gdb调试艺术之定义钩子命令:-D

gdb调试艺术之定义钩子命令:-D

自定义钩子命令可以在命令执行前/后执行

1.自定义命令执行前的钩子

(gdb) define hook-echo
Type commands for definition of "hook-echo".
End with a line saying just "end".
>echo "<<<"
>end
(gdb) echo
"<<<"(gdb) 

2.自定义命令执行后的钩子

(gdb) define hookpost-echo
Type commands for definition of "hookpost-echo".
End with a line saying just "end".
>echo ">>>"
>end
(gdb) echo
"<<<"">>>"(gdb) 

3.常用的自定义钩子

define hook-stop # 遇到断点或单步调试时,停顿时的钩子
....
end

define hook-run # 执行run命令时的钩子
...
end

define hook-continue # 执行continue命令时的钩子
...
end

经典用法示例:

1.程序执行时忽略SIGUSR1信号引起的运行停止

(gdb) define hook-run
> handle SIGUSR1 nostop
> end

2.汇编调试时, 跟踪显示汇编以及指定寄存器的信息

(gdb) define hook-stop
Type commands for definition of "hook-stop".
End with a line saying just "end".
>p /x $eax
>p /x $ebx
>disas $rip + 5
>end
(gdb) b main
Breakpoint 1 at 0x5fe
(gdb) r
Starting program: /tmp/a.out 
$1 = 0x555545fa
$2 = 0x0
Dump of assembler code for function main:
   0x00005555555545fa <+0>:	push   %rbp
   0x00005555555545fb <+1>:	mov    %rsp,%rbp
=> 0x00005555555545fe <+4>:	mov    -0xc(%rbp),%edx
   0x0000555555554601 <+7>:	mov    -0x8(%rbp),%eax
   0x0000555555554604 <+10>:	add    %edx,%eax
   0x0000555555554606 <+12>:	mov    %eax,-0x4(%rbp)
   0x0000555555554609 <+15>:	mov    -0xc(%rbp),%eax
   0x000055555555460c <+18>:	sub    -0x8(%rbp),%eax
   0x000055555555460f <+21>:	mov    %eax,-0x4(%rbp)
   0x0000555555554612 <+24>:	mov    -0xc(%rbp),%eax
   0x0000555555554615 <+27>:	imul   -0x8(%rbp),%eax
   0x0000555555554619 <+31>:	mov    %eax,-0x4(%rbp)
   0x000055555555461c <+34>:	mov    $0x0,%eax
   0x0000555555554621 <+39>:	pop    %rbp
   0x0000555555554622 <+40>:	retq   
End of assembler dump.

Breakpoint 1, 0x00005555555545fe in main ()