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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-l2"><a class="reference internal" href="../chapter5/1process.html">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="../chapter5/2core-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="../chapter5/3implement-process-mechanism.html">进程管理机制的设计实现</a></li>
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<li class="toctree-l1 current has-children"><a class="reference internal" href="index.html">第六章：文件系统与I/O重定向</a><input checked="" class="toctree-checkbox" id="toctree-checkbox-14" name="toctree-checkbox-14" role="switch" type="checkbox"/><label for="toctree-checkbox-14"><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"><a class="reference internal" href="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="2fs-implementation-2.html">简易文件系统 easy-fs (下)</a></li>
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<li class="toctree-l2 current current-page"><a class="current reference internal" href="#">在内核中使用 easy-fs</a></li>
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<li class="toctree-l2"><a class="reference internal" href="4exercise.html">chapter6练习</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../chapter7/1pipe.html">管道</a></li>
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</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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</ul>
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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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||
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|
||
|
||
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||
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|
||
</aside>
|
||
<div class="main">
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||
<div class="content">
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<article role="main">
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||
<div class="content-icon-container">
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<div class="theme-toggle-container theme-toggle-content">
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<button class="theme-toggle">
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<div class="visually-hidden">Toggle Light / Dark / Auto color theme</div>
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<svg class="theme-icon-when-auto"><use href="#svg-sun-half"></use></svg>
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<svg class="theme-icon-when-dark"><use href="#svg-moon"></use></svg>
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<label class="toc-overlay-icon toc-content-icon" for="__toc">
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<div class="visually-hidden">Toggle table of contents sidebar</div>
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<i class="icon"><svg><use href="#svg-toc"></use></svg></i>
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|
||
<div class="section" id="easy-fs">
|
||
<h1>在内核中使用 easy-fs<a class="headerlink" href="#easy-fs" title="永久链接至标题">¶</a></h1>
|
||
<div class="section" id="id1">
|
||
<h2>块设备驱动层<a class="headerlink" href="#id1" title="永久链接至标题">¶</a></h2>
|
||
<p>在 <code class="docutils literal notranslate"><span class="pre">drivers</span></code> 子模块中的 <code class="docutils literal notranslate"><span class="pre">block/mod.rs</span></code> 中，我们可以找到内核访问的块设备实例 <code class="docutils literal notranslate"><span class="pre">BLOCK_DEVICE</span></code> ：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/drivers/block/mod.rs</span>
|
||
|
||
<span class="k">type</span> <span class="nc">BlockDeviceImpl</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">virtio_blk</span>::<span class="n">VirtIOBlock</span><span class="p">;</span><span class="w"></span>
|
||
|
||
<span class="n">lazy_static</span><span class="o">!</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">pub</span><span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="k">ref</span><span class="w"> </span><span class="n">BLOCK_DEVICE</span>: <span class="nc">Arc</span><span class="o"><</span><span class="k">dyn</span><span class="w"> </span><span class="n">BlockDevice</span><span class="o">></span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arc</span>::<span class="n">new</span><span class="p">(</span><span class="n">BlockDeviceImpl</span>::<span class="n">new</span><span class="p">());</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>在 qemu 上，我们使用 <code class="docutils literal notranslate"><span class="pre">VirtIOBlock</span></code> 访问 VirtIO 块设备，并将它全局实例化为 <code class="docutils literal notranslate"><span class="pre">BLOCK_DEVICE</span></code> ，使内核的其他模块可以访问。</p>
|
||
<p>在启动 Qemu 模拟器的时候，我们可以配置参数来添加一块 VirtIO 块设备：</p>
|
||
<div class="highlight-makefile notranslate"><div class="highlight"><pre><span></span><span class="linenos"> 1</span><span class="c"># os/Makefile</span>
|
||
<span class="linenos"> 2</span>
|
||
<span class="linenos"> 3</span><span class="nv">FS_IMG</span> <span class="o">:=</span> ../user/target/<span class="k">$(</span>TARGET<span class="k">)</span>/<span class="k">$(</span>MODE<span class="k">)</span>/fs.img
|
||
<span class="linenos"> 4</span>
|
||
<span class="linenos"> 5</span><span class="nf">run</span><span class="o">:</span> <span class="n">build</span>
|
||
<span class="linenos"> 6</span> @qemu-system-riscv64 <span class="se">\</span>
|
||
<span class="linenos"> 7</span> -machine virt <span class="se">\</span>
|
||
<span class="linenos"> 8</span> -nographic <span class="se">\</span>
|
||
<span class="linenos"> 9</span> -bios <span class="k">$(</span>BOOTLOADER<span class="k">)</span> <span class="se">\</span>
|
||
<span class="linenos">10</span> -device loader,file<span class="o">=</span><span class="k">$(</span>KERNEL_BIN<span class="k">)</span>,addr<span class="o">=</span><span class="k">$(</span>KERNEL_ENTRY_PA<span class="k">)</span> <span class="se">\</span>
|
||
<span class="hll"><span class="linenos">11</span> -drive <span class="nv">file</span><span class="o">=</span><span class="k">$(</span>FS_IMG<span class="k">)</span>,if<span class="o">=</span>none,format<span class="o">=</span>raw,id<span class="o">=</span>x0 <span class="se">\</span>
|
||
</span><span class="hll"><span class="linenos">12</span> -device virtio-blk-device,drive<span class="o">=</span>x0,bus<span class="o">=</span>virtio-mmio-bus.0
|
||
</span></pre></div>
|
||
</div>
|
||
<ul class="simple">
|
||
<li><p>第 11 行，我们为虚拟机添加一块虚拟硬盘，内容为我们之前通过 <code class="docutils literal notranslate"><span class="pre">easy-fs-fuse</span></code> 工具打包的包含应用 ELF 的 easy-fs 镜像，并命名为 <code class="docutils literal notranslate"><span class="pre">x0</span></code> 。</p></li>
|
||
<li><p>第 12 行，我们将硬盘 <code class="docutils literal notranslate"><span class="pre">x0</span></code> 作为一个 VirtIO 总线中的一个块设备接入到虚拟机系统中。 <code class="docutils literal notranslate"><span class="pre">virtio-mmio-bus.0</span></code> 表示 VirtIO 总线通过 MMIO 进行控制，且该块设备在总线中的编号为 0 。</p></li>
|
||
</ul>
|
||
<p><strong>内存映射 I/O</strong> (MMIO, Memory-Mapped I/O) 指通过特定的物理内存地址来访问外设的设备寄存器。查阅资料，可知 VirtIO 总线的 MMIO 物理地址区间为从 0x10001000 开头的 4KiB 。</p>
|
||
<p>在 <code class="docutils literal notranslate"><span class="pre">config</span></code> 子模块中我们硬编码 Qemu 上的 VirtIO 总线的 MMIO 地址区间（起始地址，长度）。在创建内核地址空间的时候需要建立页表映射：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/config.rs</span>
|
||
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">MMIO</span>: <span class="kp">&</span><span class="p">[(</span><span class="kt">usize</span><span class="p">,</span><span class="w"> </span><span class="kt">usize</span><span class="p">)]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&</span><span class="p">[</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">(</span><span class="mh">0x10001000</span><span class="p">,</span><span class="w"> </span><span class="mh">0x1000</span><span class="p">),</span><span class="w"></span>
|
||
<span class="p">];</span><span class="w"></span>
|
||
|
||
<span class="c1">// os/src/mm/memory_set.rs</span>
|
||
|
||
<span class="k">use</span><span class="w"> </span><span class="k">crate</span>::<span class="n">config</span>::<span class="n">MMIO</span><span class="p">;</span><span class="w"></span>
|
||
|
||
<span class="k">impl</span><span class="w"> </span><span class="n">MemorySet</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="sd">/// Without kernel stacks.</span>
|
||
<span class="w"> </span><span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">new_kernel</span><span class="p">()</span><span class="w"> </span>-> <span class="nc">Self</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="o">..</span><span class="p">.</span><span class="w"></span>
|
||
<span class="w"> </span><span class="fm">println!</span><span class="p">(</span><span class="s">"mapping memory-mapped registers"</span><span class="p">);</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="n">pair</span><span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="n">MMIO</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">memory_set</span><span class="p">.</span><span class="n">push</span><span class="p">(</span><span class="n">MapArea</span>::<span class="n">new</span><span class="p">(</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">(</span><span class="o">*</span><span class="n">pair</span><span class="p">).</span><span class="mf">0.</span><span class="n">into</span><span class="p">(),</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">((</span><span class="o">*</span><span class="n">pair</span><span class="p">).</span><span class="mi">0</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">(</span><span class="o">*</span><span class="n">pair</span><span class="p">).</span><span class="mi">1</span><span class="p">).</span><span class="n">into</span><span class="p">(),</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">MapType</span>::<span class="n">Identical</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">MapPermission</span>::<span class="n">R</span><span class="w"> </span><span class="o">|</span><span class="w"> </span><span class="n">MapPermission</span>::<span class="n">W</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">),</span><span class="w"> </span><span class="nb">None</span><span class="p">);</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">memory_set</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>这里我们进行的是透明的恒等映射，让内核可以兼容于直接访问物理地址的设备驱动库。</p>
|
||
<p>由于设备驱动的开发过程比较琐碎，我们这里直接使用已有的 <a class="reference external" href="https://github.com/rcore-os/virtio-drivers">virtio-drivers</a> crate，感兴趣的同学可以自行了解。</p>
|
||
</div>
|
||
<div class="section" id="id2">
|
||
<h2>内核索引节点层<a class="headerlink" href="#id2" title="永久链接至标题">¶</a></h2>
|
||
<p>内核将 <code class="docutils literal notranslate"><span class="pre">easy-fs</span></code> 提供的 <code class="docutils literal notranslate"><span class="pre">Inode</span></code> 进一步封装为 OS 中的索引节点 <code class="docutils literal notranslate"><span class="pre">OSInode</span></code> 。</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/fs/inode.rs</span>
|
||
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">struct</span> <span class="nc">OSInode</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">readable</span>: <span class="kt">bool</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">writable</span>: <span class="kt">bool</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inner</span>: <span class="nc">UPSafeCell</span><span class="o"><</span><span class="n">OSInodeInner</span><span class="o">></span><span class="p">,</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">struct</span> <span class="nc">OSInodeInner</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">offset</span>: <span class="kt">usize</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inode</span>: <span class="nc">Arc</span><span class="o"><</span><span class="n">Inode</span><span class="o">></span><span class="p">,</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p><code class="docutils literal notranslate"><span class="pre">OSInode</span></code> 就表示进程中一个被打开的常规文件或目录。 <code class="docutils literal notranslate"><span class="pre">readable/writable</span></code> 分别表明该文件是否允许通过 <code class="docutils literal notranslate"><span class="pre">sys_read/write</span></code> 进行读写，读写过程中的偏移量 <code class="docutils literal notranslate"><span class="pre">offset</span></code> 和 <code class="docutils literal notranslate"><span class="pre">Inode</span></code> 则加上互斥锁丢到 <code class="docutils literal notranslate"><span class="pre">OSInodeInner</span></code> 中。</p>
|
||
</div>
|
||
<div class="section" id="id3">
|
||
<h2>文件描述符层<a class="headerlink" href="#id3" title="永久链接至标题">¶</a></h2>
|
||
<p><code class="docutils literal notranslate"><span class="pre">OSInode</span></code> 也是要一种要放到进程文件描述符表中，通过 <code class="docutils literal notranslate"><span class="pre">sys_read/write</span></code> 进行读写的文件，我们需要为它实现 <code class="docutils literal notranslate"><span class="pre">File</span></code> Trait ：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/fs/inode.rs</span>
|
||
|
||
<span class="k">impl</span><span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="n">OSInode</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">fn</span> <span class="nf">readable</span><span class="p">(</span><span class="o">&</span><span class="bp">self</span><span class="p">)</span><span class="w"> </span>-> <span class="kt">bool</span> <span class="p">{</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">readable</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">fn</span> <span class="nf">writable</span><span class="p">(</span><span class="o">&</span><span class="bp">self</span><span class="p">)</span><span class="w"> </span>-> <span class="kt">bool</span> <span class="p">{</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">writable</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">fn</span> <span class="nf">read</span><span class="p">(</span><span class="o">&</span><span class="bp">self</span><span class="p">,</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">buf</span>: <span class="nc">UserBuffer</span><span class="p">)</span><span class="w"> </span>-> <span class="kt">usize</span> <span class="p">{</span><span class="w"></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">inner</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">inner</span><span class="p">.</span><span class="n">lock</span><span class="p">();</span><span class="w"></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">total_read_size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="k">usize</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="n">slice</span><span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="n">buf</span><span class="p">.</span><span class="n">buffers</span><span class="p">.</span><span class="n">iter_mut</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">read_size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">inner</span><span class="p">.</span><span class="n">inode</span><span class="p">.</span><span class="n">read_at</span><span class="p">(</span><span class="n">inner</span><span class="p">.</span><span class="n">offset</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">slice</span><span class="p">);</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">read_size</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="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inner</span><span class="p">.</span><span class="n">offset</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">read_size</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">total_read_size</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">read_size</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">total_read_size</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">fn</span> <span class="nf">write</span><span class="p">(</span><span class="o">&</span><span class="bp">self</span><span class="p">,</span><span class="w"> </span><span class="n">buf</span>: <span class="nc">UserBuffer</span><span class="p">)</span><span class="w"> </span>-> <span class="kt">usize</span> <span class="p">{</span><span class="w"></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">inner</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">inner</span><span class="p">.</span><span class="n">lock</span><span class="p">();</span><span class="w"></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">total_write_size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="k">usize</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="n">slice</span><span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="n">buf</span><span class="p">.</span><span class="n">buffers</span><span class="p">.</span><span class="n">iter</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">write_size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">inner</span><span class="p">.</span><span class="n">inode</span><span class="p">.</span><span class="n">write_at</span><span class="p">(</span><span class="n">inner</span><span class="p">.</span><span class="n">offset</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">slice</span><span class="p">);</span><span class="w"></span>
|
||
<span class="w"> </span><span class="fm">assert_eq!</span><span class="p">(</span><span class="n">write_size</span><span class="p">,</span><span class="w"> </span><span class="n">slice</span><span class="p">.</span><span class="n">len</span><span class="p">());</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inner</span><span class="p">.</span><span class="n">offset</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">write_size</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">total_write_size</span><span class="w"> </span><span class="o">+=</span><span class="w"> </span><span class="n">write_size</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">total_write_size</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p><code class="docutils literal notranslate"><span class="pre">read/write</span></code> 的实现也比较简单，只需遍历 <code class="docutils literal notranslate"><span class="pre">UserBuffer</span></code> 中的每个缓冲区片段，调用 <code class="docutils literal notranslate"><span class="pre">Inode</span></code> 写好的 <code class="docutils literal notranslate"><span class="pre">read/write_at</span></code> 接口就好了。注意 <code class="docutils literal notranslate"><span class="pre">read/write_at</span></code> 的起始位置是在 <code class="docutils literal notranslate"><span class="pre">OSInode</span></code> 中维护的 <code class="docutils literal notranslate"><span class="pre">offset</span></code> ，这个 <code class="docutils literal notranslate"><span class="pre">offset</span></code> 也随着遍历的进行被持续更新。在 <code class="docutils literal notranslate"><span class="pre">read/write</span></code> 的全程需要获取 <code class="docutils literal notranslate"><span class="pre">OSInode</span></code> 的互斥锁，保证两个进程无法同时访问同个文件。</p>
|
||
<p>本章我们为 <code class="docutils literal notranslate"><span class="pre">File</span></code> Trait 新增了 <code class="docutils literal notranslate"><span class="pre">readable/writable</span></code> 两个抽象接口，从而在 <code class="docutils literal notranslate"><span class="pre">sys_read/sys_write</span></code> 的时候进行简单的访问权限检查。</p>
|
||
</div>
|
||
<div class="section" id="id4">
|
||
<h2>文件系统相关内核机制实现<a class="headerlink" href="#id4" title="永久链接至标题">¶</a></h2>
|
||
<div class="section" id="id5">
|
||
<h3>文件系统初始化<a class="headerlink" href="#id5" title="永久链接至标题">¶</a></h3>
|
||
<p>为了使用 <code class="docutils literal notranslate"><span class="pre">easy-fs</span></code> 提供的抽象，内核需要进行一些初始化操作。我们需要从块设备 <code class="docutils literal notranslate"><span class="pre">BLOCK_DEVICE</span></code> 上打开文件系统，并从文件系统中获取根目录的 inode 。</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/fs/inode.rs</span>
|
||
|
||
<span class="n">lazy_static</span><span class="o">!</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">pub</span><span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="k">ref</span><span class="w"> </span><span class="n">ROOT_INODE</span>: <span class="nc">Arc</span><span class="o"><</span><span class="n">Inode</span><span class="o">></span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">efs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">EasyFileSystem</span>::<span class="n">open</span><span class="p">(</span><span class="n">BLOCK_DEVICE</span><span class="p">.</span><span class="n">clone</span><span class="p">());</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">Arc</span>::<span class="n">new</span><span class="p">(</span><span class="n">EasyFileSystem</span>::<span class="n">root_inode</span><span class="p">(</span><span class="o">&</span><span class="n">efs</span><span class="p">))</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">};</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>这之后就可以使用根目录的 inode <code class="docutils literal notranslate"><span class="pre">ROOT_INODE</span></code> ，在内核中调用 <code class="docutils literal notranslate"><span class="pre">easy-fs</span></code> 的相关接口了。例如，在文件系统初始化完毕之后，调用 <code class="docutils literal notranslate"><span class="pre">list_apps</span></code> 函数来打印所有可用应用的文件名：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/fs/inode.rs</span>
|
||
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">list_apps</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="fm">println!</span><span class="p">(</span><span class="s">"/**** APPS ****"</span><span class="p">);</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="n">app</span><span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="n">ROOT_INODE</span><span class="p">.</span><span class="n">ls</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></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="n">app</span><span class="p">);</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></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="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
</div>
|
||
<div class="section" id="sys-open">
|
||
<h3>通过 sys_open 打开文件<a class="headerlink" href="#sys-open" title="永久链接至标题">¶</a></h3>
|
||
<p>在内核中也定义一份打开文件的标志 <code class="docutils literal notranslate"><span class="pre">OpenFlags</span></code> ：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/fs/inode.rs</span>
|
||
|
||
<span class="n">bitflags</span><span class="o">!</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">pub</span><span class="w"> </span><span class="k">struct</span> <span class="nc">OpenFlags</span>: <span class="kt">u32</span> <span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">RDONLY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">WRONLY</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">RDWR</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">CREATE</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="mi">9</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">TRUNC</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="mi">10</span><span class="p">;</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
|
||
<span class="k">impl</span><span class="w"> </span><span class="n">OpenFlags</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="sd">/// Do not check validity for simplicity</span>
|
||
<span class="w"> </span><span class="sd">/// Return (readable, writable)</span>
|
||
<span class="w"> </span><span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">read_write</span><span class="p">(</span><span class="o">&</span><span class="bp">self</span><span class="p">)</span><span class="w"> </span>-> <span class="p">(</span><span class="kt">bool</span><span class="p">,</span><span class="w"> </span><span class="kt">bool</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="bp">self</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="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">,</span><span class="w"> </span><span class="kc">false</span><span class="p">)</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">contains</span><span class="p">(</span><span class="bp">Self</span>::<span class="n">WRONLY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">(</span><span class="kc">false</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w"></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="w"> </span><span class="p">(</span><span class="kc">true</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">)</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>它的 <code class="docutils literal notranslate"><span class="pre">read_write</span></code> 方法可以根据标志的情况返回要打开的文件是否允许读写。简单起见，这里假设标志自身一定合法。</p>
|
||
<p>接着，我们实现 <code class="docutils literal notranslate"><span class="pre">open_file</span></code> 内核函数，可根据文件名打开一个根目录下的文件：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/fs/inode.rs</span>
|
||
|
||
<span class="k">pub</span><span class="w"> </span><span class="k">fn</span> <span class="nf">open_file</span><span class="p">(</span><span class="n">name</span>: <span class="kp">&</span><span class="kt">str</span><span class="p">,</span><span class="w"> </span><span class="n">flags</span>: <span class="nc">OpenFlags</span><span class="p">)</span><span class="w"> </span>-> <span class="nb">Option</span><span class="o"><</span><span class="n">Arc</span><span class="o"><</span><span class="n">OSInode</span><span class="o">>></span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="p">(</span><span class="n">readable</span><span class="p">,</span><span class="w"> </span><span class="n">writable</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">flags</span><span class="p">.</span><span class="n">read_write</span><span class="p">();</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">flags</span><span class="p">.</span><span class="n">contains</span><span class="p">(</span><span class="n">OpenFlags</span>::<span class="n">CREATE</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">inode</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ROOT_INODE</span><span class="p">.</span><span class="n">find</span><span class="p">(</span><span class="n">name</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="c1">// clear size</span>
|
||
<span class="w"> </span><span class="n">inode</span><span class="p">.</span><span class="n">clear</span><span class="p">();</span><span class="w"></span>
|
||
<span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">Arc</span>::<span class="n">new</span><span class="p">(</span><span class="n">OSInode</span>::<span class="n">new</span><span class="p">(</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">readable</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">writable</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inode</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">)))</span><span class="w"></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="w"> </span><span class="c1">// create file</span>
|
||
<span class="w"> </span><span class="n">ROOT_INODE</span><span class="p">.</span><span class="n">create</span><span class="p">(</span><span class="n">name</span><span class="p">)</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">.</span><span class="n">map</span><span class="p">(</span><span class="o">|</span><span class="n">inode</span><span class="o">|</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">Arc</span>::<span class="n">new</span><span class="p">(</span><span class="n">OSInode</span>::<span class="n">new</span><span class="p">(</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">readable</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">writable</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inode</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">))</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">})</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></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="w"> </span><span class="n">ROOT_INODE</span><span class="p">.</span><span class="n">find</span><span class="p">(</span><span class="n">name</span><span class="p">)</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">.</span><span class="n">map</span><span class="p">(</span><span class="o">|</span><span class="n">inode</span><span class="o">|</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">flags</span><span class="p">.</span><span class="n">contains</span><span class="p">(</span><span class="n">OpenFlags</span>::<span class="n">TRUNC</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inode</span><span class="p">.</span><span class="n">clear</span><span class="p">();</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">Arc</span>::<span class="n">new</span><span class="p">(</span><span class="n">OSInode</span>::<span class="n">new</span><span class="p">(</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">readable</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">writable</span><span class="p">,</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">inode</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">))</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">})</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>这里主要是实现了 <code class="docutils literal notranslate"><span class="pre">OpenFlags</span></code> 各标志位的语义。例如只有 <code class="docutils literal notranslate"><span class="pre">flags</span></code> 参数包含 <cite>CREATE</cite> 标志位才允许创建文件；而如果文件已经存在，则清空文件的内容。</p>
|
||
<p>在其基础上， <code class="docutils literal notranslate"><span class="pre">sys_open</span></code> 也就很容易实现了。</p>
|
||
</div>
|
||
<div class="section" id="sys-exec">
|
||
<h3>通过 sys_exec 加载并执行应用<a class="headerlink" href="#sys-exec" title="永久链接至标题">¶</a></h3>
|
||
<p>有了文件系统支持后， <code class="docutils literal notranslate"><span class="pre">sys_exec</span></code> 所需的表示应用 ELF 格式数据改为从文件系统中获取：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="linenos"> 1</span><span class="c1">// os/src/syscall/process.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">sys_exec</span><span class="p">(</span><span class="n">path</span>: <span class="o">*</span><span class="k">const</span><span class="w"> </span><span class="kt">u8</span><span class="p">,</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">args</span>: <span class="o">*</span><span class="k">const</span><span class="w"> </span><span class="kt">usize</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="kd">let</span><span class="w"> </span><span class="n">token</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current_user_token</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos"> 5</span><span class="kd">let</span><span class="w"> </span><span class="n">path</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">translated_str</span><span class="p">(</span><span class="n">token</span><span class="p">,</span><span class="w"> </span><span class="n">path</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos"> 6</span><span class="kd">let</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">args_vec</span>: <span class="nb">Vec</span><span class="o"><</span><span class="nb">String</span><span class="o">></span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Vec</span>::<span class="n">new</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos"> 7</span><span class="k">loop</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos"> 8</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">arg_str_ptr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">translated_ref</span><span class="p">(</span><span class="n">token</span><span class="p">,</span><span class="w"> </span><span class="n">args</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos"> 9</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="n">arg_str_ptr</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">10</span><span class="w"> </span><span class="k">break</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">11</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">12</span><span class="w"> </span><span class="n">args_vec</span><span class="p">.</span><span class="n">push</span><span class="p">(</span><span class="n">translated_str</span><span class="p">(</span><span class="n">token</span><span class="p">,</span><span class="w"> </span><span class="n">arg_str_ptr</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="o">*</span><span class="k">const</span><span class="w"> </span><span class="kt">u8</span><span class="p">));</span><span class="w"></span>
|
||
<span class="linenos">13</span><span class="w"> </span><span class="k">unsafe</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">14</span><span class="w"> </span><span class="n">args</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">args</span><span class="p">.</span><span class="n">add</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">15</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">16</span><span class="p">}</span><span class="w"></span>
|
||
<span class="hll"><span class="linenos">17</span><span class="k">if</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">app_inode</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">open_file</span><span class="p">(</span><span class="n">path</span><span class="p">.</span><span class="n">as_str</span><span class="p">(),</span><span class="w"> </span><span class="n">OpenFlags</span>::<span class="n">RDONLY</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
</span><span class="hll"><span class="linenos">18</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">all_data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">app_inode</span><span class="p">.</span><span class="n">read_all</span><span class="p">();</span><span class="w"></span>
|
||
</span><span class="hll"><span class="linenos">19</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">task</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">current_task</span><span class="p">().</span><span class="n">unwrap</span><span class="p">();</span><span class="w"></span>
|
||
</span><span class="hll"><span class="linenos">20</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">argc</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">args_vec</span><span class="p">.</span><span class="n">len</span><span class="p">();</span><span class="w"></span>
|
||
</span><span class="hll"><span class="linenos">21</span><span class="w"> </span><span class="n">task</span><span class="p">.</span><span class="n">exec</span><span class="p">(</span><span class="n">all_data</span><span class="p">.</span><span class="n">as_slice</span><span class="p">(),</span><span class="w"> </span><span class="n">args_vec</span><span class="p">);</span><span class="w"></span>
|
||
</span><span class="hll"><span class="linenos">22</span><span class="w"> </span><span class="n">argc</span><span class="w"> </span><span class="k">as</span><span class="w"> </span><span class="kt">isize</span><span class="w"></span>
|
||
</span><span class="hll"><span class="linenos">23</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><span class="hll"><span class="linenos">24</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="w"></span>
|
||
</span><span class="hll"><span class="linenos">25</span><span class="p">}</span><span class="w"></span>
|
||
</span></pre></div>
|
||
</div>
|
||
<p>注意上面代码片段中的高亮部分。当执行获取应用的 ELF 数据的操作时，首先调用 <code class="docutils literal notranslate"><span class="pre">open_file</span></code> 函数，以只读的方式在内核中打开应用文件并获取它对应的 <code class="docutils literal notranslate"><span class="pre">OSInode</span></code> 。接下来可以通过 <code class="docutils literal notranslate"><span class="pre">OSInode::read_all</span></code> 将该文件的数据全部读到一个向量 <code class="docutils literal notranslate"><span class="pre">all_data</span></code> 中：</p>
|
||
<p>之后，就可以从向量 <code class="docutils literal notranslate"><span class="pre">all_data</span></code> 中拿到应用中的 ELF 数据，当解析完毕并创建完应用地址空间后该向量将会被回收。</p>
|
||
<p>同样的，我们在内核中创建初始进程 <code class="docutils literal notranslate"><span class="pre">initproc</span></code> 也需要替换为基于文件系统的实现：</p>
|
||
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="c1">// os/src/task/mod.rs</span>
|
||
|
||
<span class="n">lazy_static</span><span class="o">!</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="w"> </span><span class="k">pub</span><span class="w"> </span><span class="k">static</span><span class="w"> </span><span class="k">ref</span><span class="w"> </span><span class="n">INITPROC</span>: <span class="nc">Arc</span><span class="o"><</span><span class="n">TaskControlBlock</span><span class="o">></span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arc</span>::<span class="n">new</span><span class="p">({</span><span class="w"></span>
|
||
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">inode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">open_file</span><span class="p">(</span><span class="s">"ch6b_initproc"</span><span class="p">,</span><span class="w"> </span><span class="n">OpenFlags</span>::<span class="n">RDONLY</span><span class="p">).</span><span class="n">unwrap</span><span class="p">();</span><span class="w"></span>
|
||
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">v</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">inode</span><span class="p">.</span><span class="n">read_all</span><span class="p">();</span><span class="w"></span>
|
||
<span class="w"> </span><span class="n">TaskControlBlock</span>::<span class="n">new</span><span class="p">(</span><span class="n">v</span><span class="p">.</span><span class="n">as_slice</span><span class="p">())</span><span class="w"></span>
|
||
<span class="w"> </span><span class="p">});</span><span class="w"></span>
|
||
<span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
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<li><a class="reference internal" href="#id1">块设备驱动层</a></li>
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