Keil™, An ARM® Company

RealView Linker and Utilities Guide

Type 2, one load region and non contiguous execution regions

5.4.2. Type 2, 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.

Example 5.25 shows the scatter-loading description equivalent to using ‑‑ro‑base 0x010000 ‑‑rw‑base 0x040000.

Example 5.25. 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.
                     ; Since 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.
    }
}

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.

rwpi example variant

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

Example 5.26 shows the scatter-loading description equivalent to using ‑‑ro‑base 0x010000 ‑‑rw‑base 0x018000 ‑‑rwpi.

Example 5.26. 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 ARM Limited. All rights reserved.ARM DUI 0377A