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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

Scatter-loading images with a complex memory map

7.1.7 Scatter-loading images with a complex memory map

For images with a complex memory map, you cannot specify the memory map using only linker command-line options. Such images require the use of a scatter file.

The following figure shows a complex memory map:
Figure 7-2 Complex memory map
Complex memory map

The following example shows the corresponding scatter-loading description that loads the segments from the program1.o and program2.o files into memory:
LOAD_ROM_1 0x0000              ; Start address for first load region (0x0000)
{
    EXEC_ROM_1 0x0000          ; Start address for first exec region (0x0000)
    {
        program1.o (+RO)       ; Place all code and RO data from
                               ; program1.o into this exec region
    }
    DRAM 0x18000 0x8000        ; Start address for this exec region (0x18000),
                               ; Maximum size of this exec region (0x8000)
    {
        program1.o (+RW, +ZI)  ; Place all RW and ZI data from
                               ; program1.o into this exec region
    }
}
LOAD_ROM_2 0x4000              ; Start address for second load region (0x4000)
{
    EXEC_ROM_2 0x4000
    {
        program2.o (+RO)       ; Place all code and RO data from
                               ; program2.o into this exec region
    }
    SRAM 0x8000 0x8000
    {
        program2.o (+RW, +ZI)  ; Place all RW and ZI data from
                               ; program2.o into this exec region
    }
}

Caution

The scatter-loading description in this example specifies the location for code and data for program1.o and program2.o only. If you link an additional module, for example, program3.o, and use this description file, the location of the code and data for program3.o is not specified.
Unless you want to be very rigorous in the placement of code and data, ARM® recommends that you use the * or .ANY specifier to place leftover code and data.
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