Building applications for execute-only memory
Placing code in execute-only memory prevents users from trivially reading that code.
NoteLink Time Optimization does not honor the
armclang -mexecute-onlyoption. If you use the
-Omaxoptions, then the compiler cannot generate execute-only code and produces a warning.
To build an application with code in execute-only memory:
Compile your C or C++ code using the
armclang --target=arm-arm-none-eabi -march=armv7-m -mexecute-only -c test.c -o test.o
-mexecute-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 execute-only code sections in the ELF object file are marked with the
Specify the memory map to the linker using either of the
+XOselector in a scatter file.
armlink --xo-baseoption on the command-line.
armlink --xo-base=0x8000 test.o -o test.axfResults:
The XO execution region is placed in a separate load region from the RO, RW, and ZI execution regions.
NoteIf 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.