一、gdb的简介

GDB是一个由GNU开源组织发布的，Unix/Linux操作系统下的，基于命令行的，功能强大的程序调试工具。

二、gdb源码安装方法

Linux系统及其衍生版本有的默认安装了gdb调试器，但有些默认不安装。

1、检查系统是否默认安装

执行gdb -v指令，如果提示gdb: command not found则没有安装，否则表示安装。

root@openwifi-55:~# gdb -v
GNU gdb (Ubuntu 10.1-2ubuntu2) 10.1.90.20210411-git
Copyright (C) 2021 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.

2、使用自动工具安装

使用yum -y install gdb或apt-get -y install gdb指令，使用包管理器进行自动安装。

[16:55@root ~]$yum install -y gdb
base-debuginfo                                                   | 2.5 kB  00:00:00     
centos-sclo-rh-debuginfo                                         | 3.0 kB  00:00:00     
docker-ce-stable-debuginfo                                       | 3.5 kB  00:00:00     
epel-debuginfo/x86_64/metalink                                   | 5.2 kB  00:00:00     
epel-debuginfo                                                   | 3.0 kB  00:00:00     
(1/2): epel-debuginfo/x86_64/primary_db                          | 896 kB  00:00:00     
(2/2): base-debuginfo/x86_64/primary_db                          | 2.7 MB  00:01:08     
Loading mirror speeds from cached hostfile
 * base: mirrors.aliyun.com
 * centos-sclo-rh: mirrors.aliyun.com
 * epel: hkg.mirror.rackspace.com
 * epel-debuginfo: hkg.mirror.rackspace.com
 * extras: mirrors.aliyun.com
 * updates: mirrors.aliyun.com
Resolving Dependencies
--> Running transaction check
---> Package gdb.x86_64 0:7.6.1-120.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

========================================================================================
 Package         Arch               Version                      Repository        Size
========================================================================================
Installing:
 gdb             x86_64             7.6.1-120.el7                base             2.4 M

Transaction Summary
========================================================================================
Install  1 Package

Total size: 2.4 M
Installed size: 7.0 M
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : gdb-7.6.1-120.el7.x86_64                                             1/1 
  Verifying  : gdb-7.6.1-120.el7.x86_64                                             1/1 

Installed:
  gdb.x86_64 0:7.6.1-120.el7                                                            

Complete!
[16:56@root ~]$gdb -v
GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-120.el7
Copyright (C) 2013 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 "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.

3、使用源码安装

3.1 下载源码

GDB的源码下载网页：点击进入GDB源码下载页面
gdb-11.1版本下载链接: gdb-11.1.tar.xz 或 : gdb-11.1.tar.gz

3.2 上传源码

[17:00@root /usr/local/src]$rz
rz waiting to receive.
Starting zmodem transfer.  Press Ctrl+C to cancel.
Transferring gdb-11.1.tar.gz...
  100%   36967 KB    9241 KB/sec    00:00:04       0 Errors   
Transferring gdb-11.1.tar.xz...
  100%   21524 KB    10762 KB/sec    00:00:02       0 Errors  

[17:00@root /usr/local/src]$ls
gdb-11.1.tar.gz  gdb-11.1.tar.xz

3.3 解压源码包

（1）针对tar.gz文件，可以通过tar -zxvf gdb-11.1.tar.gz解压。
（2）针对tar.xz文件，可以通过xz -d gdb-11.1.tar.xz和tar -xvf gdb-11.1.tar解压。

3.4 准备依赖列表并开始编译

解压完成后，进入gdb-11.1目录，创建gdb_build-11.1目录并进入，然后执行../configure指令，等待执行完毕后，如果没报错，则编译成功。

[17:06@root /usr/local/src]$ls
gdb-11.1  gdb-11.1.tar  gdb-11.1.tar.gz
[17:06@root /usr/local/src]$cd gdb-11.1/
[17:07@root /usr/local/src/gdb-11.1]$mkdir gdb_build-11.1
[17:07@root /usr/local/src/gdb-11.1]$cd gdb_build-11.1/
[17:07@root /usr/local/src/gdb-11.1/gdb_build-11.1]$../configure 
checking build system type... x86_64-pc-linux-gnu
checking host system type... x86_64-pc-linux-gnu
(省略输出).....
checking where to find the target windres... host tool
checking where to find the target windmc... host tool
checking whether to enable maintainer-specific portions of Makefiles... no
configure: creating ./config.status
config.status: creating Makefile
[17:08@root /usr/local/src/gdb-11.1/gdb_build-11.1]$make
等待结果(时间较长)....

3.5 安装

执行make install指令安装，如果没报错，则重新连接后即可执行gdb -v测试安装结果

[17:08@root /usr/local/src/gdb-11.1/gdb_build-11.1]$make install
(省略输出)....
[17:29@zhouchao ~]$gdb -v
GNU gdb (GDB) 11.1
Copyright (C) 2021 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.

三、gdb使用流程

1、编译源程序,增加-g参数

通过gcc -g xxx.c -o xxx指令增加-g参数，指定生成的程序是可调试的。

gcc -g test.c -o test

2、启动gdb,准备调试

通过gdb xxx或gdb -q xxx指令，加载执行程序。其中-q表示不打印gdb版本信息,界面干净。

gdb test 
gdb -q test //表示不打印gdb版本信息，界面较为干净

//执行结果如下：
[11:40@zhouchao ~/test]$gdb test   
GNU gdb (Ubuntu 10.1-2ubuntu2) 10.1.90.20210411-git
Copyright (C) 2021 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 "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from test...
(gdb)_

注意

如果程序已经运行，则可使用attach指令

• 通过ps(ps -ef | grep [进程名])或pidof(pidof [进程名])指令找到进程id
• 启动gdb后，执行attach [进程ID]指令

如果attach进程时报如下错误,可切换到root用户，修改/etc/sysctl.d/10-ptrace.conf配置文件中的kernel.yama.ptrace_scope = 0,将其值改为0即可.

Could not attach to process.  If your uid matches the uid of the target 
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.

3、查看源码(list)

通过list指令查看源码（默认显示10行），通过回车键可翻页。

(gdb) list
1       #include <stdio.h>
2
3       void ShowRevertNum(int iNum)
4       {
5           while (iNum > 10)
6           {
7               printf("%d", iNum % 10);
8               iNum = iNum / 10;
9           }
10          printf("%d\n", iNum);
(gdb) 
11      }
12
13      int main(void)
14      {
15          int iNum;
16          printf("Please input a number :");
17          scanf("%d", &iNum);
18          printf("After revert : ");
19          ShowRevertNum(iNum);
20      }
(gdb) _

4、设置断点（break）

通过break [文件名]:[行号]/[函数名]指令设置断点。通过info breakpoints查看断点信息。

(gdb) break 15
Breakpoint 1 at 0x1231: file test.c, line 16.
(gdb) break ShowRevertNum
Breakpoint 2 at 0x1198: file test.c, line 5.
(gdb) break test.c:10
Breakpoint 3 at 0x11fd: file test.c, line 10.
(gdb) info breakpoints
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x0000000000001231 in main at test.c:16
2       breakpoint     keep y   0x0000000000001198 in ShowRevertNum at test.c:5
3       breakpoint     keep y   0x00000000000011fd in ShowRevertNum at test.c:10
(gdb) _

5、运行程序(run)

通过run指令运行程序，直到结束或遇到断点等待下一个命令

(gdb) run
Starting program: /home/zhouchao/test/test 

Breakpoint 1, main () at test.c:16
16          printf("Please input a number :");
(gdb) _

6、单步执行(c、s、n)

通过continue、step、next指令实现单步执行。

(gdb) continue
Continuing.
Please input a number :1234

Breakpoint 2, ShowRevertNum (iNum=1234) at test.c:5
5           while (iNum > 10)
(gdb) next
7               printf("%d", iNum % 10);
(gdb) next
8               iNum = iNum / 10;
(gdb) continue
Continuing.

Breakpoint 3, ShowRevertNum (iNum=1) at test.c:10
10          printf("%d\n", iNum);
(gdb) step
__printf (format=0x555555556007 "%d\n") at printf.c:28
28      printf.c: No such file or directory.
(gdb) continue
Continuing.
After revert : 4321
[Inferior 1 (process 1708210) exited normally]
(gdb) _

7、查看变量的值

通过print和whatis指令查看变量的值和类型

Breakpoint 2, ShowRevertNum (iNum=1234) at test.c:5
5           while (iNum > 10)
(gdb) print iNum
$1 = 1234
(gdb) whatis iNum
type = int
(gdb) _

8、退出gdb

通过quit命令退出gdb

(gdb) q
A debugging session is active.

        Inferior 1 [process 1708219] will be killed.

Quit anyway? (y or n) y

四、gdb基本命令

1、示例操作

[15:18@zhouchao ~/test]$gdb test -q
Reading symbols from test...
(gdb) l
1       #include <stdio.h>
2
3       void ShowRevertNum(int iNum)
4       {
5           while (iNum > 10)
6           {
7               printf("%d", iNum % 10);
8               iNum = iNum / 10;
9           }
10          printf("%d\n", iNum);
(gdb) b 10
Breakpoint 1 at 0x11fd: file test.c, line 10.
(gdb) b ShowRevertNum 
Breakpoint 2 at 0x1198: file test.c, line 5.
(gdb) i b
Num     Type           Disp Enb Address            What
1       breakpoint     keep y   0x00000000000011fd in ShowRevertNum at test.c:10
2       breakpoint     keep y   0x0000000000001198 in ShowRevertNum at test.c:5
(gdb) r
Starting program: /home/zhouchao/test/test 
Please input a number :1234

Breakpoint 2, ShowRevertNum (iNum=1234) at test.c:5
5           while (iNum > 10)
(gdb) watch iNum
Hardware watchpoint 3: iNum
(gdb) n
7               printf("%d", iNum % 10);
(gdb) n
8               iNum = iNum / 10;
(gdb) n

Hardware watchpoint 3: iNum

Old value = 1234
New value = 123
ShowRevertNum (iNum=123) at test.c:5
5           while (iNum > 10)
(gdb) c
Continuing.

Hardware watchpoint 3: iNum

Old value = 123
New value = 12
ShowRevertNum (iNum=12) at test.c:5
5           while (iNum > 10)
(gdb) until 10

Hardware watchpoint 3: iNum

Old value = 12
New value = 1
ShowRevertNum (iNum=1) at test.c:5
5           while (iNum > 10)
(gdb) ret 0
Make ShowRevertNum return now? (y or n) y
#0  0x0000555555555275 in main () at test.c:19
19          ShowRevertNum(iNum);
(gdb) c
Continuing.
Watchpoint 3 deleted because the program has left the block
in which its expression is valid.
After revert : 432[Inferior 1 (process 1716443) exited normally]
(gdb) _