Red zone (computing)

Red Zone is a term designating the fixed size area in memory beyond the stack pointer that has not been "allocated". This region of memory is not to be modified by interrupt/exception/signal handlers. This allows the space to be used for temporary data without the extra overhead of modifying the stack pointer. The x86-64 ABI mandates a 128 byte red zone. The OpenRISC 1200 toolchain assumes a 128 byte red zone though it is not documented.