What is virtual memory? Where do code, stack and heap physically live?
Essence
Every process sees its own virtual address space — a contiguous range of addresses not tied to physical RAM directly. Translation from virtual to physical addresses is done by the MMU via page tables maintained by the kernel (XNU). A page on arm64 iOS is 16 KB.
Why: process isolation (you cannot read another process's memory), protection (code pages read-only + execute, data pages no-execute), lazy allocation (an address is "reserved", physical memory is provided on first touch), and sharing one physical copy of libraries among processes.
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