ELF可执行文件中.dynamic .dynsym和.dynstr之间的区别

问题描述

我的初步知识是：

• .dynamic 包含以下库：可执行文件需要加载


• .dynsym 包含外部符号，如 setsockopt@GLIBC_2.0


• .dynstr 包含函数要求的字符串

• .dynamic contains libraries that the executable needs to load
• .dynsym contains external symbols such as setsockopt@GLIBC_2.0
• .dynstr contains strings of function requirements

总体而言，对于这些部分如何共同创建二进制文件-尤其是 .dynsym 和，我有些困惑。 dynstr 。所以我的问题有两个。我上面的陈述正确吗？如果是这样，这三个部分如何协同工作以创建二进制文件？

Overall, I am a bit confused as to how these sections work together to create a binary - specifically .dynsym and .dynstr. So my question is two-fold. Are my statements above correct? If so, how do these three sections work together to create a binary?

推荐答案

.dynsym 部分包含一组固定长度 Elf32_Sym 或 Elf64_Sym 的记录。

The .dynsym section contains a set of fixed-length records of type Elf32_Sym or Elf64_Sym.

是固定的长度条目，它们本身无法描述二进制文件输出或导入的任意长度符号（字符串）。

Since these are fixed length entries, they can not by themselves describe arbitrary length symbols (strings) that the binary exports or imports.

因此，这些条目不包含字符串。相反，它们在 .dynstr （在 .st_name 字段中）中包含一个偏移量，并且在此偏移量处找到符号名称。

Therefore these entries don't contain the strings. Instead, they contain an offset into .dynstr (in the .st_name field), and the symbol name is found at this offset.

因此， .dynsym 包含setsockopt @ GLIBC_2是不正确的.0和 .dynstr 包含函数要求的字符串（无论最后一条语句表示什么）。

So it's not true that ".dynsym contains setsockopt@GLIBC_2.0" and that ".dynstr contains strings of function requirements" (whatever that last statement means).

.dynsym 包含 Elf32_Sym 或 Elf64_sym 导入的符号 setsockopt ，并在 .dynstr setsockopt 字符串的偏移量/ code>部分。

The .dynsym contains an Elf32_Sym or an Elf64_sym describing an imported symbol setsockopt, and referencing the offset of "setsockopt" string in the .dynstr section.

同样， .dynamic 包含可执行文件需要加载的库是错误的-该节不包含任何库。

Likewise, ".dynamic contains libraries that the executable needs to load" is false -- the section doesn't contain any libraries.

它包含固定长度的 Elf64_Dyn 或 Elf32_Dyn ，其中一些（例如带有 .d_tag == DT_NEEDED 或 DT_RPATH ）可以引用stri ngs .dynstr 的偏移量。动态加载程序以某种方式解释这些条目-对于 DT_NEEDED 为必须加载另一个库，对于 DT_RPATH 例如必须搜索这些用冒号分隔的路径等等。

It contains fixed length entries of Elf64_Dyn or Elf32_Dyn, some of which (such as ones with .d_tag == DT_NEEDED or DT_RPATH) may reference strings from .dynstr via their offsets. The dynamic loader interprets these entries in certain way -- for DT_NEEDED as "must load this other library", for DT_RPATH as "must search these colon-separated paths", etc.

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