Building applications for execute-only memory
Placing code in execute-only memory prevents users from trivially reading that code.
To build an application with code in execute-only memory:
Compile your C or C++ code or assemble your ARM assembly code using the
armcc -c --execute_only test.c -o test.o
--execute_onlyoption prevents the compiler from generating any data accesses to the code sections.
To keep code and data in separate sections, the compiler disables the placement of literal pools inline with code.
Compiled code sections have the
AREA ||.text||, CODE, EXECONLY, ALIGN=1
The assembler faults any attempts to define data in an
Specify the memory map to the linker using either of the following:
+XOselector in a scatter file.
armlink --xo-baseoption on the command-line.
armlink --xo-base=0x8000 test.o -o test.axf
The XO execution region is placed in a separate load region from the RO, RW, and ZI execution regions.Note
If you do not specify
--xo-base, then by default:
- The XO execution region is placed immediately before the RO
execution region, at address
- All execution regions are in the same load region.