openwrt helloworld

前些日子又搞起了OpenWRT，之前一直只是使用shell或者Lua实现自己的想法，随着C渐渐使用的顺畅了，打算学习下OpenWRT上程序的编写以及交叉编译。
首先列下目录结构

lee@ubuntu:~/OpenWrt-SDK-ar71xx-for-linux-i486-gcc-4.6-linaro_uClibc-0.9.33.2/package$ tree

.

|-- hiOpenWRT

| |-- Makefile

| `-- src

| |-- hiOpenwrt.c

| `-- Makefile

|-- Makefile

`-- rules.mk

    这是在OpenWRT-SDK/package下的文件结构，需要自己建的目录有hiOpenwrt/
和hiOpenwrt/src/ ；需要自己建的文件有:
src下的hiOpenwrt.c

#include <stdlib.h>

#include <stdio.h>

int main(void){

    printf("Hi,OpenWRT!\n");

    return 0;

}

src下Makefile：src下Makefile：

# build hiOpenwrt executable when user executes "make"

hiOpenwrt: hiOpenwrt.o

$(CC) $(LDFLAGS) hiOpenwrt.o -o hiOpenwrt

hiOpenwrt.o: hiOpenwrt.c

$(CC) $(CFLAGS) -c hiOpenwrt.c

#remove object files and executable when user executes "make clean"

clean:

rm *.o hiOpenwrt

当然，在hiOpenwrt/Makefile也需要写，只不过这个要求比较多，格式如下：

点击(此处)折叠或打开

#-----官方文档如下

This is the OpenWrt SDK. It contains a stripped-down version of the buildroot. You can use it to test/develop packages without having to compile your own toolchain or any of the libraries included with OpenWrt.

To use it, just put your buildroot-compatible package directory in the subdir 'package/' and run 'make' from this directory.

#------ OPENWRT集成非官方包之Makefile规则

include $(TOPDIR)/rules.mk

PKG_NAME:=[软件包名字 和文件夹名称一样]

PKG_VERSION:=[软件包版本 自己写个]

PKG_RELEASE:=1

PKG_BUILD_DIR := $(BUILD_DIR)/$(PKG_NAME)

include $(INCLUDE_DIR)/package.mk

define Package/$(PKG_NAME)

SECTION:=utils

CATEGORY:=[软件包在menuconfig里的位置 比如Base system]

DEPENDS:=[依赖包 两个之间通过空格分隔 前面加+为默认显示 选中该软件包自动选中依赖包 不加+为默认不显示 选中依赖包才显示]

TITLE:=[标题]

PKGARCH:=[平台 比如ar71xx 全部写all]

MAINTAINER:=[作者]

endef

define Package/$(PKG_NAME)/description

[软件包简介]

endef

#非本目录下的源码文件, 拷贝到此相应目录下.

# 如../../xucommon/xucommon.c, 则将 xucommon.c 拷贝到此目录下的源码的 ../../

define Build/Prepare

mkdir -p $(PKG_BUILD_DIR)

$(CP) ./src/* $(PKG_BUILD_DIR)/

endef

define Build/Configure

endef

define Build/Compile

endef

define Package/$(PKG_NAME)/conffiles

[升级时保留文件/备份时备份文件 一个文件一行]

endef

define Package/$(PKG_NAME)/install

$(CP) ./files/* $(1)/

endef

define Package/$(PKG_NAME)/preinst

[安装前执行的脚本 记得加上#!/bin/sh 没有就空着]

#!/bin/sh

uci -q batch <<-EOF >/dev/null

delete ucitrack.@aria2[-1]

add ucitrack aria2

set ucitrack.@aria2[-1].init=aria2

commit ucitrack

EOF

exit 0

endef

define Package/$(PKG_NAME)/postinst

[安装后执行的脚本 记得加上#!/bin/sh 没有就空着]

#!/bin/sh

rm -f /tmp/luci-indexcache

exit 0

endef

Package/$(PKG_NAME)/prerm

[删除前执行的脚本 记得加上#!/bin/sh 没有就空着]

endef

Package/$(PKG_NAME)/postrm

[删除后执行的脚本 记得加上#!/bin/sh 没有就空着]

endef

$(eval $(call BuildPackage,$(PKG_NAME)))

自己的hiOpenwrt的Makefile自己的hiOpenwrt的Makefile

点击(此处)折叠或打开

##############################################

# OpenWrtMakefile for hiOpenwrt program

#

#

# Most ofthe variables used here are defined in

# theinclude directives below. We just need to

# specifya basic description of the package,

# whereto build our program, where to find

# thesource files, and where to install the

# compiled program on the router.

#

# Be verycareful of spacing in this file.

# Indentsshould be tabs, not spaces, and

# thereshould be no trailing whitespace in

# linesthat are not commented.

#

##############################################

include $(TOPDIR)/rules.mk

# Nameand release number of this package

PKG_NAME:=hiOpenWRT

PKG_RELEASE:=1

# Thisspecifies the directory where we're going to build the program.

# Theroot build directory, $(BUILD_DIR), is by default the build_mipsel

#directory in your OpenWrt SDK directory

PKG_BUILD_DIR:= $(BUILD_DIR)/$(PKG_NAME)

include $(INCLUDE_DIR)/package.mk

# Specifypackage information for this program.

# Thevariables defined here should be self explanatory.

# If youare running Kamikaze, delete the DESCRIPTION

#variable below and uncomment the Kamikaze define

# directivefor the description below

define Package/$(PKG_NAME)

SECTION:=utils

CATEGORY:=Utilities

TITLE:=hiOpenwrt-- prints a snarky message

endef

# Specifywhat needs to be done to prepare for building the package.

# In ourcase, we need to copy the source files to the build directory.

# This isNOT the default. The default uses thePKG_SOURCE_URL and the

#PKG_SOURCE which is not defined here to download the source from the web.

# Inorder to just build a simple program that we have just written, it is

# mucheasier to do it this way.

define Build/Prepare

mkdir -p $(PKG_BUILD_DIR)

$(CP) ./src/* $(PKG_BUILD_DIR)/

endef

# We donot need to define Build/Configure or Build/Compile directives

# Thedefaults are appropriate for compiling a simple program such as this one

# Specifywhere and how to install the program. Since we only have one file,

# thehelloworld executable, install it by copying it to the /bin directory on

# therouter. The $(1) variable represents the root directory on the router running

#OpenWrt. The $(INSTALL_DIR) variable contains a command to prepare the install

#directory if it does not already exist. Likewise $(INSTALL_BIN) contains the

# commandto copy the binary file from its current location (in our case the build

#directory) to the install directory.

define Package/$(PKG_NAME)/install

$(INSTALL_DIR) $(1)/bin

$(INSTALL_BIN) $(PKG_BUILD_DIR)/hiOpenwrt $(1)/bin/

endef

# Thisline executes the necessary commands to compile our program.

# Theabove define directives specify all the information needed, but this

# linecalls BuildPackage which in turn actually uses this information to

# build apackage.

$(eval $(call BuildPackage,$(PKG_NAME)))

生成ipk的命令：

make package/hiOpenWRT/compile V=s

加上V=s的目的是为了详细打印。

生成出来的ipk文件将在bin/ar71xx/packages/下，同时，也可以在build_dir/ build_dir/下找到可执行文件以及源码。

lee@ubuntu:~/OpenWrt-SDK-ar71xx-for-linux-i486-gcc-4.6-linaro_uClibc-0.9.33.2$ tree | head -n 20

.

|-- bin

| |-- ar71xx

| | `-- packages

| | `-- hiOpenWRT_1_ar71xx.ipk

| `-- packages

|-- build_dir

| `-- build_dir

| `-- hiOpenWRT

| |-- hiOpenwrt

| |-- hiOpenwrt.c

| |-- hiOpenwrt.o

| |-- ipkg-ar71xx

| | `-- hiOpenWRT

| | |-- bin

| | | `-- hiOpenwrt

| | `-- CONTROL

| | `-- control

| `-- Makefile

|-- Config.in

一点总结：

    目录结构很重要，如果目录结构不正确，那么Openwrt是不可能正确编译出ipk的。
    在学习编译过程中出现了很多处错误，最让我头疼的是Makefile的格式，这部分很容易错误而编译失败。
Makefile编写规则：

target ... : prerequisites ...

<tab>command

...

...

target也就是一个目标文件，可以是Object File，也可以是执行文件。还可以是一个标签

（Label），对于标签这种特性，在后续的“伪目标”章节中会有叙述。

prerequisites就是，要生成那个target所需要的文件或是目标。

command也就是make需要执行的命令。（任意的Shell命令）

这是一个文件的依赖关系，也就是说，target这一个或多个的目标文件依赖于prerequisi

tes中的文件，其生成规则定义在command中。说白一点就是说，prerequisites中如果有一个以上的文件比target文件要新的话，command所定义的命令就会被执行。这就是 Makefile的规则。也就是Makefile中最核心的内容。