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<li class="toctree-l2"><a class="reference internal" href="../chapter4/3sv39-implementation-1.html">实现 SV39 多级页表机制（上）</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../chapter4/7exercise.html">chapter4练习</a></li>
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<li class="toctree-l1 current has-children"><a class="reference internal" href="index.html">第五章：进程及进程管理</a><input checked="" class="toctree-checkbox" id="toctree-checkbox-13" name="toctree-checkbox-13" role="switch" type="checkbox"/><label for="toctree-checkbox-13"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="current">
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<li class="toctree-l2 current current-page"><a class="current reference internal" href="#">与进程有关的重要系统调用</a></li>
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<li class="toctree-l2"><a class="reference internal" href="2core-data-structures.html">进程管理的核心数据结构</a></li>
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<li class="toctree-l2"><a class="reference internal" href="3implement-process-mechanism.html">进程管理机制的设计实现</a></li>
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<li class="toctree-l2"><a class="reference internal" href="4exercise.html">chapter5练习</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../chapter6/1file-descriptor.html">文件与文件描述符</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../chapter6/1fs-interface.html">文件系统接口</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../chapter6/2fs-implementation-1.html">简易文件系统 easy-fs (上)</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../chapter6/2fs-implementation-2.html">简易文件系统 easy-fs (下)</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../chapter8/5exercise.html">chapter8 练习</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
<p class="caption" role="heading"><span class="caption-text">附录</span></p>
|
||
<ul>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../appendix-a/index.html">附录 A：Rust 系统编程资料</a><input class="toctree-checkbox" id="toctree-checkbox-17" name="toctree-checkbox-17" role="switch" type="checkbox"/><label for="toctree-checkbox-17"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
||
</ul>
|
||
</li>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../appendix-b/index.html">附录 B：常见工具的使用方法</a><input class="toctree-checkbox" id="toctree-checkbox-18" name="toctree-checkbox-18" role="switch" type="checkbox"/><label for="toctree-checkbox-18"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
||
</ul>
|
||
</li>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../appendix-c/index.html">附录 C：深入机器模式：RustSBI</a><input class="toctree-checkbox" id="toctree-checkbox-19" name="toctree-checkbox-19" role="switch" type="checkbox"/><label for="toctree-checkbox-19"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
||
</ul>
|
||
</li>
|
||
<li class="toctree-l1"><a class="reference internal" href="../appendix-d/index.html">附录 D：RISC-V相关信息</a></li>
|
||
</ul>
|
||
<p class="caption" role="heading"><span class="caption-text">开发注记</span></p>
|
||
<ul>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../setup-sphinx.html">修改和构建本项目</a><input class="toctree-checkbox" id="toctree-checkbox-20" name="toctree-checkbox-20" role="switch" type="checkbox"/><label for="toctree-checkbox-20"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
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<li class="toctree-l1 has-children"><a class="reference internal" href="../rest-example.html">reStructuredText 基本语法</a><input class="toctree-checkbox" id="toctree-checkbox-21" name="toctree-checkbox-21" role="switch" type="checkbox"/><label for="toctree-checkbox-21"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
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<div class="main">
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<div class="visually-hidden">Toggle Light / Dark / Auto color theme</div>
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<i class="icon"><svg><use href="#svg-toc"></use></svg></i>
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|
||
<div class="section" id="id1">
|
||
<h1>与进程有关的重要系统调用<a class="headerlink" href="#id1" title="永久链接至标题">¶</a></h1>
|
||
<div class="section" id="id2">
|
||
<h2>重要系统调用<a class="headerlink" href="#id2" title="永久链接至标题">¶</a></h2>
|
||
<div class="section" id="fork">
|
||
<h3>fork 系统调用<a class="headerlink" href="#fork" title="永久链接至标题">¶</a></h3>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="sd">/// 功能：由当前进程 fork 出一个子进程。</span>
|
||
<span class="sd">/// 返回值：对于子进程返回 0，对于当前进程则返回子进程的 PID 。</span>
|
||
<span class="sd">/// syscall ID：220</span>
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">sys_fork</span><span class="p">()</span><span class="w"> </span>-> <span class="kt">isize</span><span class="p">;</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
</div>
|
||
<div class="section" id="exec">
|
||
<h3>exec 系统调用<a class="headerlink" href="#exec" title="永久链接至标题">¶</a></h3>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="sd">/// 功能：将当前进程的地址空间清空并加载一个特定的可执行文件，返回用户态后开始它的执行。</span>
|
||
<span class="sd">/// 参数：字符串 path 给出了要加载的可执行文件的名字；</span>
|
||
<span class="sd">/// 返回值：如果出错的话（如找不到名字相符的可执行文件）则返回 -1，否则不应该返回。</span>
|
||
<span class="sd">/// 注意：path 必须以 "\0" 结尾，否则内核将无法确定其长度</span>
|
||
<span class="sd">/// syscall ID：221</span>
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">sys_exec</span><span class="p">(</span><span class="n">path</span>: <span class="kp">&</span><span class="kt">str</span><span class="p">)</span><span class="w"> </span>-> <span class="kt">isize</span><span class="p">;</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>利用 <code class="docutils literal notranslate"><span class="pre">fork</span></code> 和 <code class="docutils literal notranslate"><span class="pre">exec</span></code> 的组合，我们能让创建一个子进程，并令其执行特定的可执行文件。</p>
|
||
</div>
|
||
<div class="section" id="waitpid">
|
||
<h3>waitpid 系统调用<a class="headerlink" href="#waitpid" title="永久链接至标题">¶</a></h3>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="sd">/// 功能：当前进程等待一个子进程变为僵尸进程，回收其全部资源并收集其返回值。</span>
|
||
<span class="sd">/// 参数：pid 表示要等待的子进程的进程 ID，如果为 -1 的话表示等待任意一个子进程；</span>
|
||
<span class="sd">/// exit_code 表示保存子进程返回值的地址，如果这个地址为 0 的话表示不必保存。</span>
|
||
<span class="sd">/// 返回值：如果要等待的子进程不存在则返回 -1；否则如果要等待的子进程均未结束则返回 -2；</span>
|
||
<span class="sd">/// 否则返回结束的子进程的进程 ID。</span>
|
||
<span class="sd">/// syscall ID：260</span>
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">sys_waitpid</span><span class="p">(</span><span class="n">pid</span>: <span class="kt">isize</span><span class="p">,</span><span class="w"> </span><span class="n">exit_code</span>: <span class="o">*</span><span class="k">mut</span><span class="w"> </span><span class="kt">i32</span><span class="p">)</span><span class="w"> </span>-> <span class="kt">isize</span><span class="p">;</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p><code class="docutils literal notranslate"><span class="pre">sys_waitpid</span></code> 在用户库中被封装成两个不同的 API， <code class="docutils literal notranslate"><span class="pre">wait(exit_code:</span> <span class="pre">&mut</span> <span class="pre">i32)</span></code> 和 <code class="docutils literal notranslate"><span class="pre">waitpid(pid:</span> <span class="pre">usize,</span> <span class="pre">exit_code:</span> <span class="pre">&mut</span> <span class="pre">i32)</span></code>，
|
||
前者用于等待任意一个子进程，后者用于等待特定子进程。它们实现的策略是如果子进程还未结束，就以 yield 让出时间片：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="linenos"> 1</span><span class="c1">// user/src/lib.rs</span>
|
||
<span class="linenos"> 2</span>
|
||
<span class="linenos"> 3</span><span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">wait</span><span class="p">(</span><span class="n">exit_code</span>: <span class="kp">&</span><span class="nc">mut</span><span class="w"> </span><span class="kt">i32</span><span class="p">)</span><span class="w"> </span>-> <span class="kt">isize</span> <span class="p">{</span><span class="w"></span>
|
||
<span class="linenos"> 4</span><span class="w"> </span><span class="k">loop</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos"> 5</span><span class="w"> </span><span class="k">match</span><span class="w"> </span><span class="n">sys_waitpid</span><span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">exit_code</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="o">*</span><span class="k">mut</span><span class="w"> </span><span class="n">_</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos"> 6</span><span class="w"> </span><span class="o">-</span><span class="mi">2</span><span class="w"> </span><span class="o">=></span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="n">sys_yield</span><span class="p">();</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos"> 7</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">=></span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">n</span><span class="p">;</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos"> 8</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos"> 9</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">10</span><span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="section" id="id3">
|
||
<h2>应用程序示例<a class="headerlink" href="#id3" title="永久链接至标题">¶</a></h2>
|
||
<p>借助这三个重要系统调用，我们可以开发功能更强大的应用。下面是两个案例： <strong>用户初始程序-init</strong> 和 <strong>shell程序-user_shell</strong> 。</p>
|
||
<div class="section" id="initproc">
|
||
<h3>用户初始程序-initproc<a class="headerlink" href="#initproc" title="永久链接至标题">¶</a></h3>
|
||
<p>在内核初始化完毕后创建的第一个进程，是 <strong>用户初始进程</strong> (Initial Process) ，它将通过
|
||
<code class="docutils literal notranslate"><span class="pre">fork+exec</span></code> 创建 <code class="docutils literal notranslate"><span class="pre">user_shell</span></code> 子进程，并将被用于回收僵尸进程。</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="linenos"> 1</span><span class="c1">// user/src/bin/ch5b_initproc.rs</span>
|
||
<span class="linenos"> 2</span>
|
||
<span class="linenos"> 3</span><span class="cp">#![no_std]</span><span class="w"></span>
|
||
<span class="linenos"> 4</span><span class="cp">#![no_main]</span><span class="w"></span>
|
||
<span class="linenos"> 5</span>
|
||
<span class="linenos"> 6</span><span class="cp">#[macro_use]</span><span class="w"></span>
|
||
<span class="linenos"> 7</span><span class="k">extern</span><span class="w"> </span><span class="k">crate</span><span class="w"> </span><span class="n">user_lib</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos"> 8</span>
|
||
<span class="linenos"> 9</span><span class="k">use</span><span class="w"> </span><span class="n">user_lib</span>::<span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">10</span><span class="w"> </span><span class="n">fork</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">11</span><span class="w"> </span><span class="n">wait</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">12</span><span class="w"> </span><span class="n">exec</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">13</span><span class="w"> </span><span class="n">yield_</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">14</span><span class="p">};</span><span class="w"></span>
|
||
<span class="linenos">15</span>
|
||
<span class="linenos">16</span><span class="cp">#[no_mangle]</span><span class="w"></span>
|
||
<span class="linenos">17</span><span class="k">fn</span> <span class="nf">main</span><span class="p">()</span><span class="w"> </span>-> <span class="kt">i32</span> <span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">18</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">fork</span><span class="p">()</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">19</span><span class="w"> </span><span class="n">exec</span><span class="p">(</span><span class="s">"ch5b_user_shell</span><span class="se">\0</span><span class="s">"</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">20</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">21</span><span class="w"> </span><span class="k">loop</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">22</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">exit_code</span>: <span class="kt">i32</span> <span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">23</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">wait</span><span class="p">(</span><span class="o">&</span><span class="k">mut</span><span class="w"> </span><span class="n">exit_code</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">24</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">25</span><span class="w"> </span><span class="n">yield_</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">26</span><span class="w"> </span><span class="k">continue</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">27</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">28</span><span class="w"> </span><span class="fm">println!</span><span class="p">(</span><span class="w"></span>
|
||
<span class="linenos">29</span><span class="w"> </span><span class="s">"[initproc] Released a zombie process, pid={}, exit_code={}"</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">30</span><span class="w"> </span><span class="n">pid</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">31</span><span class="w"> </span><span class="n">exit_code</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">32</span><span class="w"> </span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">33</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">34</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">35</span><span class="w"> </span><span class="mi">0</span><span class="w"></span>
|
||
<span class="linenos">36</span><span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<ul class="simple">
|
||
<li><p>第 19 行为 <code class="docutils literal notranslate"><span class="pre">fork</span></code> 出的子进程分支，通过 <code class="docutils literal notranslate"><span class="pre">exec</span></code> 启动shell程序 <code class="docutils literal notranslate"><span class="pre">user_shell</span></code> ，
|
||
注意我们需要在字符串末尾手动加入 <code class="docutils literal notranslate"><span class="pre">\0</span></code> 。</p></li>
|
||
<li><p>第 21 行开始则为父进程分支，表示用户初始程序-initproc自身。它不断循环调用 <code class="docutils literal notranslate"><span class="pre">wait</span></code> 来等待并回收系统中的僵尸进程占据的资源。
|
||
如果回收成功的话则会打印一条报告信息给出被回收子进程的 PID 和返回值；否则就 <code class="docutils literal notranslate"><span class="pre">yield_</span></code> 交出 CPU 资源并在下次轮到它执行的时候再回收看看。</p></li>
|
||
</ul>
|
||
</div>
|
||
<div class="section" id="shell-user-shell">
|
||
<h3>shell程序-user_shell<a class="headerlink" href="#shell-user-shell" title="永久链接至标题">¶</a></h3>
|
||
<p>user_shell 需要捕获用户输入并进行解析处理，为此添加一个能获取用户输入的系统调用：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="sd">/// 功能：从文件中读取一段内容到缓冲区。</span>
|
||
<span class="sd">/// 参数：fd 是待读取文件的文件描述符，切片 buffer 则给出缓冲区。</span>
|
||
<span class="sd">/// 返回值：如果出现了错误则返回 -1，否则返回实际读到的字节数。</span>
|
||
<span class="sd">/// syscall ID：63</span>
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">sys_read</span><span class="p">(</span><span class="n">fd</span>: <span class="kt">usize</span><span class="p">,</span><span class="w"> </span><span class="n">buffer</span>: <span class="kp">&</span><span class="nc">mut</span><span class="w"> </span><span class="p">[</span><span class="kt">u8</span><span class="p">])</span><span class="w"> </span>-> <span class="kt">isize</span><span class="p">;</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>实际调用时，我们必须要同时向内核提供缓冲区的起始地址及长度：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// user/src/syscall.rs</span>
|
||
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">sys_read</span><span class="p">(</span><span class="n">fd</span>: <span class="kt">usize</span><span class="p">,</span><span class="w"> </span><span class="n">buffer</span>: <span class="kp">&</span><span class="nc">mut</span><span class="w"> </span><span class="p">[</span><span class="kt">u8</span><span class="p">])</span><span class="w"> </span>-> <span class="kt">isize</span> <span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">syscall</span><span class="p">(</span><span class="n">SYSCALL_READ</span><span class="p">,</span><span class="w"> </span><span class="p">[</span><span class="n">fd</span><span class="p">,</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="n">as_mut_ptr</span><span class="p">()</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="kt">usize</span><span class="p">,</span><span class="w"> </span><span class="n">buffer</span><span class="p">.</span><span class="n">len</span><span class="p">()])</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>我们在用户库中将其进一步封装成每次能够从 <strong>标准输入</strong> 中获取一个字符的 <code class="docutils literal notranslate"><span class="pre">getchar</span></code> 函数。</p>
|
||
<p>shell程序 <code class="docutils literal notranslate"><span class="pre">user_shell</span></code> 实现如下：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="linenos"> 1</span><span class="c1">// user/src/bin/ch5b_user_shell.rs</span>
|
||
<span class="linenos"> 2</span>
|
||
<span class="linenos"> 3</span><span class="cp">#![no_std]</span><span class="w"></span>
|
||
<span class="linenos"> 4</span><span class="cp">#![no_main]</span><span class="w"></span>
|
||
<span class="linenos"> 5</span>
|
||
<span class="linenos"> 6</span><span class="k">extern</span><span class="w"> </span><span class="k">crate</span><span class="w"> </span><span class="n">alloc</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos"> 7</span>
|
||
<span class="linenos"> 8</span><span class="cp">#[macro_use]</span><span class="w"></span>
|
||
<span class="linenos"> 9</span><span class="k">extern</span><span class="w"> </span><span class="k">crate</span><span class="w"> </span><span class="n">user_lib</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">10</span>
|
||
<span class="linenos">11</span><span class="k">const</span><span class="w"> </span><span class="n">LF</span>: <span class="kt">u8</span> <span class="o">=</span><span class="w"> </span><span class="mh">0x0a</span><span class="k">u8</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">12</span><span class="k">const</span><span class="w"> </span><span class="n">CR</span>: <span class="kt">u8</span> <span class="o">=</span><span class="w"> </span><span class="mh">0x0d</span><span class="k">u8</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">13</span><span class="k">const</span><span class="w"> </span><span class="n">DL</span>: <span class="kt">u8</span> <span class="o">=</span><span class="w"> </span><span class="mh">0x7f</span><span class="k">u8</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">14</span><span class="k">const</span><span class="w"> </span><span class="n">BS</span>: <span class="kt">u8</span> <span class="o">=</span><span class="w"> </span><span class="mh">0x08</span><span class="k">u8</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">15</span>
|
||
<span class="linenos">16</span><span class="k">use</span><span class="w"> </span><span class="n">alloc</span>::<span class="n">string</span>::<span class="nb">String</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">17</span><span class="k">use</span><span class="w"> </span><span class="n">user_lib</span>::<span class="p">{</span><span class="n">fork</span><span class="p">,</span><span class="w"> </span><span class="n">exec</span><span class="p">,</span><span class="w"> </span><span class="n">waitpid</span><span class="p">,</span><span class="w"> </span><span class="n">yield_</span><span class="p">};</span><span class="w"></span>
|
||
<span class="linenos">18</span><span class="k">use</span><span class="w"> </span><span class="n">user_lib</span>::<span class="n">console</span>::<span class="n">getchar</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">19</span>
|
||
<span class="linenos">20</span><span class="cp">#[no_mangle]</span><span class="w"></span>
|
||
<span class="linenos">21</span><span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">main</span><span class="p">()</span><span class="w"> </span>-> <span class="kt">i32</span> <span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">22</span><span class="w"> </span><span class="fm">println!</span><span class="p">(</span><span class="s">"Rust user shell"</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">23</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">line</span>: <span class="nb">String</span> <span class="o">=</span><span class="w"> </span><span class="nb">String</span>::<span class="n">new</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">24</span><span class="w"> </span><span class="fm">print!</span><span class="p">(</span><span class="s">">> "</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">25</span><span class="w"> </span><span class="k">loop</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">26</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">getchar</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">27</span><span class="w"> </span><span class="k">match</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="hll"><span class="linenos">28</span><span class="w"> </span><span class="n">LF</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">CR</span><span class="w"> </span><span class="o">=></span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
</span><span class="linenos">29</span><span class="w"> </span><span class="fm">println!</span><span class="p">(</span><span class="s">""</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">30</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="o">!</span><span class="n">line</span><span class="p">.</span><span class="n">is_empty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">31</span><span class="w"> </span><span class="n">line</span><span class="p">.</span><span class="n">push</span><span class="p">(</span><span class="sc">'\0'</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">32</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fork</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">33</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">34</span><span class="w"> </span><span class="c1">// child process</span>
|
||
<span class="linenos">35</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">exec</span><span class="p">(</span><span class="n">line</span><span class="p">.</span><span class="n">as_str</span><span class="p">())</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">36</span><span class="w"> </span><span class="fm">println!</span><span class="p">(</span><span class="s">"Error when executing!"</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">37</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">38</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">39</span><span class="w"> </span><span class="fm">unreachable!</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">40</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">41</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">exit_code</span>: <span class="kt">i32</span> <span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">42</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">exit_pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">waitpid</span><span class="p">(</span><span class="n">pid</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="kt">usize</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="k">mut</span><span class="w"> </span><span class="n">exit_code</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">43</span><span class="w"> </span><span class="fm">assert_eq!</span><span class="p">(</span><span class="n">pid</span><span class="p">,</span><span class="w"> </span><span class="n">exit_pid</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">44</span><span class="w"> </span><span class="fm">println!</span><span class="p">(</span><span class="w"></span>
|
||
<span class="linenos">45</span><span class="w"> </span><span class="s">"Shell: Process {} exited with code {}"</span><span class="p">,</span><span class="w"></span>
|
||
<span class="linenos">46</span><span class="w"> </span><span class="n">pid</span><span class="p">,</span><span class="w"> </span><span class="n">exit_code</span><span class="w"></span>
|
||
<span class="linenos">47</span><span class="w"> </span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">48</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">49</span><span class="w"> </span><span class="n">line</span><span class="p">.</span><span class="n">clear</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">50</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">51</span><span class="w"> </span><span class="fm">print!</span><span class="p">(</span><span class="s">">> "</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">52</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="hll"><span class="linenos">53</span><span class="w"> </span><span class="n">BS</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">DL</span><span class="w"> </span><span class="o">=></span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
</span><span class="linenos">54</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="o">!</span><span class="n">line</span><span class="p">.</span><span class="n">is_empty</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">55</span><span class="w"> </span><span class="fm">print!</span><span class="p">(</span><span class="s">"{}"</span><span class="p">,</span><span class="w"> </span><span class="n">BS</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="kt">char</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">56</span><span class="w"> </span><span class="fm">print!</span><span class="p">(</span><span class="s">" "</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">57</span><span class="w"> </span><span class="fm">print!</span><span class="p">(</span><span class="s">"{}"</span><span class="p">,</span><span class="w"> </span><span class="n">BS</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="kt">char</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">58</span><span class="w"> </span><span class="n">line</span><span class="p">.</span><span class="n">pop</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">59</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">60</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="hll"><span class="linenos">61</span><span class="w"> </span><span class="n">_</span><span class="w"> </span><span class="o">=></span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
</span><span class="linenos">62</span><span class="w"> </span><span class="fm">print!</span><span class="p">(</span><span class="s">"{}"</span><span class="p">,</span><span class="w"> </span><span class="n">c</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="kt">char</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">63</span><span class="w"> </span><span class="n">line</span><span class="p">.</span><span class="n">push</span><span class="p">(</span><span class="n">c</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="kt">char</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">64</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">65</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">66</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">67</span><span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>可以看到，在以第 25 行开头的主循环中，每次都是调用 <code class="docutils literal notranslate"><span class="pre">getchar</span></code> 获取一个用户输入的字符，
|
||
并根据它相应进行一些动作。第 23 行声明的字符串 <code class="docutils literal notranslate"><span class="pre">line</span></code> 则维护着用户当前输入的命令内容，它也在不断发生变化。</p>
|
||
<ul>
|
||
<li><p>如果用户输入回车键（第 28 行），那么user_shell 会 fork 出一个子进程（第 34 行开始）并试图通过
|
||
<code class="docutils literal notranslate"><span class="pre">exec</span></code> 系统调用执行一个应用，应用的名字在字符串 <code class="docutils literal notranslate"><span class="pre">line</span></code> 中给出。如果 exec 的返回值为 -1 ，
|
||
说明在应用管理器中找不到对应名字的应用，此时子进程就直接打印错误信息并退出；否则子进程将开始执行目标应用。</p>
|
||
<p>fork 之后的 user_shell 进程自己的逻辑可以在第 41 行找到。它在等待 fork 出来的子进程结束并回收掉它的资源，还会顺带收集子进程的退出状态并打印出来。</p>
|
||
</li>
|
||
<li><p>如果用户输入退格键（第 53 行），首先我们需要将屏幕上当前行的最后一个字符用空格替换掉，
|
||
这可以通过输入一个特殊的退格字节 <code class="docutils literal notranslate"><span class="pre">BS</span></code> 来实现。其次，user_shell 进程内维护的 <code class="docutils literal notranslate"><span class="pre">line</span></code> 也需要弹出最后一个字符。</p></li>
|
||
<li><p>如果用户输入了一个其他字符（第 61 行），就接将它打印在屏幕上，并加入到 <code class="docutils literal notranslate"><span class="pre">line</span></code> 中。</p></li>
|
||
<li><p>按键 <code class="docutils literal notranslate"><span class="pre">Ctrl+A</span></code> 再输入 <code class="docutils literal notranslate"><span class="pre">X</span></code> 来退出qemu模拟器。</p></li>
|
||
</ul>
|
||
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|
||
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|
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<ul>
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<li><a class="reference internal" href="#">与进程有关的重要系统调用</a><ul>
|
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<li><a class="reference internal" href="#id2">重要系统调用</a><ul>
|
||
<li><a class="reference internal" href="#fork">fork 系统调用</a></li>
|
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<li><a class="reference internal" href="#exec">exec 系统调用</a></li>
|
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<li><a class="reference internal" href="#shell-user-shell">shell程序-user_shell</a></li>
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