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Implementation of Embedded OS

Learn how to build a Linux kernel image for PXA270 in the implementation of Embedded OS Lab1. Follow step-by-step instructions to set up the environment, install the toolchain, configure and compile the Linux kernel, and convert it to a U-Boot bootable image.

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Implementation of Embedded OS

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  1. Implementation of Embedded OS Lab1 Linux Kernel Compilation

  2. Goal Learn how to build Linux kernel image for PXA270. / 18

  3. Environment • Host System • Windows XP • Build System • VirtualBox + Ubuntu 8.04 • Target System • Creator XScale PXA270 • Software • Toolchain • Linux for PXA270 • linux-2.6.15.3-creator-pxa270.patch • mkimage utility • Bootloader image • Root filesystem image (20M) • You can download them from RSWiki IEOS Course Software / 18

  4. Setting up Environment / 18 • Install VirtualBox, Ubuntu 8.04, and development tools. • Please refer to the slides of lab1 from the course Computer System Laboratory (CSL). • Check the evaluation board. • Please refer to the slides of lab2 from CSL.

  5. Installing Toolchain / 18 • Install the toolchain (cross compiler) for PXA270. • Step1: download the toolchain. • % wget http://eraser.csie.ntu.edu.tw/courses/ieos/10101/lab1/arm-linux-toolchain-bin.4.0.2.tar.gz • Step2: extract the tar.gz file to home directory. • % tar zxvf arm-linux-toolchain-bin.4.0.2.tar.gz -C $HOME • Step3: append installation directory (bin) to PATH. • By adding “export PATH=$PATH:$HOME/arm-unknown-linux-gnu/bin” to $HOME/.bashrc • Don’t forget to logout and login again to make the change effective. • Test the newly installed cross-compiler. • % arm-unknown-linux-gnu-gcc–v • You will see the version number (4.0.2) in the output.

  6. Compiling Linux Kernel (1/3) • Step1: download Linux source codes (mt-linux-2.6.15.3.tar.gz) for PXA270. • Step2: extract the source codes. • Step3: apply the patch. • % cd pxa270/create-pxa270 • % wget http://eraser.csie.ntu.edu.tw/courses/ieos/10101/lab1/linux-2.6.15.3-creator-pxa270.patch • % patch -p0 < linux-2.6.15.3-creator-pxa270.patch / 18

  7. Compiling Linux Kernel (2/3) • Step4: configure the Linux kernel. • Please make sure the toolchainpath has been specified in PATH and the C development library (libc6-dev) has been installed. • % cd ../linux • % make mrproper • % make creator_pxa270_defconfig • The “make<platform>_defconfig” command will create .config by the default symbol values from arch/<architecture>/configs/<platform>_defconfig • To customize the configuration, please refer to page 9 of this slides. • Step5: compile Linux kernel. • % make –j4 / 18

  8. Compiling Linux Kernel (3/3) ELF Header Uncompressed Kernel ELF Header Decompression Function Decompression Function Compressed Kernel Compressed Kernel (c) (b) (a) • There are three output files in the source tree. • ./vmlinux: uncompressed image in ELF format • ./arch/arm/boot/compressed/vmlinux: compressed image in ELF format • ./arch/arm/boot/zImage: compressed image in raw format / 18

  9. Configuring Linux Kernel (1/2) • The Linux kernel build system (Kbuild) supports a variety of configuration methods, and the most commonly used method is: • % make menuconfig • Please install libncurses5-dev package in Ubuntu. / 18

  10. Configuring Linux Kernel (2/2) built-in • Many features and drivers are available as modules, and it is possible to choose whether to build them into the kernel. • Please always build modules into the kernel, i.e., <*>, in our Labs. • In lab1, you need to add the NIC driver into the kernel as follows. • Once the kernel has been configured, you can quit the kernel configuration menu via Esc key or the Exit menu item. • Choose “Yes” to save the new configuration. / 18

  11. Memory Layout of PXA270 (1/3) • The Creator XScale PXA270 board has 32MB flash and 64MB SDRAM. • Flash memory ranges from 0x00000000 to 0x02000000. • SDRAM ranges from 0xa0000000 to 0xa4000000. • The locations and sizes of kernel image and root filesystemare specified in Linux kernel (in arch/arm/mach-pxa/mach-creator-pxa270.c). • The structure of creator_pxa270_partitions[] is at line 248. / 18

  12. Memory Layout of PXA270 (2/3) 0xa0000000 0x00000000 U-Boot 0x00080000 Linux kernel 0x00480000 0xa1080000 U-Boot (TFTP) Root Filesystem 0x01880000 0xa3f80000 U-Boot (domingo) 0x02000000 0xa4000000 Flash RAM / 18

  13. Memory Layout of PXA270 (3/3) static structmtd_partition creator_pxa270_partitions[] = { ... },{ name: "Kernel", offset: 0x00080000, size: 0x00400000, // 4M mask_flags: MTD_WRITEABLE },{ name: "Filesystem", offset: 0x00480000, size: 0x01400000, // 20M } ... Based on the memory layout, we can configure the partition of the flash in Linux kernel as follows. / 18

  14. Converting to U-Boot Bootable Image (1/2) • Since U-Boot has its own format for kernel images, we need to convert the Linux kernel image (vmlinux) to U-Boot bootable image (uImage). • Step1: get the raw binary file. • % arm-unknown-linux-gnu-objcopy -O binary -R .note -R .comment -S arch/arm/boot/compressed/vmlinuxlinux.bin • Step2: compress the raw binary. • % gzip -9 linux.bin / 18

  15. Converting to U-Boot Bootable Image (2/2) • Step3: add the header of U-Boot bootable image. • % chmod +x mkimage • % ./mkimage -A arm -O linux -T kernel -C gzip-a 0xa0008000 -e 0xa0008000 -n "IEOS Lab1 Kernel" -d linux.bin.gz uImage • mkimage can be downloaded from our course website (mkimage). • You can see the mkimageusage by executing without arguments. • The resulting uImage is the U-Boot image we want. / 18

  16. Flashing / 18 • Please refer to the slides of lab2 from CSL for the steps of copying bootloader, kernel, and filesystem. • Use the following files instead. • Bootloader: u-boot.bin • Linux kernel: the one you just compiled (uImage). • Filesystem: rootfs_20M

  17. Testing Your Kernel Image (1/2) • After resetting PXA270, you will see your own Linux kernel is booted. • U-Boot will display the image name “IEOS Lab1 Kernel” when loading the kernel image. • After Linux is booted, use df -h to check the size of filesystem. • You will see the size of root filesystem (/dev/mtdblock3). / 18

  18. Testing Your Kernel Image (2/2) • Check the NIC driver has been compiled into the kernel. • Please use ifconfig eth0 to check your network card. / 18

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