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   <section id="stack-overflow-check">
 <h1>Stack Overflow Check<a class="headerlink" href="#stack-overflow-check" title="Permalink to this heading"></a></h1>
 <section id="overview">
 <h2>Overview<a class="headerlink" href="#overview" title="Permalink to this heading"></a></h2>
 <dl class="simple">
 <dt>Currently NuttX supports three types of stack overflow detection:</dt><dd><ol class="arabic simple">
 <li><p>Stack Overflow Software Check During Function Call</p></li>
 <li><p>Stack Overflow Software Check During Context Switching</p></li>
 <li><p>Stack Overflow Hardware Check</p></li>
 <li><p>Stack Canary Check</p></li>
 </ol>
 </dd>
 <dt>The software stack detection during function call includes two implementation ideas:</dt><dd><ol class="arabic simple">
 <li><p>Implemented by coloring the stack memory</p></li>
 <li><p>Implemented by comparing the sp and sl registers</p></li>
 </ol>
 </dd>
 <dt>The software stack detection during context switching includes two implementation ideas:</dt><dd><ol class="arabic simple">
 <li><p>Implemented by coloring the stack memory</p></li>
 <li><p>Implemented by checking the bottom memory of the stack and the sp register</p></li>
 </ol>
 </dd>
 </dl>
 </section>
 <section id="support">
 <h2>Support<a class="headerlink" href="#support" title="Permalink to this heading"></a></h2>
 <p>Software and hardware stack overflow detection implementation,
 currently only implemented on ARM Cortex-M (32-bit) series chips
 Stack Canary Check is available on all platforms</p>
 </section>
 <section id="stack-overflow-software-check-during-function-call">
 <h2>Stack Overflow Software Check During Function Call<a class="headerlink" href="#stack-overflow-software-check-during-function-call" title="Permalink to this heading"></a></h2>
 <ol class="arabic">
 <li><dl>
 <dt>Memory Coloring Implementation Principle</dt><dd><ol class="arabic simple">
 <li><p>Before using the stack, Thread will refresh the stack area to 0xdeadbeef</p></li>
 <li><p>When Thread is running, it will overwrite 0xdeadbeef</p></li>
 <li><p>up_check_tcbstack() detects 0xdeadbeef to get the stack peak value</p></li>
 </ol>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>Enable CONFIG_STACK_COLORATION</p>
 </dd>
 </dl>
 </dd>
 </dl>
 </li>
 <li><dl>
 <dt>Compare sp and sl</dt><dd><p>When compiling the program, keep r10 and use r10 as stackbase::
 ‘’’
 ARCHOPTIMIZATION += -finstrument-functions -ffixed-r10</p>
 <p>Each function will automatically add the following when entering and exiting:
 __cyg_profile_func_enter
 __cyg_profile_func_exit</p>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>Enable CONFIG_ARMV8M_STACKCHECK or CONFIG_ARMV7M_STACKCHECK</p>
 </dd>
 </dl>
 </dd>
 </dl>
 </li>
 </ol>
 </section>
 <section id="stack-overflow-software-check-during-context-switching">
 <h2>Stack Overflow Software Check During Context Switching<a class="headerlink" href="#stack-overflow-software-check-during-context-switching" title="Permalink to this heading"></a></h2>
 <ol class="arabic simple">
 <li><p>Determine by detecting the number of bytes specified at the bottom of the stack.</p></li>
 <li><p>Check if the sp register is out of bounds.</p></li>
 </ol>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>Set the detection length by STACKCHECK_MARGIN</p>
 </dd>
 </dl>
 </section>
 <section id="stack-overflow-hardware-check">
 <h2>Stack Overflow Hardware Check<a class="headerlink" href="#stack-overflow-hardware-check" title="Permalink to this heading"></a></h2>
 <ol class="arabic simple">
 <li><p>Set MSPLIM PSPLIM when context switching</p></li>
 <li><p>Each time sp is operated, the hardware automatically compares sp and PSPLIM. If sp is lower than PSPLIM, crash</p></li>
 </ol>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>Enable CONFIG_ARMV8M_STACKCHECK_HARDWARE</p>
 </dd>
 </dl>
 </section>
 <section id="stack-canary-check">
 <h2>Stack Canary Check<a class="headerlink" href="#stack-canary-check" title="Permalink to this heading"></a></h2>
 <ol class="arabic simple">
 <li><p>Add a canary value to the stack</p></li>
 <li><p>When the thread is running, the canary value is overwritten</p></li>
 <li><p>When the thread is running, the canary value is compared with the original value</p></li>
 <li><p>If the value is different, it means that the stack is overflowed</p></li>
 </ol>
 <dl class="simple">
 <dt>Usage:</dt><dd><p>Enable CONFIG_STACK_CANARIES</p>
 </dd>
 </dl>
 </section>
 </section>


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	<section id="stack-overflow-check">
	<h1>Stack Overflow Check<a class="headerlink" href="#stack-overflow-check" title="Permalink to this heading"></a></h1>
	<section id="overview">
	<h2>Overview<a class="headerlink" href="#overview" title="Permalink to this heading"></a></h2>
	<dl class="simple">
	<dt>Currently NuttX supports three types of stack overflow detection:</dt><dd><ol class="arabic simple">
	<li><p>Stack Overflow Software Check During Function Call</p></li>
	<li><p>Stack Overflow Software Check During Context Switching</p></li>
	<li><p>Stack Overflow Hardware Check</p></li>
	<li><p>Stack Canary Check</p></li>
	</ol>
	</dd>
	<dt>The software stack detection during function call includes two implementation ideas:</dt><dd><ol class="arabic simple">
	<li><p>Implemented by coloring the stack memory</p></li>
	<li><p>Implemented by comparing the sp and sl registers</p></li>
	</ol>
	</dd>
	<dt>The software stack detection during context switching includes two implementation ideas:</dt><dd><ol class="arabic simple">
	<li><p>Implemented by coloring the stack memory</p></li>
	<li><p>Implemented by checking the bottom memory of the stack and the sp register</p></li>
	</ol>
	</dd>
	</dl>
	</section>
	<section id="support">
	<h2>Support<a class="headerlink" href="#support" title="Permalink to this heading"></a></h2>
	<p>Software and hardware stack overflow detection implementation,
	currently only implemented on ARM Cortex-M (32-bit) series chips
	Stack Canary Check is available on all platforms</p>
	</section>
	<section id="stack-overflow-software-check-during-function-call">
	<h2>Stack Overflow Software Check During Function Call<a class="headerlink" href="#stack-overflow-software-check-during-function-call" title="Permalink to this heading"></a></h2>
	<ol class="arabic">
	<li><dl>
	<dt>Memory Coloring Implementation Principle</dt><dd><ol class="arabic simple">
	<li><p>Before using the stack, Thread will refresh the stack area to 0xdeadbeef</p></li>
	<li><p>When Thread is running, it will overwrite 0xdeadbeef</p></li>
	<li><p>up_check_tcbstack() detects 0xdeadbeef to get the stack peak value</p></li>
	</ol>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>Enable CONFIG_STACK_COLORATION</p>
	</dd>
	</dl>
	</dd>
	</dl>
	</li>
	<li><dl>
	<dt>Compare sp and sl</dt><dd><p>When compiling the program, keep r10 and use r10 as stackbase::
	‘’’
	ARCHOPTIMIZATION += -finstrument-functions -ffixed-r10</p>
	<p>Each function will automatically add the following when entering and exiting:
	__cyg_profile_func_enter
	__cyg_profile_func_exit</p>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>Enable CONFIG_ARMV8M_STACKCHECK or CONFIG_ARMV7M_STACKCHECK</p>
	</dd>
	</dl>
	</dd>
	</dl>
	</li>
	</ol>
	</section>
	<section id="stack-overflow-software-check-during-context-switching">
	<h2>Stack Overflow Software Check During Context Switching<a class="headerlink" href="#stack-overflow-software-check-during-context-switching" title="Permalink to this heading"></a></h2>
	<ol class="arabic simple">
	<li><p>Determine by detecting the number of bytes specified at the bottom of the stack.</p></li>
	<li><p>Check if the sp register is out of bounds.</p></li>
	</ol>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>Set the detection length by STACKCHECK_MARGIN</p>
	</dd>
	</dl>
	</section>
	<section id="stack-overflow-hardware-check">
	<h2>Stack Overflow Hardware Check<a class="headerlink" href="#stack-overflow-hardware-check" title="Permalink to this heading"></a></h2>
	<ol class="arabic simple">
	<li><p>Set MSPLIM PSPLIM when context switching</p></li>
	<li><p>Each time sp is operated, the hardware automatically compares sp and PSPLIM. If sp is lower than PSPLIM, crash</p></li>
	</ol>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>Enable CONFIG_ARMV8M_STACKCHECK_HARDWARE</p>
	</dd>
	</dl>
	</section>
	<section id="stack-canary-check">
	<h2>Stack Canary Check<a class="headerlink" href="#stack-canary-check" title="Permalink to this heading"></a></h2>
	<ol class="arabic simple">
	<li><p>Add a canary value to the stack</p></li>
	<li><p>When the thread is running, the canary value is overwritten</p></li>
	<li><p>When the thread is running, the canary value is compared with the original value</p></li>
	<li><p>If the value is different, it means that the stack is overflowed</p></li>
	</ol>
	<dl class="simple">
	<dt>Usage:</dt><dd><p>Enable CONFIG_STACK_CANARIES</p>
	</dd>
	</dl>
	</section>
	</section>


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