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Makefile
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main.c
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README.md

main.o 和 prog 里面的函数区别

  1. objdump -dx main.o 0000000000000000 <main>: 0: f3 0f 1e fa endbr64 4: 55 push %rbp 5: 48 89 e5 mov %rsp,%rbp 8: 48 83 ec 10 sub $0x10,%rsp c: be 02 00 00 00 mov $0x2,%esi 11: 48 8d 05 [00 00 00 00] lea 0x0(%rip),%rax # 18 <main+0x18> 14: R_X86_64_PC32 array-0x4 18: 48 89 c7 mov %rax,%rdi 1b: e8 [00 00 00 00] call 20 <main+0x20> 1c: R_X86_64_PLT32 sum-0x4 20: 89 45 fc mov %eax,-0x4(%rbp) 23: 8b 45 fc mov -0x4(%rbp),%eax 26: c9 leave 27: c3 ret
  2. objdump -d prog 0000000000001129 <main>: 1129: f3 0f 1e fa endbr64 112d: 55 push %rbp 112e: 48 89 e5 mov %rsp,%rbp 1131: 48 83 ec 10 sub $0x10,%rsp 1135: be 02 00 00 00 mov $0x2,%esi 113a: 48 8d 05 [cf 2e 00 00] lea 0x2ecf(%rip),%rax # 4010 <array>, 这个地址也是pc relative 1141 + 2ecf = 4010 1141: 48 89 c7 mov %rax,%rdi 1144: e8 [08 00 00 00] call 1151 <sum> 1149: 89 45 fc mov %eax,-0x4(%rbp) 114c: 8b 45 fc mov -0x4(%rbp),%eax 114f: c9 leave 1150: c3 ret
  3. 首先我们可以非常明显的看到 再重定位之前main函数的起始地址是零，call指令的目标地址是零；在重定位之后，main函数的起始地址编了，call指令的目标地址也被填充好了
  4. 使用 objdump -D prog 可以看到array的地址 0000000000004010 : 4010: 01 00 add %eax,(%rax) 4012: 00 00 add %al,(%rax) 4014: 02 00 add (%rax),%al ...