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MontaVista LinuxProfessional EditionJump Start Training

Embedded Linux Technology Inc.,

Taiwan Branch

Email: jesse@emblit.co.jp

TEL: 02-23784056

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Agenda

• 10:10 ~ 11:00– Preparing Development

System

– Development Environment

– Boot ROM

• 11:10 ~ 12:00– Boot Configure and

Download

– MontaVista Development Tools (I)

• 13:10 ~ 14:00 – MontaVista Development

Tools (II)

• 14:10 ~ 15:00– File Systems

– Kernel Modules

• 15:10 ~ 16:00– MontaVista Realtime

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Preparing Development System• MontaVista Software Package Installation• Supported Host Distributions

– MVL PE 2.1: MVL PE 3.0:• Mandrake 7.2, 8.0 and 8.1 8.1• RedHat 6.2, 7.0, 7.1 and 7.2 7.2 and 7.3• SuSE 7.3 7.3• Yellow Dog 2.1 2.1• Solaris 7 and 8 7 and 8• VMware[tm] Workstation 3.1 on Windows(R) NT/2000/XP

with a Red Hat 7.2 Host

• Host Configuration– NFS, bootp, tftp, firewall, $PATH, …– $PATH: /opt/hardhat/devkit/host/bin

/opt/hardhat/devkit/arm/xscale_be/bin

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Development Environment

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Boot ROM• Possible Duties

– Turn on various chip enables (so RAM exists)

– Initialize I/O chips possibly including serial port to report Boot ROM success/fail and a network or disk device interface to boot the OS

– Perform system self-test, report results– Provide an command line interface (CLI)– Receive S Records into RAM, and then

burn that compressed data into Flash

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Boot ROM• Contents

– Board- and CPU architecture-specific initialization code

– Ability to download the operating system image through one or more mechanisms

– Transfer control to that software– May also assist in debugging the

application system, and running system integrity tests

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Boot ROM• Booting the Target System

– Step #1: Press the target Reset button (if it has one) or apply power to the target

– Boot ROM begins executing for the very first time

– Step #1A: Boot ROM looks to you for help.– Step #1B: Configure Boot ROM according

to how you want it to boot your test software. Tell Boot ROM to remember those settings.

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Boot ROM

• Booting the Target System (cont’d)– Step #2: Press target Reset or cycle

the power– Boot ROM downloads your test

software and jumps into it– Your test software is now running– Repeat Step #2 as needed

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Boot ROM• Who, in general, creates Boot ROMs?• Who is responsible for the Boot ROM

you will be using?• Redboot: frequently used Xscale bootstrap

– Developed by RedHat

– How to get source and toolchain for Redboot

– URL: http://sources.redhat.com/redboot

– “Embedded Software Development with eCOS”, A. J. Massa, Prentice Hall

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Boot Config. & Download• Assumptions for the Lab Equipment

– Using BOOTP and TFTP to transfer the booting operating system from the host system disk to the target system memory

– A portion of the host’s file system will be available to the target operating system by an NFS mount

• The Steps– Step B - Build the target binary (vmlinux)– Step C - Configure the target & host network

capabilities– Step D - Download the binary to the target– Step E - Execute program(s) on the target

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Boot Config. & Download

• Step B - Build the target binary (vmlinux)– Linux uses the make utility extensively.– Sources organized into subdirectories– vmlinux built from archives and libraries– If compressed, it is then called vmlinuz– Booter and optional RAM disk are then added

and the composite is named zvmlinuz, zImage or bzImage

– Some boards need S-Records / other formats– Convert as needed (zsrec utility, etc...)

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Boot Config. & Download• Step C: Configure the host network

capabilities– BOOTP (uses DHCP)– TFTP Daemon– NFS Information– Minicom– Refer to the MontaVista Linux

Professional Edition User’s Guide and Quick Start Guide for your LSP

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Boot Config. & Download

• Step D: Download the binary to the target– Configure the target board (as previously described)– Configure any host daemons (as previously

described)– Interconnect host and target– Activate the target’s firmware to retrieve the

previously built zImage binary file and transfer control into it

– The first part of zImage, the Linux Boot Loader, uncompresses Linux and places it at the appropriate memory address

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Boot Config. & Download• Step D: Download the binary to the target (cont’d)

– The Linux Boot Loader also uncompresses the RAM disk image, if present, and places it in memory

– Finally, the Linux Boot Loader transfers control to the uncompressed Linux image

– (vmlinux) along with a command line describing the RAM disk image (if present)

– Linux initializes itself including the hardware Memory Management Unit (MMU) that translates logical (or virtual) addresses into physical (or real addresses.)

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Loading: Image Loader

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Loading: Linux Boot Loader

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Loading: Linux Startup

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Boot Config. & Download

• Step E: Execute program(s) on the target– Linux mounts the initial file system from RAM Disk, or

NFS Disk, or Local Disk.– Linux, in init/main.c searches for the init first as /sbin/init, then as /etc/init, then /bin/init and finally /bin/sh (any of which could be a binary executable, a shell script, or any other file that Linux knows how to execute) and then executes it.

– Typically, it is the /sbin/init program that is executed at this point.

– /sbin/init processes the /etc/inittab file. See man init and man inittab for complete details on starting your own application programs via the init process.

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Development Tools• Kdevelop

– Enhanced for development of remote targets by MontaVista

– Integrated Development Environment (IDE)– Microsoft Visual C++ -like– Brief tutorial included in MontaVista Linux

Professional Edition, Reference Guide– More extensive instructions are available in

the on-line help within kdevelop itself.– Works best with C and C++– Works with Assembler also

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Development Tools

• GNU gcc and g++– gcc - C Compiler– g++ - C++ Compiler– A family of compilers for various target CPUs– A front-end for the build process including

preprocessor, compiler, assembler and linker

• Assembler and Linker– as – ld

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Development Tools

• Binutils: a collection of binary tools– ar - Manages object file archives– nm - List symbols from object files– objcopy - Copy and translate object

files– size - List text, data and bss sizes– strip - Remove symbols– addr2line - Convert addresses to file

and line

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Development Tools

• make and Makefile– Traditional Unix tool– Almost anything you can do by hand (and

then some) can be done through a Makefile

– Lots of good books from which to learn– Notably "Managing Projects with Make"

(Pub: O’Reilly)

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Development Tools• A simple Makefile example

# Makefile for ferretCC=xsacle_be-gccTARGET=/opt/hardhat/devkit/arm/xscale_be/target

all: installinstall: ferretcp ferret $(TARGET)

ferret: ferret.c Makefile$(CC) -D_REENTRANT -O $< -o $@ -lpthread

clean:- rm -f ferret.o ferret $(TARGET)/ferret

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Development Tools

• Source Debugging– gdb (on host) with gdbserver (on target)– Preparing the object files (compiling with -g

and –ggdb option)• No optimization makes it easier to follow execution

but performance may change dramatically when recompiled with full optimization

• Full optimization may lead to surprising leaps and jumps when executing and "watching" with gdb

• Optimization is optional for user-level applications but in the kernel it is mandatory.

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Development Tools

• Source Debugging– Starting the gdbserver on the target

• Receives requests from gdb on host• Sends answers to gdb on host• gdbserver is very small• Symbol table and source files on host system• Full (-g or -ggdb) contents needed only on host• Only the executable binary is on the target

– Connecting gdb and gdbserver– DDD: GUI front-end for gdb

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Development Tools

• Learning more about gdb– The GNU Web-Site, http://www.gnu.org/– Books, see “Beginning Linux Programming”,

Richard Stones and Neil Matthew , WROX Press, Ltd., 1-861002-97-1.

– Use the help command in gdb itself.

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Development Tools

• Target Configuration Tool (TCT)– The tool that customize your Kernel and file

system– Features

• Project and Configuration Management• Kernel Configure• Package Selector• Dependencies Check• The targetpkg Utility• Library Optimzation Tool (LOT)

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Development Tools

• Linux Trace Toolkit (LTT)– Fully-featured tracing system for the Linux kernel. It

includes both the kernel components required for tracing and the user-level tools required to view the traces.

– Micro-second event time-stamps– Minimal performance overhead (< 2.5 %). – Multi-platform support– Friendly GUI with event graph, system and per-process

analysis, and raw event descriptions.

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Development Tools

• Linux Trace Toolkit (LTT) Usage Steps– Enable Linux "Kernel Tracing" configuration– Create the tracer device entry in target's /dev if

they are not available in your file system.– Start the trace daemon in target:

tracedaemon -ts10 /dev/tracer ./out.trace ./out.proc

– Run "tracevisualizer" in host and load the above out.trace and out.proc files

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Development Tools• Kernel GDB (KGDB)

– Source debugging of the Kernel– Requirements:

• Enabling the CONFIG_KGDB entry in the Kernel Hacking section

• Recompile with -ggdb• Enable frame pointers• Connect serial port• Download and boot target• Launch DDD and gdb to use the serial port• Upon connection, set breakpoints and go

– Kernel Modules Debugging

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File Systems

• File Systems Supported (partial list)– EXT2/3– ReiserFS– XFS– CramFS– JFFS/JFFS2– Network File System (NFS)

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File Systems

• How Do I Enable a Local Root File System?• A practice: Use ramdisk as root file system

– Kernel configuration: • Edit kernel bootup command line option: “root=/dev/ram”

• Block devices: enable RAMDISK support, init ramdisk support, default ramdisk size 4096kB

• File Systems: Disable network file system as root option

• Networking Options: Disable IP auto configuration in bootp

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File Systems

• Use ramdisk as root file system (cont’d):– Use TCT to generate my root file system,

convert to ext2 format and compress it.– Download to the target and run

    <Redboot> load –r –v –b 0xnnnnnnnn <ramdisk>

<Redboot> load –r –v –b 0xuuuuuuuu <kernel>    <Redboot> go 0xuuuuuuuu

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File Systems• Use ramdisk as root file system (cont’d):

# rm -rf /tmp/tmpmnt# mkdir /tmp/tmpmnt# rm -rf /tmp/ramrootfs# dd if=/dev/zero of=/tmp/ramrootfs bs=1k count=10240# mke2fs -F -m 0 -i 2000 /tmp/ramrootfs# mount -o loop -t ext2 /tmp/ramrootfs /tmp/tmpmnt# cd /tmp/tmpmnt# cp -av /my_workdir/my_filesystem/pxa250/fs1/* .# cd /tmp# umount /tmp/tmpmnt# cat /tmp/ramrootfs | gzip -9 > /tftpboot/pxa250.ram

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File Systems• Use JFFS/JFFS2 as root file system

– You have to use /opt/hardhat/devkit/arm/xscale_be/target/sbin/mkfs.jffs2 to make your jffs2 file system.

– The mkfs.jffs2 needs /usr/lib/libz.so.1 ; /lib/libc.so.6 ; /lib/ld-linux.so.2

– Bootup your target with root=nfs or /dev/ram which contains the above binaries and your target file system directory.

– Run /usr/sbin/mkfs.jffs2 -d <target dir> -o my.jffs2

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File Systems

• Use JFFS/JFFS2 as root file system (cont’d)– Rebuild the kernel with

"root=/dev/mtdblock? rw ip=off" – Use Redboot commands to download the

my.jffs2 and the new kernel– Reboot the system with the new kernel and

jffs2 file system.

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Kernel Modules

• An object file (e.g., myfile.o) that is dynamically loaded and added to the kernel at run-time

• Often used to add/remove optional items to/from the system such as device drivers

• Useful when kernel footprint or alternative drivers is an issue

• May also be used with proprietary code to avoid licensing issues in GPL

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Kernel Modules• Often have a custom /proc interface

built-in to the module– Written by the kernel module programmer– Can be written to provide both a read and a write interface

– Typically used initially to assist in kernel module debugging

– But the long-term use is typically to help the system administrator either by providing information about system configuration and operation, and allowing parameters in the kernel module to be modified as may be needed by the administrator

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Kernel Modules

• Loading and Unloading Modules– insmod - Install (load) a module– rmmod - Remove (unload) a module– lsmod - List installed modules– depmod - Show dependencies of a module– modprobe - Loads a module and its dependencies– modinfo - Displays information about a module

• Start-Up– insmod may be used in /etc/init.d/* and /etc/rc*.d/*

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Kernel Modules• A Simple Kernel Module

#include <linux/module.h>#include <linux/init.h>#include <linux/kernel.h>static int __init my_init_module(void){

printk("<1> Yup, I’m here!\n"); /* Logged to /dev/console */return 0;

}static void __exit my_cleanup_module(void){

printk("<1> And now I’m leaving.\n"); /* Logged to /dev/console */

}module_init(my_init_module);module_exit(my_cleanup_module);

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Kernel Modules

• Kernel Module Compiling– Kernel modules need to be built using the kernel

headers rather than the user-space headers– <architecture-prefix>-gcc -D__KERNEL__ -Wall -

O2 -I <path-to-kernel>/include -I <path-to-kernel>/arch/<architecture> -DMODULE -c mymod.c

– When more than one '-I' option is used, the directories are scanned in left-to-right order. These directories are searched before the standard system directories.

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Kernel Modules

• Compiling with version information is only necessary when compiling a module for a kernel that has "CONFIG_MODVERSIONS" enabled.

• Version mismatch: # insmod mymod.o mod1.o: kernel-module version mismatch mod1.o was compiled for kernel version 2.4.17_mvl21 while this kernel is version 2.4.17_mvl21-cllf.

• Solutions:– Insmod –f– recompile the module with "version information" in the kernel

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Kernel Modules

• How do I compile a module with "version information" in the kernel?– <architecture-prefix>-gcc -

D__KERNEL__ -Wall -O2 -I<path-to-kernel>/include -I <path-to-kernel>/arch/<architecture> -DMODULE -DMODVERSIONS -include <path-to-kernel>/include/linux/version.h -c mymod.c

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Kernel Modules

• depmod - Module Dependencies Database– Creates a database of module dependencies– Scans modules in /lib/modules– Generates /lib/modules/*/modules.dep

• * will be replaced by the kernel version and build number

– Update when adding new modules to the system that should be automatically inserted

– Modules that will be loaded manually do not need to be in the database

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Kernel Modules• depmod Example

# insmod lp

./lp.o: unresolved symbol parport_register_device_R9b846d61

./lp.o: unresolved symbol parport_release_R93e35225

./lp.o: unresolved symbol parport_claim_or_block_Rca62ba8c

./lp.o: unresolved symbol parport_unregister_device_Re6842bfb

./lp.o: unresolved symbol parport_enumerate_R6a5c148b

# depmod -a

/lib/modules/2.2.12-20b/modules.dep

/lib/modules/2.2.12-20b/misc/lp.o: /lib/modules/2.2.12-20b/misc/parport.o

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Kernel Modules

• modprobe - Load Module and its Dependencies– May be used instead of insmod– Check dependency database– Loads dependent modules in the correct order– Checks /etc/conf.modules for parameters– Can pass additional parameters

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Kernel Modules

• Passing Values to the Module– modprobe parport_pc.o demo=1– This works with insmod also– In the module’s source

/* parport_pc.c */#ifdef MODULEstatic int demo = 0;MODULE_PARM(demo, "i");MODULE_PARM_DESC(demo, "Demo variable, defaults to 0");

#endif

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Kernel Modules

• Add Module via Linux Configuration Process– Used when a kernel module must be built

at the same time as the kernel; Not required for simple testing of the kernel module

– Steps• First: Add a selection to the kernel configuration• Second: Add the object module to kernel Makefile

• Third: Configure and Build the Linux kernel

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Kernel Modules

• Add Module via Linux Configuration Process– Step #1: Add a selection to the configuration

• Locate the appropriate [Cc]onfig.in file• Add the appropriate lines for your module

– To allow "y", "m" or "n" selection:– tristate ’User-readable description goes

here’ CONFIG_YOURSYMBOL

• Refer to Documentation/Configure.help and Documentation/kbuild/config-language.txt

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Kernel Modules

• Add Module via Linux Configuration Process– Step #2: Add the object module to Makefile

• Determine appropriate <path-to-kernel>/ drivers/*/Makefile

• Add command to include your module•obj-$(CONFIG_YOURSYMBOL) +=

yourfilename.o• Copy source files to same directory• If necessary, add compile options, etc. to Makefile

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Kernel Modules

• Add Module via Linux Configuration Process– Step #3: Build the linux kernel

• make config OR make menuconfig OR make xconfig OR make oldconfig

• make dep OR make depend• make bzImage OR make zImage• make modules• make

INSTALL_MOD_PATH=/opt/hardhat/devkit/mips/fp_le/target/lib/modules install_modules

• the modules should end up in the target’s /lib/modules directory.

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Kernel Modules

• Kernel Modules Source Level Debugging– Instructs insmod to generate a load map for the module

when it gets loaded into memory.• [target linux] insmod –m module.o > module.map

• [target linux] grep “.text” module.map

• [gdb] add-symbol-file module.o XXXXXXXX

XXXXXXXX = address of ‘.text’ section from grep command.

– precludes the ability to debug the module’s ‘init’method.

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MontaVista Realtime• MontaVista provides following improvements for

real-time performance of the Linux kernel : – MontaVista Real-Time Scheduler

• To meet real-time performance requirements while preserving the standard Linux programming model and APIs.

• All that necessary is to use the standard Linux real-time priority options provided within its POSIX function calls.

– Preemptible Kernel• Reduces the latency of the kernel when reacting to real-time or

interactive events by allowing a low-priority process to be preempted, even if it is in kernel mode executing a system call.

• This feature allows applications that need real-time response – such as audio and other multimedia applications – to run more reliably, even when the system is under an increased load due to other lower-priority processes.

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MontaVista Realtime– In the following instances, preemption should

not occur, and the Preemptible Kernel does not allow it:

• while handling interrupts• while doing “bottom half” processing• while holding a spinlock, writelock, or readlock• while the kernel is executing the scheduler itself• At all other times, the MontaVista algorithm allows

preemption. Also, whenever the system exits from one of the above states, it tests to see if preemption is called for. If so, the current task is preempted.

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MontaVista Realtime

• Enabling the MontaVista Real-Time Scheduler

– Start make menuconfig or make xconfig, enable Real Time Scheduler.

– Enter a value for the Maximum Priority option.

– Save your changes. – Rebuild the kernel

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MontaVista Realtime

• To enable the MontaVista Preemptible Kernel, complete the following steps: 1.Start make menuconfig or make xconfig

2.Select “General setup”

3.Enable “Preemptible kernel support”

4.Enable “Break selected locks”

5.Rebuild the kernel

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MontaVista Realtime

• Pthread Programming– The ‘P’ is for POSIX, Portable Operating

System Interface– IEEE Standard– Section 1003.1c defines Pthreads

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MontaVista Realtime

• Threads, An Alternative View– Some engineers prefer to view things

differently in Linux. Even though Linux is a process-based operating system, they choose to view a process as a container.

– In this view, the process does not execute code. It simply provides the space and other properties in which threads may execute.

– When a process is created (via fork) in this view, one thread of execution is automatically started.

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MontaVista Realtime

• Threads, An Alternative View (cont’d)– That initial thread begins at the place we call main. It could then create additional threads within the same process.

– When any thread wishes to terminate, it calls pthread_exit. That one thread is then terminated.

– If any one thread wishes to terminate the entire process (and all threads within it), that thread may call exit.

– Finally, if all threads, one by one, call pthread_exit, when the last thread is gone, Linux will remove the process.

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MontaVista Realtime

• POSIX Thread Execution Priorities– The greater the numerical priority value, the

more important the thread.– POSIX recommends at least 99 priorities

above zero (MontaVista supports range: 99~2047)

– root priviledge is required to use the elevated priority numbers (1-99).

– SCHED_FIFO or SCHED_RR must be used at elevated priority numbers.

– SCHED_OTHER ("fairness") is not permitted at elevated priorities.

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MontaVista Realtime

• POSIX Policies– SCHED_FIFO

• Processes (threads) run “First In First Out”• use the elevated priority numbers • Most commonly used "real-time" scheme• Used when process(es) are known to use

relatively brief "bursts" of CPU time• Permits the highest priority process

(thread) to run "at will"• Starvation of lower priorities can occur

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MontaVista Realtime

• POSIX Policies– SCHED_RR (Round Robin)

• SCHED_RR is SCHED_FIFO with "quanta"• A "Quanta" is a period of time after which the

process (thread) is moved behind others of the same priority

• May be used when the process(es) are known to have long periods of intensive execution and more than one process uses this priority

• Also use the elevated priority numbers• Processes run until they say they want to wait, or

until their quanta is exhausted

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MontaVista Realtime

• POSIX Policies– SCHED_OTHER

• In Linux, it is implemented as the normal scheduling policy (let’s be fair and let everyone run)

• Only available at POSIX priority zero• Lower priority than SCHED_FIFO and

SCHED_RR

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MontaVista Realtime

• Choosing Priorities for SCHED_FIFO, SCHED_RR & SCHED_OTHER– High priorities (99--)

• I/O intensive (reactive)• Critical (time-sensitive) operations• High repetition rate• NOTE: Processes MUST wait -- busy spins

are bad

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MontaVista Realtime

• Choosing Priorities for SCHED_FIFO, SCHED_RR & SCHED_OTHER– Low priorities (1++)

• Less vital (less catastrophic if not done) activities• CPU intensive operations• Consider SCHED_RR

– Priority zero• Must use SCHED_OTHER• Non-realtime activities• Batch operations (compiling, etc...)• Time-consuming computations• Human interface

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MontaVista Realtime

• Pthread Coding Requirements– Include files

•unistd.h•pthread.h•semaphore.h

– Compiler flags: -D_REENTRANT• Required for some architectures• Ignored when unnecessary

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MontaVista Realtime

• Pthread Functions Briefly– pthread_create - Create a new thread– pthread_exit - "Me" exit– pthread_join - Wait for a given thread

to pthread_exit– pthread_cancel - Attempt to terminate

a thread– pthread_self - Who am I?– pthread_detach - Save no resources if I pthread_exit later (can’t be joined)

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MontaVista Realtime

• Pthread Attribute Preparationint pthread_attr_init(pthread_attr_t *attr);

– Setup pthread attribute object– Usually defaulted at pthread_create– Can be changed as thread runs

• sched_setscheduler()• sched_setparam()

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MontaVista Realtime• Making Yourself Realtime

#include <sched.h>struct sched_param sched_params;/* Change our priority to as high as possible and use SCHED_FIFO */

sched_params.sched_priority = sched_get_priority_max(SCHED_FIFO);

if (0 != sched_setscheduler(getpid(), SCHED_FIFO, &sched_params)) {

printf("sched_setscheduler failed (YOU MUST BE ROOT TO USE THIS)\n");

exit(1);}

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MontaVista Realtime

• Study more: – Posix.4: Programming for the RealWorld, Bill

O. Gallmeister, O’Reilly & Associates, 1-56592-074-0.

– Pthreads Programming, Bradford Nichols, Dick Buttlar, and Jacqueline Proulx Farrell, O’Reilly & Associates, Inc., 1-56592-115-1.

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Notes

• /opt/hardhat/devkit/arm/xscale_le/target• /etc/bootptab, /etc/xinetd.d/bootps• /etc/exports• /etc/xinetd.d/tftp• /etc/dhcpd.conf• /etc/init.d/nfs restart• /etc/redhat-release• /mnt/cdrom/bin/hhl-host-install• Redboot> fis create ; fis delete ; fis list