GDB

On this page you will find all you need to debug your userspace applications running on your Armadeus board.

Note: First of all, be sure to have installed the Toolchain on your Host.

Compile your program with debug symbols

• Use -g option of gcc:

 $ make shell_env
 $ . armadeus_env.sh
 $ export PATH=$PATH:$ARMADEUS_TOOLCHAIN_PATH

 $ arm-linux-gcc -g -o hello hello.c

• If you have a Makefile for your project, you probably have a CFLAGS variable, so add it -g. Ex:

CFLAGS=-W -Wall -g

Debugging a program running on your APF remotely from your Host (through Ethernet)

• On the target launch your program like that:

 # gdbserver 192.168.0.2:2345 program [args]

192.168.0.2 is the IP address of your Host and 2345 the port number to use (examples).

• On your Host launch:

 []$ arm-linux-gdb program
 (gdb) set solib-absolute-prefix ./buildroot/output/build/staging_dir/
 (gdb) target remote 192.168.0.10:2345

192.168.0.10 is the address of your target

Note: Only continue / c can be used to start the program, because it is already running when you launch GDB on your host.

 (gdb) break main
 (gdb) continue
...
 (gdb) next
...

• If the program is already running, gdbserver can attach itself to the process, if you give him its PID

 # ps
... get process PID
 # gdbserver 192.168.0.2:2345 --attach PID

Note: Core dump analysis doesn't seem to work in this use case (ie on the Host with arm-linux-gdb) !!

Debugging directly on your APF (may require more memory)

• You have to build gdb for the target:

 $ make menuconfig

Toolchain  --->
        *** Gdb Options ***
    [*] Build gdb debugger for the Target

 $ make

Then you can either reflash your rootfs, or copy $ARMADEUS_ROOTFS_DIR/usr/bin/gdb to your board, to a SD or to a NFS export.

• After installation, launch gdb on your APF:

 # gdb your_prog

If you need argument passing:

 # gdb --args your_prog your_args

To debug a Core dump:

 # gdb your_prog -c your_core_file

Troubleshots

pthread debugging

• If you see that kind of error message when using gdb:

dlopen failed on 'libthread_db.so.1' - File not found
GDB will not be able to debug pthreads.

Don't worry ! ;-)
libthread_db.so (db == debug) is a library that is needed when you want to debug programs using pthread. You will have to reconfigure the uClibc to get it build:

$ make uclibc-menuconfig

General Library Settings  --->
    ...
    [*] POSIX Threading Support
    [*]   Build pthreads debugging support
    ...

• Save your uClibc config and make it standard for next build:

$ cp buildroot/output/toolchain/uClibc-0.9.30.3/.config buildroot/target/device/armadeus/apfXX/uClibc.config.arm

• Then rebuild all the toolchain (this will erase your local modifications !!)

$ rm -rf buildroot/output
$ make

Links

• Debugging with GDB manual
• http://www.kegel.com/linux/gdbserver.html
• Déboguage avec gdb
• DDD (GDB graphical front end)
• KGDB (for kernel debugging)