Position Independent Code (PIC) in x64 Assembly: Stack Anchor Technique, Sectionless Shellcode & ASLR-Safe Payloads
Standard Assembly code with absolute addresses breaks under ASLR — fixed addresses become invalid at runtime. PIC solves this via RIP-relative addressing: all memory references computed as offsets from the current instruction pointer. The Stack Anchor technique carves a 32KB R/W region (sub rsp,0x8000 + and rsp,-16 + mov rbp,rsp), providing writable storage without .data or .bss sections. Read-only templates in .text are copied to the stack via rep movsb for runtime modification. Result: a single position-independent code block deployable anywhere in memory — standard for shellcode, injection payloads, and fileless implants.