Linux共享库取决于dlopen使用RTLD_LOCAL打开的另一个共享库中的符号

问题描述

我有一个共享库 libmain.so ，由宿主程序使用 dlopen("libmain.so"，RTLD_LOCAL)加载，在某些情况下， libmain.so 将同时使用 dlopen 加载另一个共享库 libpatch.so .问题是 libpatch.so取决于libmain.so中的符号，那么我该如何解决呢?

I have a shared library libmain.so, loaded by the host program with dlopen("libmain.so", RTLD_LOCAL), and under some conditions, libmain.so will load another shared library, libpatch.so, also with dlopen. The problem is, libpatch.so depends on symbols inside libmain.so, so how can I solve this?

1. 由于权限原因，不能将 RTLD_LOCAL 更改为 RTLD_GLOBAL .

那里是一个与此非常相似的问题首先，解决该问题的方法是使 libpatch.so 成为 libmain.so 的依赖项，以便在 libmain.so 时将其加载已加载，但我的 libpatch.so 应该有条件地加载，当链接 libmain.so 时， libpatch.so 可能不存在.

There is a question quite similar to this one, the solution to that problem is to make libpatch.so a dependency of libmain.so, so it will be loaded when libmain.so is loaded, but my libpatch.so should be loaded conditionally, libpatch.so might not be there when libmain.so is linked.

我要解决的原始问题是:

the original problem I want to solve is:

进程运行时，我们可能会发现 libmain.so 中的函数 SomeFunction 中存在错误，，但是该进程无法重新启动，并且 libmain.so 无法重新加载，因此我们必须为 libpatch.so 提供错误修复功能 SomeFunction ，然后发送一个向进程发出信号，使其加载 libpatch.so ，并在 libpatch.so 中使用 SomeFunction ，而不是在 libmain中的越野车之一.so .但是， SomeFunction 依赖于全局变量 GlobalVar ，并且它可能已在 libmain.so 中更改，因此我们要链接 SomeFunction 到 libmain.so 里面，但是 libmain.so 是用 RTLD_LOCAL 加载的，GlobalVar 不能加载 libpatch.so 时被引用.

When the process is running, we may find that there is a bug in function SomeFunction inside libmain.so, but the process cannot be restarted and libmain.so cannot be reloaded, so we have to provide a libpatch.so with bug-fixed function SomeFunction, and send a signal to the process, make it to load libpatch.so, and use SomeFunction in libpatch.so instead the buggy one in libmain.so. However, SomeFunction depends on a global variable GlobalVar, and it might have changed in libmain.so, so we want to link SomeFunction to it inside libmain.so, but libmain.so is loaded with RTLD_LOCAL, GlobalVar cannot be referenced when libpatch.so is loading.

推荐答案

从libmain.so编译libpatch.so所需的符号列表.建立一个包含这些符号地址的数据结构.并非针对libmain.so而是针对此数据结构构建libpatch.so.将其实例传递给libpatch.so初始化函数.

Compile a list of symbols from libmain.so needed by libpatch.so. Build a data structure that contains addresses of these symbols. Build libpatch.so not against libmain.so but against this data structure. Pass an instance of it to libpatch.so initialisation function.

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