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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

Linker User Guide

Specifying stack and heap using the scatter file

Specifying stack and heap using the scatter file

The ARM C library provides multiple implementations of the function __user_setup_stackheap(), and can select the correct one for you automatically from information given in a scatter file.

To select the two region memory model, define two special execution regions in your scatter file named ARM_LIB_HEAP and ARM_LIB_STACK. Both regions have the EMPTY attribute. This causes the library to select the non-default implementation of __user_setup_stackheap() that uses the value of the symbols:

  • Image$$ARM_LIB_STACK$$Base
    
  • Image$$ARM_LIB_STACK$$ZI$$Limit
    
  • Image$$ARM_LIB_HEAP$$Base
    
  • Image$$ARM_LIB_HEAP$$ZI$$Limit
    

Only one ARM_LIB_STACK or ARM_LIB_HEAP region can be specified, and you must allocate a size, for example:

LOAD_FLASH ...
{
    ...
    ARM_LIB_STACK 0x40000 EMPTY -0x20000  ; Stack region growing down
    { }
    ARM_LIB_HEAP 0x28000000 EMPTY 0x80000 ; Heap region growing up
    { }
    ...
}

You can use a combined stack and heap region by defining a single execution region named ARM_LIB_STACKHEAP, with the EMPTY attribute. This causes __user_setup_stackheap() to use the value of the symbols Image$$ARM_LIB_STACKHEAP$$Base and Image$$ARM_LIB_STACKHEAP$$ZI$$Limit.

Note

If you re-implement __user_setup_stackheap(), this overrides all library implementations.

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Reference

Using ARM® C and C++ Libraries and Floating-Point Support:

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