Offset for stack pointer

Posted Aug 27, 2025 13:27 UTC (Wed) by jreiser (subscriber, #11027)
In reply to: Abstraction by jrtc27
Parent article: Shadow-stack control in clone3()

On amd64 (x86_64), by OS and compiler convention there is also a "red zone" at [rsp - 128, rsp), also for the purpose of code optimization: the space may be used without requiring explicit instructions to allocate it. This may be somewhat invisible because it is in the same direction as regular stack growth, but it still affects creation of threads, and even signal handling.