1 =================================
2 Kernel Memory Layout on ARM Linux
3 =================================
4
5 Russell King <rmk@arm.linux.org
6
7 November 17, 2005 (2.6.15
8
9 This document describes the virtual memory lay
10 kernel uses for ARM processors. It indicates
11 free for platforms to use, and which are used
12
13 The ARM CPU is capable of addressing a maximum
14 space, and this must be shared between user sp
15 kernel, and hardware devices.
16
17 As the ARM architecture matures, it becomes ne
18 certain regions of VM space for use for new fa
19 this document may reserve more VM space over t
20
21 =============== =============== ==============
22 Start End Use
23 =============== =============== ==============
24 ffff8000 ffffffff copy_user_page
25 For SA11xx and
26 setup a minica
27
28 ffff4000 ffffffff cache aliasing
29
30 ffff1000 ffff7fff Reserved.
31 Platforms must
32
33 ffff0000 ffff0fff CPU vector pag
34 The CPU vector
35 CPU supports v
36 register V bit
37
38 fffe0000 fffeffff XScale cache f
39 in proc-xscale
40 cache. (XScale
41
42 fffe8000 fffeffff DTCM mapping a
43 DTCM mounted i
44
45 fffe0000 fffe7fff ITCM mapping a
46 ITCM mounted i
47
48 ffc80000 ffefffff Fixmap mapping
49 by fix_to_virt
50
51 ffc00000 ffc7ffff Guard region
52
53 ff800000 ffbfffff Permanent, fix
54 firmware provi
55
56 fee00000 feffffff Mapping of PCI
57 mapping within
58
59 VMALLOC_START VMALLOC_END-1 vmalloc() / io
60 Memory returne
61 be dynamically
62 Machine specif
63 located here t
64 VMALLOC_START
65 of the high_me
66 is equal to 0x
67
68 PAGE_OFFSET high_memory-1 Kernel direct-
69 This maps the
70 maps all platf
71
72 PKMAP_BASE PAGE_OFFSET-1 Permanent kern
73 One way of map
74 space.
75
76 MODULES_VADDR MODULES_END-1 Kernel module
77 Kernel modules
78 placed here us
79
80 TASK_SIZE MODULES_VADDR-1 KASAn shadow m
81 The range from
82 of the memory
83 per byte of me
84
85 00001000 TASK_SIZE-1 User space map
86 Per-thread map
87 the mmap() sys
88
89 00000000 00000fff CPU vector pag
90 CPUs which do
91 place their ve
92 dereferences b
93 space are also
94 =============== =============== ==============
95
96 Please note that mappings which collide with t
97 in a non-bootable kernel, or may cause the ker
98 at run time.
99
100 Since future CPUs may impact the kernel mappin
101 must not access any memory which is not mapped
102 to TASK_SIZE address range. If they wish to a
103 must set up their own mappings using open() an
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