Memory Management¶

Physical Memory-Management¶

Virtual Memory-Management¶

Kernel Address Space¶

x86¶

Begin	End	Description
0x00000000	0x00100000	Only in the kernel address space (not in application address spaces) - the real mode IVT and AP startup code.
0x00100000	0x50000000	Reserved for the userspace process sections (.text, .data, etc)
0x50000000	0x70000000	Userspace process heap
0x70000000	0xB0000000	Userspace stacks
0xC0000000	0xD0000000	The kernel's heap
0xD0000000	0xF0000000	Reserved for memory regions
0xF0000000	0xF0400000	Reserved for the stack of free physical pages
0xFA000000	0xFF3F6000	Kernel module load region
0xFF3F7000	0xFF3FF000	The initial kernel stack (32kB)
0xFF400000	0xFF7FF000	The kernel image (code, data, bss sections)
0xFF7FF000	0xFF800000	The kernel virtual address space's page directory
0xFFBFD000	0xFFBFF000	Temporary virtual address space (used to create other virtual address spaces)
0xFFBFF000	0xFFC00000	This address space's page directory
0xFFC00000	0x100000000	Reserved for this address space's page tables

There should be something at 0xB0000000, but I can't remember what it is at this point. - Matt

x64¶

Begin	End	Description
0x0000000000000000	0x0000800000000000	Reserved for the userspace process
0xFFFF800000000000	0xFFFFXXXXXXXXXXXX	Physical memory
0xFFFFFFFF7FC00000	0xFFFFFFFF80000000	Reserved for the stack of free physical pages (below 4GB)
0xFFFFFFFF80000000	0xFFFFFFFF88000000	The kernel image (code, data, bss sections)
0xFFFFFFFF88000000	0xFFFFFFFF90000000	The kernel's heap
0xFFFFFFFF90000000	0xFFFFFFFFF0000000	Reserved for memory regions
0xFFFFFFFFF0000000	0xFFFFFFFFF1000000	Kernel modules

Mips32¶

Begin	End	Description
0x00000000	0x80000000	Reserved for the userspace process (KUSEG)
0x80000000	0xA0000000	Kernel accessible area, windowed onto the first 512MB of physical RAM, Cached (KSEG0)
0xA0000000	0xC0000000	Kernel accessible area, windowed onto the first 512MB of physical RAM, Uncached (KSEG1)
0xC0000000	0xFFFFFFFF	Kernel accessible area, paged (KSEG2)
0x80000000	0x80100000	ROM Monitor
0x80100000	0x80XXXXXX	Kernel .code/.data/.bss
0xC0000000	0xC0100000	Page table, covering 32-bits (1MB large)
0xC0100000	0xCXXXXXXX	Kernel heap

It should be noted that the page table is located in the KSEG2 (paged) area. This is so that addresses can be patched up quickly without actually requiring 1MB of physical RAM. In the case where the translation entry for the page table is not itself in the TLB, a double fault is encountered and the kernel (running from KSEG0) loads the relevant piece of page table into the TLB and returns to the user program.

PowerPC (32-bit)¶

Begin	End	Description
0x00000000	0x00003000	Interrupt vector table
0x00800000	0x01000000	Bootloader
0x01000000	0x80000000	User accessible space
0x80000000	0xA0000000	OF mapped devices - PCI etc
0xA0000000	0xC0000000	Reserved for memory regions
0xC0000000	0xC0100000	Initial kernel page tables
0xC0100000	0xC0xxxxxx	Processor page table
0xD0000000	0xE0000000	Kernel heap
0xE0000000	0xF0000000	Kernel text/data, and modules
0xF0000000	0xFFFFFFFF	Open Firmware