Linker User Guide

Scatter file to ELF mapping

ARM Compiler toolchain v5.02 for µVision Using the Linker

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Scatter file to ELF mapping

For simple images, ELF executable files contain segments:

a load region is represented by an ELF Program Segment with type PT_LOAD
an execution region is represented by up to three ELF Sections:
- one for RO
- one for RW
- one for ZI.

For example, you might have a scatter file similar to the following:

Example 40. Scatter file

LOAD 0x8000
{
    EXEC_ROM +0
    {
        *(+RO)
    }
    RAM +0
    {
        *(+RW,+ZI)
    }
    HEAP +0x100 EMPTY 0x100
    {
    }
    STACK +0 EMPTY 0x400
    {
    }
}

This scatter file creates a single Program Segment with type PT_LOAD for the load region with address 0x8000.

A single Output Section with type SHT_PROGBITS is created to represent the contents of EXEC_ROM. Two Output Sections are created to represent RAM. The first has a type SHT_PROGBITS and contains the initialized read/write data. The second has a type of SHT_NOBITS and describes the zero-initialized data.

The heap and stack are described in the ELF file by SHT_NOBITS sections.

Enter the following fromelf command to see the scatter-loaded sections in the image:

fromelf --text -v my_image.axf

To display the symbol table, enter the command:

fromelf --text -s -v my_image.axf

The following is an example of the fromelf output showing the LOAD, EXEC_ROM, RAM, HEAP, and STACK sections:

Example 41. Scatter-loaded sections in the ELF image

...
========================================================================

** Program header #0

    Type          : PT_LOAD (1)
    File Offset   : 52 (0x34)
    Virtual Addr  : 0x00008000
    Physical Addr : 0x00008000
    Size in file  : 764 bytes (0x2fc)
    Size in memory: 2140 bytes (0x85c)
    Flags         : PF_X + PF_W + PF_R + PF_ARM_ENTRY (0x80000007)
    Alignment     : 4
========================================================================

** Section #1

    Name        : EXEC_ROM
...
    Addr        : 0x00008000
    File Offset : 52 (0x34)
    Size        : 740 bytes (0x2e4)
...
====================================

** Section #2

    Name        : RAM
...
    Addr        : 0x000082e4
    File Offset : 792 (0x318)
    Size        : 20 bytes (0x14)
...
====================================

** Section #3

    Name        : RAM
...
    Addr        : 0x000082f8
    File Offset : 812 (0x32c)
    Size        : 96 bytes (0x60)
...
====================================

** Section #4

    Name        : HEAP
...
    Addr        : 0x00008458
    File Offset : 812 (0x32c)
    Size        : 256 bytes (0x100)
...
====================================

** Section #5

    Name        : STACK
...
    Addr        : 0x00008558
    File Offset : 812 (0x32c)
    Size        : 1024 bytes (0x400)
...

Linker User Guide

Scatter file to ELF mapping

Scatter file to ELF mapping

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