MontaVista Linux Professional Edition Jump Start Training

1
MontaVista LinuxProfessional EditionJump Start
Training

• Embedded Linux Technology Inc.,
• Taiwan Branch
• Email jesse_at_emblit.co.jp
• TEL [phone]

2
Agenda

• 1010 1100
• Preparing Development System
• Development Environment
• Boot ROM
• 1110 1200
• Boot Configure and Download
• MontaVista Development Tools (I)

• 1310 1400
• MontaVista Development Tools (II)
• 1410 1500
• File Systems
• Kernel Modules
• 1510 1600
• MontaVista Realtime

3
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
• VMwaretm 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

4
Development Environment
5
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

6
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

7
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.

8
Boot ROM

• Booting the Target System (contd)
• 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

9
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

10
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 hosts 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

11
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...)

12
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 Users Guide and Quick Start Guide for
  your LSP

13
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 targets 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
  (contd)
• 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.)

15
Loading Image Loader
16
Loading Linux Boot Loader
17
Loading Linux Startup
18
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.

19
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

20
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

21
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

22
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
  OReilly)

23
Development Tools

• A simple Makefile example
• Makefile for ferret
• CCxsacle_be-gcc
• TARGET/opt/hardhat/devkit/arm/xscale_be/target
• all install
• install ferret
• cp ferret (TARGET)
• ferret ferret.c Makefile
• (CC) -D_REENTRANT -O lt -o _at_ -lpthread
• clean
• - rm -f ferret.o ferret (TARGET)/ferret

24
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.

25
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

26
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.

27
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)

28
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 (lt 2.5 ).
• Multi-platform support
• Friendly GUI with event graph, system and
  per-process analysis, and raw event descriptions.

29
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 targettracedaemon
  -ts10 /dev/tracer ./out.trace ./out.proc
• Run "tracevisualizer" in host and load the above
  out.trace and out.proc files

30
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

31
File Systems

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

32
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

33
File Systems

• Use ramdisk as root file system (contd)
• Use TCT to generate my root file system, convert
  to ext2 format and compress it.
• Download to the target and run    ltRedbootgt load
  r v b 0xnnnnnnnn ltramdiskgt
• ltRedbootgt load r v b 0xuuuuuuuu
  ltkernelgt    ltRedbootgt go 0xuuuuuuuu

34
File Systems

• Use ramdisk as root file system (contd)
• rm -rf /tmp/tmpmnt
• mkdir /tmp/tmpmnt
• rm -rf /tmp/ramrootfs
• dd if/dev/zero of/tmp/ramrootfs bs1k
  count10240
• 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 gt /tftpboot/pxa250.ra
  m

35
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 rootnfs or /dev/ram
  which contains the above binaries and your target
  file system directory.
• Run /usr/sbin/mkfs.jffs2 -d lttarget dirgt -o
  my.jffs2

36
File Systems

• Use JFFS/JFFS2 as root file system (contd)
• Rebuild the kernel with "root/dev/mtdblock? rw
  ipoff" 
• Use Redboot commands to download the my.jffs2 and
  the new kernel
• Reboot the system with the new kernel and jffs2
  file system.

37
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

38
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

39
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/

40
Kernel Modules

• A Simple Kernel Module
• include ltlinux/module.hgt
• include ltlinux/init.hgt
• include ltlinux/kernel.hgt
• static int __init my_init_module(void)
• printk("lt1gt Yup, Im here!\n") / Logged to
  /dev/console /
• return 0
• static void __exit my_cleanup_module(void)
• printk("lt1gt And now Im leaving.\n") / Logged
  to /dev/console /
• module_init(my_init_module)
• module_exit(my_cleanup_module)

41
Kernel Modules

• Kernel Module Compiling
• Kernel modules need to be built using the kernel
  headers rather than the user-space headers
• ltarchitecture-prefixgt-gcc -D__KERNEL__ -Wall -O2
  -I ltpath-to-kernelgt/include -I ltpath-to-kernelgt/ar
  ch/ltarchitecturegt -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.

42
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

43
Kernel Modules

• How do I compile a module with "version
  information" in the kernel?
• ltarchitecture-prefixgt-gcc -D__KERNEL__ -Wall -O2
  -Iltpath-to-kernelgt/include -I ltpath-to-kernelgt/arc
  h/ltarchitecturegt -DMODULE -DMODVERSIONS -include
  ltpath-to-kernelgt/include/linux/version.h -c
  mymod.c

44
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

45
Kernel Modules

• depmod Example
• insmod lp
• ./lp.o unresolved symbol parport_register_device_
  R9b846d61
• ./lp.o unresolved symbol parport_release_R93e3522
  5
• ./lp.o unresolved symbol parport_claim_or_block_R
  ca62ba8c
• ./lp.o unresolved symbol parport_unregister_devic
  e_Re6842bfb
• ./lp.o unresolved symbol parport_enumerate_R6a5c1
  48b
• 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

46
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

47
Kernel Modules

• Passing Values to the Module
• modprobe parport_pc.o demo1
• This works with insmod also
• In the modules source
• / parport_pc.c /
• ifdef MODULE
• static int demo 0
• MODULE_PARM(demo, "i")
• MODULE_PARM_DESC(demo, "Demo variable, defaults
  to 0")
• endif

48
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

49
Kernel Modules

• Add Module via Linux Configuration Process
• Step 1 Add a selection to the configuration
• Locate the appropriate Cconfig.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

50
Kernel Modules

• Add Module via Linux Configuration Process
• Step 2 Add the object module to Makefile
• Determine appropriate ltpath-to-kernelgt/
  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

51
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 targets
  /lib/modules directory.

52
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 gt 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 modules
  initmethod.

53
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.

54
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.

55
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

56
MontaVista Realtime

• To enable the MontaVista Preemptible Kernel,
  complete the following steps
• Start make menuconfig or make xconfig
• Select General setup
• Enable Preemptible kernel support
• Enable Break selected locks
• Rebuild the kernel

57
MontaVista Realtime

• Pthread Programming
• The P is for POSIX, Portable Operating System
  Interface
• IEEE Standard
• Section 1003.1c defines Pthreads

58
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.

59
MontaVista Realtime

• Threads, An Alternative View (contd)
• 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.

60
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 992047)
• 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.

61
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

62
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

63
MontaVista Realtime

• POSIX Policies
• SCHED_OTHER
• In Linux, it is implemented as the normal
  scheduling policy (lets be fair and let everyone
  run)
• Only available at POSIX priority zero
• Lower priority than SCHED_FIFO and SCHED_RR

64
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

65
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

66
MontaVista Realtime

• Pthread Coding Requirements
• Include files
• unistd.h
• pthread.h
• semaphore.h
• Compiler flags -D_REENTRANT
• Required for some architectures
• Ignored when unnecessary

67
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 (cant be joined)

68
MontaVista Realtime

• Pthread Attribute Preparation
• int 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()

69
MontaVista Realtime

• Making Yourself Realtime
• include ltsched.hgt
• struct sched_param sched_params
• / Change our priority to as high as possible and
  use SCHED_FIFO /
• sched_params.sched_priority sched_get_priority_m
  ax(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)

70
MontaVista Realtime

• Study more
• Posix.4 Programming for the RealWorld, Bill O.
  Gallmeister, OReilly Associates,
  1-56592-074-0.
• Pthreads Programming, Bradford Nichols, Dick
  Buttlar, and Jacqueline Proulx Farrell, OReilly
  Associates, Inc., 1-56592-115-1.

71
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
• Redbootgt fis create fis delete fis list