About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / x86 / x86_64 / mm.txt




Custom Search

Based on kernel version 4.1. Page generated on 2015-06-28 12:15 EST.

1	
2	<previous description obsolete, deleted>
3	
4	Virtual memory map with 4 level page tables:
5	
6	0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
7	hole caused by [48:63] sign extension
8	ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for hypervisor
9	ffff880000000000 - ffffc7ffffffffff (=64 TB) direct mapping of all phys. memory
10	ffffc80000000000 - ffffc8ffffffffff (=40 bits) hole
11	ffffc90000000000 - ffffe8ffffffffff (=45 bits) vmalloc/ioremap space
12	ffffe90000000000 - ffffe9ffffffffff (=40 bits) hole
13	ffffea0000000000 - ffffeaffffffffff (=40 bits) virtual memory map (1TB)
14	... unused hole ...
15	ffffec0000000000 - fffffc0000000000 (=44 bits) kasan shadow memory (16TB)
16	... unused hole ...
17	ffffff0000000000 - ffffff7fffffffff (=39 bits) %esp fixup stacks
18	... unused hole ...
19	ffffffff80000000 - ffffffffa0000000 (=512 MB)  kernel text mapping, from phys 0
20	ffffffffa0000000 - ffffffffff5fffff (=1525 MB) module mapping space
21	ffffffffff600000 - ffffffffffdfffff (=8 MB) vsyscalls
22	ffffffffffe00000 - ffffffffffffffff (=2 MB) unused hole
23	
24	The direct mapping covers all memory in the system up to the highest
25	memory address (this means in some cases it can also include PCI memory
26	holes).
27	
28	vmalloc space is lazily synchronized into the different PML4 pages of
29	the processes using the page fault handler, with init_level4_pgt as
30	reference.
31	
32	Current X86-64 implementations only support 40 bits of address space,
33	but we support up to 46 bits. This expands into MBZ space in the page tables.
34	
35	->trampoline_pgd:
36	
37	We map EFI runtime services in the aforementioned PGD in the virtual
38	range of 64Gb (arbitrarily set, can be raised if needed)
39	
40	0xffffffef00000000 - 0xffffffff00000000
41	
42	-Andi Kleen, Jul 2004
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.