Linker&Loader

threesunscao

This book is intended for several overlapping audiences:
• Students: Courses in compiler construction and operating systems
have generally given scant treatment to linking and loading, often
because the linking process seemed trivial or obvious. Although
this was arguably true when the languages of interest were Fortran,
Pascal, and C, and operating systems didn’t use memory mapping
or shared libraries, it’s much less true now. C++, Java, and other
object-oriented languages require a much more sophisticated linking
environment. Memory mapped executable program, shared libraries,
and dynamic linking affect many parts of an operating system,
and an operating system designer disregards linking issues at
his or her peril.
• Practicing programmers also need to be aware of what linkers do,
again particularly for modern languages. C++ places unique demands
on a linker, and large C++ programs are prone to develop
hard-to-diagnose bugs due to unexpected things that happen at link
time. (The best known are static constructors that run in an an order
the programmer wasn’t expecting.) Linker features such as
shared libraries and dynamic linking offer great flexibility and
power, when used appropriately,
• Language designers and developers need to be aware of what linkers
do and can do as they build languages and compilers. Programming
tasks had been handled hand for 30 years are automated in
C++, depending on the linker to handle the details. (Consider what
a programmer has to do to get the equivalent of C++ templates in
C, or ensuring that the initialization routines in each of a hundred
C source files are called before the body of the program starts.)
Future languages will automate even more program-wide bookkeeping
tasks, with more powerful linkers doing the work. Linkers
will also be more involved in global program optimization, since
the linker is the only stage of the compiler process that handles the
entire program’s code together and can do transformations that affect
the entire program as a unit.

Chapter 0: Front Matter ........................................................ 1
Dedication .............................................................................................. 1
Introduction ............................................................................................ 1
Who is this book for? ......................................................................... 2
Chapter summaries ............................................................................. 3
The project ......................................................................................... 4
Acknowledgements ............................................................................ 5
Contact us ........................................................................................... 6
Chapter 1: Linking and Loading ........................................... 7
What do linkers and loaders do? ............................................................ 7
Address binding: a historical perspective .............................................. 7
Linking vs. loading .............................................................................. 10
Two-pass linking .............................................................................. 12
Object code libraries ........................................................................ 15
Relocation and code modification .................................................... 17
Compiler Drivers .................................................................................. 18
Linker command languages ............................................................. 19
Linking: a true-life example ................................................................. 20
Exercises .............................................................................................. 25
Chapter 2: Architectural Issues ........................................... 27
Application Binary Interfaces .............................................................. 27
Memory Addresses .............................................................................. 28
Byte Order and Alignment ............................................................... 28
Address formation ................................................................................ 30
Instruction formats ............................................................................... 31
Procedure Calls and Addressability ..................................................... 32
Procedure calls ................................................................................. 33
2 Table of Contents
Data and instruction references ............................................................ 36
IBM 370 ........................................................................................... 37
SPARC ............................................................................................. 40
SPARC V8 ................................................................................... 40
SPARC V9 ................................................................................... 42
Intel x86 ........................................................................................... 43
Paging and Virtual Memory ................................................................. 45
The program address space .............................................................. 48
Mapped files ..................................................................................... 49
Shared libraries and programs ......................................................... 51
Position-independent code ............................................................... 51
Intel 386 Segmentation ........................................................................ 53
Embedded architectures ....................................................................... 55
Address space quirks ........................................................................ 56
Non-uniform memory ...................................................................... 56
Memory alignment ........................................................................... 57
Exercises .............................................................................................. 57
Chapter 3: Object Files ........................................................ 59
What goes into an object file? .............................................................. 59
Designing an object format .............................................................. 60
The null object format: MS-DOS .COM files ...................................... 61
Code sections: Unix a.out files ............................................................. 61
a.out headers .................................................................................... 64
Interactions with virtual memory ..................................................... 65
Relocation: MS-DOS EXE files ........................................................... 72
Symbols and relocation ........................................................................ 74
Relocatable a.out .................................................................................. 75
Relocation entries ............................................................................. 78
Symbols and strings ......................................................................... 80
a.out summary .................................................................................. 82
Unix ELF ............................................................................................. 82
Relocatable files ............................................................................... 85
ELF executable files ......................................................................... 92
ELF summary ................................................................................... 94
Table of Contents 3
IBM 360 object format ......................................................................... 94
ESD records ..................................................................................... 95
TXT records ..................................................................................... 97
RLD records ..................................................................................... 97
END records ..................................................................................... 98
Summary .......................................................................................... 98
Microsoft Portable Executable format ................................................. 99
PE special sections ......................................................................... 105
Running a PE executable ............................................................... 107
PE and COFF ................................................................................. 107
PE summary ................................................................................... 108
Intel/Microsoft OMF files .................................................................. 108
OMF records .................................................................................. 110
Details of an OMF file ................................................................... 111
Summary of OMF .......................................................................... 114
Comparison of object formats ............................................................ 114
Project ................................................................................................ 115
Exercises ............................................................................................ 117
Chapter 4: Storage allocation ............................................ 119
Segments and addresses ..................................................................... 119
Simple storage layout ......................................................................... 120
Multiple segment types ...................................................................... 121
Segment and page alignment ............................................................. 124
Common blocks and other special segments ..................................... 125
Common ......................................................................................... 125
C++ duplicate removal ................................................................... 127
Initializers and finalizers ................................................................ 130
IBM pseudo-registers ..................................................................... 131
Special tables ................................................................................. 134
X86 segmented storage allocation ................................................. 134
Linker control scripts ......................................................................... 136
Embedded system storage allocation ................................................. 138
Storage allocation in practice ............................................................. 138
Storage allocation in Unix a.out linkers ......................................... 139
4 Table of Contents
Storage allocation in ELF .............................................................. 141
Storage allocation in Windows linkers .......................................... 144
Exercises ............................................................................................ 146
Project ................................................................................................ 147
Chapter 5: Symbol management ....................................... 149
Binding and name resolution ............................................................. 149
Symbol table formats ......................................................................... 150
Module tables ................................................................................. 153
Global symbol table ....................................................................... 154
Symbol resolution .......................................................................... 157
Special symbols ............................................................................. 158
Name mangling .................................................................................. 158
Simple C and Fortran name mangling ........................................... 158
C++ type encoding: types and scopes ............................................ 160
Link-time type checking ................................................................ 163
Weak external and other kinds of symbols ........................................ 164
Maintaining debugging information .................................................. 164
Line number information ............................................................... 164
Symbol and variable information ................................................... 165
Practical issues ............................................................................... 166
Exercises ............................................................................................ 167
Project ................................................................................................ 167
Chapter 6: Libraries ........................................................... 169
Purpose of libraries ............................................................................ 169
Library formats .................................................................................. 169
Using the operating system ............................................................ 169
Unix and Windows Archive files ................................................... 170
Unix archives ............................................................................. 170
Extension to 64 bits ........................................................................ 174
Intel OMF libraries ........................................................................ 174
Creating libraries ................................................................................ 176
Searching libraries ............................................................................. 177
Table of Contents 5
Performance issues ............................................................................. 179
Weak external symbols ...................................................................... 179
Exercises ............................................................................................ 181
Project ................................................................................................ 181
Chapter 7: Relocation ......................................................... 183
Hardware and software relocation ..................................................... 183
Link time and load time relocation .................................................... 184
Symbol and segment relocation ......................................................... 185
Symbol lookups ............................................................................. 186
Basic relocation techniques ................................................................ 186
Instruction relocation ..................................................................... 188
X86 instruction relocation .......................................................... 189
SPARC instruction relocation .................................................... 189
ECOFF segment relocation ............................................................ 191
ELF relocation ............................................................................... 193
OMF relocation .............................................................................. 193
Relinkable and relocatable output formats ........................................ 194
Other relocation formats .................................................................... 194
Chained references ......................................................................... 195
Bit maps ......................................................................................... 195
Special segments ............................................................................ 196
Relocation special cases ..................................................................... 197
Exercises ............................................................................................ 197
Project ................................................................................................ 198
Chapter 8: Loading and overlays ...................................... 201
Basic loading ...................................................................................... 201
Basic loading, with relocation ............................................................ 202
Position-independent code ................................................................. 203
TSS/360 position independent code ............................................... 203
Per-routine pointer tables ............................................................... 206
Table of Contents ........................................................................... 207
ELF position independent code ..................................................... 208
6 Table of Contents
PIC costs and benefits .................................................................... 212
Bootstrap loading ............................................................................... 213
Tree structured overlays ..................................................................... 214
Defining overlays ........................................................................... 217
Implementation of overlays ........................................................... 220
Overlay fine points ......................................................................... 222
Data ............................................................................................ 222
Duplicated code ......................................................................... 222
Multiple regions ......................................................................... 223
Overlay summary ........................................................................... 223
Exercises ............................................................................................ 223
Project ................................................................................................ 224
Chapter 9: Shared libraries ............................................... 227
Binding time ...................................................................................... 230
Shared libraries in practice ................................................................. 231
Address space management ............................................................... 231
Structure of shared libraries ............................................................... 232
Creating shared libraries .................................................................... 233
Creating the jump table .................................................................. 234
Creating the shared library ............................................................. 235
Creating the stub library ................................................................. 235
Version naming .............................................................................. 237
Linking with shared libraries ............................................................. 238
Running with shared libraries ............................................................ 238
The malloc hack, and other shared library problems ......................... 240
Exercises ............................................................................................ 243
Project ................................................................................................ 244
Chapter 10: Dynamic Linking and Loading .................... 247
ELF dynamic linking ......................................................................... 248
Contents of an ELF file ...................................................................... 248
Loading a dynamically linked program ............................................. 253
Starting the dynamic linker ............................................................ 253
Table of Contents 7
Finding the libraries ....................................................................... 254
Shared library initialization ............................................................ 255
Lazy procedure linkage with the PLT ................................................ 256
Other peculiarities of dynamic linking .............................................. 258
Static initializations ........................................................................ 258
Library versions ............................................................................. 259
Dynamic loading at runtime ............................................................... 260
Microsoft Dynamic Link Libraries .................................................... 260
Imported and exported symbols in PE files ................................... 261
Lazy binding .................................................................................. 266
DLLs and threads ........................................................................... 267
OSF/1 pseudo-static shared libraries ................................................. 267
Making shared libraries fast ............................................................... 268
Comparison of dynamic linking approaches ...................................... 270
Exercises ............................................................................................ 271
Project ................................................................................................ 271
Chapter 11: Advanced techniques ..................................... 273
Techniques for C++ ........................................................................... 273
Trial linking .................................................................................... 274
Duplicate code elimination ............................................................ 276
Database approaches ...................................................................... 278
Incremental linking and relinking ...................................................... 278
Link time garbage collection ............................................................. 281
Link time optimization ....................................................................... 282
Link time code generation ................................................................. 284
Link-time profiling and instrumentation ........................................ 284
Link time assembler ....................................................................... 285
Load time code generation ............................................................. 285
The Java linking model ...................................................................... 287
Loading Java classes ...................................................................... 288
Exercises ............................................................................................ 290
Project ................................................................................................ 291
8 Table of Contents
Chapter 12: References ...................................................... 293
Perl books ....................................................................................... 295

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Hugo801122

好东西哦，多谢！