Uploaded byAnil Kumar Pugalia
Linux Kernel Overview
The document provides an overview of the Linux kernel, including its architecture, startup process, functionality, configuration, and compilation. It discusses the differences between micro and monolithic kernels. It also explains the Linux kernel architecture with user space and kernel space separated by a system call interface. Key aspects covered include process management, memory management, device management, and the kernel build system.
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Overview of Linux Kernel and rights reserved by SysPlay Workshops.
Expectation from the workshop including W's of Kernel, Architecture, Startup, Functionality, Configuration, and Compilation.
Kernel as the core of the Operating System, emphasizing major functionalities like IPC, memory management, process management.
Comparison of Microkernel vs Monolithic kernel, covering their definitions, and advantages like flexibility and performance.
Linux Architecture including User Space, Kernel Space, and their interactions through System Call interface.
Definition of processes and threads, distinctions in single/multi-threaded and single/multi-process scenarios.
Step-by-step initialization during the Linux Kernel startup, including CPU setup, minimal driver initialization, and moving to User Space.
Key functions of Linux Kernel: Process Management, Memory Management, Device/Storage/Network Management.
Introduction to Linux Kernel Source Code and components of Kernel Build System including Makefile and configuration for compilation.
Different methods of configuring kernel such as menuconfig and options related to code maturity, module support, and device drivers.
Processes related to cleaning, building the kernel image, and specifics for embedded systems including bootloader image creation.
Various command-line arguments for Linux kernel like console, root, initrd, essential for kernel operation.
Recap of key aspects of Linux Kernel discussed: Architecture, Startup, Functionality, Configuration, and Compilation.
Interactive session inviting queries related to the Linux Kernel presentation.
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Linux Kernel Overview
- 1. © 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Overview
- 2. 2© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. What to Expect? W's of Kernel Linux Architecture Linux Kernel Startup Linux Kernel Functionality Linux Kernel Configuration Linux Kernel Compilation
- 3. 3© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. What is a Kernel? Core of a System The Operating System
- 4. 4© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. OS Core OS Core could be further classified as the following major functionalities Inter Process Communication Minimal Memory Management Low-level Process Management & Scheduling Low-level Input / Output
- 5. 5© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Types of Kernels Micro kernel Also called the Modular kernel Contains only the OS Core Other OS stuff are typically provided as services Examples: Amoeba, Mach, QNX Monolithic kernel Contains all the OS related stuff Either built into it statically or loaded dynamically Examples: VxWorks, Linux
- 6. 6© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Micro vs Monolithic Advantages Micro Kernel Flexible Modular Easy to implement Monolithic Kernel Performance
- 7. 7© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Architecture User Space (is the usage platform) System Call I/F (the connector) Kernel Space (provides functionalities & facilities to use) Hardware (is what is to be used)
- 8. 8© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Architecture Details User Space Memory where user processes run Doing typical computation tasks And accesses kernel space for privileged tasks Through System Call interface Kernel Space This is protected space Place of all privileged happening I/O access, Memory access, … (System Resources access) Kernel processes can access User processes but not vice versa These levels are achieved by processor states How does system call switches user to kernel space? Check Which space is executing command from root? Do we need these levels and system calls if the kernel image and root file system are read only?
- 9. 9© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Process vs Thread Single Process Single Threaded Single Process Multi-Threaded Multi-Process Single Threaded Multi-Process Multi-Threaded What is Linux User Space? What about the Kernel Space? Need for Single vs Multi
- 10. 10© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Startup CPU / Platform specific Initialization CPU Speed Setup MMU Setup Board Id Setup Minimal Driver Initialization: FS specific Mounting Root File System Remaining Driver Initialization Doing Initcall & Freeing Initial Memory Moving to User Space by Jumping to the first user process init
- 11. 11© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Functional Overview Process Management Memory Management Device Management Storage Management Network Management
- 12. 12© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Source Let's get down to the Source Code
- 13. 13© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Build System Key components Makefile Kconfig Configuring the Makefile Setting up the kernel version (specially for the Desktops) For Cross Compilation, need to setup ARCH CROSS_COMPILE Or, invoke make with these options
- 14. 14© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Configuration Methods make config make menuconfig make xconfig Others make defconfig make oldconfig make <board_specific>_defconfig Check: Where is the menuconfig target?
- 15. 15© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Configuration Code Maturity level Options General Setup Loadable Module Support Block Layer Networking Device Drivers File Systems Kernel Hacking Security Options Cryptographic Options Library Routines
- 16. 16© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Compilation Cleaning Methods make clean – Simple clean make mrproper – Complete sweep clean, incl. Configs Also called Building the Kernel After configuring the kernel, we are all set to build it Build Methods make vmlinux – To build everything configured for a kernel image make modules – To build only configured modules make – To build everything configured (kernel image & modules) make modules_prepare – To only prepare for building modules
- 17. 17© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Images Kernel Image should be understood by Stage 2 Bootloader Default kernel compilation builds vmlinux vmlinux is understood only by the desktop bootloaders So, for embedded systems, we would typically have to do the following Creating linux.bin using <cross>-objcopy Example: arm-linux-objcopy -O binary vmlinux linux.bin And then, convert it into the bootloader specific image using some bootloader utility. For u-boot, it is done using mkimage Example: mkimage -A arm -O linux -T kernel -C none -a 20008000 -e 20008000 -n “Custom” -d linux.bin uImage.arm
- 18. 18© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Linux Kernel Arguments console root initrd mem resume ...
- 19. 19© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. What all have we learnt? W's of Kernel Linux Architecture Linux Kernel Startup Linux Kernel Functionality Linux Kernel Configuration Linux Kernel Compilation
- 20. 20© 2010-17 SysPlayWorkshops <workshop@sysplay.in> All Rights Reserved. Any Queries?