使用外部程序将输入发送到 GDB scanf

Question

每当使用外部程序触发 scanf 时，如何向 GDB 发送输入？

c文件：

#include<stdio.h>

void main()
{
    int x;
    int y;
    printf("input x: ");
    scanf("%d",&x);
    printf("input y: ");
    scanf("%d",&y);

}

Java外部程序：

public class Debugger extends Thread{

        public void run(){
        Process p = null;
        try {
        p = Runtime.getRuntime().exec("gdb a.out --interpreter=console");
       new Thread(new SyncPipe(p.getErrorStream(), System.err)).start();
       new Thread(new SyncPipe(p.getInputStream(), System.out)).start();
        PrintWriter stdin = new PrintWriter(p.getOutputStream());

        stdin.flush();
        stdin.println("break main");
        stdin.flush();
        stdin.println("run");
        stdin.flush();
        stdin.println("s");
        stdin.flush();
        stdin.println("45");
        stdin.flush();

       // stdin.close();


        } catch (Exception e) {
            e.printStackTrace();
        }
        }
    }

class SyncPipe implements Runnable
{

    public SyncPipe(InputStream istrm, OutputStream ostrm) {
      istrm_ = istrm;
      ostrm_ = ostrm;

  }

  public void run() {

      try
      {   
          int length;
           byte[] buffer = new byte[1024];

          for ( length = 0; (length = istrm_.read(buffer)) != -1; ){

              ostrm_.write(buffer, 0, length);
          } 

      }
      catch (Exception e)
      {
          e.printStackTrace();
      }


  }


  private final OutputStream ostrm_;
  private final InputStream istrm_;
}

外部程序的 GDB 输出：

GNU gdb (Ubuntu/Linaro 7.3-0ubuntu2) 7.3-2011.08
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i686-linux-gnu".
For bug reporting instructions, please see:
<http://bugs.launchpad.net/gdb-linaro/>...
Reading symbols from /home/charmae/workspace/AVT/a.out...done.
(gdb) Breakpoint 1 at 0x804843d: file file4.c, line 7.
(gdb) Starting program: /home/charmae/workspace/AVT/a.out 

Breakpoint 1, main () at file4.c:7
7       printf("input of x: ");
(gdb) 8     scanf("%d",&x);
(gdb) Undefined command: "45".  Try "help".
(gdb) 

Answer 1

您可以像在 shell 中一样重定向输入

(gdb) run < input.txt

或者，您可以在另一个终端中运行该程序并通过 PID 连接到它：

gdb --pid $(pgrep myprogram.name)

最后，你可以使用直接调用来做类似的黑客攻击dup2/dup3（但我认为你不需要这样做，它不会对用户友好）