ARM Compiler toolchain Using the Linker - ARM Information Center

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7.5 Load$$ execution region symbols Accessing and managing symbols with armlink The linker performs an extra address assignment and relocation pass for relocations that refer to load addresses after RW compression. This delayed relocation permits more information about load addresses to be used in linker-defined symbols. Note Load$$region_name symbols apply only to execution regions, and Load$$LR$$load_region_name symbols apply only to load regions. The following table shows the symbols that the linker generates for every Load$$ execution region present in the image. All the symbols refer to execution addresses after the C library is initialized. Symbol Description Load$$region_name$$Base Load address of the region. Load$$region_name$$Length Region length in bytes. All symbols in this table refer to load addresses before the C library is initialized. Be aware of the following: • The symbols are absolute because section-relative symbols can only have execution addresses. • The symbols take into account RW compression. Table 7-2 Load$$ execution region symbols Load$$region_name$$Limit Address of the byte beyond the end of the execution region. Load$$region_name$$RO$$Base Address of the RO output section in this execution region. Load$$region_name$$RO$$Length Length of the RO output section in bytes. Load$$region_name$$RO$$Limit Address of the byte beyond the end of the RO output section in the execution region. Load$$region_name$$RW$$Base Address of the RW output section in this execution region. Load$$region_name$$RW$$Length Length of the RW output section in bytes. Load$$region_name$$RW$$Limit Address of the byte beyond the end of the RW output section in the execution region. Load$$region_name$$ZI$$Base Load address of the ZI output section in this execution region. Load$$region_name$$ZI$$Length Load length of the ZI output section in bytes. The Load Length of ZI is zero unless region_name has the ZEROPAD scatter-loading keyword set. If ZEROPAD is set then: Load Length = Image$$region_name$$ZI$$Length Load$$region_name$$ZI$$Limit Load address of the byte beyond the end of the ZI output section in the execution region. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 7-7 ID080411 Non-Confidential
7.5.1 See also Accessing and managing symbols with armlink • The symbols do not include ZI output section because it does not exist before the C library is initialized. • All relocations from RW compressed execution regions must be performed before compression, because the linker cannot resolve a delayed relocation on compressed data. • If the linker detects a relocation from an RW-compressed region to a linker-defined symbol that depends on RW compression, then the linker disables compression for that region. • Any zero bytes written to the file are visible. Therefore, the Limit and Length values must take into account the zero bytes written into the file. Concepts • Optimization with RW data compression on page 5-13 • Region-related symbols on page 7-5 • Image$$ execution region symbols on page 7-6 • Load$$LR$$ load region symbols on page 7-9 • Region name values when not scatter-loading on page 7-10. Reference: Linker Reference: • Execution region attributes on page 4-11 ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 7-8 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
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
Page 67 and 68: 4.25 Specifying user libraries when
Page 69 and 70: 4.27 Use of the strict family of op
Page 71 and 72: 5.1 Elimination of common debug sec
Page 73 and 74: 5.3 Elimination of unused sections
Page 75 and 76: 5.4 Elimination of unused virtual f
Page 77 and 78: • --scatter=file on page 2-142. C
Page 79 and 80: 5.6.1 See also Using linker optimiz
Page 81 and 82: 3. Creates the output image. 5.7.3
Page 83 and 84: 5.9 How the linker chooses a compre
Page 85 and 86: 5.11 How compression is applied 5.1
Page 87 and 88: 5.13 Inlining functions with the li
Page 89 and 90: Reference Assembler Reference: •
Page 91 and 92: 5.16 About reordering of tail calli
Page 93 and 94: 5.18 About merging comment sections
Page 95 and 96: 6.1 Linker options for getting info
Page 97 and 98: 6.3 Example of using the --info lin
Page 99 and 100: 6.4 How to find where a symbol is p
Page 101 and 102: • Load$$LR$$ load region symbols
Page 103 and 104: 7.2 Accessing linker-defined symbol
Page 105: 7.4 Image$$ execution region symbol
Page 109 and 110: 7.7 Region name values when not sca
Page 111 and 112: 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
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
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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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Change Topics affected Revisions fo
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