ARM Compiler toolchain Using the Linker - ARM Information Center

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8.21 Automatic placement of __at sections Using scatter files The automatic placement of __at sections is enabled by default. This feature is controlled by the linker command-line option, --autoat. Note You cannot use __at section placement with position independent execution regions. When linking with the --autoat option, the __at sections are not placed by the scatter-loading selectors. Instead, the linker places the __at section in a compatible region. If no compatible region is found, the linker creates a load and execution region for the __at section. All linker --autoat created execution regions have the UNINIT scatter-loading attribute. If you require a ZI __at section to be zero-initialized then it must be placed within a compatible region. A linker --autoat created execution region must have a base address that is at least 4 byte-aligned. The linker produces an error message if any region is incorrectly aligned. A compatible region is one where: • The __at address lies within the execution region base and limit, where limit is the base address + maximum size of execution region. If no maximum size is set, the linker sets the limit for placing __at sections as the current size of the execution region without __at sections plus a constant, 10240 bytes. • The execution region meets at least one of the following conditions: — it has a selector that matches the __at section by the standard scatter-loading rules — it has at least one section of the same type (RO, RW or ZI) as the __at section — it does not have the EMPTY attribute. Note The linker considers an __at section with type RW compatible with RO. The following example shows the sections .ARM.__at_0x0 type RO, .ARM.__at_0x2000 type RW, .ARM.__at_0x4000 type ZI, and .ARM.__at_0x8000 type ZI: Example 8-11 Automatic placement of __at sections LR1 0x0 { ER_RO 0x0 0x2000 { *(+RO) ; .ARM.__at_0x0 lies within the bounds of ER_RO } ER_RW 0x2000 0x2000 { *(+RW) ; .ARM.__at_0x2000 lies within the bounds of ER_RW } ER_ZI 0x4000 0x2000 { *(+ZI) ; .ARM.__at_0x4000 lies within the bounds of ER_ZI } } ; the linker creates a load and execution region for the __at section ; .ARM.__at_0x8000 because it lies outside all candidate regions. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-39 ID080411 Non-Confidential
8.21.1 See also Using scatter files Concepts • Using __attribute__((section("name"))) on page 8-35 • Using __at sections to place sections at a specific address on page 8-37 • Restrictions on placing __at sections on page 8-38 • Manual placement of __at sections on page 8-41 • Placing a key in flash memory using __at on page 8-42 • Placing a structure over a peripheral register using __at on page 8-43. Linker Reference: • About execution region descriptions on page 4-8. Reference Linker Reference: • --autoat, --no_autoat on page 2-17 • --ro_base=address on page 2-135 • --rw_base=address on page 2-139 • --zi_base=address on page 2-193 • Execution region attributes on page 4-11. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-40 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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7.4 Image$$ execution region symbol
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7.5.1 See also Accessing and managi
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7.7 Region name values when not sca
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7.9 Importing linker-defined symbol
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7.11 Section-related symbols 7.11.1
Page 115 and 116: 7.13 Input section symbols 7.13.1 S
Page 117 and 118: 7.15 Creating a symdefs file 7.15.1
Page 119 and 120: 7.17 Reading a symdefs file 7.17.1
Page 121 and 122: 7.18.2 See also 0x0000814D T __argv
Page 123 and 124: 7.20 Specifying steering files on t
Page 125 and 126: 7.22 Steering file format 7.22.1 Se
Page 127 and 128: 7.24 Using $Super$$ 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 and 156: 8.14 Examples of using placement al
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
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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
Page 191 and 192: Using scatter files Example 8-25 Po
Page 193 and 194: Using scatter files • The ER_ZI e
Page 195 and 196: Using scatter files Example 8-29 Sc
Page 197 and 198: Chapter 9 GNU ld script support in
Page 199 and 200: 9.2 Typical use cases for using ld
Page 201 and 202: Reference Linker Reference: • --l
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Page 209 and 210: 9.7.1 See also } .dynamic : { *(.dy
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Page 215 and 216: 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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BPABI and SysV shared libraries and
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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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