OKMX-C GDB Remote Debugging Skills

In the field of embedded development, debugging is a critical step to ensure the stable operation of a program. For developers using the OKMX8MP-C development board, mastering GDB remote debugging techniques can significantly enhance development efficiency. GDB, short for The GNU Project Debugger, is a comprehensive debugging tool under Linux. GDB supports a variety of debugging methods, including setting breakpoints, single-step execution, printing variables, observing variables, examining registers, and viewing the call stack.

In Linux environment software development, GDB is the primary debugging tool used to debug C and C programs. OKMX8MP-C's 5.4.70 version comes with default support for gdbserver, and our provided development environment also supports gdb by default. Next, will detail how to perform GDB remote debugging on the OKMX8MP-C.

1. Preparation Before Compilation Before performing GDB debugging, it is essential to ensure that the application has been correctly compiled and includes debugging information. This can be achieved by adding the -g option during compilation. For example:

forlinx@ubuntu:~$ $CC -g test_bug.c -o test_bug

This command will compile the test_bug.c source file and generate an executable file test_bug with debugging information included. This way, GDB can accurately locate the corresponding positions in the source code during subsequent debugging processes.

After compilation, the generated executable file needs to be copied to the development board. This is typically achieved via serial port, network, or other file transfer methods. In this example, we assume that the test_bug file has been copied to the / directory on the development board.

1. Development Board IP and Starting gdbserver Settings Next, you need to set the IP address on the development board and start the gdbserver service. The specific steps are as follows:

Set the IP Address:

Use the ifconfig command to set the IP address for the development board. For example:

ifconfig eth0 172.16.0.109

Here, the development board's IP address is set to 172.16.0.109

Start gdbserver on the development board, specifying the listening port number and the program to be debugged. For example:

gdbserver 172.16.0.109:2345 /test_bug

This command will start gdbserver and listen on port 2345 for connection requests from the GDB client.

root@OK8MP:~# ifconfig eth0 172.16.0.109
root@OK8MP:~# gdbserver 172.16.0.109:2345 test_bug
Process /home/root/test_bug created; pid = 1356
Listening on port 2345
On the virtual machine or host, set an IP address within the same network segment as the development board and use the ping command to test connectivity with the development board.

Ensure successful pinging of the development board's IP address, which is a prerequisite for remote debugging.

1. Starting the GDB Client and Connecting to the Development Board Start the GDB client:

On the virtual machine or host, use the aarch64-poky-linux-gdb command to start the GDB client and specify the program to be debugged. For example:

forlinx@ubuntu:~/ aarch64-poky-linux-gdb test_bug
GNU gdb (GDB) 8.3.1
Copyright (C) 2019 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 "--host=x86_64-pokysdk-linux --target=aarch64-poky-linux".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
http://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_bug...
(gdb)
Connect to the board:

In the GDB client, use the target remote command to connect to gdbserver on the board. For example:

(gdb) target remote 172.16.0.109:2345
Remote debugging using 172.16.0.109:2345
Reading /lib/ld-linux-aarch64.so.1 from remote target...
warning: File transfers from remote targets can be slow. Use "set sysroot" to access file s locally instead.
Reading /lib/ld-linux-aarch64.so.1 from remote target...
Reading symbols from target:/lib/ld-linux-aarch64.so.1...
Reading /lib/ld-2.30.so from remote target...
Reading /lib/.debug/ld-2.30.so from remote target...
Reading /lib/.debug/ld-2.30.so from remote target...
Reading symbols from target:/lib/.debug/ld-2.30.so...
0x0000fffff7fcf080 in _start () from target:/lib/ld-linux-aarch64.so.1
(gdb)
At this point, the GDB client connects to gdbserver on the board and is ready to begin remote debugging.

1. Remote Debugging Upon successful connection, you can start using various GDB debugging commands for remote debugging. Below are some commonly used debugging commands:

l (list): Lists source code.

b (break): Sets a breakpoint.

n (next): Steps through the code line by line.

s (step): Steps into functions for line-by-line execution.

c (continue): Continues program execution.

p (print): Prints the value of a variable.

For example, use the l command to view the source code at the current location:

(gdb) l
12 }
13
14 void A(int *p)
15 {
16 B(p);
17 }
18
19 void A2(int *p)
20 {
21 C(p);
(gdb)

Then, you can use the B command to set a breakpoint on a line, such as line 16:

bash copy code

(gdb) b 16

Breakpoint 1 at 0x...: file test_bug.c, line 16.

Use the c command to continue executing the program. The program will pause at the breakpoint, waiting for further debugging.

1. Debugging Techniques and Precautions Breakpoint Management: Setting breakpoints appropriately can significantly improve debugging efficiency. Use the d command to delete breakpoints. Use the info b command to view all current breakpoints.

Variable Monitoring: Use the watch command to monitor variable changes. GDB will automatically pause execution when the variable's value changes.

Multithreaded Debugging: If program is multithreaded, use thread command to switch threads for debugging.

Security Considerations: Ensuring network environment security is crucial during remote debugging. Use SSH tunnels or other encryption methods to protect debugging data transmission.

That's all OKMX8MP-C GDB remote debugging skills. This powerful tool enables efficient issue resolution and development enhancement.

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