ARM Compiler toolchain Using the Linker - ARM Information Center

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8.1 About scatter-loading 8.1.1 See also Using scatter files The scatter-loading mechanism enables you to specify the memory map of an image to the linker using a description in a text file. Scatter-loading gives you complete control over the grouping and placement of image components. You can use scatter-loading to create simple images, but it is generally only used for images that have a complex memory map. That is, where multiple memory regions are scattered in the memory map at load and execution time. An image memory map is made up of regions and output sections. Every region in the memory map can have a different load and execution address. To construct the memory map of an image, the linker must have: • grouping information that describes how input sections are grouped into output sections and regions • placement information that describes the addresses where regions are to be located in the memory maps. When the linker creates an image using a scatter file, it creates some region-related symbols. The linker creates these special symbols only if your code references them. Concepts • The image structure on page 4-3 • Region-related symbols on page 7-5 • When to use scatter-loading on page 8-4 • Scatter file to ELF mapping on page 8-67. Developing Software for ARM ® Processors: • Scatter-loading file with link to bit-band objects on page 3-16. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-3 ID080411 Non-Confidential
8.2 When to use scatter-loading 8.2.1 See also Using scatter files The command-line options to the linker give some control over the placement of data and code, but complete control of placement requires more detailed instructions than can be entered on the command line. Situations where scatter-loading is either required or very useful: Complex memory maps Code and data that must be placed into many distinct areas of memory require detailed instructions on where to place the sections in the memory space. Different types of memory Many systems contain a variety of physical memory devices such as flash, ROM, SDRAM, and fast SRAM. A scatter-loading description can match the code and data with the most appropriate type of memory. For example, interrupt code might be placed into fast SRAM to improve interrupt response time but infrequently-used configuration information might be placed into slower flash memory. Memory-mapped peripherals The scatter-loading description can place a data section at a precise address in the memory map so that memory mapped peripherals can be accessed. Functions at a constant location A function can be placed at the same location in memory even though the surrounding application has been modified and recompiled. This is useful for jump table implementation. Using symbols to identify the heap and stack Symbols can be defined for the heap and stack location when the application is linked. Scatter-loading is usually required for implementing embedded systems because these use ROM, RAM, and memory-mapped peripherals. Concepts • About scatter-loading on page 8-3. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-4 ID080411 Non-Confidential
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® ARM Copyright © 2010-2011 ARM.
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Contents ARM Compiler toolchain Usi
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Contents 7.15 Creating a symdefs fi
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Chapter 1 Conventions and feedback
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Chapter 2 Overview of the linker Th
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Concepts • Demand paging on page
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2.3 Linker command-line options lis
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• --keep_protected_symbols on pag
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• --eager_load_debug, --no_eager_
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2.5 What the linker outputs 2.5.1 S
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Chapter 3 Linking models supported
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3.2 Bare-metal linking model 3.2.1
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Linking models supported by armlink
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3.5.1 See also • There are restri
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3.7 Concepts common to both BPABI a
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Image structure and generation •
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4.1.1 See also Image structure and
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4.3 Load view and execution view of
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4.4 Methods of specifying an image
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4.5 Types of simple image 4.5.1 See
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4.10 About specifying an initial en
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4.11.2 Example 4.11.3 See also The
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4.13 Section alignment with the lin
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Reference Linker Reference: • --a
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4.16 Overview of veneers 4.16.1 See
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4.18 Veneer types 4.18.1 See also I
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4.20 Reuse of veneers when scatter-
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4.22 About weak references and defi
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BL init_foo ;Rest of code END 4.22.
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Image structure and generation 4.24
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4.25 Specifying user libraries when
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4.27 Use of the strict family of op
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5.1 Elimination of common debug sec
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5.3 Elimination of unused sections
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5.4 Elimination of unused virtual f
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• --scatter=file on page 2-142. C
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Page 85 and 86: 5.11 How compression is applied 5.1
Page 87 and 88: 5.13 Inlining functions with the li
Page 89 and 90: Reference Assembler Reference: •
Page 91 and 92: 5.16 About reordering of tail calli
Page 93 and 94: 5.18 About merging comment sections
Page 95 and 96: 6.1 Linker options for getting info
Page 97 and 98: 6.3 Example of using the --info lin
Page 99 and 100: 6.4 How to find where a symbol is p
Page 101 and 102: • Load$$LR$$ load region symbols
Page 103 and 104: 7.2 Accessing linker-defined symbol
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Page 109 and 110: 7.7 Region name values when not sca
Page 111 and 112: 7.9 Importing linker-defined symbol
Page 113 and 114: 7.11 Section-related symbols 7.11.1
Page 115 and 116: 7.13 Input section symbols 7.13.1 S
Page 117 and 118: 7.15 Creating a symdefs file 7.15.1
Page 119 and 120: 7.17 Reading a symdefs file 7.17.1
Page 121 and 122: 7.18.2 See also 0x0000814D T __argv
Page 123 and 124: 7.20 Specifying steering files on t
Page 125 and 126: 7.22 Steering file format 7.22.1 Se
Page 127 and 128: 7.24 Using $Super$$ and $Sub$$ to p
Page 129: Using scatter files • Images with
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Page 135 and 136: 8.4.1 See also Concepts • About s
Page 137 and 138: 8.5.1 See also } SRAM 0x8000 0x8000
Page 139 and 140: 8.7 Specifying stack and heap using
Page 141 and 142: 8.9 Creating root execution regions
Page 143 and 144: 8.9.2 See also Tasks • Using the
Page 145 and 146: 8.11 Placing functions and data at
Page 147 and 148: Using scatter files RAM 0x200000 (0
Page 149 and 150: Using scatter files • Using __at
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Page 153 and 154: } } .ANY1(+RO) ; evenly distributed
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Page 157 and 158: Using scatter files 8.15 Example of
Page 159 and 160: 8.16 Examples of using sorting algo
Page 161 and 162: 8.17 Selecting veneer input section
Page 163 and 164: Compiler Reference: • __attribute
Page 165 and 166: 8.20 Restrictions on placing __at s
Page 167 and 168: 8.21.1 See also Using scatter files
Page 169 and 170: 8.23 Placing a key in flash memory
Page 171 and 172: 8.25 Placement of sections with ove
Page 173 and 174: 8.25.1 See also Using scatter files
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Page 177 and 178: 8.29 Example of placing ARM C++ lib
Page 179 and 180: 8.31 Reserving an empty region Usin
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8.32 About creating regions on page
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8.33 Overalignment of execution reg
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8.35 Expression evaluation in scatt
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8.37 Equivalent scatter-loading des
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Using scatter files Example 8-23 Po
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Using scatter files Example 8-25 Po
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Using scatter files • The ER_ZI e
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Using scatter files Example 8-29 Sc
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Chapter 9 GNU ld script support in
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9.2 Typical use cases for using ld
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Reference Linker Reference: • --l
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9.5 Recommendations for using ld sc
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.data : { __data_start = .; *(.data
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9.6.4 See also .got 0 : { *(.got.pl
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9.7.1 See also } .dynamic : { *(.dy
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9.8.1 See also { *(.bss .bss.*) . =
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Chapter 10 BPABI and SysV shared li
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BPABI and SysV shared libraries and
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10.3 Concepts common to all BPABI m
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10.5 Symbol visibility for BPABI mo
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10.6 Automatic import and export fo
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10.8 Symbol versioning for BPABI mo
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10.10 Linker options for SysV model
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10.13 Addressing modes in the SysV
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10.17 Linker options for bare metal
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10.21 Addressing modes in the BPABI
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10.23 About symbol versioning 10.23
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10.25 Example of creating versioned
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10.27 Linker options for enabling i
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Chapter 11 Features of the Base Pla
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Features of the Base Platform linki
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11.2 Example scatter file for the B
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Features of the Base Platform linki
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Change Topics affected Revisions fo
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