ARM Compiler toolchain Using the Linker - ARM Information Center

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10.11 SysV memory model 10.11.1 See also BPABI and SysV shared libraries and executables System V (SysV) files have a standard memory model that is described in the generic ELF specification. There are several platform operating systems that use the SysV format, for example, ARM Linux. Because of the standard memory model, there are no configuration options available for the SysV memory model. The linker ignores any scatter file that you specify on the command-line and uses the standard memory map defined by the generic ELF specification. Concepts • Linker options for SysV models on page 10-13 • Automatic dynamic symbol table rules in the SysV memory model on page 10-15 • Addressing modes in the SysV memory model on page 10-17 • Thread local storage in the SysV memory model on page 10-18 • Related linker command-line options for the SysV memory model on page 10-19 Other information • ELF for the ARM Architecture, http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044-/index.html. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 10-14 ID080411 Non-Confidential
BPABI and SysV shared libraries and executables 10.12 Automatic dynamic symbol table rules in the SysV memory model The following rules apply to the System V (SysV) memory model: Executable An undefined symbol reference is an undefined symbol error. Global symbols with STV_HIDDEN or STV_INTERNAL visibility are never exported to the dynamic symbol table. Global symbols with STV_PROTECTED or STV_DEFAULT visibility are not exported to the dynamic symbol table unless you specify the --export_all or --export_dynamic option. Shared library An undefined symbol reference with STV_DEFAULT visibility is treated as imported and is placed in the dynamic symbol table. An undefined symbol reference without STV_DEFAULT visibility is an undefined symbol error. Global symbols with STV_HIDDEN or STV_INTERNAL visibility are never exported to the dynamic symbol table. 10.12.1 Symbol definitions defined for compatibility with glibc Note STV_HIDDEN or STV_INTERNAL global symbols that are required for relocation can be placed in the dynamic symbol table, however the linker changes them into local symbols to prevent them from being accessed from outside the shared library. Global symbols with STV_PROTECTED or STV_DEFAULT visibility are always exported to the dynamic symbol table. To improve SysV compatibility with glibc, the linker defines the following symbols if the corresponding sections exist in an object: • for .init_array sections: — __init_array_start — __init_array_end • for .fini_array sections: — __fini_array_start — __fini_array_end • for ARM.exidx sections: — __exidx_start — __exidx_end • for .preinit_array sections: — __preinit_array_start — __preinit_array_end • __executable_start • etext • _etext • __etext • __data_start • edata • _edata • __bss_start ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 10-15 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$$ execution region symbol
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7.5.1 See also Accessing and managi
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7.7 Region name values when not sca
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7.9 Importing linker-defined symbol
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7.11 Section-related symbols 7.11.1
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7.13 Input section symbols 7.13.1 S
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7.15 Creating a symdefs file 7.15.1
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7.17 Reading a symdefs file 7.17.1
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7.18.2 See also 0x0000814D T __argv
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7.20 Specifying steering files on t
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7.22 Steering file format 7.22.1 Se
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7.24 Using $Super$$ and $Sub$$ to p
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Using scatter files • Images with
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8.2 When to use scatter-loading 8.2
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• --startup=symbol, --no_startup
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8.4.1 See also Concepts • About s
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8.5.1 See also } SRAM 0x8000 0x8000
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8.7 Specifying stack and heap using
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8.9 Creating root execution regions
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8.9.2 See also Tasks • Using the
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8.11 Placing functions and data at
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Using scatter files RAM 0x200000 (0
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Using scatter files • Using __at
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Developing Software for ARM ® Proc
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} } .ANY1(+RO) ; evenly distributed
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8.14 Examples of using placement al
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Using scatter files 8.15 Example of
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8.16 Examples of using sorting algo
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8.17 Selecting veneer input section
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Compiler Reference: • __attribute
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8.20 Restrictions on placing __at s
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8.21.1 See also Using scatter files
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8.23 Placing a key in flash memory
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8.25 Placement of sections with ove
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8.25.1 See also Using scatter files
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Page 239 and 240: 10.23 About symbol versioning 10.23
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Page 249 and 250: 11.2 Example scatter file for the B
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Page 253: Change Topics affected Revisions fo
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