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impl uprobe
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yunwei37
@@ -4,6 +4,35 @@ eBPF (Extended Berkeley Packet Filter) 是 Linux 内核上的一个强大的网
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本文是 eBPF 入门开发实践指南的第二篇，主要介绍 eBPF 的基本框架和开发流程。
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## 下载安装 eunomia-bpf 开发工具
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可以通过以下步骤下载和安装 eunomia-bpf：
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下载 ecli 工具，用于运行 eBPF 程序：
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```console
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$ wget https://aka.pw/bpf-ecli -O ecli && chmod +x ./ecli
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$ ./ecli -h
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Usage: ecli [--help] [--version] [--json] [--no-cache] url-and-args
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```
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下载编译器工具链，用于将 eBPF 内核代码编译为 config 文件或 WASM 模块：
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```console
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$ wget https://github.com/eunomia-bpf/eunomia-bpf/releases/latest/download/eunomia.tar.gz
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$ tar -xvf eunomia.tar.gz -C ~
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$ export PATH=$PATH:~/.eunomia/bin
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$ ecc -h
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eunomia-bpf compiler
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Usage: ecc [OPTIONS] <SOURCE_PATH> [EXPORT_EVENT_HEADER]
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```
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也可以使用 docker 镜像进行编译：
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```console
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$ docker run -it -v `pwd`/:/src/ yunwei37/ebpm:latest # 使用 docker 进行编译。`pwd` 应该包含 *.bpf.c 文件和 *.h 文件。
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```
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## Hello World - minimal eBPF program
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```c
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@@ -38,13 +67,21 @@ int handle_tp(void *ctx)
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$ ecc hello.bpf.c
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Compiling bpf object...
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Packing ebpf object and config into package.json...
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```console
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```
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或使用 docker 镜像进行编译：
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```shell
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docker run -it -v `pwd`/:/src/ yunwei37/ebpm:latest
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```
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然后使用 ecli 运行编译后的程序：
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```console
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$ sudo ecli ./package.json
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Runing eBPF program...
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```
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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：
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```console
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@@ -1,79 +1,105 @@
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---
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layout: post
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title: bootstrap
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date: 2022-10-10 16:18
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category: bpftools
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author: yunwei37
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tags: [bpftools, examples, uprobe, perf event]
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summary: an example of a simple (but realistic) BPF application prints bash commands from all running bash shells on the system.
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---
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# eBPF 入门开发实践指南五：使用 uprobe 捕获 bash 的 readline 函数调用
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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。
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本文是 eBPF 入门开发实践指南的第五篇，主要介绍如何使用 uprobe 捕获 bash 的 readline 函数调用。
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This prints bash commands from all running bash shells on the system.
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## 使用 uprobe 捕获 bash 的 readline 函数调用
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## System requirements:
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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。
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- Linux kernel > 5.5
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- Eunomia's [ecli](https://github.com/eunomia-bpf/eunomia-bpf/tree/master/ecli) installed
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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：
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```c
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/* SPDX-License-Identifier: GPL-2.0 */
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/* Copyright (c) 2021 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 "bashreadline.h"
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## Run
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#define TASK_COMM_LEN 16
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#define MAX_LINE_SIZE 80
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- Compile:
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/* Format of u[ret]probe section definition supporting auto-attach:
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* u[ret]probe/binary:function[+offset]
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*
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* binary can be an absolute/relative path or a filename; the latter is resolved to a
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* full binary path via bpf_program__attach_uprobe_opts.
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*
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* Specifying uprobe+ ensures we carry out strict matching; either "uprobe" must be
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* specified (and auto-attach is not possible) or the above format is specified for
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* auto-attach.
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*/
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SEC("uprobe//bin/bash:readline")
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int BPF_KRETPROBE(printret, const void *ret) {
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char str[MAX_LINE_SIZE];
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char comm[TASK_COMM_LEN];
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u32 pid;
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```shell
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docker run -it -v `pwd`/:/src/ yunwei37/ebpm:latest
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```
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if (!ret)
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return 0;
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or
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bpf_get_current_comm(&comm, sizeof(comm));
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```shell
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ecc bashreadline.bpf.c bashreadline.h
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```
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pid = bpf_get_current_pid_tgid() >> 32;
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bpf_probe_read_user_str(str, sizeof(str), ret);
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- Run:
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```console
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$ sudo ./ecli run eunomia-bpf/examples/bpftools/bootstrap/package.json
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TIME PID STR
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11:17:34 28796 whoami
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11:17:41 28796 ps -ef
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11:17:51 28796 echo "Hello eBPF!"
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```
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## details in bcc
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bpf_printk("PID %d (%s) read: %s ", pid, comm, str);
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return 0;
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};
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char LICENSE[] SEC("license") = "GPL";
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```
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Demonstrations of bashreadline, the Linux eBPF/bcc version.
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This prints bash commands from all running bash shells on the system. For
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example:
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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。
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# ./bashreadline
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TIME PID COMMAND
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05:28:25 21176 ls -l
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05:28:28 21176 date
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05:28:35 21176 echo hello world
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05:28:43 21176 foo this command failed
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05:28:45 21176 df -h
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05:29:04 3059 echo another shell
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05:29:13 21176 echo first shell again
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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。
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When running the script on Arch Linux, you may need to specify the location
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of libreadline.so library:
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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。
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# ./bashreadline -s /lib/libreadline.so
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TIME PID COMMAND
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11:17:34 28796 whoami
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11:17:41 28796 ps -ef
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11:17:51 28796 echo "Hello eBPF!"
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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：
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```c
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SEC("uprobe//bin/bash:readline")
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```
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这表示我们要捕获的是 /bin/bash 二进制文件中的 readline 函数。
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接下来，我们需要使用 BPF_KRETPROBE 宏来定义探针函数，例如：
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```c
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BPF_KRETPROBE(printret, const void *ret)
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```
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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。
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编译运行上述代码：
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The entered command may fail. This is just showing what command lines were
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entered interactively for bash to process.
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```console
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$ ecc bashreadline.bpf.c bashreadline.h
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Compiling bpf object...
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Packing ebpf object and config into package.json...
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$ sudo ecli package.json
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Runing eBPF program...
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```
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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：
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```console
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$ sudo cat /sys/kernel/debug/tracing/trace_pipe
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PID 12345 (bash) read: ls -l
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PID 12345 (bash) read: date
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PID 12345 (bash) read: echo "Hello eBPF!"
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```
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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。
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请注意，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)。
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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。
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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.
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It works by tracing the return of the readline() function using uprobes
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(specifically a uretprobe).
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```
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@@ -1,13 +0,0 @@
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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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/* Copyright (c) 2021 Facebook */
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#ifndef __BASHREADLINE_H
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#define __BASHREADLINE_H
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#define MAX_LINE_SIZE 80
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struct str_t {
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__u32 pid;
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char str[MAX_LINE_SIZE];
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};
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#endif /* __BASHREADLINE_H */
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