近年來，由於Linux結合了可靠性高，效能佳，有良好的工具，具有
遷移性，組態自由度高等優點，已經有愈來愈多廠商採用Linux做為
電子產品內部的作業系統。然而因為Linux核心程式非常複雜，加上
各種產品可能皆有各自不同的平台。因此Linux常常需要被移植到不
同的平台上。

在本篇論文中，我們詳述如何將Linux 移植到一個類似舊有，但目前
核心沒有支援的新平台。此外，我們提出二種除錯技巧來解決我們在
本篇論文中所遇到的問題。其中一種能讓我們更容易地利用ICE來
追蹤模組;另一種則能讓我們能透過/proc檔案系統來存取處理器的
內部暫存器，而不用每次都為了除錯去寫程式來存取內部暫存器
的資料。

透過這二種除錯技巧，我們能夠有效地降低系統開發
與除錯的時間。

In recent years, more and more vendors adopt Linux to be the embedded operating
system for their electronic products because of its combination of reliability, performance,
good tool chains, portability, and configurability. However, Linux kernel is complex, and
different electronic products may use different platforms. For this reason, it often requires
that Linux be ported to different platforms.

In this thesis, we describe the details of how we port Linux to a new platform which is
similar to but not exactly the same as another platform and thus is not currently supported by
the kernel. Moreover, we propose two robust debugging techniques to solve the problems we
had encountered in this thesis. One is to make it easier to trace a module with ICE; the other is
to allow us to access the internal registers of the processor through the /proc filesystem rather
than write a program every time we need to access those internal registers for the purpose of,
say, debugging.

By using these techniques, we show that the time required to port and debug a Linux
kernel can be definitely reduced.

Contents
Acknowledgments iv
List of Tables iii
List of Figures iv
List of Listings v

Chapter 1 Introduction 1
1.1 Embedded Linux System . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Motivations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Organization of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Chapter 2 Platform 4
2.1 Evaluation Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2 Linux Kernel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3 Toolchain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Chapter 3 Porting Linux 8
3.1 Boot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.1 head.s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1.2 Boot Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2 Machine Registration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3 Serial Console . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4 GPIO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.5 Root Filesystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.6 Device Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3.7 Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.8 NFS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.8.1 Result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Chapter 4 A Tiny Tool for Simplifying Tracing Modules with ICE 31
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.2 Design and Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.1 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.2 The Inline Functions . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.2.3 Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Chapter 5 Controlling Machine State via the /proc Filesystem 38
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.2 Design and Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.2.1 The /proc Filesystem . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.2.2 The ioremap() Function . . . . . . . . . . . . . . . . . . . . . . . . 39
5.2.3 Read/Write on the /proc Filesystem . . . . . . . . . . . . . . . . . . 40
5.2.4 Multi-registers Access . . . . . . . . . . . . . . . . . . . . . . . . . 43
5.2.5 Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Chapter 6 Conclusion and Future Works 51

Appendix A Building A Root Filesystem from Scratch 56
Appendix B Complete Source Code for the Tool Described in Chapter 4 62
Appendix C Complete Source Code for the Module Described in Chapter 5 65

List of Tables
A.1 Programs for the target platform . . . . . . . . . . . . . . . . . . . . . . . . 58
A.2 Libraries for the target platform . . . . . . . . . . . . . . . . . . . . . . . . 61

List of Figures
1.1 Embedded Linux architecture . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1 Block diagram of Creator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Block diagram of the CPU board . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Files modified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2 Linker will insert head-s3c2410 into the head.o . . . . . . . . . . . . . . . . 11
3.3 PORT-H control registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.4 Network filesystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.1 Disable interrupt then trace module with ICE . . . . . . . . . . . . . . . . . 32
4.2 Program status register format . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.3 Snapshot of ICE debug mode . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.1 Diagram of MMU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5.2 IO REG2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.3 Diagram showing our mechanism . . . . . . . . . . . . . . . . . . . . . . . 44

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