https://blog.csdn.net/sunao2002002/article/details/78515805
查看elf文件
以一个简单的C程序为例：
#include <stdio.h>
#include <string.h>
int main(int argc, char**argv)
{
printf("build date: %s %s\n", __DATE__, __TIME__);
return 0;
}
编译、执行
➜ ~ gcc test.c -o test
➜ ~ ./test
build date: Nov 12 2017 22:07:06
➜ ~
查看elf文件头信息–readelf -h
➜ ~ readelf -h test
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x400430
Start of program headers: 64 (bytes into file)
Start of section headers: 6624 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 9
Size of section headers: 64 (bytes)
Number of section headers: 31
Section header string table index: 28
查看Sections—readelf -S
➜ ~ readelf -S test
There are 31 section headers, starting at offset 0x19e0:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .interp PROGBITS 0000000000400238 00000238
000000000000001c 0000000000000000 A 0 0 1
[ 2] .note.ABI-tag NOTE 0000000000400254 00000254
0000000000000020 0000000000000000 A 0 0 4
[ 3] .note.gnu.build-i NOTE 0000000000400274 00000274
0000000000000024 0000000000000000 A 0 0 4
[ 4] .gnu.hash GNU_HASH 0000000000400298 00000298
000000000000001c 0000000000000000 A 5 0 8
[ 5] .dynsym DYNSYM 00000000004002b8 000002b8
0000000000000060 0000000000000018 A 6 1 8
[ 6] .dynstr STRTAB 0000000000400318 00000318
000000000000003f 0000000000000000 A 0 0 1
[ 7] .gnu.version VERSYM 0000000000400358 00000358
0000000000000008 0000000000000002 A 5 0 2
[ 8] .gnu.version_r VERNEED 0000000000400360 00000360
0000000000000020 0000000000000000 A 6 1 8
[ 9] .rela.dyn RELA 0000000000400380 00000380
0000000000000018 0000000000000018 A 5 0 8
[10] .rela.plt RELA 0000000000400398 00000398
0000000000000030 0000000000000018 AI 5 24 8
[11] .init PROGBITS 00000000004003c8 000003c8
000000000000001a 0000000000000000 AX 0 0 4
[12] .plt PROGBITS 00000000004003f0 000003f0
0000000000000030 0000000000000010 AX 0 0 16
[13] .plt.got PROGBITS 0000000000400420 00000420
0000000000000008 0000000000000000 AX 0 0 8
[14] .text PROGBITS 0000000000400430 00000430
00000000000001a2 0000000000000000 AX 0 0 16
[15] .fini PROGBITS 00000000004005d4 000005d4
0000000000000009 0000000000000000 AX 0 0 4
[16] .rodata PROGBITS 00000000004005e0 000005e0
000000000000002c 0000000000000000 A 0 0 4
[17] .eh_frame_hdr PROGBITS 000000000040060c 0000060c
0000000000000034 0000000000000000 A 0 0 4
[18] .eh_frame PROGBITS 0000000000400640 00000640
00000000000000f4 0000000000000000 A 0 0 8
[19] .init_array INIT_ARRAY 0000000000600e10 00000e10
0000000000000008 0000000000000000 WA 0 0 8
[20] .fini_array FINI_ARRAY 0000000000600e18 00000e18
0000000000000008 0000000000000000 WA 0 0 8
[21] .jcr PROGBITS 0000000000600e20 00000e20
0000000000000008 0000000000000000 WA 0 0 8
[22] .dynamic DYNAMIC 0000000000600e28 00000e28
00000000000001d0 0000000000000010 WA 6 0 8
[23] .got PROGBITS 0000000000600ff8 00000ff8
0000000000000008 0000000000000008 WA 0 0 8
[24] .got.plt PROGBITS 0000000000601000 00001000
0000000000000028 0000000000000008 WA 0 0 8
[25] .data PROGBITS 0000000000601028 00001028
0000000000000010 0000000000000000 WA 0 0 8
[26] .bss NOBITS 0000000000601038 00001038
0000000000000008 0000000000000000 WA 0 0 1
[27] .comment PROGBITS 0000000000000000 00001038
0000000000000034 0000000000000001 MS 0 0 1
[28] .shstrtab STRTAB 0000000000000000 000018cd
000000000000010c 0000000000000000 0 0 1
[29] .symtab SYMTAB 0000000000000000 00001070
0000000000000648 0000000000000018 30 47 8
[30] .strtab STRTAB 0000000000000000 000016b8
0000000000000215 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), l (large)
I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)
➜ ~
查看符号表，并排序 – readelf -s
通过readelf -s命令可以查看符号表。
通过awk命令可以提取出类型、符号名、大小等信息。
通过sort可以对符号表进行排序。
通过grep命令可以提取出OBJ或者FUNCTION。
这些命令的组合，可以实现很多强大的功能。
如下图查看test里面最大的函数：
➜ ~ readelf -s test |awk '{print $3"\t"$4"\t"$8}' |grep FUNC |sort -rh |head -n 5
101 FUNC __libc_csu_init
47 FUNC main
42 FUNC _start
2 FUNC __libc_csu_fini
0 FUNC register_tm_clones
如下图查看test里面最大的变量：
➜ ~ readelf -s test |awk '{print $3"\t"$4"\t"$8}' |grep OBJ |sort -rh |head -n 1
4 OBJECT _IO_stdin_used