1# LiteOS-M Kernel<a name="EN-US_TOPIC_0000001096757661"></a> 2 3- [Introduction](#section11660541593) 4- [Directory Structure](#section161941989596) 5- [Constraints](#section119744591305) 6- [Usage](#section3732185231214) 7- [Contribution](#section1371123476307) 8- [Repositories Involved](#section1371113476307) 9 10## Introduction<a name="section11660541593"></a> 11 12OpenHarmony LiteOS-M is a lightweight operating system kernel designed for the Internet of Things (IoT) field. It features small footprint, low power consumption, and high performance. It has a simple code structure, including the minimum kernel function set, kernel abstraction layer, optional components, and project directory. The LiteOS-M kernel is divided into the hardware layer and hardware-irrelevant layers. The hardware layer provides a unified hardware abstraction layer (HAL) interface for easier hardware adaptation. A range of compilation toolchains can be used with different chip architectures to meet the expansion of diversified hardware and compilation toolchains in the Artificial Intelligence of Things (AIoT) field. 13**Figure1** shows the architecture of the LiteOS-M kernel. 14 15**Figure 1** Architecture of the OpenHarmony LiteOS-M kernel<a name="fig0865152210223"></a> 16 17 18 19## Directory Structure<a name="section161941989596"></a> 20 21The directory structure is as follows. For more details, see [arch_spec.md](arch_spec.md). 22 23``` 24/kernel/liteos_m 25├── arch # Code of the kernel instruction architecture layer 26│ ├── arm # Code of the ARM32 architecture 27│ │ ├── arm9 # Code of the ARM9 architecture 28│ │ ├── cortex-m3 # Code of the cortex-m3 architecture 29│ │ ├── cortex-m33 # Code of the cortex-m33 architecture 30│ │ ├── cortex-m4 # Code of the cortex-m4 architecture 31│ │ ├── cortex-m7 # Code of the cortex-m7 architecture 32│ │ └── include # Arm architecture public header file directory 33│ ├── csky # Code of the csky architecture 34│ │ └── v2 # Code of the csky v2 architecture 35│ ├── include # APIs exposed externally 36│ ├── risc-v # Code of the risc-v architecture 37│ │ ├── nuclei # Code of the nuclei system technology risc-v architecture 38│ │ └── riscv32 # Code of the risc-v official common architecture 39│ └── xtensa # Code of the xtensa architecture 40│ └── lx6 # Code of the lx6 xtensa architecture 41├── components # Optional components 42│ ├── backtrace # Backtrace support 43│ ├── cppsupport # C++ support 44│ ├── cpup # CPU percent (CPUP) 45│ ├── dynlink # Dynamic loading and linking 46│ ├── exchook # Exception hooks 47│ ├── fs # File systems 48│ ├── lmk # Low memory killer functions 49│ ├── lms # Lite memory sanitizer functions 50│ ├── net # Networking functions 51│ ├── power # Power management 52│ ├── shell # Shell function 53│ ├── fs # File systems 54│ └── trace # Trace tool 55├── drivers # driver Kconfig 56├── kal # Kernel abstraction layer 57│ ├── cmsis # CMSIS API support 58│ └── posix # POSIX API support 59├── kernel # Minimum kernel function set 60│ ├── include # APIs exposed externally 61│ └── src # Source code of the minimum kernel function set 62├── testsuites # Kernel testsuites 63├── tools # Kernel tools 64├── utils # Common directory 65``` 66 67## Constraints<a name="section119744591305"></a> 68 69OpenHarmony LiteOS-M supports only C and C++. 70 71Applicable architecture: See the directory structure for the arch layer. 72 73As for dynamic loading module, the shared library to be loaded needs signature verification or source restriction to ensure security. 74 75## Usage<a name="section3732185231214"></a> 76 77The OpenHarmony LiteOS-M kernel build system is a modular build system based on Generate Ninja (GN) and Ninja. It supports module-based configuration, tailoring, and assembling, and helps you build custom products. This document describes how to build a LiteOS-M project based on GN and Ninja. For details about the methods such as GCC+gn, IAR, and Keil MDK, visit the community websites. 78 79### Setting Up the Environment 80 81Before setting up the environment for a development board, you must set up the basic system environment for OpenHarmony first. The basic system environment includes the OpenHarmony build environment and development environment. For details, see [Setting Up Development Environment](https://gitee.com/openharmony/docs/blob/master/en/device-dev/quick-start/Readme-EN.md). 82 83### Obtaining the OpenHarmony Source Code 84 85For details about how to obtain the source code, see [Source Code Acquisition](https://gitee.com/openharmony/docs/blob/HEAD/en/device-dev/get-code/sourcecode-acquire.md). This document assumes that the clone directory is `~/openHarmony` after the complete OpenHarmony repository code is obtained. 86 87### Example projects 88 89Qemu simulator: `arm_mps2_an386、esp32、riscv32_virt、SmartL_E802`. For details about how to compile and run, see [qemu guide](https://gitee.com/openharmony/device_qemu). 90 91Bestechnic: `bes2600`. For details about how to compile and run, see [Bestechnic developer guide](https://gitee.com/openharmony/device_soc_bestechnic). 92 93### Community Porting Project Links 94 95The LiteOS-M kernel porting projects for specific development boards are provided by community developers. The following provides the links to these projects. If you have porting projects for more development boards, you can provide your links to share your projects. 96 97- Cortex-M3: 98 99 - STM32F103 https://gitee.com/rtos_lover/stm32f103_simulator_keil 100 101 This repository provides the Keil project code for building the OpenHarmony LiteOS-M kernel based on the STM32F103 chip architecture. This code supports build in Keil MDK mode. 102 103- Cortex-M4: 104 105 - STM32F429IGTb https://gitee.com/harylee/stm32f429ig_firechallenger 106 107 This repository provides the project code for porting the OpenHarmony LiteOS-M kernel to support the STM32F429IGTb development board. The code supports build in Ninja, GCC, and IAR modes. 108 109## Contribution<a name="section1371123476307"></a> 110 111[How to involve](https://gitee.com/openharmony/docs/blob/master/en/contribute/how-to-contribute.md) 112 113[Commit message spec](https://gitee.com/openharmony/kernel_liteos_m/wikis/Commit%20message%E8%A7%84%E8%8C%83) 114 115[Liteos-M kernel coding style guide](https://gitee.com/openharmony/kernel_liteos_m/wikis/OpenHarmony%E8%BD%BB%E5%86%85%E6%A0%B8%E7%BC%96%E7%A0%81%E8%A7%84%E8%8C%83) 116 117How to contribute a chip based on Liteos-M kernel: 118 119[Mini System SoC Porting Guide](https://gitee.com/openharmony/docs/blob/master/en/device-dev/porting/Readme-EN.md) 120 121## Repositories Involved<a name="section1371113476307"></a> 122 123[Kernel Subsystem](https://gitee.com/openharmony/docs/blob/master/en/readme/kernel.md) 124 125[kernel\_liteos\_m](https://gitee.com/openharmony/kernel_liteos_m/blob/master/README.md) 126
