Linux内核编译流程

Process of the Linux kernel building（Linux内核编译流程）

Introduction（简介）

I won’t tell you how to build and install a custom Linux kernel on your machine. If you need help with this, you can find many resourcesthat
will help you do it. Instead, we will learn what occurs when you execute

make

in the root directory of the Linux kernel
source code.

在本文中，我不会告诉你如何在你的机器上编译和安装你自定义的Linux内核。如果你需要这么做，你可以找多许多这样的资源来帮助你完成这样的工作。在这里，我们会学到当你在Linux内核代码根目录里面执行

make

命令时会发生什么。

When I started to study the source code of the Linux kernel, the makefile was the first file that I opened. And it was scary
:). The makefilecontained

1591

lines
of code when I wrote this part and the kernel was the 4.2.0-rc3 release.

当我开始学习Linux内核源码的时候， makefile 是我第一个打开的文件，而且它真的很恐怖。当我写这篇文档的时候，Linux内核是4.2.0-rc3版本，而那个 含有

1591

行代码。

This makefile is the top makefile in the Linux kernel source code and the kernel building starts here. Yes, it is big, but moreover, if you’ve read the sourc
4000
e code of the Linux kernel you may have noted that all directories containing source code has its own
makefile. Of course it is not possible to describe how each source file is compiled and linked, so we will only study the standard compilation case. You will not find here building of the kernel’s documentation, cleaning of the kernel source code, tags generation, cross-compilation related
stuff, etc… We will start from the

make

execution with the standard kernel configuration file and will finish with the
building of the bzImage.

这里说的makefile指的是Linux内核源码顶层的makefile，内核编译就是从这个makefile开始的。是的，它很庞大，但是，如果你读过内核源码就会发现每个目录下都有自己的makefile。当然描述每个文件的编译链接过程是不现实的，因此我们仅仅研究一个标准的编译例子。在这篇文档中你不会找到如何生成Linux内核文档，清理内核源码，ctags生成，交叉编译(等这些内容。我们会从以标准配置文件执行

make

命令开始，到生成bzImage结束。

It would be better if you’re already familiar with the make util, but I will try to describe every piece of code in this part anyway.

如果你熟悉make util更好，但我也会尝试详细描述代码的的方方面面。

So let’s start.

那么，让我们开始吧。

Preparation before the kernel compilation（编译前准备）

There are many things to prepare before the kernel compilation can be started. The main point here is to find and configure

the type of compilation, to parse command line arguments that are passed to

make

, etc… So let’s dive into the top

Makefile

of
Linux kernel.

在开始编译前，有很多准备工作要做。这些准备工作主要是寻找和配置编译类型、解析传递给

make

命令的命令行参数等。所以让我们深入研究Linux内核的顶层

Makefile

。

The top

Makefile

of Linux kernel is responsible for building two major products: vmlinux (the
resident kernel image) and the modules (any module files). The Makefile of the Linux kernel starts with the definition of
following variables:

Linux 内核顶层的Makefile负责编译两类主要的目标：vmlinux和modules。Makefile从定义下面这些变量开始：

<code class="language-Makefile hljs ini has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-setting" style="box-sizing: border-box;">VERSION = <span class="hljs-value" style="box-sizing: border-box;"><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span></span></span>
<span class="hljs-setting" style="box-sizing: border-box;">PATCHLEVEL = <span class="hljs-value" style="box-sizing: border-box;"><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span></span></span>
<span class="hljs-setting" style="box-sizing: border-box;">SUBLEVEL = <span class="hljs-value" style="box-sizing: border-box;"><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span></span></span>
<span class="hljs-setting" style="box-sizing: border-box;">EXTRAVERSION = <span class="hljs-value" style="box-sizing: border-box;">-rc3</span></span>
<span class="hljs-setting" style="box-sizing: border-box;">NAME = <span class="hljs-value" style="box-sizing: border-box;">Hurr durr I'ma sheep</span></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

These variables determine the current version of Linux kernel and are used in different places, for example in the forming of the

KERNELVERSION

variable
in the same

Makefile

:

这些变量定义了当前Linux内核的版本，它们被用在许多不同的地方，例如组成同一

Makefile

中的变量

KERNELVERSION

：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-constant" style="box-sizing: border-box;">KERNELVERSION</span> = <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">VERSION</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">PATCHLEVEL</span>),.<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">PATCHLEVEL</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">SUBLEVEL</span>),.<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">SUBLEVEL</span>)))<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">EXTRAVERSION</span>)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

After this we can see a couple of

ifeq

conditions that check some of the parameters passed to

make

.
The Linux kernel

makefiles

provides a special

make
help

target that prints all available targets and some of the command line arguments that can be passed to

make

.
For example :

make V=1

=> verbose build. The first

ifeq

checks
whether the

V=n

option is passed to

make

:

在这之后，我们可以看到一些

ifeq

语句对用于检查传递给

make

命令的参数。Linux内核的

makefiles

提供了一个特殊的编译目标

make
help

用语打印出所有可能的编译目标和一些传递给

make

命令的命令行参数。例如，

make
V=1

=> verbose build. 第
1bb8b
一个

ifeq

检查是否

V=n

参数被传递给命令

make

<code class="language-Makefile hljs cmake has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ifeq (<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"$(origin V)"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"command line"</span>)
KBUILD_VERBOSE = $(V)
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">endif</span>
ifndef KBUILD_VERBOSE
KBUILD_VERBOSE = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">endif</span>

ifeq ($(KBUILD_VERBOSE),<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>)
quiet =
Q =
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>
quiet=quiet_
Q = @
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">endif</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">export</span> quiet Q KBUILD_VERBOSE</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>

If this option is passed to

make

, we set the

KBUILD_VERBOSE

variable
to the value of

V

option. Otherwise we set the

KBUILD_VERBOSE

variable
to zero. After this we check the value of

KBUILD_VERBOSE

variable and set values of the

quiet

and

Q

variables
depending on the value of

KBUILD_VERBOSE

variable. The

@

symbols
suppress the output of command. And if it is present before a command the output will be something like this:

CC scripts/mod/empty.o

instead
of

Compiling .... scripts/mod/empty.o

. In the end we just export all of these variables.

如果该参数被传递给

make

，我们设置

KBUILD_VERBOSE

变量的值为参数

V

的值，否则我们设置变量

KBUILD_VERBOSE

的值为0。然后，根据

KBUILD_VERBOSE

的值设置变量

quiet

和

Q

的值。符号

@

阻止了命令的输出。如果该符号出现在命令的前面，那么该命令的输出将会是这样

CC
scripts/mod/empty.o

而不是

Compiling .... scripts/mod/empty.o

。最后，我们将export出这些变量。

The next

ifeq

statement checks that

O=/dir

option
was passed to the

make

. This option allows to locate all output files in the given

dir

:

接下来的

ifeq

检查是否

O=/dir

选项被传递给

make

命令。
这个选项使得编译所得的文件输出到指定的目录

dir

中:

<code class="language-Makefile hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ifeq (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_SRC),)

ifeq (<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"$(origin O)"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"command line"</span>)
KBUILD_OUTPUT := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>O)
endif

ifneq (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_OUTPUT),)
saved-output := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_OUTPUT)
KBUILD_OUTPUT := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>shell mkdir -p <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_OUTPUT) && cd <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_OUTPUT) \
&& /bin/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">pwd</span>)
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_OUTPUT),, \
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">error</span> failed to create output directory <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"$(saved-output)"</span>))

sub-make: FORCE
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>Q)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>MAKE) -C <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_OUTPUT) KBUILD_SRC=<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>CURDIR) \
-f <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>CURDIR)/Makefile <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">filter</span>-out _all sub-make,<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>MAKECMDGOALS))

skip-makefile := <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>
endif # ifneq (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_OUTPUT),)
endif # ifeq (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_SRC),)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li></ul>

We check the

KBUILD_SRC

that represents the top directory of the kernel source code and whether it is empty (it is empty
when the makefile is executed for the first time). We then set the

KBUILD_OUTPUT

variable to the value passed with the

O

option
(if this option was passed). In the next step we check this

KBUILD_OUTPUT

variable and if it is set, we do following things:

* Store the value of

KBUILD_OUTPUT

in the temporary

saved-output

variable;

* Try to create the given output directory;

* Check that directory created, in other way print error message;

* If the custom output directory was created successfully, execute

make

again with the new directory (see the

-C

option).

我们检查代表Linux内核源码根目录的变量

KBUILD_SRC

的值是否为空（当第一次执行makefile的时候该值为空）。接着我们设置变量

KBUILD_OUTPUT

的值为通过选项

O

传递进来的值。接下来我们判断

KBUILD_OUTPUT

值，如果已设置，我们执行下面的操作：

* 将变量

KBUILD_OUTPUT

的值存储在临时变量

saved-output

中;

* 尝试创建指定的输出目录;

* 判断制定的输出目录是否已创建，否者输出错误信息;

* 如果指定的输出目录已创建，使用新的目录再次执行

make

命令，（参考

－C

选项）

The next

ifeq

statements check that the

C

or

M

options
passed to

make

:

下一个

ifeq

语句检查是否选项

C

或者

M

被传递给命令

make

：

<code class="language-Makefile hljs perl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ife<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">q ("<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>origin C)</span><span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">", "</span>command line<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">")
KBUILD_CHECKSRC = <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>C)
endif
ifndef KBUILD_CHECKSRC
KBUILD_CHECKSRC = 0
endif

ifeq ("</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>origin M)<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">", "</span>command line<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">")
KBUILD_EXTMOD := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>M)
endif</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

The

C

option tells the

makefile

that
we need to check all

c

source code with a tool provided by the

$CHECK

environment
variable, by default it is sparse. The second

M

option
provides build for the external modules (will not see this case in this part). We also check whether the

KBUILD_SRC

variable
is set, and if it isn’t, we set the

srctree

variable to

.

:

选项

C

告诉

makefile

我们需要使用环境变量

$CHECK

来检查所有的

c

代码,
默认的工具时 sparse. 第二个

M

选项
提供了对外部模块的编译 (本例中不会涉及到). 我们也会检查变量

KBUILD_SRC

的值是否已设置, 如果没有, 我们设置变量

srctree

为代表当前目录的

.

:

<code class="language-Makefile hljs perl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ife<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">q (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>KBUILD_SRC)</span>,)
srctree := .
endif

objtree := .
src     := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>srctree)
obj     := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>objtree)

export srctree objtree VPATH</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

That tells

Makefile

that the kernel source tree will be in the current directory where

make

was
executed. We then set

objtree

and other variables to this directory and export them. The next step is to get value for
the

SUBARCH

variable that represents what the underlying architecture is:

这告诉

Makefile

当

make

命令执行时，内核代码树就在当前目录下。
然后我们设置

objtree

和其它变量的值为这个目录，并export它们。下一步是获取代表目标平台架构的变量

SUBARCH

:

<code class="language-Makefile hljs haml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
-<span class="ruby" style="box-sizing: border-box;">e s/sun4u/sparc64/ \
</span>                  -<span class="ruby" style="box-sizing: border-box;">e s/arm.*<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/arm/</span> -e s/sa11<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>/arm/ \
</span>                  -<span class="ruby" style="box-sizing: border-box;">e s/s390x/s39<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>/ -e s/parisc64/parisc/ \
</span>                  -<span class="ruby" style="box-sizing: border-box;">e s/ppc.*<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/powerpc/</span> -e s/mips.*<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/mips/</span> \
</span>                  -<span class="ruby" style="box-sizing: border-box;">e s/sh[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">234</span>].*<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/sh/</span> -e s/aarch64.*<span class="hljs-regexp" style="color: rgb(0, 136, 0); box-sizing: border-box;">/arm64/</span> )</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>

As you can see, it executes the uname util that prints information about machine, operating system and architecture. As it gets the output of

uname

,
it parses the ouput and assigns the result to the

SUBARCH

variable. Now that we have

SUBARCH

,
we set the

SRCARCH

variable that provides the directory of the certain architecture and

hfr-arch

that
provides the directory for the header files:

如你所见，通过执行命令

uname

打印出机器、操作系统和架构的信息。获取

uname

命令的输出后，解析其输出，并赋值给变量

SUBARCH

。有了

SUBARCH

之后，我们设置提供对应架构目录的变量

SRCARCH

和提供头文件目录的变量

hfr-arch

:

<code class="language-Makefile hljs perl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">ife<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">q (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>ARCH)</span>,i386)
SRCARCH := x86
endif
ife<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">q (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>ARCH)</span>,x86_64)
SRCARCH := x86
endif

hdr-arch  := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>SRCARCH)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

Note

ARCH

is an alias for

SUBARCH

.
In the next step we set the

KCONFIG_CONFIG

variable that represents path to the kernel configuration file and if it was
not set before, it is set to

.config

by default:

变量

ARCH

是变量

SUBARCH

的别名。在下一步中，我们设置变量

KCONFIG_CONFIG

表示内核配置文件的路径。该变量如果在此之前没有设置，则设置为默认值

.config

:

<code class="language-Makefile hljs bash has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">KCONFIG_CONFIG  ?= .config
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">export</span> KCONFIG_CONFIG</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

and the shell that will be used during kernel compilation:

并设置在内核编译过程中所用到的 shell:

<code class="language-Makefile hljs bash has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">CONFIG_SHELL := $(shell <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -x <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"$<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$BASH</span>"</span> ]; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">echo</span> $<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$BASH</span>; \
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> [ -x /bin/bash ]; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">then</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">echo</span> /bin/bash; \
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">echo</span> sh; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">fi</span> ; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">fi</span>)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

The next set of variables are related to the compilers used during Linux kernel compilation. We set the host compilers for the

c

and

c++

and
the flags to be used with them:

下面要设置的变量与Linux内核编译过程中的编译器相关。我们设置

c

和

c++

源码的主机端（host）编译器和编译flag：

<code class="language-Makefile hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">HOSTCC       <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> gcc
HOSTCXX      <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> g<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">++</span>
HOSTCFLAGS   <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-attribute" style="box-sizing: border-box;">-Wall</span> <span class="hljs-attribute" style="box-sizing: border-box;">-Wmissing</span><span class="hljs-attribute" style="box-sizing: border-box;">-prototypes</span> <span class="hljs-attribute" style="box-sizing: border-box;">-Wstrict</span><span class="hljs-attribute" style="box-sizing: border-box;">-prototypes</span> <span class="hljs-attribute" style="box-sizing: border-box;">-O2</span> <span class="hljs-attribute" style="box-sizing: border-box;">-fomit</span><span class="hljs-attribute" style="box-sizing: border-box;">-frame</span><span class="hljs-attribute" style="box-sizing: border-box;">-pointer</span> <span class="hljs-attribute" style="box-sizing: border-box;">-std</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span>gnu89
HOSTCXXFLAGS <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-attribute" style="box-sizing: border-box;">-O2</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

Next we get to the

CC

variable that represents compiler too, so why do we need the

HOST*

variables?

CC

is
the target compiler that will be used during kernel compilation, but

HOSTCC

will be used during compilation of the set
of the

host

programs (we will see it soon). After this we can see the definition of

KBUILD_MODULES

and

KBUILD_BUILTIN

variables
that are used to determine what to compile (kernel, modules or both):

我们接下来遇到的变量

CC

也和编译器相关，那么我们为啥需要

HOST*

变量呢？

CC

是内核编译过程中的目标编译器，而

HOSTCC

在编译过程中会编译一些主机程序（后面我们会看到它们）。在这之后，我们会看到变量

KBUILD_MODULES

和

KBUILD_BUILTIN

的定义，这些变量决定了需要编译那些目标，内核、模块还是两则都是。

<code class="language-Makefile hljs perl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">KBUILD_MODULES :=
KBUILD_BUILTIN := <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>

ife<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">q (<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>MAKECMDGOALS)</span>,modules)
KBUILD_BUILTIN := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>CONFIG_MODVERSIONS),<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>)
endif</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li></ul>

Here we can see definition of these variables and the value of

KBUILD_BUILTIN

variable will depend on the

CONFIG_MODVERSIONS

kernel
configuration parameter if we pass only

modules

to

make

.
The next step is to include the

kbuild

file.

这里我们看到，如果我们仅仅传递

modules

给

make

命令，这些变量的定义和

KBUILD_BUILTIN

的值依赖于

CONFIG_MODVERSIONS

内核配置参数。下一步是包含那些

kbuild

文件.

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span> scripts/<span class="hljs-constant" style="box-sizing: border-box;">Kbuild</span>.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

The Kbuild or

Kernel
Build System

is the special infrastructure to manage the build of the kernel and its modules. The

kbuild

files has
the same syntax that makefiles do. The scripts/Kbuild.include file provides some generic definitions for the

kbuild

system.
As we included this

kbuild

files we can see definition of the variables that are related to the different tools that will
be used during kernel and modules compilation (like linker, compilers, utils from the binutils, etc…):

Kbuild

或者

Kernel
Build System

是用来控制内核或者模块编译的特殊框架。

kbuild

文件和普通makefile有相同的语法。文件

scripts/Kbuild.include

提供了

kbuild

系统的一些公共定义。我们包含了该文件后，可以看到与内核和模块编译过程中所使用的各种工具相关的各种变量定义（如链接器linker、编译器compiler、
binutils中的各种工具等）：

<code class="language-Makefile hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">AS      = $(CROSS_COMPILE)as
LD      = $(CROSS_COMPILE)ld
CC      = $(CROSS_COMPILE)gcc
CPP     = $(CC) -E
AR      = $(CROSS_COMPILE)ar
NM      = $(CROSS_COMPILE)nm
STRIP       = $(CROSS_COMPILE)strip
OBJCOPY     = $(CROSS_COMPILE)objcopy
OBJDUMP     = $(CROSS_COMPILE)objdump
AWK     = awk
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

We then define two other variables:

USERINCLUDE

and

LINUXINCLUDE

.
They contain the paths of the directories with headersc z (public for users in the first case and for kernel in the second case):

接下来我们定义两个变量

USERINCLUDE

和

LINUXINCLUDE

。他们包含了头文件目录（第一个是用户公用头文件，第二个是内核使用的头文件）。

<code class="language-Makefile hljs haml has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">USERINCLUDE    := \
-<span class="ruby" style="box-sizing: border-box;"><span class="hljs-constant" style="box-sizing: border-box;">I</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>srctree)/arch/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>hdr-arch)/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span>/uapi \
</span>        -<span class="ruby" style="box-sizing: border-box;"><span class="hljs-constant" style="box-sizing: border-box;">Iarch</span>/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>hdr-arch)/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span>/generated/uapi \
</span>        -<span class="ruby" style="box-sizing: border-box;"><span class="hljs-constant" style="box-sizing: border-box;">I</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>srctree)/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span>/uapi \
</span>        -<span class="ruby" style="box-sizing: border-box;"><span class="hljs-constant" style="box-sizing: border-box;">Iinclude</span>/generated/uapi \
</span>        -<span class="ruby" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>srctree)/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span>/linux/kconfig.h
</span>
LINUXINCLUDE    := \
-<span class="ruby" style="box-sizing: border-box;"><span class="hljs-constant" style="box-sizing: border-box;">I</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>srctree)/arch/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>hdr-arch)/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span> \
</span>        ...</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

And the standard flags for the C compiler:

以及标准的C编译器编译flag：

<code class="language-Makefile hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">KBUILD_CFLAGS   <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">:=</span> <span class="hljs-attribute" style="box-sizing: border-box;">-Wall</span> <span class="hljs-attribute" style="box-sizing: border-box;">-Wundef</span> <span class="hljs-attribute" style="box-sizing: border-box;">-Wstrict</span><span class="hljs-attribute" style="box-sizing: border-box;">-prototypes</span> <span class="hljs-attribute" style="box-sizing: border-box;">-Wno</span><span class="hljs-attribute" style="box-sizing: border-box;">-trigraphs</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>
<span class="hljs-attribute" style="box-sizing: border-box;">-fno</span><span class="hljs-attribute" style="box-sizing: border-box;">-strict</span><span class="hljs-attribute" style="box-sizing: border-box;">-aliasing</span> <span class="hljs-attribute" style="box-sizing: border-box;">-fno</span><span class="hljs-attribute" style="box-sizing: border-box;">-common</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>
<span class="hljs-attribute" style="box-sizing: border-box;">-Werror</span><span class="hljs-attribute" style="box-sizing: border-box;">-implicit</span><span class="hljs-attribute" style="box-sizing: border-box;">-function</span><span class="hljs-attribute" style="box-sizing: border-box;">-declaration</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>
<span class="hljs-attribute" style="box-sizing: border-box;">-Wno</span><span class="hljs-attribute" style="box-sizing: border-box;">-format</span><span class="hljs-attribute" style="box-sizing: border-box;">-security</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>
<span class="hljs-attribute" style="box-sizing: border-box;">-std</span><span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span>gnu89</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

It is the not last compiler flags, they can be updated by the other makefiles (for example kbuilds from

arch/

). After all
of these, all variables will be exported to be available in the other makefiles. The following two the

RCS_FIND_IGNORE

and
the

RCS_TAR_IGNORE

variables will contain files that will be ignored in the version control system:

这还不是最终的编译flags，它们可能在编译过程中被其它的makefiles修改（例如，

arch／

目录下的kbuilds）。在这之后，所有的变量都被导出。接下来的两个变量

RCS_FIND_IGNORE

和

RCS_TAR_IGNORE

包含了那些会被版本控制系统忽略的文件：

<code class="language-Makefile hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">export RCS_FIND_IGNORE <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">:=</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>( <span class="hljs-attribute" style="box-sizing: border-box;">-name</span> SCCS <span class="hljs-attribute" style="box-sizing: border-box;">-o</span> <span class="hljs-attribute" style="box-sizing: border-box;">-name</span> BitKeeper <span class="hljs-attribute" style="box-sizing: border-box;">-o</span> <span class="hljs-attribute" style="box-sizing: border-box;">-name</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>svn <span class="hljs-attribute" style="box-sizing: border-box;">-o</span>    <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>
<span class="hljs-attribute" style="box-sizing: border-box;">-name</span> CVS <span class="hljs-attribute" style="box-sizing: border-box;">-o</span> <span class="hljs-attribute" style="box-sizing: border-box;">-name</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>pc <span class="hljs-attribute" style="box-sizing: border-box;">-o</span> <span class="hljs-attribute" style="box-sizing: border-box;">-name</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>hg <span class="hljs-attribute" style="box-sizing: border-box;">-o</span> <span class="hljs-attribute" style="box-sizing: border-box;">-name</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>git <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>) <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>
<span class="hljs-attribute" style="box-sizing: border-box;">-prune</span> <span class="hljs-attribute" style="box-sizing: border-box;">-o</span>
export RCS_TAR_IGNORE <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">:=</span> <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">--</span>exclude SCCS <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">--</span>exclude BitKeeper <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">--</span>exclude <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>svn <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">\</span>
<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">--</span>exclude CVS <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">--</span>exclude <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>pc <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">--</span>exclude <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>hg <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">--</span>exclude <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>git</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

That’s all. We have finished with the all preparations, next point is the building of

vmlinux

.

就这样，我们完成了所有的准备工作，下面进入

vmlinux

的编译。

Directly to the kernel build（进入内核编译）

We have now finished all the preparations, and next step in the main makefile is related to the kernel build. Before this moment, nothing has been printed to the terminal by

make

.
But now the first steps of the compilation are started. We need to go to line 598 of the Linux kernel top makefile and
we will find the

vmlinux

target there:

我们已经完成全部的准备工作，下面进入到与内核编译相关的步骤。在此之前，终端上不会打印出

make

命令的任何输出。但从现在开始内核编译的第一步。我们跳转到内核源码顶层Makefile的第598行，我们会看到编译目标

vmlinux

的定义：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">all:</span> vmlinux
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span> arch/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">SRCARCH</span>)/<span class="hljs-constant" style="box-sizing: border-box;">Makefile</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

Don’t worry that we have missed many lines in Makefile that are between

export RCS_FIND_IGNORE.....

and

all:
vmlinux.....

. This part of the makefile is responsible for the

make *.config

targets and as I wrote in the beginning
of this part we will see only building of the kernel in a general way.

别担心，我们跳过了从

export RCS_FIND_IGNORE.....

到

all:
vmlinux.....

之间的这么多行。Makefile这部分内容与

make *.config

相关，就像我在文件开头说的那样，我们仅研究一个通用的编译过程。

The

all:

target is the default when no target is given on the command line. You can see here that we include architecture
specific makefile there (in our case it will be arch/x86/Makefile). From this moment we will continue from this makefile.
As we can see

all

target depends on the

vmlinux

target
that defined a little lower in the top makefile:

all

目标是在没有通过命令行传递任何编译目标时的默认编译目标。你可以看到，此时，我们包含了跟架构相关的makefile（在本例中是指arch/x86/Makefile）。现在我们继续研究makefile。我们看到目标

all

依赖于目标

vmlinux

,
目标

vmlinux

定义在顶层makefile下面一点：

<code class="language-Makefile hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">vmlinux: scripts/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">link</span><span class="hljs-attribute" style="box-sizing: border-box;">-vmlinux</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>sh $(vmlinux<span class="hljs-attribute" style="box-sizing: border-box;">-deps</span>) FORCE</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

The

vmlinux

is the Linux kernel in a statically linked executable file format. The scripts/link-vmlinux.sh script
links and combines different compiled subsystems into vmlinux. The second target is the

vmlinux-deps

that defined as:

vmlinux

是Linux内核的一种静态链接可执行文件格式。脚本scripts/link-vmlinux.sh链接并将编译后得各子系统打包进vmlinux。

第二个目标

vmlinux-deps

的定义如下：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">vmlinux-deps <span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:</span>= <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">KBUILD_LDS</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">KBUILD_VMLINUX_INIT</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">KBUILD_VMLINUX_MAIN</span>)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

and consists from the set of the

built-in.o

from each top directory of the Linux kernel. Later, when we will go through
all directories in the Linux kernel, the

Kbuild

will compile all the

$(obj-y)

files.
It then calls

$(LD) -r

to merge these files into one

built-in.o

file.
For this moment we have no

vmlinux-deps

, so the

vmlinux

target
will not be executed now. For me

vmlinux-deps

contains following files:

它由LInux内核源码中各顶层目录中的

built-in.o

组成。后面当我们遍历Linux内核的所有目录时，

kbuild

会编译

$(obj-y)

中的源码，然后调用

$(LD)
-r

将这些文件打包成一个

built-in.o

。现在，我们还没有生成

vmlinux-deps

，所以

vmlinux

目标还不会进行编译。对于我来说，

vmlinux-deps

包含下面这些文件：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">arch/x86/kernel/vmlinux<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.lds</span> arch/x86/kernel/head_64<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
arch/x86/kernel/head64<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>    arch/x86/kernel/head<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
init/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>             usr/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
arch/x86/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>         kernel/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
mm/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>               fs/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
ipc/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>              security/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
crypto/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>           block/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
lib/lib<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.a</span>                   arch/x86/lib/lib<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.a</span>
lib/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>              arch/x86/lib/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
drivers/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>          sound/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
firmware/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>         arch/x86/pci/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
arch/x86/power/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>   ar
367bf
ch/x86/video/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
net/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

The next target that can be executed is following:

下一个可以编译的目标是：

<code class="language-Makefile hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sort</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>vmlinux-deps)): <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>vmlinux-dirs) ;
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>vmlinux-dirs): prepare scripts
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>Q)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>MAKE) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$@</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

As we can see

vmlinux-dirs

depends on two targets:

prepare

and

scripts

.

prepare

is
defined in the top

Makefile

of the Linux kernel and executes three stages of preparations:

我们看到

vmlinux-dirs

依赖于两个目标

prepare

和

scripts

。

prepare

定义在顶层的

Makefile

中，分为3各执行阶段：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">prepare:</span> prepare<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>
<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">prepare0:</span> archprepare <span class="hljs-constant" style="box-sizing: border-box;">FORCE</span>
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=.
<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">archprepare:</span> archheaders archscripts prepare1 scripts_basic

<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">prepare1:</span> prepare2 <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>version_h) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span>/generated/utsrelease.h \
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span>/config/auto.conf
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>cmd_crmodverdir)
<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">prepare2:</span> prepare3 outputmakefile asm-generic</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

The first

prepare0

expands to the

archprepare

that
expands to the

archheaders

and

archscripts

that
defined in the

x86_64

specificMakefile.

第一个

prepare0

由

archprepare

扩展得到。而

archprepare

又由定义在

x86_64

指定Makefile中的

archheaders

and

arch
scripts

扩展得。

Let’s look on it. The

x86_64

specific makefile starts from the definition of the variables that are related to the architecture-specific
configs (defconfig, etc…). After this it defines flags for the compiling of the 16-bit code,
calculating of the

BITS

variable that can be

32

for

i386

or

64

for
the

x86_64

flags for the assembly source code, flags for the linker and many many more (all definitions you can find in
thearch/x86/Makefile).

让我们看下这个文件。

x86_64

指定的makefile，以定义一些架构相关变量开始，之后是定义一些编译16-bit代码的flag，计算

BITS

变量，可以是

i386

架构的

32

或者

x86_64

架构的
64“，定义编译汇编代码的flags，以及链接用的flags等等。

The first target is

archheaders

in the makefile generates syscall table:

该makefile中的第一个目标

archheaders

生成系统调用表：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">archheaders:</span>
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=arch/x86/entry/syscalls all</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

And the second target is

archscripts

in this makefile is:

makefile中的第二个目标

archscripts

定义如下：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">archscripts:</span> scripts_basic
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=arch/x86/tools relocs</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

We can see that it depends on the

scripts_basic

target from the top Makefile.
At the first we can see the

scripts_basic

target that executes make for the scripts/basic makefile:

我们可以看到，它依赖于定义在根Makefile中的

scripts_basic

，在目录scripts/basic中执行make命令生成目标

scripts_basic

。

<code class="language-Maklefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">scripts_basic:</span>
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=scripts/basic</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

The

scripts/basic/Makefile

contains targets for compilation of the two host programs:

fixdep

and

bin2

:

scripts/basic/Makefile

包含编译生成两个主机端程序

fixdep

和

bin2

的一些目标：

<code class="language-Makefile hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">hostprogs-y := fixdep
hostprogs-<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>CONFIG_BUILD_BIN2C)     += bin2c
always      := <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>hostprogs-y)

<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>addprefix <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/,<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">filter</span>-out fixdep,<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>always))): <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/fixdep</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

First program is

fixdep

- optimizes list of dependencies generated by gcc that
tells make when to remake a source code file.

第一个程序

fixdep

，优化GCC生成的依赖关系表，可以告诉make何时需要重新对源代码文件进行make。

The second program is

bin2c

, which depends on the value of the

CONFIG_BUILD_BIN2C

kernel
configuration option and is a very little C program that allows to convert a binary on stdin to a C include on stdout.

第二个程序

bin2c

，它依赖于内核配置选项中

CONFIG_BUILD_BIN2C

的值，它是一个非常小得C程序，可以讲标准输入中的二进制转换成标准输出中的C头文件。

You can note here a strange notation:

hostprogs-y

, etc… This notation is used in the all

kbuild

files
and you can read more about it in thedocumentation. In our case

hostprogs-y

tells

kbuild

that
there is one host program named

fixdep

that will be built from

fixdep.c

that
is located in the same directory where the

Makefile

is.

你可能会注意到这里有一个奇怪的符号

hostprogs-y

。这个符号被用在所有的

kbuild

文件中，你可以在documentation中找到跟多的描述。在这里，

hostprogs-y

告诉

kbuild

这里将有一个主机端程序

fixdep

由跟

Makefile

同一目录的

fixdep.c

生成。

The first output after we execute

make

in our terminal will be result of this

kbuild

file:

我们执行

make

命令后的第一条输出就是由这个

kbuild

文件生成的：

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$ </span>make
<span class="hljs-constant" style="box-sizing: border-box;">HOSTCC</span>  scripts/basic/fixdep</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

As

script_basic

target was executed, the

archscripts

target
will execute

make

for the arch/x86/tools makefile
with the

relocs

target:

当目标

script_basic

执行完后，目标

archscripts

会在目录arch/x86/tools中执行

make

，编译目标

relocs

:

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=arch/x86/tools relocs</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

The

relocs_32.c

and the

relocs_64.c

will
be compiled that will contain relocation information and we will see it in the

make

output:

文件

relocs_32.c

和

relocs_64.c

将会被编译，它们包含有重定向信息，我们可以看到下面的

make

输出：

<code class="language-Makefile hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  HOSTCC  arch/x86/tools/relocs_32<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
HOSTCC  arch/x86/tools/relocs_64<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
HOSTCC  arch/x86/tools/relocs_common<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
HOSTLD  arch/x86/tools/relocs</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

There is checking of the

version.h

after compiling of the

relocs.c

:

在编译

relocs.c

后，会检查文件

version.h

：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>version_h)<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>srctree)/<span class="hljs-constant" style="box-sizing: border-box;">Makefile</span> <span class="hljs-constant" style="box-sizing: border-box;">FORCE</span>
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>call filechk,version.h)
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)rm -f <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>old_version_h)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

We can see it in the output:

我们会看到这样的输出：

<code class="hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-constant" style="box-sizing: border-box;">CHK</span>     <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span>/config/kernel.release</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

and the building of the

generic

assembly headers with the

asm-generic

target
from the

arch/x86/include/generated/asm

that generated in the top Makefile of the Linux kernel.

并执行目标

asm-generic

，编译目录

arch/x86/include/generated/asm

中的

generic

汇编文件。它们是由Linux内核的根Makefile生成的。

After the

asm-generic

target the

archprepare

will
be done, so the

prepare0

target will be executed. As I wrote above:

在

asm-generic

目标之后，

archprepare

也将完成，目标

prepare0

将会被编译，像之前提到的那样：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">prepare0:</span> archprepare <span class="hljs-constant" style="box-sizing: border-box;">FORCE</span>
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=.</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

Note on the

build

. It defined in the scripts/Kbuild.include and
looks like this:

注意那个

build

，它定义在scripts/Kbuild.include文件中，看起来像这样：

<code class="language-Makefile hljs makefile has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-constant" style="box-sizing: border-box;">build</span> := -f <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(srctree)</span>/scripts/Makefile.build obj</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

Or in our case it is current source directory -

.

:

或者在本例中，它就是当前代码目录

.

：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) -f <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>srctree)/scripts/<span class="hljs-constant" style="box-sizing: border-box;">Makefile</span>.build obj=.</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

The scripts/Makefile.build tries to find the

Kbuild

file
by the given directory via the

obj

parameter, include this

Kbuild

files:

脚本scripts/Makefile.build 尝试寻找

obj

参数指定目录中的

Kbuild

文件，包含这些文件，并编译这些文件中的目标。

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">include</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>kbuild-file)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

and build targets from it.In our case

.

contains the Kbuild file
that generates the

kernel/bounds.s

and the

arch/x86/kernel/asm-offsets.s

.
After this the

prepare

target finished to work.

在本例中，当前目录

.

包含生成

kernel/bounds.s

和

arch/x86/kernel/asm-offsets.s

的Kbuild文件。在此之后，目标

prepare

就编译完成了。

The

vmlinux-dirs

also depends on the second target -

scripts

that
compiles following programs:

file2alias

,

mk_elfconfig

,

modpost

,
etc….. After scripts/host-programs compilation our

vmlinux-dirs

target can be executed.

vmlinux-dirs

也依赖与prepare的第二阶段，

scripts

编译生成了下面这些程序：

file2alias

,

mk_elfconfig

,

modpost

等。在scripts/host-programs编译完之后，目标

vmlinux-dirs

也可以开始执行了。

First of all let’s try to understand what does

vmlinux-dirs

contain. For my case it contains paths of the following kernel
directories:

首先，让我们试着去了解

vmlinux-dirs

中包含哪些内容。在本例中，它包含下面这些内核目录的路径：

<code class="hljs vbnet has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">init usr arch/x86 kernel mm fs ipc security crypto block
drivers sound firmware arch/x86/pci arch/x86/power
arch/x86/video net <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">lib</span> arch/x86/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">lib</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

We can find definition of the

vmlinux-dirs

in the top Makefile of
the Linux kernel:

在Linux内核源码根目录的Makefile中，我们可以找到

vmlinux-dirs

的定义：

<code class="language-Makefile hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">vmlinux-dirs    := $(patsubst %/,%,$(filter %/, $(init-y) $(init-m) \
$(core-y) $(core-m) $(drivers-y) $(drivers-m) \
$(net-y) $(net-m) $(libs-y) $(libs-m)))

init-y      := init/
drivers-y   := drivers/ sound/ firmware/
net-y       := net/
libs-y      := lib/
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

Here we remove the

/

symbol from the each directory with the help of the

patsubst

and

filter

functions
and put it to the

vmlinux-dirs

. So we have list of directories in the

vmlinux-dirs

and
the following code:

这里，我们通过函数

patsubst

和

filter

移除了每个目录名中的

/

，并将其赋值给了

vmlinux-dirs

，这样我们得到了包含文件夹列表的

vmlinux-dirs

变量和下面这段代码：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>vmlinux-dirs)<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">:</span> prepare scripts
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$@</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

The

$@

represents

vmlinux-dirs

here
that means that it will go recursively over all directories from the

vmlinux-dirs

and its internal directories (depens
on configuration) and will execute

make

in there. We can see it in the output:

符号

$@

代表

vmlinux-dirs

，这里的含义是，递归的进入

vmlinux-dirs

中的每个目录及其子目录，并在里面执行

make

命令，我们可以看到这样的输出：

<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  CC      init/main.o
CHK     include/generated/compile.h
CC      init/version.o
CC      init/do_mounts.o
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
CC      arch/x86/crypto/glue_helper.o
AS      arch/x86/crypto/aes-x86_64-asm_64.o
CC      arch/x86/crypto/aes_glue.o
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
AS      arch/x86/entry/entry_64.o
AS      arch/x86/entry/thunk_64.o
CC      arch/x86/entry/syscall_64.o</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul>

Source code in each directory will be compiled and linked to the

built-in.o

:

每个目录中的源码都会被编译和链接生成

built-in.o

:

<code class="hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">$ find . -name built-in.o
./arch/x86/crypto/built-in.o
./arch/x86/crypto/sha-mb/built-in.o
./arch/x86/net/built-in.o
./init/built-in.o
./usr/built-in.o
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

Ok, all buint-in.o(s) built, now we can back to the

vmlinux

target. As you remember, the

vmlinux

target
is in the top Makefile of the Linux kernel. Before the linking of the

vmlinux

it builds samples, Documentation,
etc… but I will not describe it here as I wrote in the beginning of this part.

好了，当这些buint-in.o(s)都生成后，我们可以回到目标

vmlinux

上来。你还记得，目标

vmlinux

是定义在顶层Makefile中的。在链接

vmlinux

之前，它会编译生成
samples和Documentation这些，但像我之前提到过的，我不会描述它们的编译过程。

<code class="language-Makefile hljs r has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">vmlinux: scripts/link-vmlinux.sh $(vmlinux-deps) FORCE
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">...</span>
+$(call if_changed,link-vmlinux)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

As you can see main purpose of it is a call of the scripts/link-vmlinux.sh script is linking of the all

built-in.o

(s)
to the one statically linked executable and creation of the System.map. In the end we will see following output:

你可以看到，代码主要是调用脚本scripts/link-vmlinux.sh，将所有的

built-in.o

(s)静态链接成一个可执行的文件，并生成System.map。最后我们可以看到这样的输出以及Linux源码根目录中的

vmlinux

和

System.map

：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  LINK    vmlinux
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">LD</span>      vmlinux<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
MODPOST vmlinux<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
GEN     <span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.version</span>
CHK     include/generated/compile<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.h</span>
UPD     include/generated/compile<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.h</span>
CC      init/version<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">LD</span>      init/built-<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">in</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
KSYM    <span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.tmp</span>_kallsyms1<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
KSYM    <span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.tmp</span>_kallsyms2<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">LD</span>      vmlinux
SORTEX  vmlinux
SYSMAP  System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.map</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

and

vmlinux

and

System.map

in
the root of the Linux kernel source tree:

<code class="hljs perl has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">$ ls vmlinux System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">map</span>
System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">map</span>  vmlinux</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

That’s all,

vmlinux

is ready. The next step is creation of the bzImage.

至此，

vmlinux

已经生成，下一步是生成

bzImage

。

Building bzImage（编译bzImage）

The

bzImage

file is the compressed Linux kernel image. We can get it by executing

make
bzImage

after

vmlinux

is built. That, or we can just execute

make

without
any argument and we will get

bzImage

anyway because it is default image:

bzImage

是压缩过的内核镜像。在生成

vmlinux

后，可以通过命令

make
bzImage

获得

bzImage

。或者干脆直接执行

make

命令不带任何参数，我们也能得到

bzImage

，因为它是arch/x86/kernel/Makefile的默认的编译目标：

<code class="language-Makefile hljs http has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-attribute" style="box-sizing: border-box;">all</span>: <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">bzImage</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

in the arch/x86/kernel/Makefile. Let’s look on this target, it will help us to understand how this image builds. As
I already said the

bzImage

target defined in the arch/x86/kernel/Makefile and
looks like this:

让我们看看这个目标，这有助于我们理解这个镜像文件时如何生成的。之前我们提到，

bzImage

目标定义在文件arch/x86/kernel/Makefile中，看起来像这样：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">bzImage:</span> vmlinux
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">MAKE</span>) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>build)=<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>boot) <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">KBUILD_IMAGE</span>)
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)mkdir -p <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>objtree)/arch/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">UTS_MACHINE</span>)/boot
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">Q</span>)ln -fsn ../../x86/boot/bzImage <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>objtree)/arch/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">UTS_MACHINE</span>)/boot/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$@</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

We can see here, that first of all called

make

for the boot directory, in our case it is:

到这里，我们看到第一步是在boot目录下执行

make

，在本例中，boot目录是：

<code class="language-Makefile hljs fix has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-attribute" style="box-sizing: border-box;">boot :</span>=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;"> arch/x86/boot</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

The main goal now is to build the source code in the

arch/x86/boot

and

arch/x86/boot/compressed

directories,
build

setup.bin

and

vmlinux.bin

,
and build the

bzImage

from them in the end. First target in the arch/x86/boot/Makefile is
the

$(obj)/setup.elf

:

现在的主要目标是，编译目录

arch/x86/boot

和

arch/x86/boot/compressed

中的代码，生成

setup.bin

和

vmlinux.bin

，并且最终通过它们生成

bzImage

。

arch/x86/boot/Makefile中的第一个目标是

$(obj)/setup.elf

:

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/setup.<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">elf:</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>src)/setup.ld <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span><span class="hljs-constant" style="box-sizing: border-box;">SETUP_OBJS</span>) <span class="hljs-constant" style="box-sizing: border-box;">FORCE</span>
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>call if_changed,ld)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

We already have the

setup.ld

linker script in the

arch/x86/boot

directory
and the

SETUP_OBJS

variable that expands to the all source files from the

boot

directory.
We can see first output:

在目录

arch/x86/boot

中我们已经有了

setup.ld

，变量

SETUP_OBJS

展开后得到目录

boot

中的所有源文件。我们第一次看到这样输出：

<code class="language-Makefile hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  AS      arch/x86/boot/bioscall<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/cmdline<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
AS      arch/x86/boot/copy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
HOSTCC  arch/x86/boot/mkcpustr
CPUSTR  arch/x86/boot/cpustr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.h</span>
CC      arch/x86/boot/cpu<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/cpuflags<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/cpucheck<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/early_serial_console<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/edd<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

The next source file is arch/x86/boot/header.S, but we can’t build it now because this target depends on the
following two header files:

下一个源文件是arch/x86/boot/header.S，但目前我们还不能编译它，因为它依赖于下面两个头文件：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/header.<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">o:</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/voffset.h <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/zoffset.h</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

The first is

voffset.h

generated by the

sed

script
that gets two addresses from the

vmlinux

with the

nm

util:

第一个头文件

voffset.h

是

sed

脚本通过

nm

工具获取的

vmlinux

的两个地址，它们是Linux内核的起始和结束地址：

<code class="language-C hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#<span class="hljs-keyword" style="box-sizing: border-box;">define</span> VO__end 0xffffffff82ab0000</span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#<span class="hljs-keyword" style="box-sizing: border-box;">define</span> VO__text 0xffffffff81000000</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

They are start and end of the kernel. The second is

zoffset.h

depens on the

vmlinux

target
from the arch/x86/boot/compressed/Makefile:

第二个头文件

zoffset.h

依赖于arch/x86/boot/compressed/Makefile中的目标

vmlinux

：

<code class="language-Makefile hljs ruby has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/zoffset.<span class="hljs-symbol" style="color: rgb(0, 102, 102); box-sizing: border-box;">h:</span> <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>obj)/compressed/vmlinux <span class="hljs-constant" style="box-sizing: border-box;">FORCE</span>
<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">$(</span>call if_changed,zoffset)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

The

$(obj)/compressed/vmlinux

target depends on the

vmlinux-objs-y

that
compiles source code files from the arch/x86/boot/compresseddirectory and generates

vmlinux.bin

,

vmlinux.bin.bz2

,
and compiles programm -

mkpiggy

. We can see this in the output:

目标

$(obj)/compressed/vmlinux

依赖于

vmlinux-objs-y

，编译arch/x86/boot/compressed中的代码，生成

vmlinux.bin

,

vmlinux.bin.bz2

以及程序

mkpiggy

，我们可以看到下面这些输出：

<code class="language-Makefile hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">LDS</span>     arch/x86/boot/compressed/vmlinux<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.lds</span>
AS      arch/x86/boot/compressed/head_64<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/compressed/misc<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/compressed/string<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/compressed/cmdline<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
OBJCOPY arch/x86/boot/compressed/vmlinux<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.bin</span>
BZIP2   arch/x86/boot/compressed/vmlinux<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.bin</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.bz</span>2
HOSTCC  arch/x86/boot/compressed/mkpiggy</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

Where

vmlinux.bin

is the

vmlinux

file
with debuging information and comments stripped and the

vmlinux.bin.bz2

compressed

vmlinux.bin.all

+

u32

size
of

vmlinux.bin.all

. The

vmlinux.bin.all

is

vmlinux.bin
+ vmlinux.relocs

, where

vmlinux.relocs

is the

vmlinux

that
was handled by the

relocs

program (see above). As we got these files, the

piggy.S

assembly
files will be generated with the

mkpiggy

program and compiled:

这里的

vmlinux.bin

是

vmlinux

文件去除调试信息和注释后生成的。通过程序

relocs

处理

vmlinux

后得到

vmlinux.relocs

。

vmlinux.bin.all
= vmlinux.bin + vmlinux.relocs

。

vmlinux.bin.bz2

是

vmlinux.bin.all

压缩后得到的。生成这些文件后，

mkpiggy

程序会生成汇编文件

piggy.S

并编译：

<code class="language-Makefile hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  MKPIGGY arch/x86/boot/compressed/piggy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.S</span>
AS      arch/x86/boot/compressed/piggy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

This assembly files will contain the computed offset from the compressed kernel. After this we can see that

zoffset

generated:

这个汇编文件中包含了计算得到的压缩后的内核偏移量。之后我们可以看到生成了目标

zoffset

：

<code class="language-Makefile hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  ZOFFSET arch/x86/boot/zoffset<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.h</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

As the

zoffset.h

and the

voffset.h

are
generated, compilation of the source code files from the arch/x86/boot can be continued:

当文件

zoffset.h

和

voffset.h

生成后，编译可以继续进行：

<code class="language-Makefile hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  AS      arch/x86/boot/header<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/main<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/mca<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/memory<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/pm<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
AS      arch/x86/boot/pmjump<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/printf<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/regs<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/string<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/tty<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/video<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/video-mode<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/video-vga<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/video-vesa<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span>
CC      arch/x86/boot/video-bios<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

As all source code files will be compiled, they will be linked to the

setup.elf

:

所有文件都被编译后，它们将会被链接到

setup.elf

文件中去：

<code class="language-Makefile hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">LD</span>      arch/x86/boot/setup<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.elf</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

or（或者）:

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">ld</span> -m elf_x86_64   -T arch/x86/boot/setup<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ld</span> arch/x86/boot/a20<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/bioscall<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/cmdline<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/copy<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/cpu<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/cpuflags<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/cpucheck<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/early_serial_console<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/edd<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/header<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/main<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/mca<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/memory<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/pm<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/pmjump<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/printf<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/regs<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/string<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/tty<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/video<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/video-mode<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/version<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/video-vga<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/video-vesa<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> arch/x86/boot/video-bios<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.o</span> -o arch/x86/boot/setup<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.elf</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

The last two things is the creation of the

setup.bin

that will contain compiled code from the

arch/x86/boot/*

directory:

最后两项工作是生成包含

arch/x86/boot/*

编译后代码的

setup.bin

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">objcopy  -O binary arch/x86/boot/setup<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.elf</span> arch/x86/boot/setup<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.bin</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

and the creation of the

vmlinux.bin

from the

vmlinux

:

和从

vmlinux

生成

vmlinux.bin

：

<code class="hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">objcopy  <span class="hljs-attribute" style="box-sizing: border-box;">-O</span> binary <span class="hljs-attribute" style="box-sizing: border-box;">-R</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>note <span class="hljs-attribute" style="box-sizing: border-box;">-R</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>comment <span class="hljs-attribute" style="box-sizing: border-box;">-S</span> arch/x86/boot/compressed/vmlinux arch/x86/boot/vmlinux<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>bin</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

In the end we compile host program: arch/x86/boot/tools/build.c that will create our

bzImage

from
the

setup.bin

and the

vmlinux.bin

:

接着，我们会编译一个主机端程序arch/x86/boot/tools/build.c 它会通过

setup.bin

和

vmlinux.bin

生成

bzImage

。

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">arch/x86/boot/tools/build arch/x86/boot/setup<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.bin</span> arch/x86/boot/vmlinux<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.bin</span> arch/x86/boot/zoffset<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.h</span> arch/x86/boot/bzImage</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

Actually the

bzImage

is the concatenated

setup.bin

and
the

vmlinux.bin

. In the end we will see the output which is familiar to all who once built the Linux kernel from source:

实际上，

bzImage

是

setup.bin

和

vmlinux.bin

的结合体。最后，我们会看到很熟悉的输出，如果你曾从代码开始编译过内核。

<code class="hljs vbnet has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">Setup <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">16268</span> bytes (padded <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">to</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">16384</span> bytes).
System <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4704</span> kB
CRC <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">94</span>a88f9a
Kernel: arch/x86/boot/bzImage <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">is</span> ready  (<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#5)</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

That’s all.

编译过程至此结束。

Conclusion（总结）

It is the end of this part and here we saw all steps from the execution of the

make

command to the generation of the

bzImage

.
I know, the Linux kernel makefiles and process of the Linux kernel building may seem confusing at first glance, but it is not so hard. Hope this part will help you understand the process of building the Linux kernel.

至此，本文描述了从开始执行

make

命令到生成

bzImage

整个流程。我知道Linux内核makefile和编译步骤咋一看很令人困惑，但其实也没那么难。希望本文能够帮助你理解编译Linux内核的编译流程。

Links（链接）

GNU make util
Linux kernel top Makefile
cross-compilation
Ctags
sparse
bzImage
uname
shell
Kbuild
binutils
gcc
Documentation
System.map
Relocation

转自：http://blog.csdn.net/sunao2002002/article/details/48874653