今天研究了一下busybox的编译。自己下了一个busybox-1.25.0的版本（直接从busybox官网上下载：https://busybox.net/downloads/），进行编译，遇到了一些问题，通过百度搜索和自己摸索，也成功解决了，详细记录如下：

首先交代一下系统版本和开发环境：

• 操作系统：ubuntu 12.04（64bit）
• 交叉编译工具链：arm-linux-gcc 4.4.3
• busybox源码包：busybox-1.25.0

一、修改Makefile配置

首先解压源码包：

tar -jxvf busybox-1.25.0.tar.bz2

进入busybox-1.25.0目录，修改Makefile文件如下：

ARCH ?= arm
CROSS_COMPILE ?= arm-linux-

二、修改配置文件

make menuconfig

选择Busybox Settings—>Build Options—>，选择[*] Build Busybox as a static binary（no shared libs）；

三、编译源码，解决问题

make clean
make

出现如下错误：

miscutils/nandwrite.c: In function 'nandwrite_main':
miscutils/nandwrite.c:151: error: 'MTD_FILE_MODE_RAW' undeclared (first use in this function)
miscutils/nandwrite.c:151: error: (Each undeclared identifier is reported only once
miscutils/nandwrite.c:151: error: for each function it appears in.)
scripts/Makefile.build:197: recipe for target 'miscutils/nandwrite.o' failed
make[1]: *** [miscutils/nandwrite.o] Error 1
Makefile:742: recipe for target 'miscutils' failed
make: *** [miscutils] Error 2

解决办法：

MTD_FILE_MODE_RAW在/usr/include/mtd/mtd-abi.h中定义，于是将/usr/include/mtd/mtd-abi.h拷贝到busybox的include文件中，然后在nandwrite.c文件中包含该头文件：

gedit miscutils/nandwrite.c 

修改

#include "libbb.h"
#include <mtd/mtd-user.h>

为

#include "libbb.h"
#include "mtd-abi.h"
#include <mtd/mtd-user.h>

此问题解决。继续make，又出现如下错误：

util-linux/blkdiscard.c: In function 'blkdiscard_main':
util-linux/blkdiscard.c:72: error: 'BLKSECDISCARD' undeclared (first use in this function)
util-linux/blkdiscard.c:72: error: (Each undeclared identifier is reported only once
util-linux/blkdiscard.c:72: error: for each function it appears in.)
scripts/Makefile.build:197: recipe for target 'util-linux/blkdiscard.o' failed
make[1]: *** [util-linux/blkdiscard.o] Error 1
Makefile:742: recipe for target 'util-linux' failed
make: *** [util-linux] Error 2

解决办法：

BLKSECDISCARD在/usr/include/linux/fs.h中定义，同上理，直接将/usr/include/linux/fs.h拷贝到busybox的include文件中，不过这次还要额外修改一下文件中的部分内容，否则会出现编译失败。

1、屏蔽以下4个头文件（否则编译时会提示找不到头文件）：

//#include <linux/limits.h>
//#include <linux/ioctl.h>
//#include <linux/blk_types.h>
//#include <linux/types.h>

2、屏蔽以下几个结构体（否则编译时会提示找不到类型定义）：

#if 0
struct fstrim_range {__u64 start;__u64 len;__u64 minlen;
};/* And dynamically-tunable limits and defaults: */
struct files_stat_struct {unsigned long nr_files;     /* read only */unsigned long nr_free_files;    /* read only */unsigned long max_files;        /* tunable */
};struct inodes_stat_t {int nr_inodes;int nr_unused;int dummy[5];       /* padding for sysctl ABI compatibility */
};
#endif

然后修改blkdiscard.c中对fs.h头文件的包含方式：

gedit util-linux/blkdiscard.c

修改

#include <linux/fs.h>

为

#include "fs.h"

继续make，编译能通过了。但是在链接的时候出现问题：

networking/lib.a(nslookup.o): In function `print_host':
nslookup.c:(.text.print_host+0x44): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
debianutils/lib.a(mktemp.o): In function `mktemp_main':
mktemp.c:(.text.mktemp_main+0x98): warning: the use of `mktemp' is dangerous, better use `mkstemp'
networking/lib.a(ipcalc.o): In function `ipcalc_main':
ipcalc.c:(.text.ipcalc_main+0x25c): warning: Using 'gethostbyaddr' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
libbb/lib.a(inet_common.o): In function `INET_resolve':
inet_common.c:(.text.INET_resolve+0x60): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
networking/lib.a(inetd.o): In function `reread_config_file':
inetd.c:(.text.reread_config_file+0x230): warning: Using 'getservbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
networking/lib.a(netstat.o): In function `ip_port_str':
netstat.c:(.text.ip_port_str+0x50): warning: Using 'getservbyport' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
util-linux/lib.a(nsenter.o): In function `nsenter_main':
nsenter.c:(.text.nsenter_main+0x1b0): undefined reference to `setns'
collect2: ld returned 1 exit status
Note: if build needs additional libraries, put them in CONFIG_EXTRA_LDLIBS.
Example: CONFIG_EXTRA_LDLIBS="pthread dl tirpc audit pam"
Makefile:717: recipe for target 'busybox_unstripped' failed
make: *** [busybox_unstripped] Error 1 

解决办法：

make menuconfig

Linux System Utilities—>nsenter，去掉该选项，重新编译make，又出现如下错误：

networking/lib.a(nslookup.o): In function `print_host':
nslookup.c:(.text.print_host+0x44): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
debianutils/lib.a(mktemp.o): In function `mktemp_main':
mktemp.c:(.text.mktemp_main+0x98): warning: the use of `mktemp' is dangerous, better use `mkstemp'
networking/lib.a(ipcalc.o): In function `ipcalc_main':
ipcalc.c:(.text.ipcalc_main+0x25c): warning: Using 'gethostbyaddr' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
libbb/lib.a(inet_common.o): In function `INET_resolve':
inet_common.c:(.text.INET_resolve+0x60): warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
networking/lib.a(inetd.o): In function `reread_config_file':
inetd.c:(.text.reread_config_file+0x230): warning: Using 'getservbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
networking/lib.a(netstat.o): In function `ip_port_str':
netstat.c:(.text.ip_port_str+0x50): warning: Using 'getservbyport' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
coreutils/lib.a(sync.o): In function `sync_main':
sync.c:(.text.sync_main+0x7c): undefined reference to `syncfs'
collect2: ld returned 1 exit status
Note: if build needs additional libraries, put them in CONFIG_EXTRA_LDLIBS.
Example: CONFIG_EXTRA_LDLIBS="pthread dl tirpc audit pam"
Makefile:717: recipe for target 'busybox_unstripped' failed
make: *** [busybox_unstripped] Error 1

解决办法：

make menuconfig

Coreutils—>sync选项去掉，重新make编译通过，终于顺利生成了busybox可执行文件。

OK，今天到此为止，明天再继续研究。

搞定，收工！

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篇后语：

1、编译完后对上述几个问题进行反思，发现这几个问题其实来讲可以分为2类。一类是头文件包含的问题，一类是make menuconfig配置的问题。后者，可能跟每个人的配置需求有关。但是前者的问题，我认为busybox公司完全可以将那2个头文件直接包含在源码包中，将相关代码修改成OK的状态，让我们下载过来就可以直接编译通过，免去我们这番折腾。但是为何busybox公司没有这么做呢？其中应该是有原因的，暂时想不通，待日后再仔细琢磨吧。

2、本文撰写时，使用的busybox工具源码版本是busybox-1.25.0，使用上述方法验证通过。不过，紧接着，我又验证了最新的busybox-1.26.2版本，同样使用上述方法，顺利通过，编译成功。证明本文中的方法应该对于各个版本都是通用的。

3、本文只是简单的介绍了一下使用busybox过程中遇到几个编译出错的问题的解决办法，并未对整套编译流程进行详细介绍。关于如何利用busybox工具编译出linux根文件系统的完整流程，可参见我的另外一篇博客（如何使用busybox编译和生成最简linux根文件系统（rootfs））。