MobileSubstrate：MSHookFunction示例 [英] MobileSubstrate: MSHookFunction example

问题描述

我正在尝试编写一个挂钩到C方法的MobileSubstrate插件。我试着编辑着名的ExampleHook，只需编写一个演示MSHook并将其挂钩在Initialize方法中。
这可能过于乐观，但不起作用。但我无法找到MSHookFunction（）的简单示例。互联网上几乎没有关于此的信息。我可能会误解MSHookFunction的整个概念。

I am trying to write a MobileSubstrate plugin which hooks into a C-method. I tried to edit the famous "ExampleHook", by just writing a demo MSHook and hook it in the Initialize method. This is probably too optimistic and it doesn't work. But I cannot find anywhere a simple example of a MSHookFunction(). There is barely information about this on the Internet. It might be possible I misunderstood the whole concept of MSHookFunction.

请问，有人可以用一些示例代码帮助我吗？我非常感谢任何帮助。

Please, can anybody help me out with a little example code? I would deeply appreciate any help.

祝你好运，
Marc Backes

Best regards, Marc Backes

推荐答案

我发现你已经找到了这个，但我发布了这个答案，以帮助其他人可能需要这个。

I realize you have found this, but I am posting this answer to help whoever else may be needing this.

一个简单的例子可以在iPhone Dev Wiki上的 MobileSubstrate文章，以及项目中的一个实际示例是 User Agent Faker 的此位。

A simple example can be found at the MobileSubstrate article on the iPhone Dev Wiki, and an actual example of this in a project is at this bit of User Agent Faker.

但没有实际解释，答案是什么？因此，我们走了！

But what is an answer without an actual explanation? Therefore, here we go!

void MSHookFunction（void * function，void * replacement，void ** p_original）; 是 MSHookFunction 的函数定义，这个函数会导致函数 X（）被<$插入例如，c $ c> Y（）。

void MSHookFunction(void* function, void* replacement, void** p_original); is the function definition for MSHookFunction, the magic function which causes your function X() to be interposed by Y(), for instance.

也就是说，当一个程序通常会调用 X（ ），该呼叫将被重定向到 Y（）。这几乎是函数插入的基本解释。

That is, when a program commonly would call X(), the call will be redirected to Y() instead. This is pretty much a basic explanation of function interposing.

现在，参数是什么，它们的用处是什么？

Now, what are the parameters, and their usefulness?

• function 是指向要插入的函数的函数指针。在我们的快速解释中，这将是指向 X（）的函数指针。


• replacement 是一个函数指针，指向要插入的函数 function 。在我们的快速解释中，这将是指向 Y（）的函数指针。



• p_original 是一个指向函数指针的指针，从现在开始将指向函数过去。

• function is a function pointer to the function you want to interpose. That would be a function pointer to X(), in our quick explanation.
• replacement is a function pointer to the function you want function to be interposed with. In our quick explanation, that would be a function pointer to Y().

• p_original is a pointer to a function pointer, which from now on will point to what function used to be.

原因很简单：如果你打算修改行为但不压制它，你仍然需要调用什么 X（）以前是。但是对 X（）的常见调用将无法正常工作，因为它将结束调用 Y（）而不是默认函数。

The reason this is there is simple: If you intend to modify behavior, but not suppress it, you'll still need to call what X() used to be. But a common call to X() wouldn't work as intended, as it would end calling Y() instead of the default function.

因此，你有一个函数指针来调用 X（ ）好像它没有插入。

Therefore, you have a function pointer to call X() as if it wasn't interposed.

现在，解释devwiki示例：

Now, explaining the devwiki example:

static void (*original_CFShow)(CFTypeRef obj);  // a function pointer to store the original CFShow().
void replaced_CFShow(CFTypeRef obj) {           // our replacement of CFShow().
  printf("Calling original CFShow(%p)...", obj);
  original_CFShow(obj);                         // calls the original CFShow.
  printf(" done.\n");
}
...
// hook CFShow to our own implementation.
MSHookFunction(CFShow, replaced_CFShow, &original_CFShow);
// From now on any call to CFShow will pass through replaced_CFShow first.
...
CFShow(CFSTR("test"));

在这里，我们：

1. 将指针传递给 CFShow ，我们想要更改默认行为的函数为函数参数。


2. 将指针传递给我们刚刚创建的函数， replacement_CFShow 作为替换参数。也就是说，默认情况下，只要调用 CFShow ，就会调用 replacement_CFShow 。


3. 我们将指向 original_CFShow 函数指针的指针作为 p_original 参数传递。由于我们仍然希望 CFShow 在我们的替换函数中完成，我们称之为。

1. Pass a pointer to CFShow, the function we want to change default behavior from as the function parameter.
2. Pass a pointer to the function we just created, replaced_CFShow as the replacement parameter. That is, whenever CFShow would be called by default, replaced_CFShow will be called instead.
3. We pass a pointer to the original_CFShow function pointer as the p_original parameter. Since we still want the things CFShow still does by itself to be done inside our replacement function, we call it.

这篇关于MobileSubstrate：MSHookFunction示例的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！