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   <div class="section" id="task-trace-internals">
 <h1>Task Trace Internals<a class="headerlink" href="#task-trace-internals" title="Permalink to this headline">¶</a></h1>
 <div class="section" id="overview">
 <h2>Overview<a class="headerlink" href="#overview" title="Permalink to this headline">¶</a></h2>
 <img alt="../_images/task-trace-internal.png" src="../_images/task-trace-internal.png" />
 <p>The Task Trace is constructed by the following functions.</p>
 <div class="section" id="nuttx-kernel-events-collection">
 <h3>NuttX kernel events collection<a class="headerlink" href="#nuttx-kernel-events-collection" title="Permalink to this headline">¶</a></h3>
 <p>The kernel events are collected by <code class="docutils literal notranslate"><span class="pre">sched_note_*()</span></code> API calls embedded in NuttX kernel.</p>
 <blockquote>
 <div><ul class="simple">
 <li><p>For task switch events</p>
 <ul>
 <li><p><code class="docutils literal notranslate"><span class="pre">sched_note_start()</span></code></p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">sched_note_stop()</span></code></p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">sched_note_suspend()</span></code></p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">sched_note_resume()</span></code></p></li>
 </ul>
 </li>
 <li><p>For system call events</p>
 <ul>
 <li><p><code class="docutils literal notranslate"><span class="pre">sched_note_syscall_enter()</span></code></p></li>
 <li><p><code class="docutils literal notranslate"><span class="pre">sched_note_syscall_leave()</span></code></p></li>
 </ul>
 </li>
 <li><p>For interrupt event</p>
 <ul>
 <li><p><code class="docutils literal notranslate"><span class="pre">sched_note_irqhandler()</span></code></p></li>
 </ul>
 </li>
 </ul>
 </div></blockquote>
 </div>
 <div class="section" id="filter-logic-nuttx-sched-sched-note-c">
 <h3>Filter logic (<code class="docutils literal notranslate"><span class="pre">nuttx/sched/sched_note.c</span></code>)<a class="headerlink" href="#filter-logic-nuttx-sched-sched-note-c" title="Permalink to this headline">¶</a></h3>
 <ul class="simple">
 <li><p>The <code class="docutils literal notranslate"><span class="pre">sched_note_*()</span></code> APIs are implemented here.</p></li>
 <li><p>Filter the notes and pass them to noteram driver by <code class="docutils literal notranslate"><span class="pre">sched_note_add()</span></code> API.</p></li>
 </ul>
 </div>
 <div class="section" id="noteram-device-driver-nuttx-drivers-note-noteram-driver-c">
 <h3>Noteram device driver (<code class="docutils literal notranslate"><span class="pre">nuttx/drivers/note/noteram_driver.c</span></code>)<a class="headerlink" href="#noteram-device-driver-nuttx-drivers-note-noteram-driver-c" title="Permalink to this headline">¶</a></h3>
 <ul class="simple">
 <li><p>Accumurate incoming note records into the buffer.</p></li>
 <li><p>Read the note records from the buffer by user requests.</p></li>
 <li><p>The notes are recorded in the binary format of <code class="docutils literal notranslate"><span class="pre">struct</span> <span class="pre">note_*_s</span></code>.</p></li>
 <li><p>The detail function is described in <a class="reference internal" href="../components/drivers/character/note.html"><span class="doc">Note Driver Interface</span></a>.</p></li>
 </ul>
 </div>
 <div class="section" id="notectl-device-driver-nuttx-drivers-note-notectl-driver-c">
 <h3>Notectl device driver (<code class="docutils literal notranslate"><span class="pre">nuttx/drivers/note/notectl_driver.c</span></code>)<a class="headerlink" href="#notectl-device-driver-nuttx-drivers-note-notectl-driver-c" title="Permalink to this headline">¶</a></h3>
 <ul class="simple">
 <li><p><code class="docutils literal notranslate"><span class="pre">/dev/notectl</span></code> device driver.</p></li>
 <li><p>Control the filter logic in <code class="docutils literal notranslate"><span class="pre">sched_note.c</span></code> by calling note filter APIs.</p></li>
 <li><p>The detail function is described in <a class="reference internal" href="../components/drivers/character/note.html"><span class="doc">Note Driver Interface</span></a>.</p></li>
 </ul>
 </div>
 <div class="section" id="trace-built-in-application-apps-system-trace-trace-c">
 <h3>“<code class="docutils literal notranslate"><span class="pre">trace</span></code>” Built-In Application (<code class="docutils literal notranslate"><span class="pre">apps/system/trace/trace.c</span></code>)<a class="headerlink" href="#trace-built-in-application-apps-system-trace-trace-c" title="Permalink to this headline">¶</a></h3>
 <ul class="simple">
 <li><p><code class="docutils literal notranslate"><span class="pre">trace</span></code> Built-In Application to control the trace function interactively.</p></li>
 <li><p>Read binary note records from <code class="docutils literal notranslate"><span class="pre">/dev/note</span></code> and convert into the ftrace text format which is acceptable by  <a class="reference external" href="https://www.eclipse.org/tracecompass/">“Trace Compass”</a>.</p></li>
 <li><p>The command syntax is described in <a class="reference internal" href="tasktraceuser.html"><span class="doc">Task Trace User Guide</span></a>.</p></li>
 </ul>
 </div>
 </div>
 <div class="section" id="getting-the-system-call-events">
 <h2>Getting the system call events<a class="headerlink" href="#getting-the-system-call-events" title="Permalink to this headline">¶</a></h2>
 <p>To get the system call events, two different methods are used for FLAT build and PROTECTED/KERNEL build.</p>
 <div class="section" id="flat-build">
 <h3>FLAT build<a class="headerlink" href="#flat-build" title="Permalink to this headline">¶</a></h3>
 <p>In FLAT build, a system call is just a function call into the NuttX kernel.</p>
 <img alt="../_images/syscall-flat-before.png" src="../_images/syscall-flat-before.png" />
 <p>To get the system call events, <a class="reference external" href="https://sourceware.org/binutils/docs/ld/Options.html#index-_002d_002dwrap_003dsymbol">wrapper function option</a>  of the GNU Linker is used.</p>
 <p>The mksyscall tool is fixed to generate the system call wrapper which call system call enter/leave hook.
 The wrapper supersedes the system call function call of the NuttX binary by passing <code class="docutils literal notranslate"><span class="pre">--wrap</span></code> linker option to the build system.
 The wrapper calls the system call hooks before and after calling the real system call function.</p>
 <img alt="../_images/syscall-flat-after.png" src="../_images/syscall-flat-after.png" />
 </div>
 <div class="section" id="protected-kernel-build">
 <h3>PROTECTED/KERNEL build<a class="headerlink" href="#protected-kernel-build" title="Permalink to this headline">¶</a></h3>
 <p>Different to FLAT build, in PROTECTED and KERNEL build, a system call is issued by an user space is handled as the following steps.</p>
 <ol class="arabic simple">
 <li><p>System call issued by an application code is handled by the system call proxy (automatically generated by mksyscall).</p></li>
 <li><p>System call proxy issues the supervisor call instruction to enter into the kernel space.</p></li>
 <li><p>System call handler in the kernel space calls the system call stub (automatically generated by mksyscall).</p></li>
 <li><p>System call stub calls the API implementation in the NuttX kernel.</p></li>
 </ol>
 <img alt="../_images/syscall-protected-before.png" src="../_images/syscall-protected-before.png" />
 <p>To get the system call events, the mksyscall tool is fixed to generate the system call wrapper which supersedes the system call function call in the system call stub.</p>
 <img alt="../_images/syscall-protected-after.png" src="../_images/syscall-protected-after.png" />
 </div>
 </div>
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	<li class="toctree-l5"><a class="reference internal" href="#filter-logic-nuttx-sched-sched-note-c">Filter logic (<code class="docutils literal notranslate"><span class="pre">nuttx/sched/sched_note.c</span></code>)</a></li>
	<li class="toctree-l5"><a class="reference internal" href="#noteram-device-driver-nuttx-drivers-note-noteram-driver-c">Noteram device driver (<code class="docutils literal notranslate"><span class="pre">nuttx/drivers/note/noteram_driver.c</span></code>)</a></li>
	<li class="toctree-l5"><a class="reference internal" href="#notectl-device-driver-nuttx-drivers-note-notectl-driver-c">Notectl device driver (<code class="docutils literal notranslate"><span class="pre">nuttx/drivers/note/notectl_driver.c</span></code>)</a></li>
	<li class="toctree-l5"><a class="reference internal" href="#trace-built-in-application-apps-system-trace-trace-c">“<code class="docutils literal notranslate"><span class="pre">trace</span></code>” Built-In Application (<code class="docutils literal notranslate"><span class="pre">apps/system/trace/trace.c</span></code>)</a></li>
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	<li class="toctree-l4"><a class="reference internal" href="#getting-the-system-call-events">Getting the system call events</a><ul>
	<li class="toctree-l5"><a class="reference internal" href="#flat-build">FLAT build</a></li>
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	<div class="section" id="task-trace-internals">
	<h1>Task Trace Internals<a class="headerlink" href="#task-trace-internals" title="Permalink to this headline">¶</a></h1>
	<div class="section" id="overview">
	<h2>Overview<a class="headerlink" href="#overview" title="Permalink to this headline">¶</a></h2>
	<img alt="../_images/task-trace-internal.png" src="../_images/task-trace-internal.png" />
	<p>The Task Trace is constructed by the following functions.</p>
	<div class="section" id="nuttx-kernel-events-collection">
	<h3>NuttX kernel events collection<a class="headerlink" href="#nuttx-kernel-events-collection" title="Permalink to this headline">¶</a></h3>
	<p>The kernel events are collected by <code class="docutils literal notranslate"><span class="pre">sched_note_*()</span></code> API calls embedded in NuttX kernel.</p>
	<blockquote>
	<div><ul class="simple">
	<li><p>For task switch events</p>
	<ul>
	<li><p><code class="docutils literal notranslate"><span class="pre">sched_note_start()</span></code></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">sched_note_stop()</span></code></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">sched_note_suspend()</span></code></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">sched_note_resume()</span></code></p></li>
	</ul>
	</li>
	<li><p>For system call events</p>
	<ul>
	<li><p><code class="docutils literal notranslate"><span class="pre">sched_note_syscall_enter()</span></code></p></li>
	<li><p><code class="docutils literal notranslate"><span class="pre">sched_note_syscall_leave()</span></code></p></li>
	</ul>
	</li>
	<li><p>For interrupt event</p>
	<ul>
	<li><p><code class="docutils literal notranslate"><span class="pre">sched_note_irqhandler()</span></code></p></li>
	</ul>
	</li>
	</ul>
	</div></blockquote>
	</div>
	<div class="section" id="filter-logic-nuttx-sched-sched-note-c">
	<h3>Filter logic (<code class="docutils literal notranslate"><span class="pre">nuttx/sched/sched_note.c</span></code>)<a class="headerlink" href="#filter-logic-nuttx-sched-sched-note-c" title="Permalink to this headline">¶</a></h3>
	<ul class="simple">
	<li><p>The <code class="docutils literal notranslate"><span class="pre">sched_note_*()</span></code> APIs are implemented here.</p></li>
	<li><p>Filter the notes and pass them to noteram driver by <code class="docutils literal notranslate"><span class="pre">sched_note_add()</span></code> API.</p></li>
	</ul>
	</div>
	<div class="section" id="noteram-device-driver-nuttx-drivers-note-noteram-driver-c">
	<h3>Noteram device driver (<code class="docutils literal notranslate"><span class="pre">nuttx/drivers/note/noteram_driver.c</span></code>)<a class="headerlink" href="#noteram-device-driver-nuttx-drivers-note-noteram-driver-c" title="Permalink to this headline">¶</a></h3>
	<ul class="simple">
	<li><p>Accumurate incoming note records into the buffer.</p></li>
	<li><p>Read the note records from the buffer by user requests.</p></li>
	<li><p>The notes are recorded in the binary format of <code class="docutils literal notranslate"><span class="pre">struct</span> <span class="pre">note_*_s</span></code>.</p></li>
	<li><p>The detail function is described in <a class="reference internal" href="../components/drivers/character/note.html"><span class="doc">Note Driver Interface</span></a>.</p></li>
	</ul>
	</div>
	<div class="section" id="notectl-device-driver-nuttx-drivers-note-notectl-driver-c">
	<h3>Notectl device driver (<code class="docutils literal notranslate"><span class="pre">nuttx/drivers/note/notectl_driver.c</span></code>)<a class="headerlink" href="#notectl-device-driver-nuttx-drivers-note-notectl-driver-c" title="Permalink to this headline">¶</a></h3>
	<ul class="simple">
	<li><p><code class="docutils literal notranslate"><span class="pre">/dev/notectl</span></code> device driver.</p></li>
	<li><p>Control the filter logic in <code class="docutils literal notranslate"><span class="pre">sched_note.c</span></code> by calling note filter APIs.</p></li>
	<li><p>The detail function is described in <a class="reference internal" href="../components/drivers/character/note.html"><span class="doc">Note Driver Interface</span></a>.</p></li>
	</ul>
	</div>
	<div class="section" id="trace-built-in-application-apps-system-trace-trace-c">
	<h3>“<code class="docutils literal notranslate"><span class="pre">trace</span></code>” Built-In Application (<code class="docutils literal notranslate"><span class="pre">apps/system/trace/trace.c</span></code>)<a class="headerlink" href="#trace-built-in-application-apps-system-trace-trace-c" title="Permalink to this headline">¶</a></h3>
	<ul class="simple">
	<li><p><code class="docutils literal notranslate"><span class="pre">trace</span></code> Built-In Application to control the trace function interactively.</p></li>
	<li><p>Read binary note records from <code class="docutils literal notranslate"><span class="pre">/dev/note</span></code> and convert into the ftrace text format which is acceptable by <a class="reference external" href="https://www.eclipse.org/tracecompass/">“Trace Compass”</a>.</p></li>
	<li><p>The command syntax is described in <a class="reference internal" href="tasktraceuser.html"><span class="doc">Task Trace User Guide</span></a>.</p></li>
	</ul>
	</div>
	</div>
	<div class="section" id="getting-the-system-call-events">
	<h2>Getting the system call events<a class="headerlink" href="#getting-the-system-call-events" title="Permalink to this headline">¶</a></h2>
	<p>To get the system call events, two different methods are used for FLAT build and PROTECTED/KERNEL build.</p>
	<div class="section" id="flat-build">
	<h3>FLAT build<a class="headerlink" href="#flat-build" title="Permalink to this headline">¶</a></h3>
	<p>In FLAT build, a system call is just a function call into the NuttX kernel.</p>
	<img alt="../_images/syscall-flat-before.png" src="../_images/syscall-flat-before.png" />
	<p>To get the system call events, <a class="reference external" href="https://sourceware.org/binutils/docs/ld/Options.html#index-_002d_002dwrap_003dsymbol">wrapper function option</a> of the GNU Linker is used.</p>
	<p>The mksyscall tool is fixed to generate the system call wrapper which call system call enter/leave hook.
	The wrapper supersedes the system call function call of the NuttX binary by passing <code class="docutils literal notranslate"><span class="pre">--wrap</span></code> linker option to the build system.
	The wrapper calls the system call hooks before and after calling the real system call function.</p>
	<img alt="../_images/syscall-flat-after.png" src="../_images/syscall-flat-after.png" />
	</div>
	<div class="section" id="protected-kernel-build">
	<h3>PROTECTED/KERNEL build<a class="headerlink" href="#protected-kernel-build" title="Permalink to this headline">¶</a></h3>
	<p>Different to FLAT build, in PROTECTED and KERNEL build, a system call is issued by an user space is handled as the following steps.</p>
	<ol class="arabic simple">
	<li><p>System call issued by an application code is handled by the system call proxy (automatically generated by mksyscall).</p></li>
	<li><p>System call proxy issues the supervisor call instruction to enter into the kernel space.</p></li>
	<li><p>System call handler in the kernel space calls the system call stub (automatically generated by mksyscall).</p></li>
	<li><p>System call stub calls the API implementation in the NuttX kernel.</p></li>
	</ol>
	<img alt="../_images/syscall-protected-before.png" src="../_images/syscall-protected-before.png" />
	<p>To get the system call events, the mksyscall tool is fixed to generate the system call wrapper which supersedes the system call function call in the system call stub.</p>
	<img alt="../_images/syscall-protected-after.png" src="../_images/syscall-protected-after.png" />
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