly to the start of the kernel.

Types of bootloader

Pre-Bootloader

First-StageBootloader

Second-Stage

BootloaderOS Kernel


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Exynos4412

U-boot loading process

Internal ROM

Internal SRAM

Cortex-A9

DRAM controller DRAM

Booting Device

(NAND, MMC, SD, USB)

eSSD controller

NAND controller

SD/MMC controller

UART/USB

1st BL2nd BL

OS

iROM code1

2

3


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• BL0; iRom code (boot-rom or pre-boot loader)– Simple platform independent code, stored in internal ROM– Initialize basic functions (clock, stack, heap, etc)– Load first stage boot loader (from booting device to

internal SRAM)• BL1; first boot loader

– Simple platform independent code, stored in external memory(booting device)

– Load second boot loader– Initialize NAND/MMC and DRAM controller

• BL2; second boot loader– Platform dependent complex code, stored in external

memory– Initialize clock, UART– Load OS image from booting device to DRAM– Jump to operating system

U-boot loading process


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Tools to build S-Record or U-boot images

Example code for standalone applications

Filesystem code (cramfs, ext2, jffs2, etc.)

Header files

Files generic to all architectures

Networking code

Power on self test

Real time clock drivers

Machine/arch independent API

Architecture specific files

Board dependent files

Misc architecture independent functions

Code for disk drive partition handling

Documentation

Commonly used device drivers

U-boot directory structure

/u-boot

board

common

doc

drivers

include

lib

net

examples

fs

rtc

tools

post

arch

disk

api

/u-boot


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1. Disable all interrupts2. Copy any initialized data from ROM to RAM3. Zero the uninitialized data area4. Allocate space for and initialize the stack5. Initialize the processor’s stack pointer6. Create and initialize the heap7. Execute the initializers for all global data8. Enable interrupts9. Call main loop

U-boot code sequence


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11U-boot code sequence

Setup SP for Early Board Setup

Environment (ASM->C)

Calculate Addresses (SP, Dest, GD) for Relocation

General Relocation

Copy Binary to RAM

Fix Relocation

Clear BSS

Setup SP for Common Board Setup

Setup GD and JUMP toFinal Board Setup

Low Level Initialization

lowlevel_init

cpu_init_crit

Disable MMU

Invalidate and disable Instruction & data

Cache

Disable IRQ &FIQ. Switch to supervisor mode

cpu/armv7/start.Sreset()

Reset CPU and Hardwarecpu/armv7/start.S

_start()

arm/lib/crt0.S_main()

Early Board Setup

arm/lib/crt0.Sboard_init_f()

arm/lib/crt0.Sboard_init_r()board/samsung/

lowlevel_init.Slowlevel_init()

cpu/armv7/start.S relocate_code()

Jump into main loop


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• _start() /* Entry point function */• reset() /* Reset CPU configurations */

– save_boot_params() /* Save boot parameters */– Disable the FIQ & IRQ– Switch to supervisor mode– cpu_init_crit()

• Invalidate I, D Cache• Disable I cache if CONFIG_SYS_ICACHE_OFF• Disable MMU• lowlevel_init()

• _main() /* setup initial stack & global data. And jump to C routine for board

initialization */



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• board_init_f()– arch_cpu_init // basic arch cpu dependent setup– board_early_init_f // early board initialization, UART pin setting– timer_init // initialize timer– env_init // initialize mmc/sdcard environment– init_baudrate // initialize baudrate settings– serial_init // serial communication setup– console_init_f // stage 1 init of console, configure console from

console.c– display_banner // say that we are here, print u-boot banner– print_cpuinfo // display cpu info – checkboard // display board info– init_func_i2c // initialize I2C– dram_init // configure available RAM backs– arm_pci_init



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• board_init_r()– board_init // setup chipselects specific configuration– logbuff_init_ptrs // initialize default log level– mem_malloc_init // configure malloc area– nand_init mmc_init // initialize flash/mmc– env_relocate // relocate environment or set NULL– stdio_init // setup stdio ready for use– api_init // initialize API– console_init_r // fully init console as a device– arch_misc_init // miscellaneous arch dependent initialization– misc_init_r // miscellaneous platform dependent initialization– interrupt_init // set up exceptions– enable_interrupts // enable exceptions– board_late_init // board late initialization– eth_initialize // setup ethernet– main_loop // jump to main loop & waiting for commands from

console



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15U-boot code sequence

Jump to kernel image address

main_loop()

Autoboot_mode()

Command_mode()

boot() loads() flash()tftpboot(

)

Input command

Wait for 3 seconds Key pressed within 3 seconds


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16Loading through U-boot

SDRAMSDRAM

RootFile-

System

Kernel

Booting deviceBooting device

Kernel Image

Bootloaderuboot

Root File System

Reset

Bootloaderuboot

CPUCPU

Optional compressed


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• Packing uImage– When the kernel is complied, mkimage attaches

image_header to kernel image

• Unpacking uImage– Magin number CRC check decompress get board

information kernel booting

Loading through U-boot

#define IH_MAGIC 0x27051956 /* Image Magic Number */ #define IH_NMLEN 32 /* Image Name Length */ typedef struct image_header {

uint32_t ih_magic; /* Image Header Magic Number */uint32_t ih_hcrc; /* Image Header CRC Checksum */uint32_t ih_time; /* Image Creation Timestamp */uint32_t ih_size; /* Image Data Size */uint32_t ih_load; /* Data Load Address */uint32_t ih_ep; /* Entry Point Address */uint32_t ih_dcrc; /* Image Data CRC Checksum */uint8_t ih_os; /* Operating System */uint8_t ih_arch; /* CPU architecture */uint8_t ih_type; /* Image Type */uint8_t ih_comp; /* Compression Type */uint8_t ih_name[IH_NMLEN]; /* Image Name */

} image_header_t;


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• Architecture dependent setup– setup_arch() [/arch/arm/kernel/setup.c]

• Exception(or trap) initialization– trap_init() [/arch/arm/kernel/trap.c]

• Interrupt initialization– init_IRQ() [/arch/arm/kernel/irq.c]– sotfirq_init() [/kernel/sotfirq.c]

• Scheduler initialization– sched_init() [/kernel/sched.c]

• Timer initialization– time_init() [/arch/XXX/kernel/time.c]

• Console initialization– console_init() [/driver/char/tty_io.c]

• Module initialization– init_module() [/kernel/module.c]

start_kernel


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• Memory & System initialization , Cache & Buffer initialization , File system initialization– kmem_cache_init() [/mm/slab.c]– mem_init() [/arch/a,r/mm/init.c]– kmem_cache_size() [/mm/slab.c]– fork_init() [/kernel/fork.c]– proc_caches_init() [/kernel/fork.c]– vfs_caches_init() [/fs/dcache.c]– buffer_init() [/fs/buffer.c]– page_cache_init() [/mm/filemap.c]– signals_init() [/kernel/signal.c]– proc_root_init() [/fs/proc/root.c]– ipc_init() [/ipc/util.c]

• init process creation– rest_init() [/init/main.c]

start_kernel


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systemd


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• Sysvinit– userspace launch (PID 1)– Only one process at a time running– Simply starting the system and then going to sleep

until the next reboot• Systemd

– Default init in Fedora 15 and later Leonard Poettering (2009)

– improve the software framework for expressing dependencies

– allow more processing to be done concurrently or in parallel during system booting

– reduce the computational overhead of the shell.

What is systemd?


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• Systemd in Tizen– System and service manager for tizen systemd– Ver. 43 (download

http://www.freedesktop.org/software/systemd/)– Parallelizes service execution– Socket and D-Bus activation for starting services and

daemon– on-demand starting of daemons– Managing the service processes as a group using Linux

cgroup– Supporting automount points– Snapshotting and restoring of services

What is systemd?


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• systemd Utility – monitoring and controlling systemd itself and its services– 'systemctl' developers can query or send control commend to the

systemd service manager – 'systemd-journalctl' utility to see log message

• systemd target – Tizen boot-up process is split up in various discrete steps and each

step are grouped its unit using 'Target' unit to synchronize point

– The boot-up process is highly parallelized in each target so that the order in which specific target units are reached in not deterministic

• systemd daemon – system and service manager for Tizen platform– acts as init system– 'systemd' daemonruns as user session with '--user' option– 'systemd-journald' is a system service that collects and stores log

data from the Kernel, from user processes via syslog or STDOUT/STDERR

systemd architecture


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• systemd core – manages all units such as service, socket, mount and so on,

stores all log data. – controlled by using systemd utility like 'systemctl'

• systemd library & Linux Kernel – systemd requires to enable 'cgroup' and 'autofs' option in

Kernel configuration– It also depends on dbus and some libraries such as libnotify,

libudev

systemd architecture


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• Early boot-up scripts– Most of file system are mounted and systemd related daemons are launched

Platform bootup – sysinit.target

basic.target

sysinit.target

multi-user.target

graphical.target

bootmode.target

Kernel

local-fs.target

swap.target

socket.target

-.mountboot.mountcsa.mountfsck-root.servicemedia.mountopt-usr.mountopt.mountremount-rootfs.serviceresize2fs-root.servicesystemd-remount-api-vfs.servicevar-run.mount

dev-hugepages.mountdev-mqueue.mountproc-sys-fs-binfmt_misc.automountsys-fs-fuse-connections.mountsys-kernel-config.mountsys-kernel-debug.mountsys-kernel-security.mountsystemd-ask-password-console.pathsystemd-binfmt.servicesystemd-journald.servicesystemd-modules-load.servicesystemd-random-seed-load.servicesystemd-readahead-collect.servicesystemd-readahead-replay.servicesystemd-sysctl.servicesystemd-tmpfiles-setup.service

dbus.socketsystemd-initctl.socketsystemd-journald.socketsystemd-shutdownd.sockettelnetd.socketudev-control.socketudev-kernel.socket


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• Basic boot-up– All necessary initialization for general purpose daemons are completed

Platform bootup – basic.target

basic.target

sysinit.target

multi-user.target

graphical.target

bootmode.target

Kernel

opt-var-kdb-db-libsqlfs.serviceopt-var-kdb-db-smack-labels.servicesmack-default-labeling.servicesystemd-tmpfiles-clean.timertizen-debug-level.serviceudev-trigger.serviceudev.servicevconf-setup.service


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• Select boot mode– If kernel boot parameter has ‘charger_detect_boot’, the platform boots up as

charging mode

Platform bootup – bootmote.target

basic.target

sysinit.target

multi-user.target

graphical.target

bootmode.target

Kernel

bootmode-charging.servicebootmode-graphical.service


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• Setup a multi-user system which is non-graphical support– Launching platform infrastructure daemons (such as dbus, power manager, gps

manager, telephony daemon, WRT security daemon, media server, systemd-related daemons)

Platform bootup – multi-user.target

basic.target

sysinit.target

multi-user.target

graphical.target

bootmode.target

Kernelalarm-server.serviceavsystem.servicebluetooth-address.servicebluetooth-frwk-service.servicebluetooth.servicedbus.servicedlog-main.servicedlog-radio.servicegetty.targetgps-manager.servicemedia-server.servicenfc-manager.servicepower-manager.servicepulseaudio.servicesecure-storage.servicesensor-framework.servicesystem-server.servicesystemd-ask-password-wall.pathsystemd-logind.servicesystemd-user-sessions.servicetelephony.service


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• Setup a graphical environment– System user session for app privilege daemons such as Enlightenment (window

manager)– Special target for middleware & mobile service

Platform bootup – graphical.target

basic.target

sysinit.target

multi-user.target

graphical.target

bootmode.target

Kernel

core-efl.target tizen-middleware.targetboot-animation.servicecbhm.servicee17.serviceindicator.serviceosp-app-service.servicequickpanel.servicescim.servicestarter.pathxmodmap.servicexrdb.service

[email protected]@[email protected]

calendar.servicecontacts-service.servicedownload-provider.serviceemail.servicemsg-service.servicepushd.servicesound-server.service

tizen-mobile-session.target

wrt-preinstall-widgets.service

xorg.target

xorg.service


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Systemd parsing


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• systemd– Control is moved from initramfs to systemd of Tizen platform– Run hardware init and fs mount, etc services– Bootup process run several units (.target)

• Different target can be run in parallel– Many linux distributions adopt systemd as default

• Red Hat Enterprise Linux, CentOS, Fedora, Arch Linux, openSUSE

– Do not use daemon control script (/sbin/init, /etc/init.d/*, /etc/rc*.d)

– /usr/lib/systemd• unit files: service, target, socket, device, mount,

automount, path, snapshot, swap, timer• systemd utilities: systemctl, notify, analyze, cgis, cgtop,

logictl, journalctl, nspawn

Platform bootup


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• https://wiki.tizen.org/wiki/Porting_Guide

Platform bootup

entry point

.target vs .service• .target; service grouping• .service; process run


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• /usr/lib/systemd/system

• cat sysinit.target

Parsing unit file – example (1/8)

target to parse


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• Website – http://www.freedesktop.org/wiki/software/systemd/

• systemd download– http://www.freedesktop.org/software/systemd/

Parsing unit file – example (2/8)

manpage


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Can search all function and unit, configuration of systemd

enter target index


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target unit file


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Description on unit file option


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• User awareness unit name = “System Initialization”• If emergency is running, wait• Run with local-fs.target, swap.target, sysinit.target.wants• Run after local-fs.target, swap.target, emergency.service, emergency.target• User can control service start and stop


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• [Unit], [Service], [Install], [Socket], [Swap], [Mount], …– example; telephony.service– [Unit]; general options

• unit name = Telephony daemon• Run after modem.service

– [Service]; process options• Run telephony-daemon as main process

– [Install]; actual work of unit excute• Create telephony.service symlink at multi-user.target.wants

Different Sessions


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• systemd official Site http://www.freedesktop.org/wiki/Software/systemd/

• systemd FAQ (written by developer)– http://0pointer.de/blog/projects/the-biggest-myths

References

Date post:	15-Dec-2015
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