About mapping symbols
Mapping symbols are generated by the compiler and assembler to identify inline transitions between code and data at literal pool boundaries, and between ARM code and Thumb code, such as ARM/Thumb interworking veneers.
The mapping symbols are:
Start of a sequence of ARM instructions.
Start of a sequence of Thumb instructions.
Start of a sequence of ThumbEE instructions.
Start of a sequence of data items, such as a literal pool.
armlink generates the $d.realdata mapping symbol to communicate to fromelf that the data is from a non-executable section. Therefore, the code and data sizes output by fromelf -z are the same as the output from armlink --info sizes, for example:
Code (inc. data) RO Data x y z
In this example, the y is marked with $d, and RO Data is marked with $d.realdata.
Symbols beginning with the characters $v are mapping symbols related to VFP and might be output when building for a target with VFP. Avoid using symbols beginning with $v in your source code.
Be aware that modifying an executable image with the fromelf --elf --strip=localsymbols command removes all mapping symbols from the image.