# Virtual Memory Layout on i386

GayBSD's virtual memory map is loosely based on the one from FreeBSD.

The size specifiers here are powers of two (1 KB = 1024 B).

 start address |   offset   | end address |    size    | description
:-------------:|-----------:|:-----------:|-----------:|:-----------------------
  `00000000`   |   +0       | `7fffffff`  |   2     GB | userland area
  `80000000`   |   -2    GB | `efffffff`  | ~ 1.8   GB | linear physical memory
  `f0000000`   | ~ -262  MB | `ffbfffff`  | ~ 258   MB | kernel image
  `ffc00000`   | ~ -12.2 MB | `ffffffff`  | ~ 12.2  MB | recursive page table

The linear physical memory is a direct mapping of physical RAM, which is
required because `kmalloc()` needs to be able to allocate *physically*
contiguous memory for DMA transfers.
It is also used as the heap area.
Unfortunately, because i don't have the resources to maintain it, the maximum
supported memory size on i386 is around 1.8 GB.
This is due to the required direct mapping and would require a fair bit of work
to get fixed, and 32-bit support is likely to be dropped in the near future.