/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
#define BPF_NO_GLOBAL_DATA
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>

typedef unsigned int u32;
typedef int pid_t;
const pid_t pid_filter = 0;

char LICENSE[] SEC("license") = "Dual BSD/GPL";

SEC("tp/syscalls/sys_enter_write")
int handle_tp(void *ctx)
{
	pid_t pid = bpf_get_current_pid_tgid() >> 32;
	if (pid_filter && pid != pid_filter)
		return 0;
	bpf_printk("BPF triggered from PID %d.\n", pid);
	return 0;
}

minimal is just that – a minimal practical BPF application example. It doesn't use or require BPF CO-RE, so should run on quite old kernels. It installs a tracepoint handler which is triggered once every second. It uses bpf_printk() BPF helper to communicate with the world.

$ sudo ecli  examples/bpftools/minimal/package.json
Runing eBPF program...

To see it's output, read /sys/kernel/debug/tracing/trace_pipe file as a root:

$ sudo cat /sys/kernel/debug/tracing/trace_pipe
           <...>-3840345 [010] d... 3220701.101143: bpf_trace_printk: BPF triggered from PID 3840345.
           <...>-3840345 [010] d... 3220702.101265: bpf_trace_printk: BPF triggered from PID 3840345.

minimal is great as a bare-bones experimental playground to quickly try out new ideas or BPF features.

Compile and Run with eunomia-bpf

Compile:

docker run -it -v `pwd`/:/src/ yunwei37/ebpm:latest

or compile with ecc:

$ ecc minimal.bpf.c
Compiling bpf object...
Packing ebpf object and config into package.json...

Run:

sudo ecli ./package.json

README.md Unescape Escape

eBPF 入门开发实践指南二：Hello World，基本框架和开发流程

Hello World - minimal eBPF program

Compile and Run with eunomia-bpf

README.md