ARM Compiler toolchain Using the Linker - ARM Information Center

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3.1 Overview of linking models 3.1.1 See also Linking models supported by armlink A linking model is a group of command-line options and memory maps that control the behavior of the linker. Bare-metal This model does not target any specific platform. It enables you to create an image with your own custom operating system, memory map, and, application code if required. Some limited dynamic linking support is available. You can specify additional options depending on whether or not a scatter file is in use. Partial linking This model produces a platform-independent object suitable for input to the linker in a subsequent link step. It can be used as an intermediate step in the development process and performs limited processing of input objects to produce a single output object. BPABI This model supports the DLL-like Base Platform Application Binary Interface (BPABI). It is intended to produce applications and DLLs that can run on a platform OS that varies in complexity. The memory model is restricted according to the BPABI specification. Base Platform This is an extension to the BPABI model to support scatter-loading. SysV This model supports System V (SysV) models specified in the ELF used by ARM Linux. The memory model is restricted according to the ELF specification. Related options in each model can be combined to tighten control over the output. Concepts • Bare-metal linking model on page 3-3 • Partial linking model on page 3-4 • Base Platform Application Binary Interface (BPABI) linking model on page 3-5 • Base Platform linking model on page 3-6 • SysV linking model on page 3-8 • Concepts common to both BPABI and SysV linking models on page 3-9. Reference • Chapter 10 BPABI and SysV shared libraries and executables. 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. 3-2 ID080411 Non-Confidential
3.2 Bare-metal linking model 3.2.1 See also Linking models supported by armlink The bare-metal model focuses on the conventional embedded market where the whole program, possibly including a Real-Time Operating System (RTOS), is linked in one pass. Very few assumptions can be made by the linker about the memory map of a bare metal system. Therefore, you must use the scatter-loading mechanism if you want more precise control. By default, the linker attempts to resolve all the relocations statically. However, it is also possible to create a position-independent or relocatable image. Such an image can be executed from different addresses and have its relocations resolved at load or run-time. This can be achieved using a dynamic model. With this type of model, you can: • identify the regions that can be relocated or are position-independent using a scatter file or command-line options. • identify the symbols that can be imported and exported using a steering file • identify the shared libraries that are required by the ELF file using a steering file. You can use the following options with this model: • --edit=file_list • --scatter=file. You can use the following options when scatter-loading is not used: • --reloc • --ro_base=address • --ropi • --rosplit • --rw_base=address • --rwpi • --split • --zi_base. Concepts • Methods of specifying an image memory map with the linker on page 4-8. Reference Linker Reference: • --edit=file_list on page 2-53 • --reloc on page 2-132 • --ro_base=address on page 2-135 • --ropi on page 2-136 • --rosplit on page 2-137 • --rw_base=address on page 2-139 • --rwpi on page 2-140 • --scatter=file on page 2-142 • --split on page 2-154 • --zi_base=address on page 2-193 • Chapter 3 Linker steering file command reference. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 3-3 ID080411 Non-Confidential
Page 1 and 2: ® ARM Copyright © 2010-2011 ARM.
Page 3 and 4: Contents ARM Compiler toolchain Usi
Page 5 and 6: Contents 7.15 Creating a symdefs fi
Page 7 and 8: Chapter 1 Conventions and feedback
Page 9 and 10: Chapter 2 Overview of the linker Th
Page 11 and 12: Concepts • Demand paging on page
Page 13 and 14: 2.3 Linker command-line options lis
Page 15 and 16: • --keep_protected_symbols on pag
Page 17 and 18: • --eager_load_debug, --no_eager_
Page 19 and 20: 2.5 What the linker outputs 2.5.1 S
Page 21: Chapter 3 Linking models supported
Page 25 and 26: Linking models supported by armlink
Page 27 and 28: 3.5.1 See also • There are restri
Page 29 and 30: 3.7 Concepts common to both BPABI a
Page 31 and 32: Image structure and generation •
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Page 35 and 36: 4.3 Load view and execution view of
Page 37 and 38: 4.4 Methods of specifying an image
Page 39 and 40: 4.5 Types of simple image 4.5.1 See
Page 47 and 48: 4.10 About specifying an initial en
Page 49 and 50: 4.11.2 Example 4.11.3 See also The
Page 51 and 52: 4.13 Section alignment with the lin
Page 53 and 54: Reference Linker Reference: • --a
Page 55 and 56: 4.16 Overview of veneers 4.16.1 See
Page 57 and 58: 4.18 Veneer types 4.18.1 See also I
Page 59 and 60: 4.20 Reuse of veneers when scatter-
Page 61 and 62: 4.22 About weak references and defi
Page 63 and 64: BL init_foo ;Rest of code END 4.22.
Page 65 and 66: Image structure and generation 4.24
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Page 69 and 70: 4.27 Use of the strict family of op
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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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8.27 Example of placing code in a r
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8.29 Example of placing ARM C++ lib
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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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