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Linker User Guide

Preface Overview of the Linker Linking Models Supported by armlink Image Structure and Generation Linker Optimization Features Getting Image Details Accessing and Managing Symbols with armlink Scatter-loading Features The scatter-loading mechanism Overview of scatter-loading When to use scatter-loading Linker-defined symbols that are not defined when s Specifying stack and heap using the scatter file Scatter-loading command-line options Scatter-loading images with a simple memory map Scatter-loading images with a complex memory map Scatter file with link to bit-band objects Root execution regions Root execution region and the initial entry point Root execution regions and the ABSOLUTE attribute Root execution regions and the FIXED attribute Methods of placing functions and data at specific Placement of code and data with __attribute__((sec Placement of __at sections at a specific address Restrictions on placing __at sections Automatic placement of __at sections Manual placement of __at sections Placement of a key in flash memory with an __at se Mapping a structure over a peripheral register wit Example of how to explicitly place a named section Placement of unassigned sections with the .ANY mod Placement rules when using multiple .ANY selectors Command-line options for controlling the placement Prioritization of .ANY sections Specify the maximum region size permitted for plac Examples of using placement algorithms for .ANY se Example of next_fit algorithm showing behavior of Examples of using sorting algorithms for .ANY sect Behavior when .ANY sections overflow because of li Placement of veneer input sections in a scatter fi Placement of sections with overlays Reserving an empty region Placement of ARM C and C++ library code Specifying ARM standard C and C++ libraries in a s 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 Creation of regions on page boundaries Overalignment of execution regions and input secti Preprocessing of a scatter file Example of using expression evaluation in a scatte Equivalent scatter-loading descriptions for simple Command-line options for creating simple images Type 1 image, one load region and contiguous execu Type 2 image, one load region and non-contiguous e Type 3 image, multiple load regions and non-contig How the linker resolves multiple matches when proc How the linker resolves path names when processing Scatter file to ELF mapping Scatter File Syntax Linker Command-line Options Linker Steering File Command Reference Via File Syntax

Manual placement of __at sections

7.2.9 Manual placement of __at sections

You can have direct control over the placement of __at sections, if required.

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.
The following example shows the 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")));
The following scatter file shows how the manual placement of __at sections is achieved:
LR1 0x0
    ER_RO 0x0 0x2000
        *(+RO)               ; .ARM.__at_0x0000 is selected by +RO
    ER_RO2 0x2000
        *(.ARM.__at_0x02000)  ; .ARM.__at_0x2000 is selected by the section named
                              ; .ARM.__at_0x2000
    ER2 0x4000
        *(+RW +ZI)           ; .ARM.__at_0x4000 is selected by +RW
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