# 將源程序和匯編指令映射起來 ## 例子 #include <stdio.h> typedef struct { int a; int b; int c; int d; }ex_st; int main(void) { ex_st st = {1, 2, 3, 4}; printf("%d,%d,%d,%d\n", st.a, st.b, st.c, st.d); return 0; } ## 技巧一 可以用“disas /m fun”（disas是disassemble命令縮寫）命令將函數代碼和匯編指令映射起來，以上面代碼為例： (gdb) disas /m main Dump of assembler code for function main: 11 int main(void) { 0x00000000004004c4 <+0>: push %rbp 0x00000000004004c5 <+1>: mov %rsp,%rbp 0x00000000004004c8 <+4>: push %rbx 0x00000000004004c9 <+5>: sub $0x18,%rsp 12 ex_st st = {1, 2, 3, 4}; 0x00000000004004cd <+9>: movl $0x1,-0x20(%rbp) 0x00000000004004d4 <+16>: movl $0x2,-0x1c(%rbp) 0x00000000004004db <+23>: movl $0x3,-0x18(%rbp) 0x00000000004004e2 <+30>: movl $0x4,-0x14(%rbp) 13 printf("%d,%d,%d,%d\n", st.a, st.b, st.c, st.d); 0x00000000004004e9 <+37>: mov -0x14(%rbp),%esi 0x00000000004004ec <+40>: mov -0x18(%rbp),%ecx 0x00000000004004ef <+43>: mov -0x1c(%rbp),%edx 0x00000000004004f2 <+46>: mov -0x20(%rbp),%ebx 0x00000000004004f5 <+49>: mov $0x400618,%eax 0x00000000004004fa <+54>: mov %esi,%r8d 0x00000000004004fd <+57>: mov %ebx,%esi 0x00000000004004ff <+59>: mov %rax,%rdi 0x0000000000400502 <+62>: mov $0x0,%eax 0x0000000000400507 <+67>: callq 0x4003b8 <printf@plt> 14 return 0; 0x000000000040050c <+72>: mov $0x0,%eax 15 } 0x0000000000400511 <+77>: add $0x18,%rsp 0x0000000000400515 <+81>: pop %rbx 0x0000000000400516 <+82>: leaveq 0x0000000000400517 <+83>: retq End of assembler dump. 可以看到每一條C語句下面是對應的匯編代碼。 ## 技巧二 如果只想查看某一行所對應的地址范圍，可以： (gdb) i line 13 Line 13 of "foo.c" starts at address 0x4004e9 <main+37> and ends at 0x40050c <main+72>. 如果只想查看這一條語句對應的匯編代碼，可以使用“`disassemble [Start],[End]`”命令： (gdb) disassemble 0x4004e9, 0x40050c Dump of assembler code from 0x4004e9 to 0x40050c: 0x00000000004004e9 <main+37>: mov -0x14(%rbp),%esi 0x00000000004004ec <main+40>: mov -0x18(%rbp),%ecx 0x00000000004004ef <main+43>: mov -0x1c(%rbp),%edx 0x00000000004004f2 <main+46>: mov -0x20(%rbp),%ebx 0x00000000004004f5 <main+49>: mov $0x400618,%eax 0x00000000004004fa <main+54>: mov %esi,%r8d 0x00000000004004fd <main+57>: mov %ebx,%esi 0x00000000004004ff <main+59>: mov %rax,%rdi 0x0000000000400502 <main+62>: mov $0x0,%eax 0x0000000000400507 <main+67>: callq 0x4003b8 <printf@plt> End of assembler dump. 詳情參見[gdb手冊](https://sourceware.org/gdb/onlinedocs/gdb/Machine-Code.html) ## 貢獻者 nanxiao xmj