目标文件及链接.ppt

中国科大 目标文件及链接   SimpleSection.o各段信息 $ objdump -h SimpleSection.o SimpleSection.o:???? file format elf32-i386 Sections: Idx Name?????? ??? Size?? ??? VMA?????? ? LMA????? ?? File off? Algn 0 .text???? ???? 0000005b 2**2 ?????????????? ????? CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE ?1 .data???? ????00000000? 2**2 ?????????????? ????? CONTENTS, ALLOC, LOAD, DATA ?2 .bss????? ????00000000? 2**2 ?????????????? ????? ALLOC 3 .rodata?? ???00000000? 2**0 ????????????? ?????? CONTENTS, ALLOC, LOAD, READONLY, DATA ?4 .comment? ??? 0000002a 0000009c? 2**0 ?????????????? ????? CONTENTS, READONLY ?5 .note.GNU-stack??????? 000000c6 2**0 ?????????????? ????? CONTENTS, READONLY SimpleSection.o反汇编代码 ELF文件结构描述 ELF文件头 段头表 －text节 被编译程序的机器代码 －rodata节 诸如printf语句中的格式串和switch语句的跳转表等只读数据 －data节 已初始化的全局变量 －bss节（.comm 节） 未初始化的全局变量 在目标文件中不占实际的空间 段描述符（Section header Descriptor） typedef struct { Elf32_Word??? sh_name; Elf32_Word??? sh_type; Elf32_Word??? sh_flags; ?Elf32_Addr??? sh_addr; ?Elf32_Off???? sh_offset; ?Elf32_Word??? sh_size; Elf32_Word??? sh_link; Elf32_Word??? sh_info; Elf32_Word??? sh_addralign; Elf32_Word??? sh_entsize; } Elf32_Shdr; SimpleSection.o段表信息 $ readelf -S SimpleSection.o There are 11 section headers, starting at offset 0x118: Section Headers: [Nr] Name??????Type??? ?? Addr???? Off??? Size?? ES Flg Lk Inf Al [0]????????????? ??? NULL???? ? 000000 000000 00 0 ? 0? 0 [1] .text??????? PROGBITS000034 00005b 00 AX? 0? 0? ?4 [2] .rel.text??REL???? ?? 000428 000028 08??9? 1 ??4 [3] .data???????PROGBITS000090 000008 00 WA 0? 0 ??4 [4] .bss??????? ?NOBITS?? ? 000098 000004 00 WA 0? 0 ??4 [5] .rodata???PROGBITS000098 000004 00 A? 0? 0 ??1 [6] .comment???PROGBITS000