Linux 动态库

Linux的可执行文件一般是elf格式的，在这个可执行文件的头部包含了很多重要的信息：如文件格式，加载地址，符号表等。当链接器链接生成可执行文件时，会将程序的加载地址写入可执行文件头。在程序运行时，动态加载器将可执行文件载入文件头指定的加载地址处，并加载该地址，开始从该地址处运行。由此可见，可执行文件的起始地址是在编译时就决定的：

x@QiTianM650-A245:~$ readelf -h dnsmasq.elf 
ELF Header:
  Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF32
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           ARM
  Version:                           0x1
  Entry point address:               0xa5d8
  Start of program headers:          52 (bytes into file)
  Start of section headers:          347256 (bytes into file)
  Flags:                             0x5000002, Version5 EABI, <unknown>
  Size of this header:               52 (bytes)
  Size of program headers:           32 (bytes)
  Number of program headers:         7
  Size of section headers:           40 (bytes)
  Number of section headers:         36
  Section header string table index: 33