我有一个C源文件
temp1.cvoid foo(void){}
在我的 AMD64 Archlinux 环境中，我使用命令
gcc -o test1.so -shared test1.ctest1.sotest1.soobjdump -D -j .text test1.sotest1.so: file format elf64-x86-64
Disassembly of section .text:
0000000000001020 <foo-0xc9>:
1020: 48 8d 3d e1 2f 00 00 lea 0x2fe1(%rip),%rdi # 4008 <__TMC_END__>
1027: 48 8d 05 da 2f 00 00 lea 0x2fda(%rip),%rax # 4008 <__TMC_END__>
102e: 48 39 f8 cmp %rdi,%rax
1031: 74 15 je 1048 <_init+0x48>
1033: 48 8b 05 8e 2f 00 00 mov 0x2f8e(%rip),%rax # 3fc8 <_ITM_deregisterTMCloneTable@Base>
103a: 48 85 c0 test %rax,%rax
103d: 74 09 je 1048 <_init+0x48>
103f: ff e0 jmp *%rax
1041: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
1048: c3 ret
1049: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
1050: 48 8d 3d b1 2f 00 00 lea 0x2fb1(%rip),%rdi # 4008 <__TMC_END__>
1057: 48 8d 35 aa 2f 00 00 lea 0x2faa(%rip),%rsi # 4008 <__TMC_END__>
105e: 48 29 fe sub %rdi,%rsi
1061: 48 89 f0 mov %rsi,%rax
1064: 48 c1 ee 3f shr $0x3f,%rsi
1068: 48 c1 f8 03 sar $0x3,%rax
106c: 48 01 c6 add %rax,%rsi
106f: 48 d1 fe sar %rsi
1072: 74 14 je 1088 <_init+0x88>
1074: 48 8b 05 5d 2f 00 00 mov 0x2f5d(%rip),%rax # 3fd8 <_ITM_registerTMCloneTable@Base>
107b: 48 85 c0 test %rax,%rax
107e: 74 08 je 1088 <_init+0x88>
1080: ff e0 jmp *%rax
1082: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
1088: c3 ret
1089: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
1090: f3 0f 1e fa endbr64
1094: 80 3d 6d 2f 00 00 00 cmpb $0x0,0x2f6d(%rip) # 4008 <__TMC_END__>
109b: 75 33 jne 10d0 <_init+0xd0>
109d: 55 push %rbp
109e: 48 83 3d 3a 2f 00 00 cmpq $0x0,0x2f3a(%rip) # 3fe0 <__cxa_finalize@GLIBC_2.2.5>
10a5: 00
10a6: 48 89 e5 mov %rsp,%rbp
10a9: 74 0d je 10b8 <_init+0xb8>
10ab: 48 8b 3d 4e 2f 00 00 mov 0x2f4e(%rip),%rdi # 4000 <__dso_handle>
10b2: ff 15 28 2f 00 00 call *0x2f28(%rip) # 3fe0 <__cxa_finalize@GLIBC_2.2.5>
10b8: e8 63 ff ff ff call 1020 <_init+0x20>
10bd: c6 05 44 2f 00 00 01 movb $0x1,0x2f44(%rip) # 4008 <__TMC_END__>
10c4: 5d pop %rbp
10c5: c3 ret
10c6: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
10cd: 00 00 00
10d0: c3 ret
10d1: 66 66 2e 0f 1f 84 00 data16 cs nopw 0x0(%rax,%rax,1)
10d8: 00 00 00 00
10dc: 0f 1f 40 00 nopl 0x0(%rax)
10e0: f3 0f 1e fa endbr64
10e4: e9 67 ff ff ff jmp 1050 <_init+0x50>
00000000000010e9 <foo>:
10e9: 55 push %rbp
10ea: 48 89 e5 mov %rsp,%rbp
10ed: 90 nop
10ee: 5d pop %rbp
10ef: c3 ret
我对此输出有两个问题：
foofoo为什么函数 foo 的内容没有放在文本部分的开头？
为什么要放在开头？没有要求
foo.text从文本部分开始到函数foo开始的内容是什么意思？我
您似乎在
objdumptest1.so当我运行
objdump -D -j.text test1-stripped.soDisassembly of section .text:
0000000000001040 <foo-0xb9>:
1040: 48 8d 3d c1 2f 00 00 lea 0x2fc1(%rip),%rdi # 4008 <foo+0x2f0f>
1047: 48 8d 05 ba 2f 00 00 lea 0x2fba(%rip),%rax # 4008 <foo+0x2f0f>
104e: 48 39 f8 cmp %rdi,%rax
1051: 74 15 je 1068 <__cxa_finalize@plt+0x38>
1053: 48 8b 05 7e 2f 00 00 mov 0x2f7e(%rip),%rax # 3fd8 <foo+0x2edf>
105a: 48 85 c0 test %rax,%rax
105d: 74 09 je 1068 <__cxa_finalize@plt+0x38>
105f: ff e0 jmp *%rax
...
10e8: c3 ret
10e9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
10f0: f3 0f 1e fa endbr64
10f4: e9 77 ff ff ff jmp 1070 <__cxa_finalize@plt+0x40>
00000000000010f9 <foo>:
10f9: 55 push %rbp
10fa: 48 89 e5 mov %rsp,%rbp
10fd: 90 nop
10fe: 5d pop %rbp
10ff: c3 ret
但是当我在
unstripped版本上运行
objdump 时，我看到了这个：
Disassembly of section .text:
0000000000001040 <deregister_tm_clones>:
1040: 48 8d 3d c1 2f 00 00 lea 0x2fc1(%rip),%rdi # 4008 <completed.0>
1047: 48 8d 05 ba 2f 00 00 lea 0x2fba(%rip),%rax # 4008 <completed.0>
104e: 48 39 f8 cmp %rdi,%rax
1051: 74 15 je 1068 <deregister_tm_clones+0x28>
1053: 48 8b 05 7e 2f 00 00 mov 0x2f7e(%rip),%rax # 3fd8 <_ITM_deregisterTMCloneTable>
105a: 48 85 c0 test %rax,%rax
105d: 74 09 je 1068 <deregister_tm_clones+0x28>
105f: ff e0 jmp *%rax
1061: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
1068: c3 ret
1069: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
0000000000001070 <register_tm_clones>:
1070: 48 8d 3d 91 2f 00 00 lea 0x2f91(%rip),%rdi # 4008 <completed.0>
1077: 48 8d 35 8a 2f 00 00 lea 0x2f8a(%rip),%rsi # 4008 <completed.0>
107e: 48 29 fe sub %rdi,%rsi
1081: 48 89 f0 mov %rsi,%rax
1084: 48 c1 ee 3f shr $0x3f,%rsi
1088: 48 c1 f8 03 sar $0x3,%rax
108c: 48 01 c6 add %rax,%rsi
108f: 48 d1 fe sar %rsi
1092: 74 14 je 10a8 <register_tm_clones+0x38>
1094: 48 8b 05 35 2f 00 00 mov 0x2f35(%rip),%rax # 3fd0 <_ITM_registerTMCloneTable>
109b: 48 85 c0 test %rax,%rax
109e: 74 08 je 10a8 <register_tm_clones+0x38>
10a0: ff e0 jmp *%rax
10a2: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
10a8: c3 ret
10a9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
00000000000010b0 <__do_global_dtors_aux>:
10b0: f3 0f 1e fa endbr64
10b4: 80 3d 4d 2f 00 00 00 cmpb $0x0,0x2f4d(%rip) # 4008 <completed.0>
10bb: 75 2b jne 10e8 <__do_global_dtors_aux+0x38>
10bd: 55 push %rbp
10be: 48 83 3d 02 2f 00 00 cmpq $0x0,0x2f02(%rip) # 3fc8 <__cxa_finalize>
10c5: 00
10c6: 48 89 e5 mov %rsp,%rbp
10c9: 74 0c je 10d7 <__do_global_dtors_aux+0x27>
10cb: 48 8b 3d 2e 2f 00 00 mov 0x2f2e(%rip),%rdi # 4000 <__dso_handle>
10d2: e8 59 ff ff ff call 1030 <__cxa_finalize@plt>
10d7: e8 64 ff ff ff call 1040 <deregister_tm_clones>
10dc: c6 05 25 2f 00 00 01 movb $0x1,0x2f25(%rip) # 4008 <completed.0>
10e3: 5d pop %rbp
10e4: c3 ret
10e5: 0f 1f 00 nopl (%rax)
10e8: c3 ret
10e9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
00000000000010f0 <frame_dummy>:
10f0: f3 0f 1e fa endbr64
10f4: e9 77 ff ff ff jmp 1070 <register_tm_clones>
00000000000010f9 <foo>:
10f9: 55 push %rbp
10fa: 48 89 e5 mov %rsp,%rbp
10fd: 90 nop
10fe: 5d pop %rbp
10ff: c3 ret