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Based on kernel version 3.9. Page generated on 2013-05-02 22:54 EST.

1			     Memory Layout on AArch64 Linux
2			     ==============================
3	
4	Author: Catalin Marinas <catalin.marinas@arm.com>
5	Date  : 20 February 2012
6	
7	This document describes the virtual memory layout used by the AArch64
8	Linux kernel. The architecture allows up to 4 levels of translation
9	tables with a 4KB page size and up to 3 levels with a 64KB page size.
10	
11	AArch64 Linux uses 3 levels of translation tables with the 4KB page
12	configuration, allowing 39-bit (512GB) virtual addresses for both user
13	and kernel. With 64KB pages, only 2 levels of translation tables are
14	used but the memory layout is the same.
15	
16	User addresses have bits 63:39 set to 0 while the kernel addresses have
17	the same bits set to 1. TTBRx selection is given by bit 63 of the
18	virtual address. The swapper_pg_dir contains only kernel (global)
19	mappings while the user pgd contains only user (non-global) mappings.
20	The swapper_pgd_dir address is written to TTBR1 and never written to
21	TTBR0.
22	
23	
24	AArch64 Linux memory layout:
25	
26	Start			End			Size		Use
27	-----------------------------------------------------------------------
28	0000000000000000	0000007fffffffff	 512GB		user
29	
30	ffffff8000000000	ffffffbbfffeffff	~240GB		vmalloc
31	
32	ffffffbbffff0000	ffffffbbffffffff	  64KB		[guard page]
33	
34	ffffffbc00000000	ffffffbdffffffff	   8GB		vmemmap
35	
36	ffffffbe00000000	ffffffbffbbfffff	  ~8GB		[guard, future vmmemap]
37	
38	ffffffbffbc00000	ffffffbffbdfffff	   2MB		earlyprintk device
39	
40	ffffffbffbe00000	ffffffbffbe0ffff	  64KB		PCI I/O space
41	
42	ffffffbbffff0000	ffffffbcffffffff	  ~2MB		[guard]
43	
44	ffffffbffc000000	ffffffbfffffffff	  64MB		modules
45	
46	ffffffc000000000	ffffffffffffffff	 256GB		kernel logical memory map
47	
48	
49	Translation table lookup with 4KB pages:
50	
51	+--------+--------+--------+--------+--------+--------+--------+--------+
52	|63    56|55    48|47    40|39    32|31    24|23    16|15     8|7      0|
53	+--------+--------+--------+--------+--------+--------+--------+--------+
54	 |                 |         |         |         |         |
55	 |                 |         |         |         |         v
56	 |                 |         |         |         |   [11:0]  in-page offset
57	 |                 |         |         |         +-> [20:12] L3 index
58	 |                 |         |         +-----------> [29:21] L2 index
59	 |                 |         +---------------------> [38:30] L1 index
60	 |                 +-------------------------------> [47:39] L0 index (not used)
61	 +-------------------------------------------------> [63] TTBR0/1
62	
63	
64	Translation table lookup with 64KB pages:
65	
66	+--------+--------+--------+--------+--------+--------+--------+--------+
67	|63    56|55    48|47    40|39    32|31    24|23    16|15     8|7      0|
68	+--------+--------+--------+--------+--------+--------+--------+--------+
69	 |                 |    |               |              |
70	 |                 |    |               |              v
71	 |                 |    |               |            [15:0]  in-page offset
72	 |                 |    |               +----------> [28:16] L3 index
73	 |                 |    +--------------------------> [41:29] L2 index (only 38:29 used)
74	 |                 +-------------------------------> [47:42] L1 index (not used)
75	 +-------------------------------------------------> [63] TTBR0/1
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