Rust如何开发eBPF应用?(一)

前言

eBPF是一项革命性的技术，可以在Linux内核中运行沙盒程序，而无需重新编译内核或加载内核模块。它能够在许多内核 hook 点安全地执行字节码，主要应用在云原生网络、安全、跟踪监控等方面。

eBPF 基金会 (https://ebpf.io) 是一个为 eBPF 技术而创建的非盈利性组织，隶属于 Linux 基金会，其意在推动 eBPF 更好地发展，使其得到更加广泛的运用。

下面我将介绍如何在Rust中开发基于eBPF技术的应用示例。（该示例教程主要面向具备Rust开发基础的同学）

(一)环境准备

一台VM或Linux系统主机

推荐系统：Ubuntu20.04

内存：4G以上

Rust开发工具链：v1.56~

(二)安装llvm13（编译bpf字节码需要）

apt-get update 
apt-get -y install wget build-essential software-properties-common lsb-release libelf-dev linux-headers-generic pkg-config
wget https://apt.llvm.org/llvm.sh
chmod +x llvm.sh
./llvm.sh 13
rm -f ./llvm.sh

//检验是否安装成功，输出版本号表示安装成功
llvm-config-13 --version | grep 13

(三)安装 cargo-bpf脚手架

cargo install cargo-bpf --no-default-features --features=llvm13

(四)应用示例

#1、创建用户空间代码目录
cargo new bpfdemo
cd bpfdemo
#2、创建bpf代码目录
cargo bpf new probes
ls
>>Cargo.lock  Cargo.toml  probes  src
#3、编写一个openmonitor bpf程序 输出系统打开的文件
cd probes
cargo bpf add openmonitor
cd src 
ls
>>lib.rs  openmonitor
cd openmonitor
nano main.rs

完整openmonitor/main.rs代码如下：

#![no_std]
#![no_main]

use probes::openmonitor::*;
use redbpf_probes::kprobe::prelude::*;

program!(0xFFFFFFFE, "GPL");

#[map]
static mut OPEN_PATHS: PerfMap<OpenPath> = PerfMap::with_max_entries(1024);

#[kprobe]
fn do_sys_open(regs: Registers) {
    let mut path = OpenPath::default();
    unsafe {
        let filename = regs.parm2() as *const u8;
        if bpf_probe_read_user_str(
            path.filename.as_mut_ptr() as *mut _,
            path.filename.len() as u32,
            filename as *const _,
        ) <= 0
        {
            bpf_trace_printk(b"error on bpf_probe_read_user_str\0");
            return;
        }
        OPEN_PATHS.insert(regs.ctx, &path);
    }
}

完整openmonitor/mod.rs代码如下

pub const PATHLEN: usize = 256;

#[repr(C)]
#[derive(Debug, Clone)]
pub struct OpenPath {
    pub filename: [u8; PATHLEN],
}

impl Default for OpenPath {
    fn default() -> OpenPath {
        OpenPath {
            filename: [0; PATHLEN],
        }
    }
}

#4.在probes目录下编译bpf程序,生成openmonitor.elf文件
cargo bpf build --target-dir=../target
ls ../target/bpf/programs/openmonitor/openmonitor.elf

#5.在用户空间代码中使用bpf程序，获取系统打开文件
cd ../src
nano main.rs

完整bpfdemo/src/main.rs代码如下

use futures::stream::StreamExt;
use std::{ffi::CStr, ptr};
use tracing::Level;
use tracing_subscriber::FmtSubscriber;

use redbpf::load::Loader;

use probes::openmonitor::OpenPath;

fn probe_code() -> &'static [u8] {
    include_bytes!(concat!(
        env!("CARGO_MANIFEST_DIR"),
        "/target/bpf/programs/openmonitor/openmonitor.elf"
    ))
}

#[tokio::main(flavor = "current_thread")]
async fn main() {
    let subscriber = FmtSubscriber::builder()
        .with_max_level(Level::WARN)
        .finish();
    tracing::subscriber::set_global_default(subscriber).unwrap();

    let mut loaded = Loader::load(probe_code()).expect("error on Loader::load");

    let probe = loaded
        .kprobe_mut("do_sys_open")
        .expect("error on Loaded::kprobe_mut");
    probe
        .attach_kprobe("do_sys_open", 0)
        .expect("error on KProbe::attach_kprobe");
    probe
        .attach_kprobe("do_sys_openat2", 0)
        .expect("error on KProbe::attach_kprobe");

    while let Some((map_name, events)) = loaded.events.next().await {
        if map_name == "OPEN_PATHS" {
            for event in events {
                let open_path = unsafe { ptr::read(event.as_ptr() as *const OpenPath) };
                unsafe {
                    let cfilename = CStr::from_ptr(open_path.filename.as_ptr() as *const _);
                    println!("{}", cfilename.to_string_lossy());
                };
            }
        }
    }
}

#6.在bpfdemo目录下编译运行
cargo build
cargo run

#将会输出系统实时打开的文件
>>
/proc/driver/nvidia/params
/dev/nvidia0
/proc/driver/nvidia/params
/dev/nvidia0
/proc/driver/nvidia/params
/dev/nvidia0
/etc/localtime
/lib/x86_64-linux-gnu/libcuda.so.1
/lib/x86_64-linux-gnu/libm.so.6
/etc/netconfig
/sys/fs/cgroup/unified/system.slice/systemd-udevd.service/cgroup.procs
/sys/fs/cgroup/unified/system.slice/systemd-udevd.service/cgroup.threads
/proc/3084/cmdline
/proc/3729/cmdline
/proc/3994/cmdline
/proc/8823/cmdline
/proc/2231364/cmdline
/proc/2431788/cmdline
/proc/2560949/cmdline
/sys/class/hwmon
/sys/class/hwmon/hwmon6
/sys/class/hwmon/hwmon4
/sys/class/hwmon/hwmon2
/sys/class/hwmon/hwmon0
/sys/class/hwmon/hwmon7
/sys/class/hwmon/hwmon5

完毕！