ARM Compiler toolchain Using the Linker - ARM Information Center

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11.2.1 See also LR3 0x20000 RELOC { ER_RELOCATABLE +0 { *(floatingsection) } } Features of the Base Platform linking model The linker does not have to generate dynamic relocations between LR1 and LR2 because they have fixed addresses. However, the RELOC load region LR3 might be widely separated from load regions LR1 and LR2 in the address space. Therefore, dynamic relocations are required between LR1 and LR3, and LR2 and LR3. Use the options --pltgot=direct --pltgot_opts=crosslr to ensure a PLT is generated for each load region. Concepts • Base Platform Application Binary Interface (BPABI) linking model on page 3-5 • Base Platform linking model on page 3-6 • Concepts common to both BPABI and SysV linking models on page 3-9 • Restrictions on the use of scatter files with the Base Platform model on page 11-2 Reference Linker Reference: • Load region attributes on page 4-7. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 11-6 ID080411 Non-Confidential
Features of the Base Platform linking model 11.3 Placement of PLT sequences with the Base Platform model 11.3.1 See also The linker supports Procedure Linkage Table (PLT) generation for multiple load regions containing code when in Base Platform mode (--base_platform). To turn on PLT generation when in Base Platform mode use --pltgot=option that generates PLT sequences. You can use the option --pltgot_opts=crosslr to add entries in the PLT for calls between RELOC load-regions. PLT generation for multiple Load Regions is only supported for --pltgot=direct. The --pltgot_opts=crosslr option is useful when you have multiple load regions that might be moved relative to each other when the image is dynamically loaded. The linker generates a PLT for each load region so that calls do not have to be extended to reach a distant PLT. Placement of linker generated PLT sections: • When there is only one load region there is one PLT. The linker creates a section called .plt with an object anon$$obj.o. • When there are multiple load regions, a PLT section is created for each load region that requires one. By default, the linker places the PLT section in the first execution region containing code. You can override this by specifying the exact PLT section name in the scatter file. For example, a load region with name LR Name the PLT section is called .plt_LR_NAME with an object of anon$$obj.o. To precisely name this PLT section in a scatter file, use the selector: anon$$obj.o(.plt_LR_NAME) Be aware of the following: • The linker gives an error message if the PLT for load region LR_NAME is moved out of load region LR_NAME. • The linker gives an error message if load region LR_NAME contains a mixture of RELOC and non-RELOC execution regions. This is because it cannot guarantee that the RELOC execution regions are able to reach the PLT at run-time. • --pltgot=indirect and --pltgot=sbrel are not supported for multiple load regions. Concepts • Base Platform linking model on page 3-6. Reference Linker Reference: • --base_platform on page 2-18 • --pltgot=type on page 2-121 • --pltgot_opts=mode on page 2-122. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 11-7 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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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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