ARM Compiler toolchain Using the Linker - ARM Information Center

More documents

Recommendations

Info

8.10 Using the FIXED attribute to create root regions 8.10.1 See also Using scatter files You can use the FIXED attribute in an execution region scatter file to create root regions that load and execute at fixed addresses. FIXED is used to create multiple root regions within a single load region and therefore typically a single ROM device. For example, you can use this to place a function or a block of data, such as a constant table or a checksum, at a fixed address in ROM so that it can be accessed easily through pointers. If you specify, for example, that some initialization code is to be placed at start of ROM and a checksum at the end of ROM, some of the memory contents might be unused. Use the * or .ANY module selector to flood fill the region between the end of the initialization block and the start of the data block. To make your code easier to maintain and debug, it is suggested that you use the minimum amount of placement specifications in scatter files and leave the detailed placement of functions and data to the linker. You cannot specify component objects that have been partially linked. For example, if you partially link the objects obj1.o, obj2.o, and obj3.o together to produce obj_all.o, the component object names are discarded in the resulting object. Therefore, you cannot refer to one of the objects by name, for example, obj1.o. You can refer only to the combined object obj_all.o. Note There are some situations where using FIXED and a single load region are not appropriate. Other techniques for specifying fixed locations are: • If your loader can handle multiple load regions, place the RO code or data in its own load region. • If you do not require the function or data to be at a fixed location in ROM, use ABSOLUTE instead of FIXED. The loader then copies the data from the load region to the specified address in RAM. ABSOLUTE is the default attribute. • To place a data structure at the location of memory-mapped I/O, use two load regions and specify UNINIT. UNINIT ensures that the memory locations are not initialized to zero. Concepts Linker Reference: • About execution region descriptions on page 4-8. Reference Linker Reference: • Load region attributes on page 4-7 • Execution region attributes on page 4-11 • Address attributes for load and execution regions on page 4-14. ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-17 ID080411 Non-Confidential
8.11 Placing functions and data at specific addresses Using scatter files Normally, the compiler produces RO, RW and ZI sections from a single source file. These regions contain all the code and data from the source file. To place a single function or data item at a fixed address, you must enable the linker to process the function or data separately from the rest of the input files. The linker has two methods that enable you to place a section at a specific address: • You can create a scatter file that defines an execution region at the required address with a section description that selects only one section. • For a specially-named section the linker can get the placement address from the section name. These specially-named sections are called __at sections. To place a function or variable at a specific address it must be placed in its own section. There are several ways to do this: • Place the function or data item in its own source file. • Use __attribute__((at(address))) to place variables in a separate section at a specific address. • Use __attribute__((section("name"))) to place functions and variables in a named section. • Use the AREA directive from assembly language. In assembly code, the smallest locatable unit is an AREA. • Use the --split_sections compiler option to generate one ELF section for each function in the source file. This option results in a small increase in code size for some functions because it reduces the potential for sharing addresses, data, and string literals between functions. However, this can help to reduce the final image size overall by enabling the linker to remove unused functions when you specify armlink --remove. 8.11.1 Example of placing a variable at a specific address without scatter-loading This example shows how to modify your source code to place code and data at specific addresses, and does not require a scatter file: 1. Create the source file main.c containing the following code: #include extern int sqr(int n1); int gSquared __attribute__((at(0x5000))); // Place at 0x5000 int main() { gSquared=sqr(3); printf("Value squared is: %d\n", gSquared); } 2. Create the source file function.c containing the following code: int sqr(int n1) { return n1*n1; } 3. Compile and link the sources: ARM DUI 0474C Copyright © 2010-2011 ARM. All rights reserved. 8-18 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 and 22:
Chapter 3 Linking models supported
Page 23 and 24:
3.2 Bare-metal linking model 3.2.1
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 •
Page 33 and 34:
4.1.1 See also Image structure and
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 41 and 42:
Page 43 and 44:
Page 45 and 46:
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
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 and 106: 7.4 Image$$ execution region symbol
Page 107 and 108: 7.5.1 See also Accessing and managi
Page 109 and 110: 7.7 Region name values when not sca
Page 111 and 112: 7.9 Importing linker-defined symbol
Page 113 and 114: 7.11 Section-related symbols 7.11.1
Page 115 and 116: 7.13 Input section symbols 7.13.1 S
Page 117 and 118: 7.15 Creating a symdefs file 7.15.1
Page 119 and 120: 7.17 Reading a symdefs file 7.17.1
Page 121 and 122: 7.18.2 See also 0x0000814D T __argv
Page 123 and 124: 7.20 Specifying steering files on t
Page 125 and 126: 7.22 Steering file format 7.22.1 Se
Page 127 and 128: 7.24 Using $Super$$ 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: 8.9.2 See also Tasks • Using the
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 and 164: Compiler Reference: • __attribute
Page 165 and 166: 8.20 Restrictions on placing __at s
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
Page 203 and 204:
9.5 Recommendations for using ld sc
Page 205 and 206:
.data : { __data_start = .; *(.data
Page 207 and 208:
9.6.4 See also .got 0 : { *(.got.pl
Page 209 and 210:
9.7.1 See also } .dynamic : { *(.dy
Page 211 and 212:
9.8.1 See also { *(.bss .bss.*) . =
Page 213 and 214:
Chapter 10 BPABI and SysV shared li
Page 215 and 216:
BPABI and SysV shared libraries and
Page 217 and 218:
10.3 Concepts common to all BPABI m
Page 219 and 220:
10.5 Symbol visibility for BPABI mo
Page 221 and 222:
10.6 Automatic import and export fo
Page 223 and 224:
10.8 Symbol versioning for BPABI mo
Page 225 and 226:
10.10 Linker options for SysV model
Page 227 and 228:
Page 229 and 230:
10.13 Addressing modes in the SysV
Page 231 and 232:
Page 233 and 234:
10.17 Linker options for bare metal
Page 235 and 236:
Page 237 and 238:
10.21 Addressing modes in the BPABI
Page 239 and 240:
10.23 About symbol versioning 10.23
Page 241 and 242:
10.25 Example of creating versioned
Page 243 and 244:
10.27 Linker options for enabling i
Page 245 and 246:
Chapter 11 Features of the Base Pla
Page 247 and 248:
Features of the Base Platform linki
Page 249 and 250:
11.2 Example scatter file for the B
Page 251 and 252:
Features of the Base Platform linki
Page 253:
Change Topics affected Revisions fo
show all

ARM Compiler toolchain Using the Linker - ARM Information Center

Create successful ePaper yourself

Delete template?

Save as template?