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lkd:laboratoare:01 [2024/07/07 11:47] daniel.baluta |
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| - | =====Introduction to Embedded Linux kernel development ===== | + | ===== Introduction to Embedded Linux kernel development ===== |
| In this session we will walk-through the essential software components that make the Board Suppport Package (BSP) for a hardware platform. We will demonstrate our work by booting PICO-IMX8M evaluation Kit. | In this session we will walk-through the essential software components that make the Board Suppport Package (BSP) for a hardware platform. We will demonstrate our work by booting PICO-IMX8M evaluation Kit. | ||
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| The virtual machine provided by NXP should have all the software already downloaded including all the prerequisites. In this lab we will use a prebuild uboot and rootfs image. | The virtual machine provided by NXP should have all the software already downloaded including all the prerequisites. In this lab we will use a prebuild uboot and rootfs image. | ||
| - | === Presentation === | + | ==== Presentation ==== |
| - | * follow slides at [[session 1] | + | * follow slides at {{:lkd:laboratoare:lkd_01.pdf| Session 1}} |
| + | |||
| + | ==== Practical lab ==== | ||
| + | |||
| + | You can use [[https://ocw.cs.pub.ro/courses/lkd/res/masini-virtuale | virtual machine]] setup or [[https://ocw.cs.pub.ro/courses/lkd/res/linux | native Linux setup]]. | ||
| + | |||
| + | To connect to the Linux running inside the virtual machine you can use: | ||
| + | |||
| + | <code bash> | ||
| + | ssh -p 3022 student@localhost | ||
| + | </code> | ||
| + | === 1. Explore the development environment === | ||
| + | Your work directory should look like this. | ||
| + | |||
| + | <code> | ||
| + | $ tree -L 2 /home/student/work/ | ||
| + | ├── nss-linux # Linux kernel source code | ||
| + | ├── images # prebuild binaries | ||
| + | │ ├── flash.bin | ||
| + | │ ├── Image | ||
| + | │ ├── imx8mq-pico-pi.dtb | ||
| + | │ └── rootfs.ext2 | ||
| + | └── scripts # several scripts to help with compilation and booting | ||
| + | ├── modules_install.sh | ||
| + | ├── setenv.sh | ||
| + | ├── uuu | ||
| + | └── uuu_script | ||
| + | </code> | ||
| + | |||
| + | === 2. Compile the Linux kernel === | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ source ~/work/scripts/setenv.sh | ||
| + | $ cd ~/work/nss-linux | ||
| + | $ make tn_imx8_defconfig | ||
| + | $ make -j8 | ||
| + | |||
| + | </code> | ||
| + | |||
| + | Successful compilation will create the following binaries: | ||
| + | |||
| + | * ''arch/arm64/boot/Image'' - this is the resulting Linux kernel image | ||
| + | * ''arch/arm64/boot/dts/freescale/imx8mq-pico-pi.dtb'' - device tree blob files | ||
| + | * a set of Linux kernel modules (''*.ko'') scattered around the Linux kernel working tree. | ||
| + | |||
| + | We also have prebuild binaries for ''Image'' and ''imx8mq-pico-pi.dtb'' found under ''~/work/images/'' directory to be used as a backup. | ||
| + | |||
| + | === 3. Boot the board ==== | ||
| + | |||
| + | Connect the PICO-PI-IMX8M to your laptop using the two USB cables provided as described on [[https://developer.technexion.com/docs/recover-to-factory-settings-pico-imx8m-mini | Technexion ]] webpage. | ||
| + | |||
| + | {{:lkd:laboratoare:pico-pi-imx8m-mini-cables.jpg}} | ||
| + | |||
| + | - Yellow box: debug console cable | ||
| + | - Red box: power cable (USB Type C) | ||
| + | - Magent box: boot configuration jumper location. | ||
| + | |||
| + | |||
| + | Make sure the board is in ''Serial Download Mode''. Jumper location should be set as follows: | ||
| + | |||
| + | {{:lkd:laboratoare:pico-imx8m-pi-serial-download-mode.png}}. | ||
| + | |||
| + | Now, we are ready to boot the board. Open two consoles: | ||
| + | |||
| + | |||
| + | Console #1 | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ minicom -D /dev/ttyUSB0 | ||
| + | </code> | ||
| + | |||
| + | Console #2 | ||
| + | |||
| + | <code bash> | ||
| + | # sudo ~/work/scripts/uuu ~/work/scripts/uuu_script | ||
| + | |||
| + | </code> | ||
| + | |||
| + | And then hit ''Reset'' button on the board. | ||
| + | |||
| + | |||
| + | During the booting of the board you will need to tell Virtualbox which USB devices to passthrough the Guest Linux. | ||
| + | |||
| + | {{:lkd:laboratoare:usb_filter.png}} | ||
| + | |||
| + | The final consoles should look like this. Notice Console #1 has Linux kernel booting log: | ||
| + | |||
| + | {{:lkd:laboratoare:boot_run.png?736x356}} | ||
| + | |||
| + | <note important>Use user ''root'' and password ''root'' to login on Linux running on the board </note> | ||
| + | === 4. Make a change in the Linux kernel === | ||
| + | |||
| + | Go to the Linux kernel source root tree and modify a file. | ||
| + | |||
| + | <code bash> | ||
| + | $ cd ~/work/nss-linux | ||
| + | |||
| + | $ vim ~/work/arch/arm64/kernel/setup.c | ||
| + | |||
| + | </code> | ||
| + | |||
| + | Add a simple print like in the following patch | ||
| + | |||
| + | <code c> | ||
| + | --- a/arch/arm64/kernel/setup.c | ||
| + | +++ b/arch/arm64/kernel/setup.c | ||
| + | @@ -90,6 +90,8 @@ void __init smp_setup_processor_id(void) | ||
| + | |||
| + | pr_info("Booting Linux on physical CPU 0x%010lx [0x%08x]\n", | ||
| + | (unsigned long)mpidr, read_cpuid_id()); | ||
| + | + | ||
| + | + pr_info("Hello from Embedded Linux Summer School\n"); | ||
| + | } | ||
| + | |||
| + | </code> | ||
| + | |||
| + | Now recompile the kernel. You can go back and read [[#compile_the_linux_kernel | 2. Compile the Linux kernel]]. Sequence for recompiling the kernel is as simple as: | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ cd ~/work/nss-linux | ||
| + | $ source ~/work/scripts/setenv.sh | ||
| + | $ make -j8 | ||
| + | |||
| + | </code> | ||
| + | |||
| + | Boot script ''~/work/scripts/uuu_script'' will use your newly compiled Linux kernel image. So there is no need to change anything after your recompiled the kernel. Just follow again the steps in section [[#boot_the_board |3. Boot the board ]]! | ||
| + | |||
| + | Now, with the new boot image notice the new logs on the console: | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | [ 0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd034] | ||
| + | [ 0.000000] Hello from Embedded Linux Summer School | ||
| + | [ 0.000000] Linux version 6.1.55-ga5f70b9823b6-dirty (student@nss) | ||
| + | [ 0.000000] Machine model: TechNexion PICO-IMX8MQ and PI baseboard | ||
| + | |||
| + | </code> | ||
| + | |||
| + | === 5. Make a change in the rootfs === | ||
| + | |||
| + | rootfs (or the root file system) is the filesystem that is mounted at ''/'' (root of the hierarchy) and contains all the files necessary for the operating system to boot and run. | ||
| + | |||
| + | <code bash> | ||
| + | # ls / | ||
| + | bin home lost+found proc srv var | ||
| + | boot lib media root sys | ||
| + | dev lib64 mnt run tmp | ||
| + | etc linuxrc opt sbin usr | ||
| + | </code> | ||
| + | |||
| + | In our setup, the rootfs used to boot the board can be found in ''~/work/images/rootfs.ext2''. Use the following instructions that add one of your own files into the root filesystem. | ||
| + | |||
| + | <code bash> | ||
| + | $ cd ~/work/images | ||
| + | # make a backup of the initial root filesystem | ||
| + | $ cp rootfs.ext2 rootfs.ext2.back | ||
| + | $ sudo mkdir /mnt/my_root | ||
| + | $ sudo mount -o loop rootfs.ext2 /mnt/my_root | ||
| + | |||
| + | # explore the contents of /mnt/my_root directory and notice that these are the exact files that you can find on the board | ||
| + | |||
| + | # create your own file | ||
| + | $ sudo touch /mnt/my_root/root/my_file | ||
| + | |||
| + | # unmount the filesystem | ||
| + | |||
| + | $ sudo umount /mnt/my_root | ||
| + | </code> | ||
| + | |||
| + | Now boot the board and notice that the file you created exists on the board! Follow the steps in section [[#boot_the_board |3. Boot the board ]]! | ||
| + | |||
| + | === 5. Explore the board === | ||
| + | |||
| + | After booting the board and getting the prompt explore the hardware board capabilities. | ||
| + | |||
| + | Check the current Linux kernel version: | ||
| + | <code bash> | ||
| + | $ cat /proc/version | ||
| + | </code> | ||
| + | |||
| + | Check the command line arguments used to start the Linux kernel: | ||
| + | <code bash> | ||
| + | |||
| + | $ cat /proc/cmdline | ||
| + | |||
| + | </code> | ||
| + | |||
| + | List all the cpus in the system: | ||
| + | <code bash> | ||
| + | |||
| + | $ cat /proc/cpuinfo | ||
| + | </code> | ||
| + | |||
| + | List all available free and used physical memory in the system. | ||
| + | |||
| + | <code bash> | ||
| + | $ free -h | ||
| + | |||
| + | </code> | ||
| + | |||
| + | List the physical memory map for the system: | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ cat /proc/iomem | ||
| + | </code> | ||
| + | |||
| + | Notice the address range for ''System RAM'' and for the rest of devices. | ||
| + | |||
| + | Check the current list of filesystems supported by the kernel: | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ cat /proc/filesystems | ||
| + | |||
| + | </code> | ||
| + | |||
| + | Check the current list of modules loaded in the system: | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ cat /proc/modules | ||
| + | |||
| + | </code> | ||
| + | |||
| + | Finally check the kernel log: | ||
| + | |||
| + | <code bash> | ||
| + | |||
| + | $ dmesg | ||
| + | |||
| + | </code> | ||
| - | === Practical lab === | ||
