elf 檔案初識-變數儲存
收藏可參考的文章:https://www.cnblogs.com/LiuYanYGZ/p/5574602.html
.data 初始化過的全域性變數 (含初始化靜態變數)
.bss 未初始化的全域性變數(包括 函式內外的未初始化的靜態變數)
.rodata 只讀的變數(const)
1)關於常量 和 普通變數
int* const globle_A = 10; // .rodata
const int* globle_B = 10; // .data
2)關於初始化和非初始化
#include <stdio.h>
int global_dat1[30000]; //儲存在bss段,由系統初始化為全 0,不需要儲存初始化值
int global_dat1[30000]={0,}; //儲存在bss段,由系統初始化為全 0,不需要儲存初始化值 //是否是有優化的成分待繼續追一下
int global_dat1[30000]={1,2,3,4,}; //儲存在data 段,初始化的大陣列要被儲存,所以編譯出來的檔案會大很多!
int main(void)
{
return 0;
}
3)具體例子
編譯 gcc para.c -g
然後讀出 readelf -a a.out (readelf -s)
#include <stdio.h> const int globle_A = 10; // .rodata read only data 4006b8(start addr:4006b0 len:3a) int globle_a = 20; // .data globle data 601040 (start addr:r601030 len:24) int globle_b = 21; // .data 601044 static int static_c = 30; // .data 601048 static int static_d = 31; // .data 60104c int c; // .bss uninit data area 60105c(start:601054) void print_globle(void) { printf(" %s: globle_a = %d \n", __FUNCTION__, globle_a ); } int main(void) { static int static_local_e = 40; // .data 601050 static int static_local_f; // .data 601058 int local_h = 70; char globle_b[] = "Hello world"; int globle_a = 90; register int c = 50; printf(" %s: globle_a = %d \n", __FUNCTION__, globle_a ); //printf("Hello 1 %d\n", sizeof(A)); print_globle(); return 0; }
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: 0x4004a0
Start of program headers: 64 (bytes into file)
Start of section headers: 8408 (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: 36
Section header string table index: 33
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
0000000000000078 0000000000000018 A 6 1 8
[ 6] .dynstr STRTAB 0000000000400330 00000330
000000000000005a 0000000000000000 A 0 0 1
[ 7] .gnu.version VERSYM 000000000040038a 0000038a
000000000000000a 0000000000000002 A 5 0 2
[ 8] .gnu.version_r VERNEED 0000000000400398 00000398
0000000000000030 0000000000000000 A 6 1 8
[ 9] .rela.dyn RELA 00000000004003c8 000003c8
0000000000000018 0000000000000018 A 5 0 8
[10] .rela.plt RELA 00000000004003e0 000003e0
0000000000000048 0000000000000018 AI 5 24 8
[11] .init PROGBITS 0000000000400428 00000428
000000000000001a 0000000000000000 AX 0 0 4
[12] .plt PROGBITS 0000000000400450 00000450
0000000000000040 0000000000000010 AX 0 0 16
[13] .plt.got PROGBITS 0000000000400490 00000490
0000000000000008 0000000000000000 AX 0 0 8
[14] .text PROGBITS 00000000004004a0 000004a0
0000000000000202 0000000000000000 AX 0 0 16
[15] .fini PROGBITS 00000000004006a4 000006a4
0000000000000009 0000000000000000 AX 0 0 4
[16] .rodata PROGBITS 00000000004006b0 000006b0
000000000000003a 0000000000000000 A 0 0 8
[17] .eh_frame_hdr PROGBITS 00000000004006ec 000006ec
000000000000003c 0000000000000000 A 0 0 4
[18] .eh_frame PROGBITS 0000000000400728 00000728
0000000000000114 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
0000000000000030 0000000000000008 WA 0 0 8
[25] .data PROGBITS 0000000000601030 00001030
0000000000000024 0000000000000000 WA 0 0 8
[26] .bss NOBITS 0000000000601054 00001054
000000000000000c 0000000000000000 WA 0 0 4
[27] .comment PROGBITS 0000000000000000 00001054
0000000000000035 0000000000000001 MS 0 0 1
[28] .debug_aranges PROGBITS 0000000000000000 00001089
0000000000000030 0000000000000000 0 0 1
[29] .debug_info PROGBITS 0000000000000000 000010b9
00000000000001f7 0000000000000000 0 0 1
[30] .debug_abbrev PROGBITS 0000000000000000 000012b0
00000000000000c4 0000000000000000 0 0 1
[31] .debug_line PROGBITS 0000000000000000 00001374
0000000000000048 0000000000000000 0 0 1
[32] .debug_str PROGBITS 0000000000000000 000013bc
0000000000000130 0000000000000001 MS 0 0 1
[33] .shstrtab STRTAB 0000000000000000 00001f87
000000000000014c 0000000000000000 0 0 1
[34] .symtab SYMTAB 0000000000000000 000014f0
00000000000007e0 0000000000000018 35 58 8
[35] .strtab STRTAB 0000000000000000 00001cd0
00000000000002b7 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)
There are no section groups in this file.
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000400040 0x0000000000400040
0x00000000000001f8 0x00000000000001f8 R E 8
INTERP 0x0000000000000238 0x0000000000400238 0x0000000000400238
0x000000000000001c 0x000000000000001c R 1
[Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
LOAD 0x0000000000000000 0x0000000000400000 0x0000000000400000
0x000000000000083c 0x000000000000083c R E 200000
LOAD 0x0000000000000e10 0x0000000000600e10 0x0000000000600e10
0x0000000000000244 0x0000000000000250 RW 200000
DYNAMIC 0x0000000000000e28 0x0000000000600e28 0x0000000000600e28
0x00000000000001d0 0x00000000000001d0 RW 8
NOTE 0x0000000000000254 0x0000000000400254 0x0000000000400254
0x0000000000000044 0x0000000000000044 R 4
GNU_EH_FRAME 0x00000000000006ec 0x00000000004006ec 0x00000000004006ec
0x000000000000003c 0x000000000000003c R 4
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RW 10
GNU_RELRO 0x0000000000000e10 0x0000000000600e10 0x0000000000600e10
0x00000000000001f0 0x00000000000001f0 R 1
Section to Segment mapping:
Segment Sections...
00
01 .interp
02 .interp .note.ABI-tag .note.gnu.build-id .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt .init .plt .plt.got .text .fini .rodata .eh_frame_hdr .eh_frame
03 .init_array .fini_array .jcr .dynamic .got .got.plt .data .bss
04 .dynamic
05 .note.ABI-tag .note.gnu.build-id
06 .eh_frame_hdr
07
08 .init_array .fini_array .jcr .dynamic .got
Dynamic section at offset 0xe28 contains 24 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x400428
0x000000000000000d (FINI) 0x4006a4
0x0000000000000019 (INIT_ARRAY) 0x600e10
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x600e18
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x400298
0x0000000000000005 (STRTAB) 0x400330
0x0000000000000006 (SYMTAB) 0x4002b8
0x000000000000000a (STRSZ) 90 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000015 (DEBUG) 0x0
0x0000000000000003 (PLTGOT) 0x601000
0x0000000000000002 (PLTRELSZ) 72 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x4003e0
0x0000000000000007 (RELA) 0x4003c8
0x0000000000000008 (RELASZ) 24 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffe (VERNEED) 0x400398
0x000000006fffffff (VERNEEDNUM) 1
0x000000006ffffff0 (VERSYM) 0x40038a
0x0000000000000000 (NULL) 0x0
Relocation section '.rela.dyn' at offset 0x3c8 contains 1 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000600ff8 000400000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0
Relocation section '.rela.plt' at offset 0x3e0 contains 3 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000601018 000100000007 R_X86_64_JUMP_SLO 0000000000000000 [email protected]_2.4 + 0
000000601020 000200000007 R_X86_64_JUMP_SLO 0000000000000000 [email protected]_2.2.5 + 0
000000601028 000300000007 R_X86_64_JUMP_SLO 0000000000000000 [email protected]_2.2.5 + 0
The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
Symbol table '.dynsym' contains 5 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 FUNC GLOBAL DEFAULT UND [email protected]_2.4 (2)
2: 0000000000000000 0 FUNC GLOBAL DEFAULT UND [email protected]_2.2.5 (3)
3: 0000000000000000 0 FUNC GLOBAL DEFAULT UND [email protected]_2.2.5 (3)
4: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
Symbol table '.symtab' contains 84 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000400238 0 SECTION LOCAL DEFAULT 1
2: 0000000000400254 0 SECTION LOCAL DEFAULT 2
3: 0000000000400274 0 SECTION LOCAL DEFAULT 3
4: 0000000000400298 0 SECTION LOCAL DEFAULT 4
5: 00000000004002b8 0 SECTION LOCAL DEFAULT 5
6: 0000000000400330 0 SECTION LOCAL DEFAULT 6
7: 000000000040038a 0 SECTION LOCAL DEFAULT 7
8: 0000000000400398 0 SECTION LOCAL DEFAULT 8
9: 00000000004003c8 0 SECTION LOCAL DEFAULT 9
10: 00000000004003e0 0 SECTION LOCAL DEFAULT 10
11: 0000000000400428 0 SECTION LOCAL DEFAULT 11
12: 0000000000400450 0 SECTION LOCAL DEFAULT 12
13: 0000000000400490 0 SECTION LOCAL DEFAULT 13
14: 00000000004004a0 0 SECTION LOCAL DEFAULT 14
15: 00000000004006a4 0 SECTION LOCAL DEFAULT 15
16: 00000000004006b0 0 SECTION LOCAL DEFAULT 16
17: 00000000004006ec 0 SECTION LOCAL DEFAULT 17
18: 0000000000400728 0 SECTION LOCAL DEFAULT 18
19: 0000000000600e10 0 SECTION LOCAL DEFAULT 19
20: 0000000000600e18 0 SECTION LOCAL DEFAULT 20
21: 0000000000600e20 0 SECTION LOCAL DEFAULT 21
22: 0000000000600e28 0 SECTION LOCAL DEFAULT 22
23: 0000000000600ff8 0 SECTION LOCAL DEFAULT 23
24: 0000000000601000 0 SECTION LOCAL DEFAULT 24
25: 0000000000601030 0 SECTION LOCAL DEFAULT 25
26: 0000000000601054 0 SECTION LOCAL DEFAULT 26
27: 0000000000000000 0 SECTION LOCAL DEFAULT 27
28: 0000000000000000 0 SECTION LOCAL DEFAULT 28
29: 0000000000000000 0 SECTION LOCAL DEFAULT 29
30: 0000000000000000 0 SECTION LOCAL DEFAULT 30
31: 0000000000000000 0 SECTION LOCAL DEFAULT 31
32: 0000000000000000 0 SECTION LOCAL DEFAULT 32
33: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
34: 0000000000600e20 0 OBJECT LOCAL DEFAULT 21 __JCR_LIST__
35: 00000000004004d0 0 FUNC LOCAL DEFAULT 14 deregister_tm_clones
36: 0000000000400510 0 FUNC LOCAL DEFAULT 14 register_tm_clones
37: 0000000000400550 0 FUNC LOCAL DEFAULT 14 __do_global_dtors_aux
38: 0000000000601054 1 OBJECT LOCAL DEFAULT 26 completed.7594
39: 0000000000600e18 0 OBJECT LOCAL DEFAULT 20 __do_global_dtors_aux_fin
40: 0000000000400570 0 FUNC LOCAL DEFAULT 14 frame_dummy
41: 0000000000600e10 0 OBJECT LOCAL DEFAULT 19 __frame_dummy_init_array_
42: 0000000000000000 0 FILE LOCAL DEFAULT ABS para.c
43: 0000000000601048 4 OBJECT LOCAL DEFAULT 25 static_c
44: 000000000060104c 4 OBJECT LOCAL DEFAULT 25 static_d
45: 00000000004006d8 13 OBJECT LOCAL DEFAULT 16 __FUNCTION__.2292
46: 00000000004006e5 5 OBJECT LOCAL DEFAULT 16 __FUNCTION__.2302
47: 0000000000601058 4 OBJECT LOCAL DEFAULT 26 static_local_f.2297
48: 0000000000601050 4 OBJECT LOCAL DEFAULT 25 static_local_e.2296
49: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
50: 0000000000400838 0 OBJECT LOCAL DEFAULT 18 __FRAME_END__
51: 0000000000600e20 0 OBJECT LOCAL DEFAULT 21 __JCR_END__
52: 0000000000000000 0 FILE LOCAL DEFAULT ABS
53: 0000000000600e18 0 NOTYPE LOCAL DEFAULT 19 __init_array_end
54: 0000000000600e28 0 OBJECT LOCAL DEFAULT 22 _DYNAMIC
55: 0000000000600e10 0 NOTYPE LOCAL DEFAULT 19 __init_array_start
56: 00000000004006ec 0 NOTYPE LOCAL DEFAULT 17 __GNU_EH_FRAME_HDR
57: 0000000000601000 0 OBJECT LOCAL DEFAULT 24 _GLOBAL_OFFSET_TABLE_
58: 00000000004006a0 2 FUNC GLOBAL DEFAULT 14 __libc_csu_fini
59: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
60: 0000000000601030 0 NOTYPE WEAK DEFAULT 25 data_start
61: 0000000000601054 0 NOTYPE GLOBAL DEFAULT 25 _edata
62: 00000000004006a4 0 FUNC GLOBAL DEFAULT 15 _fini
63: 0000000000000000 0 FUNC GLOBAL DEFAULT UND [email protected]@GLIBC_2
64: 0000000000000000 0 FUNC GLOBAL DEFAULT UND [email protected]@GLIBC_2.2.5
65: 0000000000000000 0 FUNC GLOBAL DEFAULT UND [email protected]@GLIBC_
66: 0000000000601030 0 NOTYPE GLOBAL DEFAULT 25 __data_start
67: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
68: 0000000000601040 4 OBJECT GLOBAL DEFAULT 25 globle_a
69: 0000000000601038 0 OBJECT GLOBAL HIDDEN 25 __dso_handle
70: 00000000004006b0 4 OBJECT GLOBAL DEFAULT 16 _IO_stdin_used
71: 00000000004006b8 4 OBJECT GLOBAL DEFAULT 16 globle_A
72: 0000000000400630 101 FUNC GLOBAL DEFAULT 14 __libc_csu_init
73: 0000000000601060 0 NOTYPE GLOBAL DEFAULT 26 _end
74: 00000000004004a0 42 FUNC GLOBAL DEFAULT 14 _start
75: 000000000060105c 4 OBJECT GLOBAL DEFAULT 26 c
76: 0000000000601054 0 NOTYPE GLOBAL DEFAULT 26 __bss_start
77: 00000000004005b9 115 FUNC GLOBAL DEFAULT 14 main
78: 0000000000400596 35 FUNC GLOBAL DEFAULT 14 print_globle
79: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _Jv_RegisterClasses
80: 0000000000601058 0 OBJECT GLOBAL HIDDEN 25 __TMC_END__
81: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
82: 0000000000400428 0 FUNC GLOBAL DEFAULT 11 _init
83: 0000000000601044 4 OBJECT GLOBAL DEFAULT 25 globle_b
Version symbols section '.gnu.version' contains 5 entries:
Addr: 000000000040038a Offset: 0x00038a Link: 5 (.dynsym)
000: 0 (*local*) 2 (GLIBC_2.4) 3 (GLIBC_2.2.5) 3 (GLIBC_2.2.5)
004: 0 (*local*)
Version needs section '.gnu.version_r' contains 1 entries:
Addr: 0x0000000000400398 Offset: 0x000398 Link: 6 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 2
0x0010: Name: GLIBC_2.2.5 Flags: none Version: 3
0x0020: Name: GLIBC_2.4 Flags: none Version: 2
Displaying notes found at file offset 0x00000254 with length 0x00000020:
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 2.6.32
Displaying notes found at file offset 0x00000274 with length 0x00000024:
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: 55ab69f6327e884925a448bcf65acbaa59cc07a9