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Signed in as <strong class="css-truncate-target">stephenxs</strong>
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Your profile
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Your stars
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<li><a class="dropdown-item" href="https://gist.github.com/" data-ga-click="Header, your gists, text:your gists">Your gists</a></li>
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Help
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Sign out
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Unwatch
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<a class="social-count js-social-count"
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href="/stephenxs/TranslateProject/watchers"
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aria-label="1 user is watching this repository">
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1
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<div class="select-menu-modal-holder">
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<div class="select-menu-modal subscription-menu-modal js-menu-content">
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<svg class="octicon octicon-x js-menu-close" role="img" aria-label="Close" viewBox="0 0 12 16" version="1.1" width="12" height="16"><path fill-rule="evenodd" d="M7.48 8l3.75 3.75-1.48 1.48L6 9.48l-3.75 3.75-1.48-1.48L4.52 8 .77 4.25l1.48-1.48L6 6.52l3.75-3.75 1.48 1.48L7.48 8z"/></svg>
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<span class="select-menu-title">Notifications</span>
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<div class="select-menu-item js-navigation-item " role="menuitem" tabindex="0">
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<span class="js-select-button-text hidden-select-button-text">
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<svg class="octicon octicon-eye" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M8.06 2C3 2 0 8 0 8s3 6 8.06 6C13 14 16 8 16 8s-3-6-7.94-6zM8 12c-2.2 0-4-1.78-4-4 0-2.2 1.8-4 4-4 2.22 0 4 1.8 4 4 0 2.22-1.78 4-4 4zm2-4c0 1.11-.89 2-2 2-1.11 0-2-.89-2-2 0-1.11.89-2 2-2 1.11 0 2 .89 2 2z"/></svg>
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Watch
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<div class="select-menu-item js-navigation-item selected" role="menuitem" tabindex="0">
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<svg class="octicon octicon-check select-menu-item-icon" viewBox="0 0 12 16" version="1.1" width="12" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M12 5l-8 8-4-4 1.5-1.5L4 10l6.5-6.5L12 5z"/></svg>
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<span class="select-menu-item-heading">Watching</span>
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<span class="description">Be notified of all conversations.</span>
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<span class="js-select-button-text hidden-select-button-text">
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<svg class="octicon octicon-eye" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M8.06 2C3 2 0 8 0 8s3 6 8.06 6C13 14 16 8 16 8s-3-6-7.94-6zM8 12c-2.2 0-4-1.78-4-4 0-2.2 1.8-4 4-4 2.22 0 4 1.8 4 4 0 2.22-1.78 4-4 4zm2-4c0 1.11-.89 2-2 2-1.11 0-2-.89-2-2 0-1.11.89-2 2-2 1.11 0 2 .89 2 2z"/></svg>
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Unwatch
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</span>
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</div>
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<div class="select-menu-item js-navigation-item " role="menuitem" tabindex="0">
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<svg class="octicon octicon-check select-menu-item-icon" viewBox="0 0 12 16" version="1.1" width="12" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M12 5l-8 8-4-4 1.5-1.5L4 10l6.5-6.5L12 5z"/></svg>
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<div class="select-menu-item-text">
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<input type="radio" name="do" id="do_ignore" value="ignore" />
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<span class="select-menu-item-heading">Ignoring</span>
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<span class="description">Never be notified.</span>
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<span class="js-select-button-text hidden-select-button-text">
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<svg class="octicon octicon-mute" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M8 2.81v10.38c0 .67-.81 1-1.28.53L3 10H1c-.55 0-1-.45-1-1V7c0-.55.45-1 1-1h2l3.72-3.72C7.19 1.81 8 2.14 8 2.81zm7.53 3.22l-1.06-1.06-1.97 1.97-1.97-1.97-1.06 1.06L11.44 8 9.47 9.97l1.06 1.06 1.97-1.97 1.97 1.97 1.06-1.06L13.56 8l1.97-1.97z"/></svg>
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Stop ignoring
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Unstar
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<a class="social-count js-social-count" href="/stephenxs/TranslateProject/stargazers"
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aria-label="0 users starred this repository">
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0
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<!-- '"` --><!-- </textarea></xmp> --></option></form><form class="unstarred js-social-form" action="/stephenxs/TranslateProject/star" accept-charset="UTF-8" method="post"><input name="utf8" type="hidden" value="✓" /><input type="hidden" name="authenticity_token" value="T+FQvVQQsz4wWUuqwveR/qoyXWYso2lO8JY57LzQgbgtkj5GbHawWd3Bo2iAoNegMTXt/lwMV06CaSZwv+9/ng==" />
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<svg class="octicon octicon-star" viewBox="0 0 14 16" version="1.1" width="14" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M14 6l-4.9-.64L7 1 4.9 5.36 0 6l3.6 3.26L2.67 14 7 11.67 11.33 14l-.93-4.74L14 6z"/></svg>
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Star
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<a class="social-count js-social-count" href="/stephenxs/TranslateProject/stargazers"
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0
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Fork
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<a href="/stephenxs/TranslateProject/network" class="social-count"
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114
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<h1 class="public ">
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<svg class="octicon octicon-repo-forked" viewBox="0 0 10 16" version="1.1" width="10" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M8 1a1.993 1.993 0 0 0-1 3.72V6L5 8 3 6V4.72A1.993 1.993 0 0 0 2 1a1.993 1.993 0 0 0-1 3.72V6.5l3 3v1.78A1.993 1.993 0 0 0 5 15a1.993 1.993 0 0 0 1-3.72V9.5l3-3V4.72A1.993 1.993 0 0 0 8 1zM2 4.2C1.34 4.2.8 3.65.8 3c0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2zm3 10c-.66 0-1.2-.55-1.2-1.2 0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2zm3-10c-.66 0-1.2-.55-1.2-1.2 0-.65.55-1.2 1.2-1.2.65 0 1.2.55 1.2 1.2 0 .65-.55 1.2-1.2 1.2z"/></svg>
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<span class="author" itemprop="author"><a class="url fn" rel="author" href="/stephenxs">stephenxs</a></span><!--
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--><span class="path-divider">/</span><!--
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--><strong itemprop="name"><a data-pjax="#js-repo-pjax-container" href="/stephenxs/TranslateProject">TranslateProject</a></strong>
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<span class="fork-flag">
|
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<span class="text">forked from <a href="/LCTT/TranslateProject">LCTT/TranslateProject</a></span>
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<nav class="reponav js-repo-nav js-sidenav-container-pjax container"
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<span itemprop="name">Code</span>
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<meta itemprop="position" content="1">
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<span itemprop="name">Pull requests</span>
|
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<span class="Counter">0</span>
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<meta itemprop="position" content="3">
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|
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<a data-hotkey="g b" class="js-selected-navigation-item reponav-item" data-selected-links="repo_projects new_repo_project repo_project /stephenxs/TranslateProject/projects" href="/stephenxs/TranslateProject/projects">
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Projects
|
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<span class="Counter" >0</span>
|
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</a>
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<article class="markdown-body entry-content" itemprop="text"><h1><a id="user-content-调试器到底怎样工作" class="anchor" aria-hidden="true" href="#调试器到底怎样工作"><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>调试器到底怎样工作</h1>
|
||
<p><a target="_blank" href="https://camo.githubusercontent.com/e33ffd6db8be59b39c4e0e25aa88c19f083a4134/68747470733a2f2f6f70656e736f757263652e636f6d2f73697465732f64656661756c742f66696c65732f7374796c65732f696d6167652d66756c6c2d73697a652f7075626c69632f6c6561642d696d616765732f616e6e6f79696e67627567732e706e673f69746f6b3d7977465a39394773"><img src="https://camo.githubusercontent.com/e33ffd6db8be59b39c4e0e25aa88c19f083a4134/68747470733a2f2f6f70656e736f757263652e636f6d2f73697465732f64656661756c742f66696c65732f7374796c65732f696d6167652d66756c6c2d73697a652f7075626c69632f6c6561642d696d616765732f616e6e6f79696e67627567732e706e673f69746f6b3d7977465a39394773" alt="" data-canonical-src="https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/annoyingbugs.png?itok=ywFZ99Gs" style="max-width:100%;"></a></p>
|
||
<p>供图：opensource.com</p>
|
||
<p>调试器是那些大多数（即使不是每个）开发人员在软件工程职业生涯中至少使用过一次的软件之一，但是你们中有多少人知道它们到底是如何工作的？我在悉尼 <a href="https://linux.conf.au/index.html" rel="nofollow">linux.conf.au 2018</a> 的演讲中，将讨论从头开始编写调试器...使用 <a href="https://www.rust-lang.org" rel="nofollow">Rust</a>！</p>
|
||
<p>在本文中，术语调试器/跟踪器可以互换。 “被跟踪者”是指正在被跟踪者跟踪的进程。</p>
|
||
<h3><a id="user-content-ptrace-系统调用" class="anchor" aria-hidden="true" href="#ptrace-系统调用"><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>ptrace 系统调用</h3>
|
||
<p>大多数调试器严重依赖称为 <code>ptrace(2)</code> 的系统调用，其原型如下：</p>
|
||
<pre><code>long ptrace(enum __ptrace_request request, pid_t pid, void *addr, void *data);
|
||
</code></pre>
|
||
<p>这是一个可以操纵进程几乎所有方面的系统调用；但是，在调试器可以连接到一个进程之前，“被跟踪者”必须以请求 <code>PTRACE_TRACEME</code> 调用 <code>ptrace</code>。这告诉 Linux，父进程通过 <code>ptrace</code> 连接到这个进程是合法的。但是......我们如何强制一个进程调用 <code>ptrace</code>？很简单！<code>fork/execve</code> 提供了在 <code>fork</code> 之后但在被跟踪者真正开始使用 <code>execve</code> 之前调用 <code>ptrace</code> 的简单方法。很方便地，<code>fork</code> 还会返回被跟踪者的 <code>pid</code>，这是后面使用 <code>ptrace</code> 所必需的。</p>
|
||
<p>现在被跟踪者可以被调试器追踪，重要的变化发生了：</p>
|
||
<ul>
|
||
<li>每当一个信号被传送到被调试者时，它就会停止，并且一个可以被 <code>wait</code> 系列系统调用捕获的等待事件被传送给跟踪器。</li>
|
||
<li>每个 <code>execve</code> 系统调用都会导致 <code>SIGTRAP</code> 被传递给被跟踪者。（与之前的项目相结合，这意味着被跟踪者在一个 <code>execve</code> 完全发生之前停止。）</li>
|
||
</ul>
|
||
<p>这意味着，一旦我们发出 <code>PTRACE_TRACEME</code> 请求并调用 <code>execve</code> 系统调用来实际在被跟踪者（进程上下文）中启动程序时，被跟踪者将立即停止，因为 <code>execve</code> 会传递一个 <code>SIGTRAP</code>，并且会被跟踪器中的等待事件捕获。我们如何继续？正如人们所期望的那样，<code>ptrace</code> 有大量的请求可以用来告诉被跟踪者可以继续：</p>
|
||
<ul>
|
||
<li><code>PTRACE_CONT</code>：这是最简单的。 被跟踪者运行，直到它接收到一个信号，此时等待事件被传递给跟踪器。这是最常见的实现真实世界调试器的“继续直至断点”和“永远继续”选项的方式。断点将在下面介绍。</li>
|
||
<li><code>PTRACE_SYSCALL</code>：与 <code>PTRACE_CONT</code> 非常相似，但在进入系统调用之前以及在系统调用返回到用户空间之前停止。它可以与其他请求（我们将在本文后面介绍）结合使用来监视和修改系统调用的参数或返回值。系统调用追踪程序 <code>strace</code> 很大程度上使用这个请求来获知进程发起了哪些系统调用。</li>
|
||
<li><code>PTRACE_SINGLESTEP</code>：这个很好理解。如果您之前使用过调试器（你会知道），此请求会执行下一条指令，然后立即停止。</li>
|
||
</ul>
|
||
<p>我们可以通过各种各样的请求停止进程，但我们如何获得被调试者的状态？进程的状态大多是通过其寄存器捕获的，所以当然 <code>ptrace</code> 有一个请求来获得（或修改）寄存器：</p>
|
||
<ul>
|
||
<li><code>PTRACE_GETREGS</code>：这个请求将给出被跟踪者刚刚被停止时的寄存器的状态。</li>
|
||
<li><code>PTRACE_SETREGS</code>：如果跟踪器之前通过调用 <code>PTRACE_GETREGS</code> 得到了寄存器的值，它可以在参数结构中修改相应寄存器的值并使用 <code>PTRACE_SETREGS</code> 将寄存器设为新值。</li>
|
||
<li><code>PTRACE_PEEKUSER</code> 和 <code>PTRACE_POKEUSER</code>：这些允许从被跟踪者的 <code>USER</code> 区读取信息，这里保存了寄存器和其他有用的信息。 这可以用来修改单一寄存器，而避免使用更重的 <code>PTRACE_{GET,SET}REGS</code> 请求。</li>
|
||
</ul>
|
||
<p>在调试器仅仅修改寄存器是不够的。调试器有时需要读取一部分内存，甚至对其进行修改。GDB 可以使用 <code>print</code> 得到一个内存位置或变量的值。<code>ptrace</code> 通过下面的方法实现这个功能：</p>
|
||
<ul>
|
||
<li><code>PTRACE_PEEKTEXT</code> 和 <code>PTRACE_POKETEXT</code>：这些允许读取和写入被跟踪者地址空间中的一个字。当然，使用这个功能时被跟踪者要被暂停。</li>
|
||
</ul>
|
||
<p>真实世界的调试器也有类似断点和观察点的功能。 在接下来的部分中，我将深入体系结构对调试器支持的细节。为了清晰和简洁，本文将只考虑x86。</p>
|
||
<h3><a id="user-content-体系结构的支持" class="anchor" aria-hidden="true" href="#体系结构的支持"><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>体系结构的支持</h3>
|
||
<p><code>ptrace</code> 很酷，但它是如何工作？ 在前面的部分中，我们已经看到 <code>ptrace</code> 跟信号有很大关系：<code>SIGTRAP</code> 可以在单步跟踪、<code>execve</code> 之前以及系统调用前后被传送。信号可以通过一些方式产生，但我们将研究两个具体的例子，以展示信号可以被调试器用来在给定的位置停止程序（有效地创建一个断点！）：</p>
|
||
<ul>
|
||
<li>
|
||
<p><strong>未定义的指令</strong>：当一个进程尝试执行一个未定义的指令，CPU 将产生一个异常。此异常通过 CPU 中断处理，内核中相应的中断处理程序被调用。这将导致一个 <code>SIGILL</code> 信号被发送给进程。 这依次导致进程被停止，跟踪器通过一个等待事件被通知，然后它可以决定后面做什么。在 x86 上，指令 <code>ud2</code> 被确保始终是未定义的。</p>
|
||
</li>
|
||
<li>
|
||
<p><strong>调试中断</strong>：前面的方法的问题是，<code>ud2</code> 指令需要占用两个字节的机器码。存在一条特殊的单字节指令能够触发一个中断，它是 <code>int $3</code>，机器码是 <code>0xCC</code>。 当该中断发出时，内核向进程发送一个 <code>SIGTRAP</code>，如前所述，跟踪器被通知。</p>
|
||
</li>
|
||
</ul>
|
||
<p>这很好，但如何做我们胁迫的被跟踪者执行这些指令？ 这很简单：利用 <code>ptrace</code> 的 <code>PTRACE_POKETEXT</code> 请求，它可以覆盖内存中的一个字。 调试器将使用 <code>PTRACE_PEEKTEXT</code> 读取该位置原来的值并替换为 <code>0xCC</code> ，然后在其内部状态中记录该处原来的值，以及它是一个断点的事实。 下次被跟踪者执行到该位置时，它将被通过 <code>SIGTRAP</code> 信号自动停止。 然后调试器的最终用户可以决定如何继续（例如，检查寄存器）。</p>
|
||
<p>好吧，我们已经讲过了断点，那观察点呢？ 当一个特定的内存位置被读或写，调试器如何停止程序？ 当然你不可能为了能够读或写内存而去把每一个指令都覆盖为 <code>int $3</code>。有一组调试寄存器为了更有效的满足这个目的而被设计出来：</p>
|
||
<ul>
|
||
<li><code>DR0</code> 到 <code>DR3</code>：这些寄存器中的每个都包含一个地址（内存位置），调试器因为某种原因希望被跟踪者在那些地址那里停止。 其原因以掩码方式被设定在 <code>DR7</code> 寄存器中。</li>
|
||
<li><code>DR4</code> 和 <code>DR5</code>：这些分别是 <code>DR6</code> 和 <code>DR7</code>过时的别名。</li>
|
||
<li><code>DR6</code>：调试状态。包含有关 <code>DR0</code> 到 <code>DR3</code> 中的哪个寄存器导致调试异常被引发的信息。这被 Linux 用来计算与 <code>SIGTRAP</code> 信号一起传递给被跟踪者的信息。</li>
|
||
<li><code>DR7</code>：调试控制。通过使用这些寄存器中的位，调试器可以控制如何解释DR0至DR3中指定的地址。位掩码控制监视点的尺寸（监视1,2,4或8个字节）以及是否在执行、读取、写入时引发异常，或在读取或写入时引发异常。</li>
|
||
</ul>
|
||
<p>由于调试寄存器是进程的 <code>USER</code> 区域的一部分，调试器可以使用 <code>PTRACE_POKEUSER</code> 将值写入调试寄存器。调试寄存器只与特定进程相关，因此在进程抢占并重新获得 CPU 控制权之前，调试寄存器会被恢复。</p>
|
||
<h3><a id="user-content-冰山一角" class="anchor" aria-hidden="true" href="#冰山一角"><svg class="octicon octicon-link" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>冰山一角</h3>
|
||
<p>我们已经浏览了一个调试器的“冰山”：我们已经介绍了 <code>ptrace</code>，了解了它的一些功能，然后我们看到了 <code>ptrace</code> 是如何实现的。 <code>ptrace</code> 的某些部分可以用软件实现，但其它部分必须用硬件来实现，否则实现代价会非常高甚至无法实现。</p>
|
||
<p>当然有很多我们没有涉及。例如“调试器如何知道变量在内存中的位置？”等问题由于空间和时间限制而尚未解答，但我希望你从本文中学到了一些东西；如果它激起你的兴趣，网上有足够的资源可以了解更多。</p>
|
||
<p>想要了解更多，请查看 <a href="https://linux.conf.au/index.html" rel="nofollow">linux.conf.au</a> 中 Levente Kurusa 的演讲 <a href="https://rego.linux.conf.au/schedule/presentation/91/" rel="nofollow">Let's Write a Debugger!</a>，于一月 22-26 日在悉尼举办。</p>
|
||
<hr>
|
||
<p>via: <a href="https://opensource.com/article/18/1/how-debuggers-really-work" rel="nofollow">https://opensource.com/article/18/1/how-debuggers-really-work</a></p>
|
||
<p>作者：<a href="https://opensource.com/users/lkurusa" rel="nofollow">Levente Kurusa</a>
|
||
译者：<a href="https://github.com/stephenxs">stephenxs</a>
|
||
校对：<a href="https://github.com/%E6%A0%A1%E5%AF%B9%E8%80%85ID">校对者ID</a></p>
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<p>本文由 <a href="https://github.com/LCTT/TranslateProject">LCTT</a> 原创编译，<a href="https://linux.cn/" rel="nofollow">Linux中国</a> 荣誉推出</p>
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|
||
</div>
|
||
</div>
|
||
|
||
|
||
|
||
<div id="ajax-error-message" class="ajax-error-message flash flash-error">
|
||
<svg class="octicon octicon-alert" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M8.893 1.5c-.183-.31-.52-.5-.887-.5s-.703.19-.886.5L.138 13.499a.98.98 0 0 0 0 1.001c.193.31.53.501.886.501h13.964c.367 0 .704-.19.877-.5a1.03 1.03 0 0 0 .01-1.002L8.893 1.5zm.133 11.497H6.987v-2.003h2.039v2.003zm0-3.004H6.987V5.987h2.039v4.006z"/></svg>
|
||
<button type="button" class="flash-close js-ajax-error-dismiss" aria-label="Dismiss error">
|
||
<svg class="octicon octicon-x" viewBox="0 0 12 16" version="1.1" width="12" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M7.48 8l3.75 3.75-1.48 1.48L6 9.48l-3.75 3.75-1.48-1.48L4.52 8 .77 4.25l1.48-1.48L6 6.52l3.75-3.75 1.48 1.48L7.48 8z"/></svg>
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</button>
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You can’t perform that action at this time.
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</div>
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<script crossorigin="anonymous" integrity="sha512-AJroIDzeBTsez82UXWwVAmoSz2nKhws/uQvJ8aKfadJZcvL83MIXMjRYm7MVZaKSNXvifa/OGpn54kiDBKpyLw==" type="application/javascript" src="https://assets-cdn.github.com/assets/compat-37e9ce8318a51dd51033283da82c8546.js"></script>
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<script crossorigin="anonymous" integrity="sha512-yXdDCsnuszQP/Kev3bsmDhO0vw7+hDdRtqOv8ZqtWtG6pVapIqEQJ+WHntN6PU9BgXx1Y0AE386pTmd01AlSuA==" type="application/javascript" src="https://assets-cdn.github.com/assets/frameworks-215987af1fc2831b8b9806a99f0f56e0.js"></script>
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<script crossorigin="anonymous" async="async" integrity="sha512-ORJFv+MbAalu7ppD7KnNV1XdRA059ouG2bozJ6tTdAzC9xB5vIbsiCA666gJmdwwWTzMobRHzxUKn1ywp1Onrg==" type="application/javascript" src="https://assets-cdn.github.com/assets/github-7980aa5e478c118f7f44e1202dc4e18d.js"></script>
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<div class="js-stale-session-flash stale-session-flash flash flash-warn flash-banner d-none">
|
||
<svg class="octicon octicon-alert" viewBox="0 0 16 16" version="1.1" width="16" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M8.893 1.5c-.183-.31-.52-.5-.887-.5s-.703.19-.886.5L.138 13.499a.98.98 0 0 0 0 1.001c.193.31.53.501.886.501h13.964c.367 0 .704-.19.877-.5a1.03 1.03 0 0 0 .01-1.002L8.893 1.5zm.133 11.497H6.987v-2.003h2.039v2.003zm0-3.004H6.987V5.987h2.039v4.006z"/></svg>
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<span class="signed-in-tab-flash">You signed in with another tab or window. <a href="">Reload</a> to refresh your session.</span>
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<span class="signed-out-tab-flash">You signed out in another tab or window. <a href="">Reload</a> to refresh your session.</span>
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</div>
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<div class="facebox" id="facebox" style="display:none;">
|
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<div class="facebox-popup">
|
||
<div class="facebox-content" role="dialog" aria-labelledby="facebox-header" aria-describedby="facebox-description">
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</div>
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<button type="button" class="facebox-close js-facebox-close" aria-label="Close modal">
|
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<svg class="octicon octicon-x" viewBox="0 0 12 16" version="1.1" width="12" height="16" aria-hidden="true"><path fill-rule="evenodd" d="M7.48 8l3.75 3.75-1.48 1.48L6 9.48l-3.75 3.75-1.48-1.48L4.52 8 .77 4.25l1.48-1.48L6 6.52l3.75-3.75 1.48 1.48L7.48 8z"/></svg>
|
||
</button>
|
||
</div>
|
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</div>
|
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|
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<div class="Popover js-hovercard-content position-absolute" style="display: none; outline: none;" tabindex="0">
|
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<div class="Popover-message Popover-message--bottom-left Popover-message--large Box box-shadow-large" style="width:360px;">
|
||
</div>
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||
</div>
|
||
|
||
<div id="hovercard-aria-description" class="sr-only">
|
||
Press h to open a hovercard with more details.
|
||
</div>
|
||
|
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|
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</body>
|
||
</html>
|
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