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<li class="toctree-l3"><a class="reference internal" href="#debug-logging">Debug Logging</a></li>
<li class="toctree-l3"><a class="reference internal" href="#debugging-with-openocd-and-gdb">Debugging with <code class="docutils literal notranslate"><span class="pre">openocd</span></code> and <code class="docutils literal notranslate"><span class="pre">gdb</span></code></a><ul>
<li class="toctree-l4"><a class="reference internal" href="#nuttx-aware-debugging">NuttX aware debugging</a><ul>
<li class="toctree-l5"><a class="reference internal" href="#with-openocd">With openocd</a></li>
<li class="toctree-l5"><a class="reference internal" href="#with-gdb">With gdb</a></li>
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  <section id="debugging">
<span id="id1"></span><h1>Debugging<a class="headerlink" href="#debugging" title="Permalink to this heading"></a></h1>
<p>Finding and fixing bugs is an important part of the hardware and software development process. Sometimes you also need
to use debugging techniques to understand how the system works. Two tools that are helpful are debug logging and
debugging using the GNU Debugger (gdb).</p>
<section id="debug-logging">
<h2>Debug Logging<a class="headerlink" href="#debug-logging" title="Permalink to this heading"></a></h2>
<p>NuttX has a powerful system logging facility (syslog) with <code class="docutils literal notranslate"><span class="pre">info</span></code>, <code class="docutils literal notranslate"><span class="pre">warn</span></code>, and <code class="docutils literal notranslate"><span class="pre">error</span></code> levels. You can enable
debugging for your build for the subsystem or feature by using the <code class="docutils literal notranslate"><span class="pre">menuconfig</span></code> system.</p>
<p>The debug options are available under <span class="menuselection">Build Setup ‣ Debug Options</span>. You will most likely have to enable the
following options:</p>
<ul class="simple">
<li><p><span class="menuselection">Enable Debug Features</span> — selecting this will turn on subsystem-level debugging options, they will become visible
on the page below. You can then select the ones you want.</p></li>
<li><p><span class="menuselection">Enable Error Output</span> — this will only log errors.</p></li>
<li><p><span class="menuselection">Enable Warnings Output</span> — this will log warnings and errors.</p></li>
<li><p><span class="menuselection">Enable Informational Debug Output</span> — this will produce informational output, warnings, and errors.</p></li>
</ul>
<p>You can then select from the subsystems that are available, Network, Scheduler, USB, etc. Note that you will need to
separately enable the subsystem elsewhere in the <code class="docutils literal notranslate"><span class="pre">menuconfig</span></code> system. To see the <code class="docutils literal notranslate"><span class="pre">CONFIG</span></code> define that is set,
use the arrow keys to highlight the subsystem (for instance, <span class="menuselection">Network Debug Features</span>) and type <kbd class="kbd docutils literal notranslate">?</kbd>. This will show
you that the C macro that is set is called <code class="docutils literal notranslate"><span class="pre">CONFIG_DEBUG_NET</span></code>. <code class="docutils literal notranslate"><span class="pre">debug.h</span></code> defines the <code class="docutils literal notranslate"><span class="pre">netinfo()</span></code> logging
function that will log output if this macro is set. You can search the source code for <code class="docutils literal notranslate"><span class="pre">netinfo</span></code> to see how it is
used.</p>
<a class="reference internal image-reference" href="../_images/menuconfig-debug.png"><img alt="Screenshot of menuconfig system main screen" class="align-center" src="../_images/menuconfig-debug.png" style="width: 800px;" /></a>
<p>Note that enabling all these will produce an incredible amount of logging output. Enable the level you want and
the area you’re interested in, and leave the rest disabled, save the config, and then recompile. You can see the full
list of debug feature logging functions in the file
<a class="reference external" href="https://github.com/apache/incubator-nuttx/blob/master/include/debug.h">debug.h</a>.</p>
<p>Syslog timestamps can be enabled in the configuration in <span class="menuselection">Device Drivers ‣ System Logging ‣ Prepend
timestamp to syslog message</span> (<code class="docutils literal notranslate"><span class="pre">CONFIG_SYSLOG_TIMESTAMP</span></code>).</p>
<p>You may need to do a little bit of experimenting to find the combination of logging settings that work for the problem
you’re trying to solve. See the file <a class="reference external" href="https://github.com/apache/incubator-nuttx/blob/master/include/debug.h">debug.h</a>
for available debug settings that are available.</p>
<p>There are also subsystems that enable USB trace debugging, and you can log to memory too, if you need the logging to be
faster than what the console can output.</p>
</section>
<section id="debugging-with-openocd-and-gdb">
<h2>Debugging with <code class="docutils literal notranslate"><span class="pre">openocd</span></code> and <code class="docutils literal notranslate"><span class="pre">gdb</span></code><a class="headerlink" href="#debugging-with-openocd-and-gdb" title="Permalink to this heading"></a></h2>
<p>To debug our Nucleo board using its embedded SWD debug adapter,
start <code class="docutils literal notranslate"><span class="pre">openocd</span></code> with the following command:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>openocd<span class="w"> </span>-f<span class="w"> </span>interface/st-link-v2.cfg<span class="w"> </span>-f<span class="w"> </span>target/stm32f1x.cfg
</pre></div>
</div>
<p>This will start a <code class="docutils literal notranslate"><span class="pre">gdb</span></code> server. Then, start <code class="docutils literal notranslate"><span class="pre">gdb</span></code> with:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span><span class="nb">cd</span><span class="w"> </span>nuttx/
<span class="gp">$ </span>gdb-multiarch<span class="w"> </span>nuttx/nuttx
</pre></div>
</div>
<p>Inside <code class="docutils literal notranslate"><span class="pre">gdb</span></code> console, connect to the <code class="docutils literal notranslate"><span class="pre">gdb</span></code> server with:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) target extended-remote :3333
</pre></div>
</div>
<p>You can now use standard <code class="docutils literal notranslate"><span class="pre">gdb</span></code> commands. For example, to
reset the board:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) mon reset
</pre></div>
</div>
<p>To halt the board:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) mon halt
</pre></div>
</div>
<p>To set a breakpoint:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) breakpoint nsh_main
</pre></div>
</div>
<p>and to finally start nuttx:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) continue
Continuing.

Breakpoint 1, nsh_main (argc=1, argv=0x200ddfac) at nsh_main.c:208
208     sched_getparam(0, &amp;param);
(gdb) continue
Continuing.
</pre></div>
</div>
<div class="admonition tip">
<p class="admonition-title">Tip</p>
<p>You can abbreviate <code class="docutils literal notranslate"><span class="pre">gdb</span></code> commands: <code class="docutils literal notranslate"><span class="pre">info</span> <span class="pre">b</span></code> is a shortcut for
<code class="docutils literal notranslate"><span class="pre">information</span> <span class="pre">breakpoints</span></code>; <code class="docutils literal notranslate"><span class="pre">c</span></code> works the same as <code class="docutils literal notranslate"><span class="pre">continue</span></code>, etc.</p>
</div>
<section id="nuttx-aware-debugging">
<h3>NuttX aware debugging<a class="headerlink" href="#nuttx-aware-debugging" title="Permalink to this heading"></a></h3>
<p>Since NuttX is actually an RTOS, it is useful to have <code class="docutils literal notranslate"><span class="pre">gdb</span></code> be aware of the different
tasks/threads that are running. There are two ways to do this: via <code class="docutils literal notranslate"><span class="pre">openocd</span></code>
itself or via <code class="docutils literal notranslate"><span class="pre">gdb</span></code>. Note that in both cases, you need to enable debug symbols
(<code class="docutils literal notranslate"><span class="pre">CONFIG_DEBUG_SYMBOLS</span></code>).</p>
<section id="with-openocd">
<h4>With openocd<a class="headerlink" href="#with-openocd" title="Permalink to this heading"></a></h4>
<p><code class="docutils literal notranslate"><span class="pre">openocd</span></code> supports various RTOS directly, including NuttX. It works by reading
into internal NuttX symbols which define the active tasks and their properties.
As a result, the <code class="docutils literal notranslate"><span class="pre">gdb</span></code> server will directly be aware of each task as a different
<cite>thread</cite>. The downside of this approach is that it depends on how you build NuttX
as there are some options hardcoded into
opencd. By default, it assumes:</p>
<blockquote>
<div><ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">CONFIG_DISABLE_MQUEUE=y</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">CONFIG_PAGING=n</span></code></p></li>
</ul>
</div></blockquote>
<p>If you need these options to be set differently, you will have to edit <code class="docutils literal notranslate"><span class="pre">./src/rtos/nuttx_header.h</span></code> from <code class="docutils literal notranslate"><span class="pre">openocd</span></code>,
change the corresponding settings and then rebuild it.</p>
<p>Finally, to enable NuttX integration, you need to supply an additional <code class="docutils literal notranslate"><span class="pre">openocd</span></code> argument:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>openocd<span class="w"> </span>-f<span class="w"> </span>interface/st-link-v2.cfg<span class="w"> </span>-f<span class="w"> </span>target/stm32f1x.cfg<span class="w"> </span>-c<span class="w"> </span><span class="s1">&#39;$_TARGETNAME configure -rtos nuttx&#39;</span>
</pre></div>
</div>
<p>Since <code class="docutils literal notranslate"><span class="pre">openocd</span></code> also needs to know the memory layout of certain datastructures, you need to have <code class="docutils literal notranslate"><span class="pre">gdb</span></code>
run the following commands once the <code class="docutils literal notranslate"><span class="pre">nuttx</span></code> binary is loaded:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>eval &quot;monitor nuttx.pid_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;pid
eval &quot;monitor nuttx.xcpreg_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;xcp.regs
eval &quot;monitor nuttx.state_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;task_state
eval &quot;monitor nuttx.name_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;name
eval &quot;monitor nuttx.name_size %d&quot;, sizeof(((struct tcb_s *)(0))-&gt;name)
</pre></div>
</div>
<p>One way to do this is to define a gdb <cite>hook</cite> function that will be called when running <code class="docutils literal notranslate"><span class="pre">file</span></code> command:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>define hookpost-file
  eval &quot;monitor nuttx.pid_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;pid
  eval &quot;monitor nuttx.xcpreg_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;xcp.regs
  eval &quot;monitor nuttx.state_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;task_state
  eval &quot;monitor nuttx.name_offset %d&quot;, &amp;((struct tcb_s *)(0))-&gt;name
  eval &quot;monitor nuttx.name_size %d&quot;, sizeof(((struct tcb_s *)(0))-&gt;name)
end
</pre></div>
</div>
<p>You will see that <code class="docutils literal notranslate"><span class="pre">openocd</span></code> has received the memory offsets in its output:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>Open On-Chip Debugger 0.10.0+dev-01514-ga8edbd020-dirty (2020-11-20-14:23)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : auto-selecting first available session transport &quot;swd&quot;. To override use &#39;transport select &lt;transport&gt;&#39;.
Info : target type name = cortex_m
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
15:41:23: Debugging starts
Info : CMSIS-DAP: SWD  Supported
Info : CMSIS-DAP: FW Version = 1.10
Info : CMSIS-DAP: Interface Initialised (SWD)
Info : SWCLK/TCK = 1 SWDIO/TMS = 1 TDI = 0 TDO = 0 nTRST = 0 nRESET = 1
Info : CMSIS-DAP: Interface ready
Info : clock speed 1000 kHz
Info : SWD DPIDR 0x2ba01477
Info : nrf52.cpu: hardware has 6 breakpoints, 4 watchpoints
Info : starting gdb server for nrf52.cpu on 3333
Info : Listening on port 3333 for gdb connections
Info : accepting &#39;gdb&#39; connection on tcp/3333
Error: No symbols for NuttX
Info : nRF52832-QFAA(build code: B0) 512kB Flash, 64kB RAM
undefined debug reason 8 - target needs reset
Warn : Prefer GDB command &quot;target extended-remote 3333&quot; instead of &quot;target remote 3333&quot;
Info : pid_offset: 12
Info : xcpreg_offset: 132
Info : state_offset: 26
Info : name_offset: 208
Info : name_size: 32
target halted due to debug-request, current mode: Thread
xPSR: 0x01000000 pc: 0x000000dc msp: 0x20000cf0
target halted due to debug-request, current mode: Thread xPSR: 0x01000000 pc: 0x000000dc msp: 0x20000cf0
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>You will probably see the <code class="docutils literal notranslate"><span class="pre">Error:</span> <span class="pre">No</span> <span class="pre">symbols</span> <span class="pre">for</span> <span class="pre">NuttX</span></code> error appear once at startup. This is OK
unless you see it every time you step the debugger. In this case, it would mean you did not enable debug symbols.</p>
</div>
<p>Now, You can now inspect threads:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) info threads
  Id   Target Id         Frame
* 1    Remote target     nx_start_application () at init/nx_bringup.c:261
(gdb) info registers
r0             0x0                 0
r1             0x2f                47
r2             0x0                 0
r3             0x0                 0
r4             0x0                 0
r5             0x0                 0
r6             0x0                 0
r7             0x20000ca0          536874144
r8             0x0                 0
r9             0x0                 0
r10            0x0                 0
r11            0x0                 0
r12            0x9                 9
sp             0x20000c98          0x20000c98
lr             0x19c5              6597
pc             0x1996              0x1996 &lt;nx_start_application+10&gt;
xPSR           0x41000000          1090519040
fpscr          0x0                 0
msp            0x20000c98          0x20000c98
psp            0x0                 0x0 &lt;_vectors&gt;
primask        0x0                 0
basepri        0xe0                -32
faultmask      0x0                 0
control        0x0                 0
</pre></div>
</div>
</section>
<section id="with-gdb">
<h4>With gdb<a class="headerlink" href="#with-gdb" title="Permalink to this heading"></a></h4>
<p>You can also do NuttX aware debugging using <code class="docutils literal notranslate"><span class="pre">gdb</span></code> scripting support.
The benefit is that it works also for the sim build where <code class="docutils literal notranslate"><span class="pre">openocd</span></code> is
not applicable. For this to work, you will need to enable PROC filesystem support
which will expose required task information (<code class="docutils literal notranslate"><span class="pre">CONFIG_FS_PROCFS=y</span></code>).</p>
<p>To use this approach, you can load the <code class="docutils literal notranslate"><span class="pre">nuttx/tools/nuttx-gdbinit</span></code> file. An
easy way to do this is to create a symbolic link:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span><span class="nb">cd</span><span class="w"> </span><span class="nv">$HOME</span>
<span class="gp">$ </span>ln<span class="w"> </span>-s<span class="w"> </span>nuttx/tools/nuttx-gdbinit<span class="w"> </span>.gdbinit
</pre></div>
</div>
<p>This way whenever gdb is started it will run the appropriate commands. To inspect
the threads you can now use the following <code class="docutils literal notranslate"><span class="pre">gdb</span></code> command:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>(gdb) info_nxthreads
target examined
_target_arch.name=armv7e-m
$_target_has_fpu : 0
$_target_has_smp : 0
saved current_tcb (pid=0)
* 0 Thread 0x20000308  (Name: Idle Task, State: Running, Priority: 0) 0xdc in __start()
  1 Thread 0x20001480  (Name: init, State: Waiting,Semaphore, Priority: 100) 0x7e08 in arm_switchcontext()
</pre></div>
</div>
</section>
</section>
</section>
</section>


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