“red zone” lives at the bottom of the stack (below rsp!)

a red zone is a fixed-size area in a function's stack frame beyond the return address which is not preserved by that function. The callee function may use the red zone for storing local variables without the extra overhead of modifying the stack pointer. This region of memory is not to be modified by interrupt/exception/signal handlers.

https://stackoverflow.com/questions/38042188/where-exactly-is-the-red-zone-on-x86-64

#systemProgramming