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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 Scatter File Syntax BNF notation used in scatter-loading description s Syntax of a scatter file Load region descriptions Components of a load region description Syntax of a load region description Load region attributes Inheritance rules for load region address attribut Inheritance rules for the RELOC address attribute Considerations when using a relative address +offs Execution region descriptions Components of an execution region description Syntax of an execution region description Execution region attributes Inheritance rules for execution region address att Considerations when using a relative address +offs Input section descriptions Components of an input section description Syntax of an input section description Examples of module and input section specification Expression evaluation in scatter files Expression usage in scatter files Expression rules in scatter files Execution address built-in functions for use in sc ScatterAssert function and load address related fu Symbol related function in a scatter file AlignExpr(expr, align) function GetPageSize() function SizeOfHeaders() function Example of aligning a base address in execution sp Scatter files containing relative base address loa Linker Command-line Options Linker Steering File Command Reference Via File Syntax

Scatter files containing relative base address load regions and a ZI execution region

8.6.10 Scatter files containing relative base address load regions and a ZI execution region

You might want to place zero-initialized (ZI) data in one load region, and use a relative base address for the next load region.

To place ZI data in load region LR1, and use a relative base address for the next load region LR2, for example:
LR1 0x8000
{
    er_progbits +0
    {
        *(+RO,+RW) ; Takes space in the Load Region
    }
    er_zi +0
    {
        *(+ZI) ; Takes no space in the Load Region
    }
}
LR2 +0 ; Load Region follows immediately from LR1
{
    er_moreprogbits +0
    {
        file1.o(+RO) ; Takes space in the Load Region
    }
}
Because the linker does not adjust the base address of LR2 to account for ZI data, the execution region er_zi overlaps the execution region er_moreprogbits. This generates an error when linking.
To correct this, use the ImageLimit() function with the name of the ZI execution region to calculate the base address of LR2. For example:
LR1 0x8000
{
    er_progbits +0
    {
        *(+RO,+RW) ; Takes space in the Load Region
    }
    er_zi +0
    {
        *(+ZI) ; Takes no space in the Load Region
    }
}
LR2 ImageLimit(er_zi) ; Set the address of LR2 to limit of er_zi
{
    er_moreprogbits +0
    {
        file1.o(+RO) ; Takes space in the Load Region
    }
}
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