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Linker User Guide

Conventions and feedback Overview of the linker Linking models supported by armlink Image structure and generation Using linker optimizations Getting information about images Accessing and managing symbols with armlink Using scatter files About scatter-loading When to use scatter-loading Scatter-loading command-line option Images with a simple memory map Images with a complex memory map Linker-defined symbols that are not defined when s Specifying stack and heap using the scatter file What is a root region? Creating root execution regions Using the FIXED attribute to create root regions Placing functions and data at specific addresses Placing a named section explicitly using scatter-l Placing unassigned sections with the .ANY module s Examples of using placement algorithms for .ANY se Example of next_fit algorithm showing behavior of Examples of using sorting algorithms for .ANY sect Selecting veneer input sections in scatter-loading Using __attribute__((section("name"))) t Using __at sections to place sections at a specifi Restrictions on placing __at sections Automatic placement of __at sections Manual placement of __at sections Placing a key in flash memory using __at Placing a structure over a peripheral register usi Placement of sections with overlays About placing ARM C and C++ library code Example of placing code in a root region Example of placing ARM C library code Example of placing ARM C++ library code Example of placing ARM library helper functions Reserving an empty region About creating regions on page boundaries Overalignment of execution regions and input secti Using preprocessing commands in a scatter file Expression evaluation in scatter files Using expression evaluation in a scatter file to a Equivalent scatter-loading descriptions for simple Type 1 image, one load region and contiguous execu Type 2 image, one load region and non-contiguous e Type 3 image, two load regions and non-contiguous Scatter file to ELF mapping

Manual placement of __at sections

Manual placement of __at sections

You can use the standard section placement rules to place __at sections when using the --no_autoat command-line option.


You cannot use __at section placement with position independent execution regions.

The following example shows the placement of read-only sections .ARM.__at_0x2000 and the read-write section .ARM.__at_0x4000. Load and execution regions are not created automatically in manual mode. An error is produced if an __at section cannot be placed in an execution region.

Example 22. Placement of the variables in C or C++ code

// place the RO variable in a section called .ARM.__at_0x2000
const int FOO __attribute__((section(".ARM.__at_0x2000"))) = 100;

// place the RW variable in a section called .ARM.__at_0x4000
int bar __attribute__((section(".ARM.__at_0x4000")));

Example 23. Manual placement of __at sections

LR1 0x0
    ER_RO 0x0 0x2000
        *(+RO)               ; .ARM.__at_0x0 is selected by +RO
    ER_RO2 0x2000
        *(.ARM.__at_0x2000)  ; .ARM.__at_0x2000 is selected by the section named
                             ; .ARM.__at_0x2000
    ER2 0x4000
        *(+RW +ZI)           ; .ARM.__at_0x4000 is selected by +RW

Copyright © 2007-2008, 2011-2012 ARM. All rights reserved.ARM DUI 0377D

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