update example

.gitignore

@@ -1,2 +1,3 @@
 .direnv
 /build
+*.o

README.md

@@ -1,86 +1,14 @@
-# **libbpf-starter-template**
+# **An example to show how to use libbpf for bpf relocate**
 
 ![License: MIT](https://img.shields.io/badge/License-MIT-green.svg)
 [![Build and publish](https://github.com/eunomia-bpf/libbpf-starter-template/actions/workflows/publish.yml/badge.svg)](https://github.com/eunomia-bpf/libbpf-starter-template/actions/workflows/publish.yml)
 ![GitHub stars](https://img.shields.io/github/stars/eunomia-bpf/libbpf-starter-template?style=social)
 
-Welcome to the **`libbpf-starter-template`**! This project template is designed to help you quickly start
-developing eBPF projects using libbpf in C. The template provides a solid starting point with a Makefile, 
-Dockerfile, and GitHub action, along with all necessary dependencies to simplify your development process.
-
-借助于 GitHub 模板和 Github Codespace，可以轻松构建 eBPF 项目和开发环境，一键在线编译运行 eBPF 程序。关于中文的文档和详细的 eBPF 开发教程，可以参考：https://github.com/eunomia-bpf/bpf-developer-tutorial
-
-There are other templates for other languages:
-
-- <https://github.com/eunomia-bpf/libbpf-starter-template>: eBPF project template based on the C language and the libbpf framework.
-- <https://github.com/eunomia-bpf/cilium-ebpf-starter-template>: eBPF project template based on the Go language and the cilium/ebpf framework.
-- <https://github.com/eunomia-bpf/libbpf-rs-starter-template>: eBPF project template based on the Rust language and the libbpf-rs framework.
-- <https://github.com/eunomia-bpf/eunomia-template>: eBPF project template based on the C language and the eunomia-bpf framework.
-
-## **Getting Started**
-
-To get started, simply click the "Use this template" button on the GitHub repository page. This will create
-a new repository in your account with the same files and structure as this template.
-
-### Use docker
-
-Run the following code to run the eBPF code from the cloud to your local machine in one line:
-
-```console
-$ sudo docker run --rm -it --privileged ghcr.io/eunomia-bpf/libbpf-template:latest
-TIME     EVENT COMM             PID     PPID    FILENAME/EXIT CODE
-09:25:14 EXEC  sh               28142   1788    /bin/sh
-09:25:14 EXEC  playerctl        28142   1788    /nix/store/vf3rsb7j3p7zzyjpb0a3axl8yq4z1sq5-playerctl-2.4.1/bin/playerctl
-09:25:14 EXIT  playerctl        28142   1788    [1] (6ms)
-09:25:15 EXEC  sh               28145   1788    /bin/sh
-09:25:15 EXEC  playerctl        28145   1788    /nix/store/vf3rsb7j3p7zzyjpb0a3axl8yq4z1sq5-playerctl-2.4.1/bin/playerctl
-09:25:15 EXIT  playerctl        28145   1788    [1] (6ms)
-```
-
-### Use Nix
-
-Using [direnv](https://github.com/direnv/direnv) and nix, you can quickly access a dev shell with a complete development environment.
-
-With direnv, you can automatically load the required dependencies when you enter the directory.
-This way you don't have to worry about installing dependencies to break your other project development environment.
-
-See how to install direnv and Nix:
-- direnv: https://github.com/direnv/direnv/blob/master/docs/installation.md
-- Nix: run
-```
-sh <(curl -L https://nixos.org/nix/install) --daemon
-```
-
-Then use the following command to enable direnv support in this directory.
-
-```sh
-direnv allow
-```
-
-If you want use nix flake without direnv, simply run:
-
-```sh
-nix develop
-```
-
-## **Features**
-
-This starter template includes the following features:
-
-- A **`Makefile`** that allows you to build the project in one command
-- A **`Dockerfile`** to create a containerized environment for your project
-- A **`flake.nix`** to enter a dev shell with needed dependencies
-- A GitHub action to automate your build and publish process
-  and docker image
-- All necessary dependencies for C development with libbpf
+An example to show how to use libbpf for bpf relocate
 
 ## **How to use**
 
-### **1. Create a new repository using this template**
-
-Click the "Use this template" button on the GitHub repository page to create a new repository based on this template.
-
-### **2. Clone your new repository**
+### **Clone your new repository**
 
 Clone your newly created repository to your local machine:
 
@@ -94,7 +22,7 @@ Or after clone the repo, you can update the git submodule with following command
 git submodule update --init --recursive
 ```
 
-### **3. Install dependencies**
+### **Install dependencies**
 
 For dependencies, it varies from distribution to distribution. You can refer to shell.nix and dockerfile for installation.
 
@@ -108,7 +36,7 @@ sudo apt-get install -y --no-install-recommends \
 
 to install dependencies.
 
-### **4. Build the project**
+### **Build the project**
 
 To build the project, run the following command:
 
@@ -123,13 +51,7 @@ This will compile your code and create the necessary binaries. You can you the `
 You can run the binary with:
 
 ```console
-sudo src/bootstrap
-```
-
-Or with Github Packages locally:
-
-```console
-docker run --rm -it --privileged -v $(pwd):/examples ghcr.io/eunomia-bpf/libbpf-template:latest
+sudo src/relo
 ```
 
 ### **7. GitHub Actions**

examples/Makefile

@@ -0,0 +1,20 @@
+# BPF compiler
+BPF_CC = clang
+# BPF C flags
+BPF_CFLAGS = -O2 -target bpf -c -g
+# BPF source files
+BPF_SRCS = $(wildcard *.bpf.c)
+# BPF object files
+BPF_OBJS = $(BPF_SRCS:.c=.o)
+
+all: $(BPF_OBJS) base.btf
+
+%.bpf.o: %.bpf.c
+	$(BPF_CC) $(BPF_CFLAGS) $< -o $@
+
+base.btf:
+	clang -g -c btf-base.c -o btf-base.bpf.o
+	pahole  --btf_encode_detached base.btf btf-base.bpf.o
+
+clean:
+	rm -f $(BPF_OBJS) base.btf

examples/btf-base.c

@@ -0,0 +1,15 @@
+// #define USE_NEW_VERSION
+// use a different struct
+struct data {
+        int a;
+        #ifdef USE_NEW_VERSION
+        int b;
+        #endif
+        int c;
+        int d;
+};
+
+int add_test(struct data *d) {
+    return d->a + d->c;
+}
+

examples/btf-relo.bpf.c

@@ -0,0 +1,24 @@
+#define USE_NEW_VERSION
+
+#ifndef BPF_NO_PRESERVE_ACCESS_INDEX
+#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
+#endif
+
+struct data {
+        int a;
+        #ifdef USE_NEW_VERSION
+        int b;
+        #endif
+        int c;
+        int d;
+};
+
+#ifndef BPF_NO_PRESERVE_ACCESS_INDEX
+#pragma clang attribute pop
+#endif
+
+
+int add_test(struct data *d) {
+    return d->a + d->c;
+}
+

src/Makefile

@@ -21,7 +21,7 @@ INCLUDES := -I$(OUTPUT) -I../libbpf/include/uapi -I$(dir $(VMLINUX))
 CFLAGS := -g -Wall
 ALL_LDFLAGS := $(LDFLAGS) $(EXTRA_LDFLAGS)
 
-APPS = bootstrap
+APPS = relo
 
 # Get Clang's default includes on this system. We'll explicitly add these dirs
 # to the includes list when compiling with `-target bpf` because otherwise some