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Debug Application

Debug Application

Nov 03, 2020

 

This how-to describes the process of debugging an application on the target with GDB.

 

Table of Contents

Task Dependencies (Pre-requisites)

 

Tools Required

  • GDB server on the target filesystem

  • GDB client on the host

Input Files Required

  • Application for debug

 

Output Files Produced

  • None

 

Task Description

Preparing for debug

GDB will need the application binary to contain debugging information. For this, the application needs to be compiled with the '-g' flag:

host> <toolchain>-gcc app.c -g -o app

The application binary needs to be copied over to the target filesystem. If the GDB server is not present on the target filesystem, gdbserver will also need to be compiled and transferred to the target filesystem. The instructions on the Add Files to Running Linux page may be followed for this task.

The IP of the target machine will need to be used later:

zynq> ifconfig

 

Starting the debug server

In order to debug the application a GDB server must be run on the target machine. Execute the following command to start a GDB server for the given application:

zynq> chmod u+x app zynq> gdbserver HOST:<port> app

The <port> used to connect to the GDB server may be set to 1234 (or any other free port).

Debugging the application

Now that the server is running a GDB client can connect to the server to perform debugging:

host> <toolchain>-gdb app

Once the GDB client is running instruct it to connect to a remote server:

(gdb) target remote <IP of the target>:<port>

Set a breakpoint on "main" and "cont"inue the application:

(gdb) b main (gdb) cont

At this point the host machine terminal should look similar to the following:

host> arm-xilinxa9-linux-gnueabi-gdb app GNU gdb (Sourcery G++ Lite 2010.09-62) 7.2.50.20100908-cvs Copyright (C) 2010 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=i686-pc-linux-gnu --target=arm-xilinx-linux-gnueabi". For bug reporting instructions, please see: <https://support.codesourcery.com/GNUToolchain/>... Reading symbols from /<path to>/app ...done. (gdb) target remote localhost:1234 Remote debugging using localhost:1234 warning: Unable to find dynamic linker breakpoint function. GDB will be unable to debug shared library initializers and track explicitly loaded dynamic code. 0x400aa7a0 in ?? () (gdb) b main Cannot access memory at address 0x0 Breakpoint 1 at 0x8434: file app.c, line 5. (gdb) cont Continuing. warning: Could not load shared library symbols for 3 libraries, e.g. /lib/libgcc_s.so.1. Use the "info sharedlibrary" command to see the complete listing. Do you need "set solib-search-path" or "set sysroot"? Breakpoint 1, main () at app.c:5 5 printf("Hello World!\n"); (gdb)

The next line of code can be run with the "next" or "n" command:

(gdb) n

 

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