ARM Compiler toolchain Using the Linker - ARM Information Center

Using scatter files
The following table shows the effect of +offset when used with the OVERLAY attribute. REGION1
appears immediately before REGION2 in the scatter file:
The following example shows the use of relative offsets with overlays and the effect on
execution region addresses:
EMB_APP 0x8000{
CODE 0x8000
{
*(+RO)
}
}
REGION1 is set
with OVERLAY
# REGION1 Base = CODE limit
REGION1 +0 OVERLAY
{
module1.o(*)
}
# REGION2 Base = REGION1 Base
REGION2 +0 OVERLAY
{
module2.o(*)
}
# REGION3 Base = REGION2 Base = REGION1 Base
REGION3 +0 OVERLAY
{
module3.o(*)
}
# REGION4 Base = REGION3 Limit + 4
Region4 +4 OVERLAY
{
module4.o(*)
}
Table 8-7 Using relative offset in overlays
+offset REGION2 Base Address
NO REGION1 Limit +
YES +0 REGION1 Base Address
YES REGION1 Limit +
Example 8-17 Example of relative offset in overlays
If the length of the non-overlay area is unknown, a zero relative offset can be used to specify the
start address of an overlay so that it is placed immediately after the end of the static section.
You can use the following command-line options to add extra debug information to the image:
• --emit_debug_overlay_relocs
• --emit_debug_overlay_section.
These permit an overlay-aware debugger to track which overlay is currently active.
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