ARM Compiler toolchain Using the Linker - ARM Information Center

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8.19 Using __at sections to place sections at a specific address 8.19.1 See also Using scatter files You can give a section a special name that encodes the address where it must be placed. You specify the name as follows: .ARM.__at_address Where: address is the required address of the section. You can specify this in hexadecimal or decimal. Sections in the form of .ARM.__at_address are referred to by the abbreviation __at. In the compiler, you can assign variables to __at sections by: • explicitly naming the section using the __attribute__((section(”name”))) • using the attribute __at that sets up the name of the section for you. ; place variable1 in a section called .ARM.__at_0x00008000 int variable1 __attribute__((at(0x8000))) = 10; Example 8-10 Assigning variables to __at sections ; place variable2 in a section called .ARM.__at_0x8000 int variable2 __attribute__((section(".ARM.__at_0x8000"))) = 10; Note When using __attribute__((at(address))), the part of the __at section name representing address is normalized to an 8 digit hexadecimal number. The name of the section is only significant if you are trying to match the section by name in a scatter file. The linker automatically assigns __at sections when you use the --autoat command-line option. This option is the default. Concepts • Placing functions and data at specific addresses on page 8-18 • Using __attribute__((section("name"))) on page 8-35 • Restrictions on placing __at sections on page 8-38 • Automatic placement of __at sections on page 8-39 • 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. Reference Linker Reference: • --autoat, --no_autoat on page 2-17. Compiler Reference: • __attribute__((section("name"))) function attribute on page 5-53 • __attribute__((at(address))) variable attribute on page 5-67 • __attribute__((section("name"))) variable attribute on page 5-72. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-37 ID080411 Non-Confidential
8.20 Restrictions on placing __at sections 8.20.1 See also Using scatter files The following restrictions apply when placing __at sections at specific addresses: • __at section address ranges must not overlap, unless the overlapping sections are placed in different overlay regions • __at sections are not permitted in position independent execution regions • you must not reference the linker-defined symbols $$Base, $$Limit and $$Length of an __at section • __at sections must not be used in System V (SysV) and Base Platform Application Binary Interface (BPABI) executables and BPABI dynamic link libraries (DLLs) • __at sections must have an address that is a multiple of their alignment • __at sections ignore any +FIRST or +LAST ordering constraints. Concepts • Using __at sections to place sections at a specific address on page 8-37. Other information • Base Platform ABI for the ARM Architecture, http://infocenter.arm.com/help/topic/com.arm.doc.ihi0037-/index.html. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-38 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
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
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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
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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: Compiler Reference: • __attribute
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
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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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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