提交 66966e8f 编写于 作者: O openharmony_ci 提交者: Gitee

!879 fix: 文档中无对动态加载模块待加载的共享库的限制说明。

Merge pull request !879 from Harylee/readme
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- [Options for Linking](#section17292133274)
In small devices with limited hardware resources, dynamic algorithm deployment capability is required to solve the problem that multiple algorithms cannot be deployed at the same time. The LiteOS-M kernel uses the Executable and Linkable Format \(ELF\) because it is easy to use and compatible with a wide variety of platforms. The LiteOS-M provides APIs similar to **dlopen** and **dlsym**. Apps can load and unload required algorithm libraries by using the APIs provided by the dynamic loading module. As shown in the following figure, the app obtains the corresponding information output through the API required by the third-party algorithm library. The third-party algorithm library depends on the basic APIs provided by the kernel, such as **malloc**. After the app loads the API and relocates undefined symbols, it can call the API to complete the function. The dynamic loading component supports only the Arm architecture.
In small devices with limited hardware resources, dynamic algorithm deployment capability is required to solve the problem that multiple algorithms cannot be deployed at the same time. The LiteOS-M kernel uses the Executable and Linkable Format \(ELF\) because it is easy to use and compatible with a wide variety of platforms. The LiteOS-M provides APIs similar to **dlopen** and **dlsym**. Apps can load and unload required algorithm libraries by using the APIs provided by the dynamic loading module. As shown in the following figure, the app obtains the corresponding information output through the API required by the third-party algorithm library. The third-party algorithm library depends on the basic APIs provided by the kernel, such as **malloc**. After the app loads the API and relocates undefined symbols, it can call the API to complete the function. The dynamic loading component supports only the Arm architecture.In addition, the shared library to be loaded needs signature verification or source restriction to ensure the security of the system.
**Figure 1** LiteOS-M kernel dynamic loading architecture<a name="fig3662173651419"></a>
![](figure/liteos-m-kernel-dynamic-loading-architecture.png "liteos-m-kernel-dynamic-loading-architecture")
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- [ELF共享库编译链接选项](#section17292133274)
在硬件资源有限的小设备中,需要通过算法的动态部署能力来解决无法同时部署多种算法的问题。以开发者易用为主要考虑因素,同时考虑到多平台的通用性,LiteOS-M选择业界标准的ELF方案,方便拓展算法生态。LiteOS-M提供类似于dlopen、dlsym等接口,APP通过动态加载模块提供的接口可以加载、卸载相应算法库。如图1所示,APP需要通过三方算法库所需接口获取对应信息输出,三方算法库又依赖内核提供的基本接口,如malloc等。APP加载所需接口,并对相关的未定义符号完成重定位后,APP即可调用该接口完成功能调用。目前动态加载组件只支持arm架构。
在硬件资源有限的小设备中,需要通过算法的动态部署能力来解决无法同时部署多种算法的问题。以开发者易用为主要考虑因素,同时考虑到多平台的通用性,LiteOS-M选择业界标准的ELF方案,方便拓展算法生态。LiteOS-M提供类似于dlopen、dlsym等接口,APP通过动态加载模块提供的接口可以加载、卸载相应算法库。如图1所示,APP需要通过三方算法库所需接口获取对应信息输出,三方算法库又依赖内核提供的基本接口,如malloc等。APP加载所需接口,并对相关的未定义符号完成重定位后,APP即可调用该接口完成功能调用。目前动态加载组件只支持arm架构。此外,待加载的共享库需要验签或者限制来源,确保系统的安全性。
**图 1** LiteOS-M内核动态加载架构图<a name="fig3662173651419"></a>
![](figure/LiteOS-M内核动态加载架构图.png "LiteOS-M内核动态加载架构图")
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