漫谈兼容内核之八elf映像的装入一-seebugpaper.doc

漫谈兼容内核之八 : Talk compatible with the kernel of the eight: ELF 映像的装入 ( 一 )ELF image into (a) 毛德操 Maud operation 上一篇漫谈中介绍了 Wine 的二进制映像装入和启动，现在我们来看看 ELF 映像的装入和启动。 Talk on the one described in the Wine and start loading the binary image, and now we look into the ELF image and start. 一般而言，应用软件的编程不可能是“一竿子到底”、所有的代码都自己写的，程序员不可避免地、也许是不自觉地、都会使用一些现成的程序库。 Generally speaking, application software programming can not be a pole in the end, all write their own code, programmers inevitably, perhaps unconsciously, will use some ready-made library. 对于 C 语言的编程，至少 C 程序库是一定会用到的。 For the C programming language, at least C library would definitely be used. 从编译 / 连接和运行的角度看，应用程序和库程序的连接有两种方法。 From the compile / link and run the point of view, applications, and database connectivity programs in two ways. 一种是固定的、静态的连接，就是把需要用到的库函数的目标 ( 二进制 ) 代码从程序库中抽取出来，连接进应用软件的目标映像中，或者甚至干脆把整个程序库都连接进应用软件的映像中。 One is fixed, static connections, is the need to use the library function of the target (binary) code extracted from the program library, connect the target image into the application software, or even simply to enter the library are connected application image. 这里所谓的连接包括两方面的操作，一是把库函数的目标代码“定位”在应用软件目标映像中的某个位置上。 Here the so-called connection consists of two aspects of the operation, one goal of the library function code positioning in the application software to a target location in the image. 由于不同应用软件本身的大小和结构都可能不同，库函数在目标映像中的位置是无法预先确定的。 Because different applications have their own size and structure may be different, the librarys position in the target image can not be predetermined. 为此，程序库中的代码必须是可以浮动的，即“与位置无关”的，在编译时必须加上 -fPIC 选项，这里 PIC 是“ Position-Independent Code ”的缩写。 To this end, the library code must be floating, that is position independent, and must be compiled with-fPIC option, where the PIC is the Position-Independent Code acronym. 一旦一个库函数在映像中的位置确定以后，就要使应用软件中所有对此函数的调用都指向这个函数。 Once a library function to determine the location in the image after the application software will make all the calls to thi