mirror of
https://github.com/eunomia-bpf/bpf-developer-tutorial.git
synced 2026-02-04 02:34:16 +08:00
289 lines
22 KiB
HTML
289 lines
22 KiB
HTML
<!DOCTYPE HTML>
|
||
<html lang="en" class="sidebar-visible no-js light">
|
||
<head>
|
||
<!-- Book generated using mdBook -->
|
||
<meta charset="UTF-8">
|
||
<title>eBPF 入门开发实践教程五：在 eBPF 中使用 uprobe 捕获 bash 的 readline 函数调用 - bpf-developer-tutorial</title>
|
||
|
||
|
||
<!-- Custom HTML head -->
|
||
|
||
<meta name="description" content="">
|
||
<meta name="viewport" content="width=device-width, initial-scale=1">
|
||
<meta name="theme-color" content="#ffffff" />
|
||
|
||
<link rel="icon" href="../favicon.svg">
|
||
<link rel="shortcut icon" href="../favicon.png">
|
||
<link rel="stylesheet" href="../css/variables.css">
|
||
<link rel="stylesheet" href="../css/general.css">
|
||
<link rel="stylesheet" href="../css/chrome.css">
|
||
<link rel="stylesheet" href="../css/print.css" media="print">
|
||
|
||
<!-- Fonts -->
|
||
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
|
||
<link rel="stylesheet" href="../fonts/fonts.css">
|
||
|
||
<!-- Highlight.js Stylesheets -->
|
||
<link rel="stylesheet" href="../highlight.css">
|
||
<link rel="stylesheet" href="../tomorrow-night.css">
|
||
<link rel="stylesheet" href="../ayu-highlight.css">
|
||
|
||
<!-- Custom theme stylesheets -->
|
||
|
||
</head>
|
||
<body>
|
||
<div id="body-container">
|
||
<!-- Provide site root to javascript -->
|
||
<script>
|
||
var path_to_root = "../";
|
||
var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? "navy" : "light";
|
||
</script>
|
||
|
||
<!-- Work around some values being stored in localStorage wrapped in quotes -->
|
||
<script>
|
||
try {
|
||
var theme = localStorage.getItem('mdbook-theme');
|
||
var sidebar = localStorage.getItem('mdbook-sidebar');
|
||
|
||
if (theme.startsWith('"') && theme.endsWith('"')) {
|
||
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
|
||
}
|
||
|
||
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
|
||
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
|
||
}
|
||
} catch (e) { }
|
||
</script>
|
||
|
||
<!-- Set the theme before any content is loaded, prevents flash -->
|
||
<script>
|
||
var theme;
|
||
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
|
||
if (theme === null || theme === undefined) { theme = default_theme; }
|
||
var html = document.querySelector('html');
|
||
html.classList.remove('no-js')
|
||
html.classList.remove('light')
|
||
html.classList.add(theme);
|
||
html.classList.add('js');
|
||
</script>
|
||
|
||
<!-- Hide / unhide sidebar before it is displayed -->
|
||
<script>
|
||
var html = document.querySelector('html');
|
||
var sidebar = null;
|
||
if (document.body.clientWidth >= 1080) {
|
||
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
|
||
sidebar = sidebar || 'visible';
|
||
} else {
|
||
sidebar = 'hidden';
|
||
}
|
||
html.classList.remove('sidebar-visible');
|
||
html.classList.add("sidebar-" + sidebar);
|
||
</script>
|
||
|
||
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
||
<div class="sidebar-scrollbox">
|
||
<ol class="chapter"><li class="chapter-item expanded affix "><li class="part-title">eBPF 实践教程：基于 libbpf 和 CO-RE</li><li class="chapter-item expanded "><a href="../0-introduce/index.html"><strong aria-hidden="true">1.</strong> eBPF 入门开发实践教程一：介绍 eBPF 的基本概念、常见的开发工具</a></li><li class="chapter-item expanded "><a href="../1-helloworld/index.html"><strong aria-hidden="true">2.</strong> eBPF 入门开发实践教程二：Hello World，基本框架和开发流程</a></li><li class="chapter-item expanded "><a href="../2-kprobe-unlink/index.html"><strong aria-hidden="true">3.</strong> eBPF 入门开发实践教程二：在 eBPF 中使用 kprobe 监测捕获 unlink 系统调用</a></li><li class="chapter-item expanded "><a href="../3-fentry-unlink/index.html"><strong aria-hidden="true">4.</strong> eBPF 入门开发实践教程三：在 eBPF 中使用 fentry 监测捕获 unlink 系统调用</a></li><li class="chapter-item expanded "><a href="../4-opensnoop/index.html"><strong aria-hidden="true">5.</strong> eBPF 入门开发实践教程四：在 eBPF 中捕获进程打开文件的系统调用集合，使用全局变量过滤进程 pid</a></li><li class="chapter-item expanded "><a href="../5-uprobe-bashreadline/index.html" class="active"><strong aria-hidden="true">6.</strong> eBPF 入门开发实践教程五：在 eBPF 中使用 uprobe 捕获 bash 的 readline 函数调用</a></li><li class="chapter-item expanded "><a href="../6-sigsnoop/index.html"><strong aria-hidden="true">7.</strong> eBPF 入门开发实践教程六：捕获进程发送信号的系统调用集合，使用 hash map 保存状态</a></li><li class="chapter-item expanded "><a href="../7-execsnoop/index.html"><strong aria-hidden="true">8.</strong> eBPF 入门实践教程七：捕获进程执行/退出时间，通过 perf event array 向用户态打印输出</a></li><li class="chapter-item expanded "><a href="../8-exitsnoop/index.html"><strong aria-hidden="true">9.</strong> eBPF 入门开发实践教程八：在 eBPF 中使用 exitsnoop 监控进程退出事件，使用 ring buffer 向用户态打印输出</a></li><li class="chapter-item expanded "><a href="../9-runqlat/index.html"><strong aria-hidden="true">10.</strong> eBPF 入门开发实践教程九：一个 Linux 内核 BPF 程序，通过柱状图来总结调度程序运行队列延迟，显示任务等待运行在 CPU 上的时间长度</a></li><li class="chapter-item expanded "><a href="../10-hardirqs/index.html"><strong aria-hidden="true">11.</strong> eBPF 入门开发实践教程十：在 eBPF 中使用 hardirqs 或 softirqs 捕获中断事件</a></li><li class="chapter-item expanded "><a href="../11-bootstrap/index.html"><strong aria-hidden="true">12.</strong> eBPF 入门开发实践教程十一：在 eBPF 中使用 bootstrap 开发用户态程序并跟踪 exec() 和 exit() 系统调用</a></li><li class="chapter-item expanded "><a href="../13-tcpconnlat/index.html"><strong aria-hidden="true">13.</strong> eBPF入门实践教程：使用 libbpf-bootstrap 开发程序统计 TCP 连接延时</a></li><li class="chapter-item expanded "><a href="../13-tcpconnlat/tcpconnlat.html"><strong aria-hidden="true">14.</strong> eBPF 入门实践教程：编写 eBPF 程序 tcpconnlat 测量 tcp 连接延时</a></li><li class="chapter-item expanded "><a href="../14-tcpstates/index.html"><strong aria-hidden="true">15.</strong> eBPF入门实践教程：使用 libbpf-bootstrap 开发程序统计 TCP 连接延时</a></li><li class="chapter-item expanded "><a href="../15-tcprtt/index.html"><strong aria-hidden="true">16.</strong> eBPF 入门实践教程：编写 eBPF 程序 Tcprtt 测量 TCP 连接的往返时间</a></li><li class="chapter-item expanded "><a href="../16-memleak/index.html"><strong aria-hidden="true">17.</strong> eBPF 入门实践教程：编写 eBPF 程序 Memleak 监控内存泄漏</a></li><li class="chapter-item expanded "><a href="../17-biopattern/index.html"><strong aria-hidden="true">18.</strong> eBPF 入门实践教程：编写 eBPF 程序 Biopattern: 统计随机/顺序磁盘 I/O</a></li><li class="chapter-item expanded "><a href="../18-further-reading/index.html"><strong aria-hidden="true">19.</strong> 更多的参考资料</a></li><li class="chapter-item expanded "><a href="../19-lsm-connect/index.html"><strong aria-hidden="true">20.</strong> eBPF 入门实践教程：使用 LSM 进行安全检测防御</a></li><li class="chapter-item expanded "><a href="../20-tc/index.html"><strong aria-hidden="true">21.</strong> eBPF 入门实践教程：使用 eBPF 进行 tc 流量控制</a></li><li class="chapter-item expanded affix "><li class="part-title">bcc 开发者教程</li><li class="chapter-item expanded "><a href="../bcc-documents/kernel-versions.html"><strong aria-hidden="true">22.</strong> BPF Features by Linux Kernel Version</a></li><li class="chapter-item expanded "><a href="../bcc-documents/kernel_config.html"><strong aria-hidden="true">23.</strong> Kernel Configuration for BPF Features</a></li><li class="chapter-item expanded "><a href="../bcc-documents/reference_guide.html"><strong aria-hidden="true">24.</strong> bcc Reference Guide</a></li><li class="chapter-item expanded "><a href="../bcc-documents/special_filtering.html"><strong aria-hidden="true">25.</strong> Special Filtering</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial.html"><strong aria-hidden="true">26.</strong> bcc Tutorial</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial_bcc_python_developer.html"><strong aria-hidden="true">27.</strong> bcc Python Developer Tutorial</a></li></ol>
|
||
</div>
|
||
<div id="sidebar-resize-handle" class="sidebar-resize-handle"></div>
|
||
</nav>
|
||
|
||
<div id="page-wrapper" class="page-wrapper">
|
||
|
||
<div class="page">
|
||
<div id="menu-bar-hover-placeholder"></div>
|
||
<div id="menu-bar" class="menu-bar sticky bordered">
|
||
<div class="left-buttons">
|
||
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
|
||
<i class="fa fa-bars"></i>
|
||
</button>
|
||
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
|
||
<i class="fa fa-paint-brush"></i>
|
||
</button>
|
||
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
|
||
<li role="none"><button role="menuitem" class="theme" id="light">Light</button></li>
|
||
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
|
||
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
|
||
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
|
||
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
|
||
</ul>
|
||
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
|
||
<i class="fa fa-search"></i>
|
||
</button>
|
||
</div>
|
||
|
||
<h1 class="menu-title">bpf-developer-tutorial</h1>
|
||
|
||
<div class="right-buttons">
|
||
<a href="../print.html" title="Print this book" aria-label="Print this book">
|
||
<i id="print-button" class="fa fa-print"></i>
|
||
</a>
|
||
|
||
</div>
|
||
</div>
|
||
|
||
<div id="search-wrapper" class="hidden">
|
||
<form id="searchbar-outer" class="searchbar-outer">
|
||
<input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
|
||
</form>
|
||
<div id="searchresults-outer" class="searchresults-outer hidden">
|
||
<div id="searchresults-header" class="searchresults-header"></div>
|
||
<ul id="searchresults">
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
|
||
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
|
||
<script>
|
||
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
|
||
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
|
||
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
|
||
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
|
||
});
|
||
</script>
|
||
|
||
<div id="content" class="content">
|
||
<main>
|
||
<h1 id="ebpf-入门开发实践教程五在-ebpf-中使用--uprobe-捕获-bash-的-readline-函数调用"><a class="header" href="#ebpf-入门开发实践教程五在-ebpf-中使用--uprobe-捕获-bash-的-readline-函数调用">eBPF 入门开发实践教程五：在 eBPF 中使用 uprobe 捕获 bash 的 readline 函数调用</a></h1>
|
||
<p>eBPF (Extended Berkeley Packet Filter) 是 Linux 内核上的一个强大的网络和性能分析工具，它允许开发者在内核运行时动态加载、更新和运行用户定义的代码。</p>
|
||
<p>本文是 eBPF 入门开发实践教程的第五篇，主要介绍如何使用 uprobe 捕获 bash 的 readline 函数调用。</p>
|
||
<h2 id="什么是uprobe"><a class="header" href="#什么是uprobe">什么是uprobe</a></h2>
|
||
<p>uprobe是一种用户空间探针，uprobe探针允许在用户空间程序中动态插桩，插桩位置包括：函数入口、特定偏移处，以及函数返回处。当我们定义uprobe时，内核会在附加的指令上创建快速断点指令（x86机器上为int3指令），当程序执行到该指令时，内核将触发事件，程序陷入到内核态，并以回调函数的方式调用探针函数，执行完探针函数再返回到用户态继续执行后序的指令。</p>
|
||
<p>uprobe基于文件，当一个二进制文件中的一个函数被跟踪时，所有使用到这个文件的进程都会被插桩，包括那些尚未启动的进程，这样就可以在全系统范围内跟踪系统调用。</p>
|
||
<p>uprobe适用于在用户态去解析一些内核态探针无法解析的流量，例如http2流量（报文header被编码，内核无法解码），https流量（加密流量，内核无法解密）。</p>
|
||
<h2 id="使用-uprobe-捕获-bash-的-readline-函数调用"><a class="header" href="#使用-uprobe-捕获-bash-的-readline-函数调用">使用 uprobe 捕获 bash 的 readline 函数调用</a></h2>
|
||
<p>uprobe 是一种用于捕获用户空间函数调用的 eBPF 的探针，我们可以通过它来捕获用户空间程序调用的系统函数。</p>
|
||
<p>例如，我们可以使用 uprobe 来捕获 bash 的 readline 函数调用，从而获取用户在 bash 中输入的命令行。示例代码如下：</p>
|
||
<pre><code class="language-c">#include <vmlinux.h>
|
||
#include <bpf/bpf_helpers.h>
|
||
#include <bpf/bpf_tracing.h>
|
||
|
||
#define TASK_COMM_LEN 16
|
||
#define MAX_LINE_SIZE 80
|
||
|
||
/* Format of u[ret]probe section definition supporting auto-attach:
|
||
* u[ret]probe/binary:function[+offset]
|
||
*
|
||
* binary can be an absolute/relative path or a filename; the latter is resolved to a
|
||
* full binary path via bpf_program__attach_uprobe_opts.
|
||
*
|
||
* Specifying uprobe+ ensures we carry out strict matching; either "uprobe" must be
|
||
* specified (and auto-attach is not possible) or the above format is specified for
|
||
* auto-attach.
|
||
*/
|
||
SEC("uretprobe//bin/bash:readline")
|
||
int BPF_KRETPROBE(printret, const void *ret)
|
||
{
|
||
char str[MAX_LINE_SIZE];
|
||
char comm[TASK_COMM_LEN];
|
||
u32 pid;
|
||
|
||
if (!ret)
|
||
return 0;
|
||
|
||
bpf_get_current_comm(&comm, sizeof(comm));
|
||
|
||
pid = bpf_get_current_pid_tgid() >> 32;
|
||
bpf_probe_read_user_str(str, sizeof(str), ret);
|
||
|
||
bpf_printk("PID %d (%s) read: %s ", pid, comm, str);
|
||
|
||
return 0;
|
||
};
|
||
|
||
char LICENSE[] SEC("license") = "GPL";
|
||
</code></pre>
|
||
<p>这段代码的作用是在 bash 的 readline 函数返回时执行指定的 BPF_KRETPROBE 函数，即 printret 函数。</p>
|
||
<p>在 printret 函数中，我们首先获取了调用 readline 函数的进程的进程名称和进程 ID，然后通过 bpf_probe_read_user_str 函数读取了用户输入的命令行字符串，最后通过 bpf_printk 函数打印出进程 ID、进程名称和输入的命令行字符串。</p>
|
||
<p>除此之外，我们还需要通过 SEC 宏来定义 uprobe 探针，并使用 BPF_KRETPROBE 宏来定义探针函数。</p>
|
||
<p>在 SEC 宏中，我们需要指定 uprobe 的类型、要捕获的二进制文件的路径和要捕获的函数名称。例如，上面的代码中的 SEC 宏的定义如下：</p>
|
||
<pre><code class="language-c">SEC("uprobe//bin/bash:readline")
|
||
</code></pre>
|
||
<p>这表示我们要捕获的是 /bin/bash 二进制文件中的 readline 函数。</p>
|
||
<p>接下来，我们需要使用 BPF_KRETPROBE 宏来定义探针函数，例如：</p>
|
||
<pre><code class="language-c">BPF_KRETPROBE(printret, const void *ret)
|
||
</code></pre>
|
||
<p>这里的 printret 是探针函数的名称，const void *ret 是探针函数的参数，它代表被捕获的函数的返回值。</p>
|
||
<p>然后，我们使用了 bpf_get_current_comm 函数获取当前任务的名称，并将其存储在 comm 数组中。</p>
|
||
<pre><code class="language-c"> bpf_get_current_comm(&comm, sizeof(comm));
|
||
</code></pre>
|
||
<p>使用 bpf_get_current_pid_tgid 函数获取当前进程的 PID，并将其存储在 pid 变量中。</p>
|
||
<pre><code class="language-c"> pid = bpf_get_current_pid_tgid() >> 32;
|
||
</code></pre>
|
||
<p>使用 bpf_probe_read_user_str 函数从用户空间读取 readline 函数的返回值，并将其存储在 str 数组中。</p>
|
||
<pre><code class="language-c"> bpf_probe_read_user_str(str, sizeof(str), ret);
|
||
</code></pre>
|
||
<p>最后使用 bpf_printk 函数输出 PID、任务名称和用户输入的字符串。</p>
|
||
<pre><code class="language-c"> bpf_printk("PID %d (%s) read: %s ", pid, comm, str);
|
||
</code></pre>
|
||
<p>eunomia-bpf 是一个结合 Wasm 的开源 eBPF 动态加载运行时和开发工具链，它的目的是简化 eBPF 程序的开发、构建、分发、运行。可以参考 <a href="https://github.com/eunomia-bpf/eunomia-bpf">https://github.com/eunomia-bpf/eunomia-bpf</a> 下载和安装 ecc 编译工具链和 ecli 运行时。我们使用 eunomia-bpf 编译运行这个例子。</p>
|
||
<p>编译运行上述代码：</p>
|
||
<pre><code class="language-console">$ ecc bashreadline.bpf.c
|
||
Compiling bpf object...
|
||
Packing ebpf object and config into package.json...
|
||
$ sudo ecli run package.json
|
||
Runing eBPF program...
|
||
</code></pre>
|
||
<p>运行这段程序后，可以通过查看 /sys/kernel/debug/tracing/trace_pipe 文件来查看 eBPF 程序的输出：</p>
|
||
<pre><code class="language-console">$ sudo cat /sys/kernel/debug/tracing/trace_pipe
|
||
bash-32969 [000] d..31 64001.375748: bpf_trace_printk: PID 32969 (bash) read: fff
|
||
bash-32969 [000] d..31 64002.056951: bpf_trace_printk: PID 32969 (bash) read: fff
|
||
</code></pre>
|
||
<p>可以看到，我们成功的捕获了 bash 的 readline 函数调用，并获取了用户在 bash 中输入的命令行。</p>
|
||
<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
|
||
<p>在上述代码中，我们使用了 SEC 宏来定义了一个 uprobe 探针，它指定了要捕获的用户空间程序 (bin/bash) 和要捕获的函数 (readline)。此外，我们还使用了 BPF_KRETPROBE 宏来定义了一个用于处理 readline 函数返回值的回调函数 (printret)。该函数可以获取到 readline 函数的返回值，并将其打印到内核日志中。通过这样的方式，我们就可以使用 eBPF 来捕获 bash 的 readline 函数调用，并获取用户在 bash 中输入的命令行。</p>
|
||
<p>更多的例子和详细的开发指南，请参考 eunomia-bpf 的官方文档：<a href="https://github.com/eunomia-bpf/eunomia-bpf">https://github.com/eunomia-bpf/eunomia-bpf</a></p>
|
||
<p>完整的教程和源代码已经全部开源，可以在 <a href="https://github.com/eunomia-bpf/bpf-developer-tutorial">https://github.com/eunomia-bpf/bpf-developer-tutorial</a> 中查看。</p>
|
||
|
||
</main>
|
||
|
||
<nav class="nav-wrapper" aria-label="Page navigation">
|
||
<!-- Mobile navigation buttons -->
|
||
<a rel="prev" href="../4-opensnoop/index.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||
<i class="fa fa-angle-left"></i>
|
||
</a>
|
||
|
||
<a rel="next" href="../6-sigsnoop/index.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||
<i class="fa fa-angle-right"></i>
|
||
</a>
|
||
|
||
<div style="clear: both"></div>
|
||
</nav>
|
||
</div>
|
||
</div>
|
||
|
||
<nav class="nav-wide-wrapper" aria-label="Page navigation">
|
||
<a rel="prev" href="../4-opensnoop/index.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
||
<i class="fa fa-angle-left"></i>
|
||
</a>
|
||
|
||
<a rel="next" href="../6-sigsnoop/index.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
||
<i class="fa fa-angle-right"></i>
|
||
</a>
|
||
</nav>
|
||
|
||
</div>
|
||
|
||
|
||
|
||
|
||
<script>
|
||
window.playground_copyable = true;
|
||
</script>
|
||
|
||
|
||
<script src="../elasticlunr.min.js"></script>
|
||
<script src="../mark.min.js"></script>
|
||
<script src="../searcher.js"></script>
|
||
|
||
<script src="../clipboard.min.js"></script>
|
||
<script src="../highlight.js"></script>
|
||
<script src="../book.js"></script>
|
||
|
||
<!-- Custom JS scripts -->
|
||
|
||
|
||
</div>
|
||
</body>
|
||
</html>
|