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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../https://github.com/eunomia-bpf/bpf-developer-tutorial.html">https://github.com/eunomia-bpf/bpf-developer-tutorial</a></li><li class="chapter-item expanded affix "><li class="part-title">入门文档</li><li class="chapter-item expanded "><a href="../0-introduce/index.html"><strong aria-hidden="true">1.</strong> lesson 0-introduce</a></li><li class="chapter-item expanded "><a href="../1-helloworld/index.html"><strong aria-hidden="true">2.</strong> lesson 1-helloworld</a></li><li class="chapter-item expanded "><a href="../2-kprobe-unlink/index.html"><strong aria-hidden="true">3.</strong> lesson 2-kprobe-unlink</a></li><li class="chapter-item expanded "><a href="../3-fentry-unlink/index.html"><strong aria-hidden="true">4.</strong> lesson 3-fentry-unlink</a></li><li class="chapter-item expanded "><a href="../4-opensnoop/index.html"><strong aria-hidden="true">5.</strong> lesson 4-opensnoop</a></li><li class="chapter-item expanded "><a href="../5-uprobe-bashreadline/index.html"><strong aria-hidden="true">6.</strong> lesson 5-uprobe-bashreadline</a></li><li class="chapter-item expanded "><a href="../6-sigsnoop/index.html" class="active"><strong aria-hidden="true">7.</strong> lesson 6-sigsnoop</a></li><li class="chapter-item expanded "><a href="../7-execsnoop/index.html"><strong aria-hidden="true">8.</strong> lesson 7-execsnoop</a></li><li class="chapter-item expanded "><a href="../8-exitsnoop/index.html"><strong aria-hidden="true">9.</strong> lesson 8-execsnoop</a></li><li class="chapter-item expanded "><a href="../9-runqlat/index.html"><strong aria-hidden="true">10.</strong> lesson 9-runqlat</a></li><li class="chapter-item expanded "><a href="../10-hardirqs/index.html"><strong aria-hidden="true">11.</strong> lesson 10-hardirqs</a></li><li class="chapter-item expanded affix "><li class="part-title">进阶文档和示例</li><li class="chapter-item expanded "><a href="../11-bootstrap/index.html"><strong aria-hidden="true">12.</strong> lesson 11-bootstrap</a></li><li class="chapter-item expanded "><a href="../12-profile/index.html"><strong aria-hidden="true">13.</strong> lesson 12-profile</a></li><li class="chapter-item expanded "><a href="../13-tcpconnlat/index.html"><strong aria-hidden="true">14.</strong> lesson 13-tcpconnlat</a></li><li class="chapter-item expanded "><a href="../14-tcpstates/index.html"><strong aria-hidden="true">15.</strong> lesson 14-tcpstates</a></li><li class="chapter-item expanded "><a href="../15-javagc/index.html"><strong aria-hidden="true">16.</strong> lesson 15-javagc</a></li><li class="chapter-item expanded "><a href="../16-memleak/index.html"><strong aria-hidden="true">17.</strong> lesson 16-memleak</a></li><li class="chapter-item expanded "><a href="../17-biopattern/index.html"><strong aria-hidden="true">18.</strong> lesson 17-biopattern</a></li><li class="chapter-item expanded "><a href="../18-further-reading/index.html"><strong aria-hidden="true">19.</strong> lesson 18-further-reading</a></li><li class="chapter-item expanded "><a href="../19-lsm-connect/index.html"><strong aria-hidden="true">20.</strong> lesson 19-lsm-connect</a></li><li class="chapter-item expanded "><a href="../20-tc/index.html"><strong aria-hidden="true">21.</strong> lesson 20-tc</a></li><li class="chapter-item expanded "><a href="../21-xdp/index.html"><strong aria-hidden="true">22.</strong> lesson 21-xdp</a></li><li class="chapter-item expanded affix "><li class="part-title">高级主题</li><li class="chapter-item expanded "><a href="../22-android/index.html"><strong aria-hidden="true">23.</strong> 在 Android 上使用 eBPF 程序</a></li><li class="chapter-item expanded "><a href="../30-sslsniff/index.html"><strong aria-hidden="true">24.</strong> 使用 uprobe 捕获多种库的 SSL/TLS 明文数据</a></li><li class="chapter-item expanded "><a href="../23-http/index.html"><strong aria-hidden="true">25.</strong> 使用 eBPF socket filter 或 syscall trace 追踪 HTTP 请求和其他七层协议</a></li><li class="chapter-item expanded "><a href="../29-sockops/index.html"><strong aria-hidden="true">26.</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">27.</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">28.</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">29.</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">30.</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">31.</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="../18-further-reading/ebpf-security.zh.html"><strong aria-hidden="true">32.</strong> eBPF 运行时的安全性与面临的挑战</a></li><li class="chapter-item expanded "><a href="../34-syscall/index.html"><strong aria-hidden="true">33.</strong> 使用 eBPF 修改系统调用参数</a></li><li class="chapter-item expanded "><a href="../35-user-ringbuf/index.html"><strong aria-hidden="true">34.</strong> eBPF开发实践使用 user ring buffer 向内核异步发送信息</a></li><li class="chapter-item expanded "><a href="../36-userspace-ebpf/index.html"><strong aria-hidden="true">35.</strong> 用户空间 eBPF 运行时:深度解析与应用实践</a></li><li class="chapter-item expanded "><a href="../37-uprobe-rust/index.html"><strong aria-hidden="true">36.</strong> 使用 uprobe 追踪 Rust 应用程序</a></li><li class="chapter-item expanded "><a href="../38-btf-uprobe/index.html"><strong aria-hidden="true">37.</strong> 借助 eBPF 和 BTF让用户态也能一次编译、到处运行</a></li><li class="chapter-item expanded affix "><li class="part-title">bcc 和 bpftrace 教程与文档</li><li class="chapter-item expanded "><a href="../bcc-documents/kernel-versions.html"><strong aria-hidden="true">38.</strong> BPF Features by Linux 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<h1 id="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 class="header" href="#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">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></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六篇,主要介绍如何实现一个 eBPF 工具,捕获进程发送信号的系统调用集合,使用 hash map 保存状态。</p>
<h2 id="sigsnoop"><a class="header" href="#sigsnoop">sigsnoop</a></h2>
<p>示例代码如下:</p>
<pre><code class="language-c">#include &lt;vmlinux.h&gt;
#include &lt;bpf/bpf_helpers.h&gt;
#include &lt;bpf/bpf_tracing.h&gt;
#define MAX_ENTRIES 10240
#define TASK_COMM_LEN 16
struct event {
unsigned int pid;
unsigned int tpid;
int sig;
int ret;
char comm[TASK_COMM_LEN];
};
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, MAX_ENTRIES);
__type(key, __u32);
__type(value, struct event);
} values SEC(".maps");
static int probe_entry(pid_t tpid, int sig)
{
struct event event = {};
__u64 pid_tgid;
__u32 tid;
pid_tgid = bpf_get_current_pid_tgid();
tid = (__u32)pid_tgid;
event.pid = pid_tgid &gt;&gt; 32;
event.tpid = tpid;
event.sig = sig;
bpf_get_current_comm(event.comm, sizeof(event.comm));
bpf_map_update_elem(&amp;values, &amp;tid, &amp;event, BPF_ANY);
return 0;
}
static int probe_exit(void *ctx, int ret)
{
__u64 pid_tgid = bpf_get_current_pid_tgid();
__u32 tid = (__u32)pid_tgid;
struct event *eventp;
eventp = bpf_map_lookup_elem(&amp;values, &amp;tid);
if (!eventp)
return 0;
eventp-&gt;ret = ret;
bpf_printk("PID %d (%s) sent signal %d ",
eventp-&gt;pid, eventp-&gt;comm, eventp-&gt;sig);
bpf_printk("to PID %d, ret = %d",
eventp-&gt;tpid, ret);
cleanup:
bpf_map_delete_elem(&amp;values, &amp;tid);
return 0;
}
SEC("tracepoint/syscalls/sys_enter_kill")
int kill_entry(struct trace_event_raw_sys_enter *ctx)
{
pid_t tpid = (pid_t)ctx-&gt;args[0];
int sig = (int)ctx-&gt;args[1];
return probe_entry(tpid, sig);
}
SEC("tracepoint/syscalls/sys_exit_kill")
int kill_exit(struct trace_event_raw_sys_exit *ctx)
{
return probe_exit(ctx, ctx-&gt;ret);
}
char LICENSE[] SEC("license") = "Dual BSD/GPL";
</code></pre>
<p>上面的代码定义了一个 eBPF 程序,用于捕获进程发送信号的系统调用,包括 kill、tkill 和 tgkill。它通过使用 tracepoint 来捕获系统调用的进入和退出事件,并在这些事件发生时执行指定的探针函数,例如 probe_entry 和 probe_exit。</p>
<p>在探针函数中,我们使用 bpf_map 存储捕获的事件信息,包括发送信号的进程 ID、接收信号的进程 ID、信号值和进程的可执行文件名称。在系统调用退出时我们将获取存储在 bpf_map 中的事件信息,并使用 bpf_printk 打印进程 ID、进程名称、发送的信号和系统调用的返回值。</p>
<p>最后,我们还需要使用 SEC 宏来定义探针,并指定要捕获的系统调用的名称,以及要执行的探针函数。</p>
<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-shell">docker run -it -v `pwd`/:/src/ ghcr.io/eunomia-bpf/ecc-`uname -m`:latest
</code></pre>
<p>或者</p>
<pre><code class="language-console">$ ecc sigsnoop.bpf.c
Compiling bpf object...
Generating export types...
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
systemd-journal-363 [000] d...1 672.563868: bpf_trace_printk: PID 363 (systemd-journal) sent signal 0
systemd-journal-363 [000] d...1 672.563869: bpf_trace_printk: to PID 1400, ret = 0
systemd-journal-363 [000] d...1 672.563870: bpf_trace_printk: PID 363 (systemd-journal) sent signal 0
systemd-journal-363 [000] d...1 672.563870: bpf_trace_printk: to PID 1527, ret = -3
</code></pre>
<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
<p>本文主要介绍如何实现一个 eBPF 工具,捕获进程发送信号的系统调用集合,使用 hash map 保存状态。使用 hash map 需要定义一个结构体:</p>
<pre><code class="language-c">struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, MAX_ENTRIES);
__type(key, __u32);
__type(value, struct event);
} values SEC(".maps");
</code></pre>
<p>并使用一些对应的 API 进行访问,例如 bpf_map_lookup_elem、bpf_map_update_elem、bpf_map_delete_elem 等。</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>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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