Difference between revisions of "GDB"

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On this page you will find all you need to debug your userspace applications running on your Armadeus board.
 
On this page you will find all you need to debug your userspace applications running on your Armadeus board.
  
−
First of all, be sure to have installed the [[Cross Compiler|Toolchain]]. During Buildroot's Cross Compiler configuration be sure to have choosen following options:
+
{{Note|First of all, be sure to have [[Toolchain|installed the Toolchain on your Host]].}}
−
Toolchain  ---> Build gdb server for the Target
+
−
Toolchain  ---> Build gdb for the Host
+
−
and optionally:
+
−
Toolchain  ---> Build gdb debugger for the Target
+
  
 
==Compile your program with debug symbols==
 
==Compile your program with debug symbols==
−
Use ''-g'' option of gdb:
+
* Use ''-g'' option of gcc:
 
<pre class="host">
 
<pre class="host">
 
  $ make shell_env
 
  $ make shell_env
 
  $ . armadeus_env.sh
 
  $ . armadeus_env.sh
 
  $ export PATH=$PATH:$ARMADEUS_TOOLCHAIN_PATH
 
  $ export PATH=$PATH:$ARMADEUS_TOOLCHAIN_PATH
 +
 
  $ arm-linux-gcc -g -o hello hello.c
 
  $ arm-linux-gcc -g -o hello hello.c
 +
</pre>
 +
* If you have a Makefile for your project, you probably have a CFLAGS variable, so add it -g. Ex:
 +
<pre class="host">
 +
CFLAGS=-W -Wall -g
 
</pre>
 
</pre>
  
−
==Debugging on target from Host through Ethernet==
+
==Debugging a program running on your APF remotely from your Host (through Ethernet)==
 
* On the target launch your program like that:
 
* On the target launch your program like that:
 
<pre class="apf">
 
<pre class="apf">
Line 25: Line 26:
 
* On your Host launch:
 
* On your Host launch:
 
<pre class="host">
 
<pre class="host">
−
  []$ arm-linux-gdb program_name
+
  []$ arm-linux-gdb program
−
  (gdb) set solib-absolute-prefix ./buildroot/build_armv4t/staging_dir/
+
  (gdb) set solib-absolute-prefix ./buildroot/output/build/staging_dir/
 
  (gdb) target remote 192.168.0.10:2345
 
  (gdb) target remote 192.168.0.10:2345
 
</pre>
 
</pre>
 
''192.168.0.10'' is the address of your target
 
''192.168.0.10'' is the address of your target
  
−
only ''continue (c)'' can be used to start the program, because it is already running when you launch GDB on your host.
+
{{Note|Only ''continue / c'' can be used to start the program, because it is already running when you launch GDB on your host.}}
  
−
'''Core dump analysis doesn't seem to work in this use case !!'''
+
<pre class="host">
 +
(gdb) break main
 +
(gdb) continue
 +
...
 +
(gdb) next
 +
...
 +
</pre>
  
−
==Debugging directly on target==
+
* If the program is already running, gdbserver can attach itself to the process, if you give him its PID
−
You have to build gdb for the target and have a working NFS link between your target and your host.<br>
+
<pre class="apf">
−
On target launch GDB from your NFS mount like you do it usually:
+
# ps
−
  # /mnt/host/gdb your_prog
+
... get process PID
 +
# gdbserver 192.168.0.2:2345 --attach PID
 +
</pre>
 +
 
 +
{{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:
 +
<pre class="host">
 +
$ make menuconfig
 +
</pre>
 +
<pre class="config">
 +
Toolchain  --->
 +
        *** Gdb Options ***
 +
    [*] Build gdb debugger for the Target
 +
</pre>
 +
<pre class="host">
 +
$ make
 +
</pre>
 +
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:
 +
<pre class="apf">
 +
  # gdb your_prog
 +
</pre>
 
If you need argument passing:
 
If you need argument passing:
−
  # /mnt/host/gdb --args your_prog your_args
+
<pre class="apf">
 +
  # gdb --args your_prog your_args
 +
</pre>
 
To debug a Core dump:
 
To debug a Core dump:
−
  # /mnt/host/gdb your_prog -c your_core
+
<pre class="apf">
 +
  # gdb your_prog -c your_core_file
 +
</pre>
 +
 
 +
==Troubleshots==
 +
===pthread debugging===
 +
* If you see that kind of error message when using gdb:
 +
<pre class="apf">
 +
dlopen failed on 'libthread_db.so.1' - File not found
 +
GDB will not be able to debug pthreads.
 +
</pre>
 +
Don't worry ! ;-)<br>
 +
''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:
 +
<pre class="host">
 +
$ make uclibc-menuconfig
 +
</pre>
 +
<pre class="config">
 +
General Library Settings  --->
 +
    ...
 +
    [*] POSIX Threading Support
 +
    [*]  Build pthreads debugging support
 +
    ...
 +
</pre>
 +
 
 +
* Save your uClibc config and make it standard for next build:
 +
<pre class="host">
 +
$ cp buildroot/output/toolchain/uClibc-0.9.30.3/.config buildroot/target/device/armadeus/apfXX/uClibc.config.arm
 +
</pre>
 +
 
 +
* Then rebuild all the toolchain ('''this will erase your local modifications !!''')
 +
<pre class="host">
 +
$ rm -rf buildroot/output
 +
$ make
 +
</pre>
  
 
==Links==
 
==Links==
−
* http://sources.redhat.com/gdb/current/onlinedocs/gdb_5.html
+
* [https://www.sourceware.org/gdb/current/onlinedocs/gdb/index.html Debugging with GDB manual]
 
* http://www.kegel.com/linux/gdbserver.html
 
* http://www.kegel.com/linux/gdbserver.html
−
* http://www.linux-france.org/article/memo/node119.html
+
* [http://www.linux-france.org/article/memo/node119.html Déboguage avec gdb]
−
* [[KGDB]] (for kernel debugging)
+
* [[DDD| DDD (GDB graphical front end)]]
 +
* [[KGDB|KGDB (for kernel debugging)]]
  
−
{{LanguageBar|GDB|GDB|GDB}}
 
  
 
[[Category:Debug]]
 
[[Category:Debug]]

Latest revision as of 12:40, 3 June 2016

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

Note 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 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 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

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