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<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> 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 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> 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> 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> 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"><strong aria-hidden="true">6.</strong> 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> 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> 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> 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> 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> 使用 hardirqs 或 softirqs 捕获中断事件</a></li><li class="chapter-item expanded "><a href="../11-bootstrap/index.html" class="active"><strong aria-hidden="true">12.</strong> 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> 使用 libbpf-bootstrap 开发程序统计 TCP 连接延时</a></li><li class="chapter-item expanded "><a href="../14-tcpstates/index.html"><strong aria-hidden="true">14.</strong> 使用 libbpf-bootstrap 记录 TCP 连接状态与 TCP RTT</a></li><li class="chapter-item expanded "><a href="../15-javagc/index.html"><strong aria-hidden="true">15.</strong> 使用 USDT 捕获用户态 Java GC 事件耗时</a></li><li class="chapter-item expanded "><a href="../16-memleak/index.html"><strong aria-hidden="true">16.</strong> 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">17.</strong> 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">18.</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">19.</strong> 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">20.</strong> 使用 eBPF 进行 tc 流量控制</a></li><li class="chapter-item expanded affix "><li class="part-title">eBPF 高级特性与进阶主题</li><li class="chapter-item expanded "><a href="../22-android/index.html"><strong aria-hidden="true">21.</strong> 在 Android 上使用 eBPF 程序</a></li><li class="chapter-item expanded "><a href="../23-http/index.html"><strong aria-hidden="true">22.</strong> 使用 eBPF 追踪 HTTP 请求或其他七层协议</a></li><li class="chapter-item expanded "><a href="../29-sockops/index.html"><strong aria-hidden="true">23.</strong> 使用 sockops 加速网络请求转发</a></li><li class="chapter-item expanded "><a href="../24-hide/index.html"><strong aria-hidden="true">24.</strong> 使用 eBPF 隐藏进程或文件信息</a></li><li class="chapter-item expanded "><a href="../25-signal/index.html"><strong aria-hidden="true">25.</strong> 使用 bpf_send_signal 发送信号终止进程</a></li><li class="chapter-item expanded "><a href="../26-sudo/index.html"><strong aria-hidden="true">26.</strong> 使用 eBPF 添加 sudo 用户</a></li><li class="chapter-item expanded "><a href="../27-replace/index.html"><strong aria-hidden="true">27.</strong> 使用 eBPF 替换任意程序读取或写入的文本</a></li><li class="chapter-item expanded "><a href="../28-detach/index.html"><strong aria-hidden="true">28.</strong> BPF的生命周期：使用 Detached 模式在用户态应用退出后持续运行 eBPF 程序</a></li><li class="chapter-item expanded "><a href="../30-sslsniff/index.html"><strong aria-hidden="true">29.</strong> 使用 eBPF 用户态捕获多种库的 SSL/TLS 明文数据</a></li><li class="chapter-item expanded affix "><li class="part-title">bcc tutorial</li><li class="chapter-item expanded "><a href="../bcc-documents/kernel-versions.html"><strong aria-hidden="true">30.</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">31.</strong> Kernel Configuration for BPF Features</a></li><li class="chapter-item expanded "><a href="../bcc-documents/reference_guide.html"><strong aria-hidden="true">32.</strong> bcc Reference Guide</a></li><li class="chapter-item expanded "><a href="../bcc-documents/special_filtering.html"><strong aria-hidden="true">33.</strong> Special Filtering</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial.html"><strong aria-hidden="true">34.</strong> bcc Tutorial</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial_bcc_python_developer.html"><strong aria-hidden="true">35.</strong> bcc Python Developer Tutorial</a></li></ol>
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<h1 id="ebpf-入门开发实践教程十一在-ebpf-中使用-libbpf-开发用户态程序并跟踪-exec-和-exit-系统调用"><a class="header" href="#ebpf-入门开发实践教程十一在-ebpf-中使用-libbpf-开发用户态程序并跟踪-exec-和-exit-系统调用">eBPF 入门开发实践教程十一：在 eBPF 中使用 libbpf 开发用户态程序并跟踪 exec() 和 exit() 系统调用</a></h1>
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<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>
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<p>在本教程中，我们将了解内核态和用户态的 eBPF 程序是如何协同工作的。我们还将学习如何使用原生的 libbpf 开发用户态程序，将 eBPF 应用打包为可执行文件，实现跨内核版本分发。</p>
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<h2 id="libbpf-库以及为什么需要使用它"><a class="header" href="#libbpf-库以及为什么需要使用它">libbpf 库，以及为什么需要使用它</a></h2>
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<p>libbpf 是一个 C 语言库，伴随内核版本分发，用于辅助 eBPF 程序的加载和运行。它提供了用于与 eBPF 系统交互的一组 C API，使开发者能够更轻松地编写用户态程序来加载和管理 eBPF 程序。这些用户态程序通常用于分析、监控或优化系统性能。</p>
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<p>使用 libbpf 库有以下优势：</p>
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<ul>
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<li>它简化了 eBPF 程序的加载、更新和运行过程。</li>
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<li>它提供了一组易于使用的 API，使开发者能够专注于编写核心逻辑，而不是处理底层细节。</li>
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<li>它能够确保与内核中的 eBPF 子系统的兼容性，降低了维护成本。</li>
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</ul>
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<p>同时，libbpf 和 BTF（BPF Type Format）都是 eBPF 生态系统的重要组成部分。它们各自在实现跨内核版本兼容方面发挥着关键作用。BTF（BPF Type Format）是一种元数据格式，用于描述 eBPF 程序中的类型信息。BTF 的主要目的是提供一种结构化的方式，以描述内核中的数据结构，以便 eBPF 程序可以更轻松地访问和操作它们。</p>
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<p>BTF 在实现跨内核版本兼容方面的关键作用如下：</p>
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<ul>
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<li>BTF 允许 eBPF 程序访问内核数据结构的详细类型信息，而无需对特定内核版本进行硬编码。这使得 eBPF 程序可以适应不同版本的内核，从而实现跨内核版本兼容。</li>
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<li>通过使用 BPF CO-RE（Compile Once, Run Everywhere）技术，eBPF 程序可以利用 BTF 在编译时解析内核数据结构的类型信息，进而生成可以在不同内核版本上运行的 eBPF 程序。</li>
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</ul>
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<p>结合 libbpf 和 BTF，eBPF 程序可以在各种不同版本的内核上运行，而无需为每个内核版本单独编译。这极大地提高了 eBPF 生态系统的可移植性和兼容性，降低了开发和维护的难度。</p>
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<h2 id="什么是-bootstrap"><a class="header" href="#什么是-bootstrap">什么是 bootstrap</a></h2>
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<p>Bootstrap 是一个使用 libbpf 的完整应用，它利用 eBPF 程序来跟踪内核中的 exec() 系统调用（通过 SEC("tp/sched/sched_process_exec") handle_exec BPF 程序），这主要对应于新进程的创建（不包括 fork() 部分）。此外，它还跟踪进程的 exit() 系统调用（通过 SEC("tp/sched/sched_process_exit") handle_exit BPF 程序），以了解每个进程何时退出。</p>
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<p>这两个 BPF 程序共同工作，允许捕获关于新进程的有趣信息，例如二进制文件的文件名，以及测量进程的生命周期，并在进程结束时收集有趣的统计信息，例如退出代码或消耗的资源量等。这是深入了解内核内部并观察事物如何真正运作的良好起点。</p>
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<p>Bootstrap 还使用 argp API（libc 的一部分）进行命令行参数解析，使得用户可以通过命令行选项配置应用行为。这种方式提供了灵活性，让用户能够根据实际需求自定义程序行为。虽然这些功能使用 eunomia-bpf 工具也可以实现，但是这里我们使用 libbpf 可以在用户态提供更高的可扩展性，不过也带来了不少额外的复杂度。</p>
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<h2 id="bootstrap"><a class="header" href="#bootstrap">Bootstrap</a></h2>
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<p>Bootstrap 分为两个部分：内核态和用户态。内核态部分是一个 eBPF 程序，它跟踪 exec() 和 exit() 系统调用。用户态部分是一个 C 语言程序，它使用 libbpf 库来加载和运行内核态程序，并处理从内核态程序收集的数据。</p>
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<h3 id="内核态-ebpf-程序-bootstrapbpfc"><a class="header" href="#内核态-ebpf-程序-bootstrapbpfc">内核态 eBPF 程序 bootstrap.bpf.c</a></h3>
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<pre><code class="language-c">// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
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/* Copyright (c) 2020 Facebook */
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#include "vmlinux.h"
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_core_read.h>
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#include "bootstrap.h"
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char LICENSE[] SEC("license") = "Dual BSD/GPL";
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, 8192);
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__type(key, pid_t);
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__type(value, u64);
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} exec_start SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_RINGBUF);
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__uint(max_entries, 256 * 1024);
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} rb SEC(".maps");
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const volatile unsigned long long min_duration_ns = 0;
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SEC("tp/sched/sched_process_exec")
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int handle_exec(struct trace_event_raw_sched_process_exec *ctx)
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{
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struct task_struct *task;
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unsigned fname_off;
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struct event *e;
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pid_t pid;
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u64 ts;
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/* remember time exec() was executed for this PID */
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pid = bpf_get_current_pid_tgid() >> 32;
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ts = bpf_ktime_get_ns();
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bpf_map_update_elem(&exec_start, &pid, &ts, BPF_ANY);
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/* don't emit exec events when minimum duration is specified */
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if (min_duration_ns)
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return 0;
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/* reserve sample from BPF ringbuf */
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e = bpf_ringbuf_reserve(&rb, sizeof(*e), 0);
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if (!e)
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return 0;
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|
||
/* fill out the sample with data */
|
||
task = (struct task_struct *)bpf_get_current_task();
|
||
|
||
e->exit_event = false;
|
||
e->pid = pid;
|
||
e->ppid = BPF_CORE_READ(task, real_parent, tgid);
|
||
bpf_get_current_comm(&e->comm, sizeof(e->comm));
|
||
|
||
fname_off = ctx->__data_loc_filename & 0xFFFF;
|
||
bpf_probe_read_str(&e->filename, sizeof(e->filename), (void *)ctx + fname_off);
|
||
|
||
/* successfully submit it to user-space for post-processing */
|
||
bpf_ringbuf_submit(e, 0);
|
||
return 0;
|
||
}
|
||
|
||
SEC("tp/sched/sched_process_exit")
|
||
int handle_exit(struct trace_event_raw_sched_process_template* ctx)
|
||
{
|
||
struct task_struct *task;
|
||
struct event *e;
|
||
pid_t pid, tid;
|
||
u64 id, ts, *start_ts, duration_ns = 0;
|
||
|
||
/* get PID and TID of exiting thread/process */
|
||
id = bpf_get_current_pid_tgid();
|
||
pid = id >> 32;
|
||
tid = (u32)id;
|
||
|
||
/* ignore thread exits */
|
||
if (pid != tid)
|
||
return 0;
|
||
|
||
/* if we recorded start of the process, calculate lifetime duration */
|
||
start_ts = bpf_map_lookup_elem(&exec_start, &pid);
|
||
if (start_ts)
|
||
duration_ns = bpf_ktime_get_ns() - *start_ts;
|
||
else if (min_duration_ns)
|
||
return 0;
|
||
bpf_map_delete_elem(&exec_start, &pid);
|
||
|
||
/* if process didn't live long enough, return early */
|
||
if (min_duration_ns && duration_ns < min_duration_ns)
|
||
return 0;
|
||
|
||
/* reserve sample from BPF ringbuf */
|
||
e = bpf_ringbuf_reserve(&rb, sizeof(*e), 0);
|
||
if (!e)
|
||
return 0;
|
||
|
||
/* fill out the sample with data */
|
||
task = (struct task_struct *)bpf_get_current_task();
|
||
|
||
e->exit_event = true;
|
||
e->duration_ns = duration_ns;
|
||
e->pid = pid;
|
||
e->ppid = BPF_CORE_READ(task, real_parent, tgid);
|
||
e->exit_code = (BPF_CORE_READ(task, exit_code) >> 8) & 0xff;
|
||
bpf_get_current_comm(&e->comm, sizeof(e->comm));
|
||
|
||
/* send data to user-space for post-processing */
|
||
bpf_ringbuf_submit(e, 0);
|
||
return 0;
|
||
}
|
||
</code></pre>
|
||
<p>这段代码是一个内核态 eBPF 程序（bootstrap.bpf.c），主要用于跟踪 exec() 和 exit() 系统调用。它通过 eBPF 程序捕获进程的创建和退出事件，并将相关信息发送到用户态程序进行处理。下面是对代码的详细解释。</p>
|
||
<p>首先，我们引入所需的头文件，定义 eBPF 程序的许可证以及两个 eBPF maps：exec_start 和 rb。exec_start 是一个哈希类型的 eBPF map，用于存储进程开始执行时的时间戳。rb 是一个环形缓冲区类型的 eBPF map，用于存储捕获的事件数据，并将其发送到用户态程序。</p>
|
||
<pre><code class="language-c">#include "vmlinux.h"
|
||
#include <bpf/bpf_helpers.h>
|
||
#include <bpf/bpf_tracing.h>
|
||
#include <bpf/bpf_core_read.h>
|
||
#include "bootstrap.h"
|
||
|
||
char LICENSE[] SEC("license") = "Dual BSD/GPL";
|
||
|
||
struct {
|
||
__uint(type, BPF_MAP_TYPE_HASH);
|
||
__uint(max_entries, 8192);
|
||
__type(key, pid_t);
|
||
__type(value, u64);
|
||
} exec_start SEC(".maps");
|
||
|
||
struct {
|
||
__uint(type, BPF_MAP_TYPE_RINGBUF);
|
||
__uint(max_entries, 256 * 1024);
|
||
} rb SEC(".maps");
|
||
|
||
const volatile unsigned long long min_duration_ns = 0;
|
||
</code></pre>
|
||
<p>接下来，我们定义了一个名为 handle_exec 的 eBPF 程序，它会在进程执行 exec() 系统调用时触发。首先，我们从当前进程中获取 PID，记录进程开始执行的时间戳，然后将其存储在 exec_start map 中。</p>
|
||
<pre><code class="language-c">SEC("tp/sched/sched_process_exec")
|
||
int handle_exec(struct trace_event_raw_sched_process_exec *ctx)
|
||
{
|
||
// ...
|
||
pid = bpf_get_current_pid_tgid() >> 32;
|
||
ts = bpf_ktime_get_ns();
|
||
bpf_map_update_elem(&exec_start, &pid, &ts, BPF_ANY);
|
||
|
||
// ...
|
||
}
|
||
</code></pre>
|
||
<p>然后，我们从环形缓冲区 map rb 中预留一个事件结构，并填充相关数据，如进程 ID、父进程 ID、进程名等。之后，我们将这些数据发送到用户态程序进行处理。</p>
|
||
<pre><code class="language-c"> // reserve sample from BPF ringbuf
|
||
e = bpf_ringbuf_reserve(&rb, sizeof(*e), 0);
|
||
if (!e)
|
||
return 0;
|
||
|
||
// fill out the sample with data
|
||
task = (struct task_struct *)bpf_get_current_task();
|
||
|
||
e->exit_event = false;
|
||
e->pid = pid;
|
||
e->ppid = BPF_CORE_READ(task, real_parent, tgid);
|
||
bpf_get_current_comm(&e->comm, sizeof(e->comm));
|
||
|
||
fname_off = ctx->__data_loc_filename & 0xFFFF;
|
||
bpf_probe_read_str(&e->filename, sizeof(e->filename), (void *)ctx + fname_off);
|
||
|
||
// successfully submit it to user-space for post-processing
|
||
bpf_ringbuf_submit(e, 0);
|
||
return 0;
|
||
</code></pre>
|
||
<p>最后，我们定义了一个名为 handle_exit 的 eBPF 程序，它会在进程执行 exit() 系统调用时触发。首先，我们从当前进程中获取 PID 和 TID（线程 ID）。如果 PID 和 TID 不相等，说明这是一个线程退出，我们将忽略此事件。</p>
|
||
<pre><code class="language-c">SEC("tp/sched/sched_process_exit")
|
||
int handle_exit(struct trace_event_raw_sched_process_template* ctx)
|
||
{
|
||
// ...
|
||
id = bpf_get_current_pid_tgid();
|
||
pid = id >> 32;
|
||
tid = (u32)id;
|
||
|
||
/* ignore thread exits */
|
||
if (pid != tid)
|
||
return 0;
|
||
|
||
// ...
|
||
}
|
||
</code></pre>
|
||
<p>接着，我们查找之前存储在 exec_start map 中的进程开始执行的时间戳。如果找到了时间戳，我们将计算进程的生命周期（持续时间），然后从 exec_start map 中删除该记录。如果未找到时间戳且指定了最小持续时间，则直接返回。</p>
|
||
<pre><code class="language-c"> // if we recorded start of the process, calculate lifetime duration
|
||
start_ts = bpf_map_lookup_elem(&exec_start, &pid);
|
||
if (start_ts)
|
||
duration_ns = bpf_ktime_get_ns() - *start_ts;
|
||
else if (min_duration_ns)
|
||
return 0;
|
||
bpf_map_delete_elem(&exec_start, &pid);
|
||
|
||
// if process didn't live long enough, return early
|
||
if (min_duration_ns && duration_ns < min_duration_ns)
|
||
return 0;
|
||
</code></pre>
|
||
<p>然后，我们从环形缓冲区 map rb 中预留一个事件结构，并填充相关数据，如进程 ID、父进程 ID、进程名、进程持续时间等。最后，我们将这些数据发送到用户态程序进行处理。</p>
|
||
<pre><code class="language-c"> /* reserve sample from BPF ringbuf */
|
||
e = bpf_ringbuf_reserve(&rb, sizeof(*e), 0);
|
||
if (!e)
|
||
return 0;
|
||
|
||
/* fill out the sample with data */
|
||
task = (struct task_struct *)bpf_get_current_task();
|
||
|
||
e->exit_event = true;
|
||
e->duration_ns = duration_ns;
|
||
e->pid = pid;
|
||
e->ppid = BPF_CORE_READ(task, real_parent, tgid);
|
||
e->exit_code = (BPF_CORE_READ(task, exit_code) >> 8) & 0xff;
|
||
bpf_get_current_comm(&e->comm, sizeof(e->comm));
|
||
|
||
/* send data to user-space for post-processing */
|
||
bpf_ringbuf_submit(e, 0);
|
||
return 0;
|
||
}
|
||
</code></pre>
|
||
<p>这样，当进程执行 exec() 或 exit() 系统调用时，我们的 eBPF 程序会捕获相应的事件，并将详细信息发送到用户态程序进行后续处理。这使得我们可以轻松地监控进程的创建和退出，并获取有关进程的详细信息。</p>
|
||
<p>除此之外，在 bootstrap.h 中，我们还定义了和用户态交互的数据结构：</p>
|
||
<pre><code class="language-c">/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
|
||
/* Copyright (c) 2020 Facebook */
|
||
#ifndef __BOOTSTRAP_H
|
||
#define __BOOTSTRAP_H
|
||
|
||
#define TASK_COMM_LEN 16
|
||
#define MAX_FILENAME_LEN 127
|
||
|
||
struct event {
|
||
int pid;
|
||
int ppid;
|
||
unsigned exit_code;
|
||
unsigned long long duration_ns;
|
||
char comm[TASK_COMM_LEN];
|
||
char filename[MAX_FILENAME_LEN];
|
||
bool exit_event;
|
||
};
|
||
|
||
#endif /* __BOOTSTRAP_H */
|
||
</code></pre>
|
||
<h3 id="用户态bootstrapc"><a class="header" href="#用户态bootstrapc">用户态，bootstrap.c</a></h3>
|
||
<pre><code class="language-c">// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
|
||
/* Copyright (c) 2020 Facebook */
|
||
#include <argp.h>
|
||
#include <signal.h>
|
||
#include <stdio.h>
|
||
#include <time.h>
|
||
#include <sys/resource.h>
|
||
#include <bpf/libbpf.h>
|
||
#include "bootstrap.h"
|
||
#include "bootstrap.skel.h"
|
||
|
||
static struct env {
|
||
bool verbose;
|
||
long min_duration_ms;
|
||
} env;
|
||
|
||
const char *argp_program_version = "bootstrap 0.0";
|
||
const char *argp_program_bug_address = "<bpf@vger.kernel.org>";
|
||
const char argp_program_doc[] =
|
||
"BPF bootstrap demo application.\n"
|
||
"\n"
|
||
"It traces process start and exits and shows associated \n"
|
||
"information (filename, process duration, PID and PPID, etc).\n"
|
||
"\n"
|
||
"USAGE: ./bootstrap [-d <min-duration-ms>] [-v]\n";
|
||
|
||
static const struct argp_option opts[] = {
|
||
{ "verbose", 'v', NULL, 0, "Verbose debug output" },
|
||
{ "duration", 'd', "DURATION-MS", 0, "Minimum process duration (ms) to report" },
|
||
{},
|
||
};
|
||
|
||
static error_t parse_arg(int key, char *arg, struct argp_state *state)
|
||
{
|
||
switch (key) {
|
||
case 'v':
|
||
env.verbose = true;
|
||
break;
|
||
case 'd':
|
||
errno = 0;
|
||
env.min_duration_ms = strtol(arg, NULL, 10);
|
||
if (errno || env.min_duration_ms <= 0) {
|
||
fprintf(stderr, "Invalid duration: %s\n", arg);
|
||
argp_usage(state);
|
||
}
|
||
break;
|
||
case ARGP_KEY_ARG:
|
||
argp_usage(state);
|
||
break;
|
||
default:
|
||
return ARGP_ERR_UNKNOWN;
|
||
}
|
||
return 0;
|
||
}
|
||
|
||
static const struct argp argp = {
|
||
.options = opts,
|
||
.parser = parse_arg,
|
||
.doc = argp_program_doc,
|
||
};
|
||
|
||
static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
|
||
{
|
||
if (level == LIBBPF_DEBUG && !env.verbose)
|
||
return 0;
|
||
return vfprintf(stderr, format, args);
|
||
}
|
||
|
||
static volatile bool exiting = false;
|
||
|
||
static void sig_handler(int sig)
|
||
{
|
||
exiting = true;
|
||
}
|
||
|
||
static int handle_event(void *ctx, void *data, size_t data_sz)
|
||
{
|
||
const struct event *e = data;
|
||
struct tm *tm;
|
||
char ts[32];
|
||
time_t t;
|
||
|
||
time(&t);
|
||
tm = localtime(&t);
|
||
strftime(ts, sizeof(ts), "%H:%M:%S", tm);
|
||
|
||
if (e->exit_event) {
|
||
printf("%-8s %-5s %-16s %-7d %-7d [%u]",
|
||
ts, "EXIT", e->comm, e->pid, e->ppid, e->exit_code);
|
||
if (e->duration_ns)
|
||
printf(" (%llums)", e->duration_ns / 1000000);
|
||
printf("\n");
|
||
} else {
|
||
printf("%-8s %-5s %-16s %-7d %-7d %s\n",
|
||
ts, "EXEC", e->comm, e->pid, e->ppid, e->filename);
|
||
}
|
||
|
||
return 0;
|
||
}
|
||
|
||
int main(int argc, char **argv)
|
||
{
|
||
struct ring_buffer *rb = NULL;
|
||
struct bootstrap_bpf *skel;
|
||
int err;
|
||
|
||
/* Parse command line arguments */
|
||
err = argp_parse(&argp, argc, argv, 0, NULL, NULL);
|
||
if (err)
|
||
return err;
|
||
|
||
/* Set up libbpf errors and debug info callback */
|
||
libbpf_set_print(libbpf_print_fn);
|
||
|
||
/* Cleaner handling of Ctrl-C */
|
||
signal(SIGINT, sig_handler);
|
||
signal(SIGTERM, sig_handler);
|
||
|
||
/* Load and verify BPF application */
|
||
skel = bootstrap_bpf__open();
|
||
if (!skel) {
|
||
fprintf(stderr, "Failed to open and load BPF skeleton\n");
|
||
return 1;
|
||
}
|
||
|
||
/* Parameterize BPF code with minimum duration parameter */
|
||
skel->rodata->min_duration_ns = env.min_duration_ms * 1000000ULL;
|
||
|
||
/* Load & verify BPF programs */
|
||
err = bootstrap_bpf__load(skel);
|
||
if (err) {
|
||
fprintf(stderr, "Failed to load and verify BPF skeleton\n");
|
||
goto cleanup;
|
||
}
|
||
|
||
/* Attach tracepoints */
|
||
err = bootstrap_bpf__attach(skel);
|
||
if (err) {
|
||
fprintf(stderr, "Failed to attach BPF skeleton\n");
|
||
goto cleanup;
|
||
}
|
||
|
||
/* Set up ring buffer polling */
|
||
rb = ring_buffer__new(bpf_map__fd(skel->maps.rb), handle_event, NULL, NULL);
|
||
if (!rb) {
|
||
err = -1;
|
||
fprintf(stderr, "Failed to create ring buffer\n");
|
||
goto cleanup;
|
||
}
|
||
|
||
/* Process events */
|
||
printf("%-8s %-5s %-16s %-7s %-7s %s\n",
|
||
"TIME", "EVENT", "COMM", "PID", "PPID", "FILENAME/EXIT CODE");
|
||
while (!exiting) {
|
||
err = ring_buffer__poll(rb, 100 /* timeout, ms */);
|
||
/* Ctrl-C will cause -EINTR */
|
||
if (err == -EINTR) {
|
||
err = 0;
|
||
break;
|
||
}
|
||
if (err < 0) {
|
||
printf("Error polling perf buffer: %d\n", err);
|
||
break;
|
||
}
|
||
}
|
||
|
||
cleanup:
|
||
/* Clean up */
|
||
ring_buffer__free(rb);
|
||
bootstrap_bpf__destroy(skel);
|
||
|
||
return err < 0 ? -err : 0;
|
||
}
|
||
</code></pre>
|
||
<p>这个用户态程序主要用于加载、验证、附加 eBPF 程序，以及接收 eBPF 程序收集的事件数据，并将其打印出来。我们将分析一些关键部分。</p>
|
||
<p>首先，我们定义了一个 env 结构，用于存储命令行参数：</p>
|
||
<pre><code class="language-c">static struct env {
|
||
bool verbose;
|
||
long min_duration_ms;
|
||
} env;
|
||
</code></pre>
|
||
<p>接下来，我们使用 argp 库来解析命令行参数：</p>
|
||
<pre><code class="language-c">static const struct argp_option opts[] = {
|
||
{ "verbose", 'v', NULL, 0, "Verbose debug output" },
|
||
{ "duration", 'd', "DURATION-MS", 0, "Minimum process duration (ms) to report" },
|
||
{},
|
||
};
|
||
|
||
static error_t parse_arg(int key, char *arg, struct argp_state *state)
|
||
{
|
||
// ...
|
||
}
|
||
|
||
static const struct argp argp = {
|
||
.options = opts,
|
||
.parser = parse_arg,
|
||
.doc = argp_program_doc,
|
||
};
|
||
</code></pre>
|
||
<p>main() 函数中，首先解析命令行参数，然后设置 libbpf 的打印回调函数 libbpf_print_fn，以便在需要时输出调试信息：</p>
|
||
<pre><code class="language-c">err = argp_parse(&argp, argc, argv, 0, NULL, NULL);
|
||
if (err)
|
||
return err;
|
||
|
||
libbpf_set_print(libbpf_print_fn);
|
||
</code></pre>
|
||
<p>接下来，我们打开 eBPF 脚手架（skeleton）文件，将最小持续时间参数传递给 eBPF 程序，并加载和附加 eBPF 程序：</p>
|
||
<pre><code class="language-c">skel = bootstrap_bpf__open();
|
||
if (!skel) {
|
||
fprintf(stderr, "Failed to open and load BPF skeleton\n");
|
||
return 1;
|
||
}
|
||
|
||
skel->rodata->min_duration_ns = env.min_duration_ms * 1000000ULL;
|
||
|
||
err = bootstrap_bpf__load(skel);
|
||
if (err) {
|
||
fprintf(stderr, "Failed to load and verify BPF skeleton\n");
|
||
goto cleanup;
|
||
}
|
||
|
||
err = bootstrap_bpf__attach(skel);
|
||
if (err) {
|
||
fprintf(stderr, "Failed to attach BPF skeleton\n");
|
||
goto cleanup;
|
||
}
|
||
</code></pre>
|
||
<p>然后，我们创建一个环形缓冲区（ring buffer），用于接收 eBPF 程序发送的事件数据：</p>
|
||
<pre><code class="language-c">rb = ring_buffer__new(bpf_map__fd(skel->maps.rb), handle_event, NULL, NULL);
|
||
if (!rb) {
|
||
err = -1;
|
||
fprintf(stderr, "Failed to create ring buffer\n");
|
||
goto cleanup;
|
||
}
|
||
</code></pre>
|
||
<p>handle_event() 函数会处理从 eBPF 程序收到的事件。根据事件类型（进程执行或退出），它会提取并打印事件信息，如时间戳、进程名、进程 ID、父进程 ID、文件名或退出代码等。</p>
|
||
<p>最后，我们使用 ring_buffer__poll() 函数轮询环形缓冲区，处理收到的事件数据：</p>
|
||
<pre><code class="language-c">while (!exiting) {
|
||
err = ring_buffer__poll(rb, 100 /* timeout, ms */);
|
||
// ...
|
||
}
|
||
</code></pre>
|
||
<p>当程序收到 SIGINT 或 SIGTERM 信号时，它会最后完成清理、退出操作，关闭和卸载 eBPF 程序：</p>
|
||
<pre><code class="language-c">cleanup:
|
||
/* Clean up */
|
||
ring_buffer__free(rb);
|
||
bootstrap_bpf__destroy(skel);
|
||
|
||
return err < 0 ? -err : 0;
|
||
}
|
||
</code></pre>
|
||
<h2 id="安装依赖"><a class="header" href="#安装依赖">安装依赖</a></h2>
|
||
<p>构建示例需要 clang、libelf 和 zlib。包名在不同的发行版中可能会有所不同。</p>
|
||
<p>在 Ubuntu/Debian 上，你需要执行以下命令：</p>
|
||
<pre><code class="language-shell">sudo apt install clang libelf1 libelf-dev zlib1g-dev
|
||
</code></pre>
|
||
<p>在 CentOS/Fedora 上，你需要执行以下命令：</p>
|
||
<pre><code class="language-shell">sudo dnf install clang elfutils-libelf elfutils-libelf-devel zlib-devel
|
||
</code></pre>
|
||
<h2 id="编译运行"><a class="header" href="#编译运行">编译运行</a></h2>
|
||
<p>编译运行上述代码：</p>
|
||
<pre><code class="language-console">$ git submodule update --init --recursive
|
||
$ make
|
||
BPF .output/bootstrap.bpf.o
|
||
GEN-SKEL .output/bootstrap.skel.h
|
||
CC .output/bootstrap.o
|
||
BINARY bootstrap
|
||
$ sudo ./bootstrap
|
||
[sudo] password for yunwei:
|
||
TIME EVENT COMM PID PPID FILENAME/EXIT CODE
|
||
03:16:41 EXEC sh 110688 80168 /bin/sh
|
||
03:16:41 EXEC which 110689 110688 /usr/bin/which
|
||
03:16:41 EXIT which 110689 110688 [0] (0ms)
|
||
03:16:41 EXIT sh 110688 80168 [0] (0ms)
|
||
03:16:41 EXEC sh 110690 80168 /bin/sh
|
||
03:16:41 EXEC ps 110691 110690 /usr/bin/ps
|
||
03:16:41 EXIT ps 110691 110690 [0] (49ms)
|
||
03:16:41 EXIT sh 110690 80168 [0] (51ms)
|
||
</code></pre>
|
||
<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
|
||
<p>通过这个实例，我们了解了如何将 eBPF 程序与用户态程序结合使用。这种结合为开发者提供了一个强大的工具集，可以实现跨内核和用户空间的高效数据收集和处理。通过使用 eBPF 和 libbpf，您可以构建更高效、可扩展和安全的监控和性能分析工具。</p>
|
||
<p>如果您希望学习更多关于 eBPF 的知识和实践，可以访问我们的教程代码仓库 <a href="https://github.com/eunomia-bpf/bpf-developer-tutorial">https://github.com/eunomia-bpf/bpf-developer-tutorial</a> 或网站 <a href="https://eunomia.dev/zh/tutorials/">https://eunomia.dev/zh/tutorials/</a> 以获取更多示例和完整的教程。</p>
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