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<ol class="chapter"><li class="chapter-item expanded affix "><li class="part-title">eBPF 入门开发实践教程</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"><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" class="active"><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 affix "><li class="part-title">eBPF入门实践教程</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 Guide</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>
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<h1 id="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 class="header" href="#ebpf-入门开发实践教程十在-ebpf-中使用-hardirqs-或-softirqs-捕获中断事件">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></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>本文是 eBPF 入门开发实践教程的第十篇，在 eBPF 中。</p>
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<h2 id="hardirqs是什么"><a class="header" href="#hardirqs是什么">hardirqs是什么？</a></h2>
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<p>hardirqs 是 bcc-tools 工具包的一部分，该工具包是一组用于在 Linux 系统上执行系统跟踪和分析的实用程序。
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hardirqs 是一种用于跟踪和分析 Linux 内核中的中断处理程序的工具。它使用 BPF（Berkeley Packet Filter）程序来收集有关中断处理程序的数据，
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并可用于识别内核中的性能问题和其他与中断处理相关的问题。</p>
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<h2 id="实现原理"><a class="header" href="#实现原理">实现原理</a></h2>
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<p>在 Linux 内核中，每个中断处理程序都有一个唯一的名称，称为中断向量。hardirqs 通过检查每个中断处理程序的中断向量，来监控内核中的中断处理程序。当内核接收到一个中断时，它会查找与该中断相关的中断处理程序，并执行该程序。hardirqs 通过检查内核中执行的中断处理程序，来监控内核中的中断处理程序。另外，hardirqs 还可以通过注入 BPF 程序到内核中，来捕获内核中的中断处理程序。这样，hardirqs 就可以监控内核中执行的中断处理程序，并收集有关它们的信息。</p>
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<h2 id="代码实现"><a class="header" href="#代码实现">代码实现</a></h2>
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<pre><code class="language-c">// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2020 Wenbo Zhang
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#include <vmlinux.h>
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#include <bpf/bpf_core_read.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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#include "hardirqs.h"
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#include "bits.bpf.h"
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#include "maps.bpf.h"
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#define MAX_ENTRIES 256
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const volatile bool filter_cg = false;
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const volatile bool targ_dist = false;
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const volatile bool targ_ns = false;
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const volatile bool do_count = false;
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struct {
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__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
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__type(key, u32);
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__type(value, u32);
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__uint(max_entries, 1);
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} cgroup_map SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
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__uint(max_entries, 1);
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__type(key, u32);
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__type(value, u64);
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} start SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, MAX_ENTRIES);
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__type(key, struct irq_key);
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__type(value, struct info);
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} infos SEC(".maps");
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static struct info zero;
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static int handle_entry(int irq, struct irqaction *action)
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{
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if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
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return 0;
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if (do_count) {
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struct irq_key key = {};
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struct info *info;
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bpf_probe_read_kernel_str(&key.name, sizeof(key.name), BPF_CORE_READ(action, name));
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info = bpf_map_lookup_or_try_init(&infos, &key, &zero);
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if (!info)
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return 0;
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info->count += 1;
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return 0;
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} else {
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u64 ts = bpf_ktime_get_ns();
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u32 key = 0;
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if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
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return 0;
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bpf_map_update_elem(&start, &key, &ts, BPF_ANY);
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return 0;
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}
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}
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static int handle_exit(int irq, struct irqaction *action)
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{
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struct irq_key ikey = {};
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struct info *info;
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u32 key = 0;
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u64 delta;
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u64 *tsp;
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if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
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return 0;
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tsp = bpf_map_lookup_elem(&start, &key);
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if (!tsp)
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return 0;
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delta = bpf_ktime_get_ns() - *tsp;
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if (!targ_ns)
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delta /= 1000U;
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bpf_probe_read_kernel_str(&ikey.name, sizeof(ikey.name), BPF_CORE_READ(action, name));
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info = bpf_map_lookup_or_try_init(&infos, &ikey, &zero);
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if (!info)
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return 0;
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if (!targ_dist) {
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info->count += delta;
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} else {
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u64 slot;
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slot = log2(delta);
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if (slot >= MAX_SLOTS)
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slot = MAX_SLOTS - 1;
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info->slots[slot]++;
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}
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return 0;
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}
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SEC("tp_btf/irq_handler_entry")
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int BPF_PROG(irq_handler_entry_btf, int irq, struct irqaction *action)
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{
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return handle_entry(irq, action);
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}
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SEC("tp_btf/irq_handler_exit")
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int BPF_PROG(irq_handler_exit_btf, int irq, struct irqaction *action)
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{
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return handle_exit(irq, action);
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}
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SEC("raw_tp/irq_handler_entry")
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int BPF_PROG(irq_handler_entry, int irq, struct irqaction *action)
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{
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return handle_entry(irq, action);
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}
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SEC("raw_tp/irq_handler_exit")
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int BPF_PROG(irq_handler_exit, int irq, struct irqaction *action)
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{
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return handle_exit(irq, action);
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}
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char LICENSE[] SEC("license") = "GPL";
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</code></pre>
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<p>这是一个 BPF（Berkeley Packet Filter）程序。BPF 程序是小型程序，可以直接在 Linux 内核中运行，用于过滤和操纵网络流量。这个特定的程序似乎旨在收集内核中中断处理程序的统计信息。它定义了一些地图（可以在 BPF 程序和内核的其他部分之间共享的数据结构）和两个函数：handle_entry 和 handle_exit。当内核进入和退出中断处理程序时，分别执行这些函数。handle_entry 函数用于跟踪中断处理程序被执行的次数，而 handle_exit 则用于测量中断处理程序中花费的时间。</p>
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<h2 id="运行代码"><a class="header" href="#运行代码">运行代码</a></h2>
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<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>
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<p>要编译这个程序，请使用 ecc 工具：</p>
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<pre><code class="language-console">$ ecc hardirqs.bpf.c
|
||
Compiling bpf object...
|
||
Packing ebpf object and config into package.json...
|
||
</code></pre>
|
||
<p>然后运行：</p>
|
||
<pre><code class="language-console">sudo ecli ./package.json
|
||
</code></pre>
|
||
<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
|
||
<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>
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