Keil Logo Arm Logo

Technical Support

On-Line Manuals

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

Type 2 image, one load region and non-contiguous execution regions

Type 2 image, one load region and non-contiguous execution regions

An image of this type consists of a single load region in the load view and three execution regions in the execution view. It is similar to images of type 1 except that the RW execution region is not contiguous with the RO execution region.

--ro_base=address1 specifies the load and execution address of the region containing the RO output section. --rw_base=address2 specifies the execution address for the RW execution region.

The following example shows the scatter-loading description equivalent to using --ro_base=0x010000 --rw_base=0x040000:

Example 36. Single load region and multiple execution regions

LR_1 0x010000        ; Defines the load region name as LR_1
{
    ER_RO +0         ; The first execution region is called ER_RO and starts at end of previous region.
                     ; Because there is no previous region, the address is 0x010000.
    {
        * (+RO)      ; All RO sections are placed consecutively into this region.
    }
    ER_RW 0x040000   ; Second execution region is called ER_RW and starts at 0x040000.
    {
        * (+RW)      ; All RW sections are placed consecutively into this region.
    }
    ER_ZI +0         ; The last execution region is called ER_ZI.
                     ; The address is 0x040000 + size of ER_RW region.
    {
        * (+ZI)      ; All ZI sections are placed consecutively here.
    }
}

In this example:

  • This description creates an image with one load region, named LR_1, with a load address of 0x010000.

  • The image has three execution regions, named ER_RO, ER_RW, and ER_ZI, that contain the RO, RW, and ZI output sections respectively. The RO region is a root region. The execution address of ER_RO is 0x010000.

  • The ER_RW execution region is not contiguous with ER_RO. Its execution address is 0x040000.

  • The ER_ZI execution region is placed immediately following the end of the preceding execution region, ER_RW.

Show/hiderwpi example variant

This is similar to images of type 2 with --rw_base where the RW execution region is separate from the RO execution region. However, --rwpi marks the execution regions containing the RW output section as position-independent.

The following example shows the scatter-loading description equivalent to using --ro_base=0x010000 --rw_base=0x018000 --rwpi:

Example 37. Position-independent data

LR_1 0x010000           ; The first load region is at 0x010000.
{
    ER_RO +0            ; Default ABSOLUTE attribute is inherited from parent. The execution address
                        ; is 0x010000	. The code and RO data cannot be moved.
    {
        * (+RO)         ; All the RO sections go here.
    }
    ER_RW 0x018000 PI   ; PI attribute overrides ABSOLUTE
    {
        * (+RW)         ; The RW sections are placed at 0x018000 and they can be moved.
    }
    ER_ZI +0            ; ER_ZI region placed after ER_RW region.
    {
        * (+ZI)         ; All the ZI sections are placed consecutively here.
    }
}

ER_RO, the RO execution region, inherits the ABSOLUTE attribute from the load region LR_1. The next execution region, ER_RW, is marked as PI. Also, because the ER_ZI region has an offset of +0, it inherits the PI attribute from the ER_RW region.

Similar scatter-loading descriptions can also be written to correspond to the usage of other combinations of --ropi and --rwpi with type 2 and type 3 images.

Copyright © 2007-2008, 2011-2012 ARM. All rights reserved.ARM DUI 0377D
Non-ConfidentialID062912

Keil logo

Arm logo
Important information

This site uses cookies to store information on your computer. By continuing to use our site, you consent to our cookies.