<h1 id="tor">Tor子系统——报错模块</h1>
<p><a href="/post/note_tor_index"><strong>Tor笔记目录索引</strong></a></p>
<p>Tor报错模块位于<code>src/lib/err/</code>文件夹，用于监听Tor运行过程中发生的错误，并输出错误信息</p>
<h2 id="heading">子系统结构</h2>
<p><a href="/post/note_tor_subsystem_winprocess#tor">子系统结构定义解释</a></p>
<pre style="background-color:#fff"><span style="font-weight:bold">const</span> subsys_fns_t sys_torerr <span style="font-weight:bold">=</span> {
  .name <span style="font-weight:bold">=</span> <span style="color:#b84">&#34;err&#34;</span>,
  <span style="color:#998;font-style:italic">/* Low-level error handling is a diagnostic feature, we want it to init
</span><span style="color:#998;font-style:italic">   * right after windows process security, and shutdown last.
</span><span style="color:#998;font-style:italic">   * (Security never shuts down.) */</span>
  .level <span style="font-weight:bold">=</span> <span style="font-weight:bold">-</span><span style="color:#099">99</span>,
  .supported <span style="font-weight:bold">=</span> <span style="color:#999">true</span>,
  .initialize <span style="font-weight:bold">=</span> subsys_torerr_initialize,
  .shutdown <span style="font-weight:bold">=</span> subsys_torerr_shutdown
};
</pre><h2 id="heading-1">初始化子系统</h2>
<p>该系统初始化首先会将<code>version</code>拼接到<code>bt_version</code>中（类似<code>Tor version 0.4.4.0-alpha-dev (git-a6509cb86744f8f2)</code>的格式）</p>
<p>接下来会用到sigaction<sup id="fnref:1"><a href="#fn:1" class="footnote-ref" role="doc-noteref">1</a></sup>，这是一个监听信号的库，当进程收到信号时，会执行对应的函数，在这里设置的是<code>SA_SIGINFO</code>函数，说明使用<code>sa_sigaction</code>对应的函数接收信号，而非<code>sa_handler</code></p>
<p>这里会接收如下信号<sup id="fnref:2"><a href="#fn:2" class="footnote-ref" role="doc-noteref">2</a></sup> <sup id="fnref:3"><a href="#fn:3" class="footnote-ref" role="doc-noteref">3</a></sup></p>
<table>
<thead>
<tr>
<th style="text-align:left">信号</th>
<th style="text-align:left">解释</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align:left"><code>SIGSEGV</code></td>
<td style="text-align:left">发生段错误时触发<sup id="fnref:4"><a href="#fn:4" class="footnote-ref" role="doc-noteref">4</a></sup></td>
</tr>
<tr>
<td style="text-align:left"><code>SIGILL</code></td>
<td style="text-align:left">非法访问时触发</td>
</tr>
<tr>
<td style="text-align:left"><code>SIGFPE</code></td>
<td style="text-align:left">算术错误如除零、溢出时触发<sup id="fnref:5"><a href="#fn:5" class="footnote-ref" role="doc-noteref">5</a></sup></td>
</tr>
<tr>
<td style="text-align:left"><code>SIGBUS</code></td>
<td style="text-align:left">发生总线错误时触发<sup id="fnref:6"><a href="#fn:6" class="footnote-ref" role="doc-noteref">6</a></sup></td>
</tr>
<tr>
<td style="text-align:left"><code>SIGSYS</code></td>
<td style="text-align:left">发生系统调用错误</td>
</tr>
<tr>
<td style="text-align:left"><code>SIGIO</code></td>
<td style="text-align:left">发生IO错误时触发</td>
</tr>
</tbody>
</table>
<p>当有以上信号发生时（错误信号），会回调<code>src/lib/err/backtrace.c</code>的<code>static void crash_handler(int sig, siginfo_t *si, void *ctx_)</code>函数，并输出相应的回溯信息</p>
<h2 id="heading-2">销毁子系统</h2>
<p>在卸载时，则会取消之前监听的信号</p>
<h2 id="heading-3">参考资料</h2>
<section class="footnotes" role="doc-endnotes">
<hr>
<ol>
<li id="fn:1" role="doc-endnote">
<p><a href="https://www.cnblogs.com/wblyuyang/archive/2012/11/13/2768923.html">Linux 进程学习（四）------ sigaction 函数</a> <a href="#fnref:1" class="footnote-backref" role="doc-backlink">&#x21a9;&#xfe0e;</a></p>
</li>
<li id="fn:2" role="doc-endnote">
<p><a href="https://zh.cppreference.com/w/c/program/SIG_types">cppreference-信号</a> <a href="#fnref:2" class="footnote-backref" role="doc-backlink">&#x21a9;&#xfe0e;</a></p>
</li>
<li id="fn:3" role="doc-endnote">
<p><a href="http://gityuan.com/2015/12/20/signal/">Gityuan-Linux信号(signal)机制</a> <a href="#fnref:3" class="footnote-backref" role="doc-backlink">&#x21a9;&#xfe0e;</a></p>
</li>
<li id="fn:4" role="doc-endnote">
<p><a href="https://zh.wikipedia.org/wiki/SIGSEGV">维基百科-SIGSEGV</a> <a href="#fnref:4" class="footnote-backref" role="doc-backlink">&#x21a9;&#xfe0e;</a></p>
</li>
<li id="fn:5" role="doc-endnote">
<p><a href="https://zh.wikipedia.org/wiki/SIGFPE">维基百科-SIGFPE</a> <a href="#fnref:5" class="footnote-backref" role="doc-backlink">&#x21a9;&#xfe0e;</a></p>
</li>
<li id="fn:6" role="doc-endnote">
<p><a href="https://zh.wikipedia.org/wiki/%E6%80%BB%E7%BA%BF%E9%94%99%E8%AF%AF">维基百科-总线错误</a> <a href="#fnref:6" class="footnote-backref" role="doc-backlink">&#x21a9;&#xfe0e;</a></p>
</li>
</ol>
</section>
