fixed addr gdt, serial

docs/mem_layout.md

@@ -17,7 +17,21 @@
 | Reserved | 0x0c8000 - 0x0f0000 | bios expansions                                 |
 | Reserved | 0x0f0000 - 0x100000 | motherboard bios                                |
 
+### Allocations
+
+- 0x00500 - 0x04000: stage 1/2 stack
+- 0x04000 - 0x06a00: globals
+- 0x07c00 - 0x07e00: stage 1 text
+- 0x07e00 - 0x08000: gpt partition header
+- 0x08000 - 0x08200: stage 2 partition table entry
+- 0x08200 - 0x0c000: stage 2 text, stage 3 stack
+- 0x0c000          : gdt
+- 0x10000          : stage 3 text
+
 0x10000: stage 3
 
-TODO: once we're in real mode, repurpose s2 and s3 for a stack
-TODO: load s4 into a separate memory region
+TODO: once we're in real mode, repurpose s2 for a stack
+TODO: load s3 into a separate memory region
+
+TODO: use some fixed known memory address for the GDT, rather than putting it in stage 2.
+      That way, we can safely overwrite stage 2 once we're done with it.