ARM Compiler toolchain Using the Linker - ARM Information Center

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0x00000200 0x00000004 Code RO 5 sec5 sections.o 0x00000204 0x00000004 Code RO 6 sec6 sections.o 8.14.2 Example for worst_fit In this example: Using scatter files • For first_fit the linker first assigns all the sections it can to ER_1, then moves on to ER_2 because that is the next available region. • For next_fit the linker does the same as first_fit. However, when ER_1 is full it is marked as FULL and is not considered again. In this example, ER_1 is completely full. ER_2 is then considered. • For best_fit the linker assigns sec1 to ER_1. It then has two regions of equal priority and specificity, but ER_1 has less space remaining. Therefore, the linker assigns sec2 to ER_1, and continues assigning sections until ER_1 is full. This example shows the image memory map when using the worst_fit algorithm. Execution Region ER_1 (Base: 0x00000100, Size: 0x0000000c, Max: 0x00000010, ABSOLUTE) Base Addr Size Type Attr Idx E Section Name Object 0x00000100 0x00000004 Code RO 1 sec1 sections.o 0x00000104 0x00000004 Code RO 3 sec3 sections.o 0x00000108 0x00000004 Code RO 5 sec5 sections.o Execution Region ER_2 (Base: 0x00000200, Size: 0x0000000c, Max: 0x00000010, ABSOLUTE) Base Addr Size Type Attr Idx E Section Name Object 0x00000200 0x00000004 Code RO 2 sec2 sections.o 0x00000204 0x00000004 Code RO 4 sec4 sections.o 0x00000208 0x00000004 Code RO 6 sec6 sections.o 8.14.3 See also The linker first assigns sec1 to ER_1. It then has two equally specific and priority regions. It assigns sec2 to the one with the most free space, ER_2 in this example. The regions now have the same amount of space remaining, so the linker assigns sec3 to the first one that appears in the scatter file, that is ER_1. Note The behavior of worst_fit is the default behavior in this version of the linker, and it is the only algorithm available and earlier linker versions. Concepts • Placing unassigned sections with the .ANY module selector on page 8-25 • Example of next_fit algorithm showing behavior of full regions, selectors, and priority on page 8-30. Reference Linker Reference: • --any_placement=algorithm on page 2-9 • --scatter=file on page 2-142. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-29 ID080411 Non-Confidential
Using scatter files 8.15 Example of next_fit algorithm showing behavior of full regions, selectors, and priority This example shows the operation of the next_fit placement algorithm for RO-CODE sections in sections.o. The input section properties and ordering are shown in the following table: The scatter file used for the examples is: LR 0x100 { ER_1 0x100 0x20 { .ANY1(+RO-CODE) } ER_2 0x200 0x20 { .ANY2(+RO) } ER_3 0x300 0x20 { .ANY3(+RO) } } Note This example has --any_contingency disabled. The next_fit algorithm is different to the others in that it never revisits a region that is considered to be full. This example also shows the interaction between priority and specificity of selectors - this is the same for all the algorithms. Execution Region ER_1 (Base: 0x00000100, Size: 0x00000014, Max: 0x00000020, ABSOLUTE) Base Addr Size Type Attr Idx E Section Name Object 0x00000100 0x00000014 Code RO 1 sec1 sections.o Execution Region ER_2 (Base: 0x00000200, Size: 0x0000001c, Max: 0x00000020, ABSOLUTE) Base Addr Size Type Attr Idx E Section Name Object Table 8-2 Input section properties Name Size sec1 0x4 sec2 0x4 sec3 0x4 sec4 0x4 sec5 0x4 sec6 0x4 ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-30 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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5.6.1 See also Using linker optimiz
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3. Creates the output image. 5.7.3
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5.9 How the linker chooses a compre
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5.11 How compression is applied 5.1
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5.13 Inlining functions with the li
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Reference Assembler Reference: •
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5.16 About reordering of tail calli
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5.18 About merging comment sections
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6.1 Linker options for getting info
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6.3 Example of using the --info lin
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6.4 How to find where a symbol is p
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• Load$$LR$$ load region symbols
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7.2 Accessing linker-defined symbol
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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 and 130: Using scatter files • Images with
Page 131 and 132: 8.2 When to use scatter-loading 8.2
Page 133 and 134: • --startup=symbol, --no_startup
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
Page 151 and 152: Developing Software for ARM ® Proc
Page 153 and 154: } } .ANY1(+RO) ; evenly distributed
Page 155: 8.14 Examples of using placement al
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
Page 175 and 176: 8.27 Example of placing code in a r
Page 177 and 178: 8.29 Example of placing ARM C++ lib
Page 179 and 180: 8.31 Reserving an empty region Usin
Page 181 and 182: 8.32 About creating regions on page
Page 183 and 184: 8.33 Overalignment of execution reg
Page 185 and 186: 8.35 Expression evaluation in scatt
Page 187 and 188: 8.37 Equivalent scatter-loading des
Page 189 and 190: Using scatter files Example 8-23 Po
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Page 193 and 194: Using scatter files • The ER_ZI e
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Page 197 and 198: Chapter 9 GNU ld script support in
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Page 201 and 202: Reference Linker Reference: • --l
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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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