1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
|
.. SPDX-License-Identifier: GPL-2.0
=====================================
Virtual Memory Layout on RISC-V Linux
=====================================
:Author: Alexandre Ghiti <alex@ghiti.fr>
:Date: 12 February 2021
This document describes the virtual memory layout used by the RISC-V Linux
Kernel.
RISC-V Linux Kernel 32bit
=========================
RISC-V Linux Kernel SV32
------------------------
TODO
RISC-V Linux Kernel 64bit
=========================
The RISC-V privileged architecture document states that the 64bit addresses
"must have bits 63–48 all equal to bit 47, or else a page-fault exception will
occur.": that splits the virtual address space into 2 halves separated by a very
big hole, the lower half is where the userspace resides, the upper half is where
the RISC-V Linux Kernel resides.
RISC-V Linux Kernel SV39
------------------------
::
========================================================================================================================
Start addr | Offset | End addr | Size | VM area description
========================================================================================================================
| | | |
0000000000000000 | 0 | 0000003fffffffff | 256 GB | user-space virtual memory, different per mm
__________________|____________|__________________|_________|___________________________________________________________
| | | |
0000004000000000 | +256 GB | ffffffbfffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
| | | | virtual memory addresses up to the -256 GB
| | | | starting offset of kernel mappings.
__________________|____________|__________________|_________|___________________________________________________________
|
| Kernel-space virtual memory, shared between all processes:
____________________________________________________________|___________________________________________________________
| | | |
ffffffc4fea00000 | -236 GB | ffffffc4feffffff | 6 MB | fixmap
ffffffc4ff000000 | -236 GB | ffffffc4ffffffff | 16 MB | PCI io
ffffffc500000000 | -236 GB | ffffffc5ffffffff | 4 GB | vmemmap
ffffffc600000000 | -232 GB | ffffffd5ffffffff | 64 GB | vmalloc/ioremap space
ffffffd600000000 | -168 GB | fffffff5ffffffff | 128 GB | direct mapping of all physical memory
| | | |
fffffff700000000 | -36 GB | fffffffeffffffff | 32 GB | kasan
__________________|____________|__________________|_________|____________________________________________________________
|
|
____________________________________________________________|____________________________________________________________
| | | |
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
__________________|____________|__________________|_________|____________________________________________________________
RISC-V Linux Kernel SV48
------------------------
::
========================================================================================================================
Start addr | Offset | End addr | Size | VM area description
========================================================================================================================
| | | |
0000000000000000 | 0 | 00007fffffffffff | 128 TB | user-space virtual memory, different per mm
__________________|____________|__________________|_________|___________________________________________________________
| | | |
0000800000000000 | +128 TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical
| | | | virtual memory addresses up to the -128 TB
| | | | starting offset of kernel mappings.
__________________|____________|__________________|_________|___________________________________________________________
|
| Kernel-space virtual memory, shared between all processes:
____________________________________________________________|___________________________________________________________
| | | |
ffff8d7ffea00000 | -114.5 TB | ffff8d7ffeffffff | 6 MB | fixmap
ffff8d7fff000000 | -114.5 TB | ffff8d7fffffffff | 16 MB | PCI io
ffff8d8000000000 | -114.5 TB | ffff8f7fffffffff | 2 TB | vmemmap
ffff8f8000000000 | -112.5 TB | ffffaf7fffffffff | 32 TB | vmalloc/ioremap space
ffffaf8000000000 | -80.5 TB | ffffef7fffffffff | 64 TB | direct mapping of all physical memory
ffffef8000000000 | -16.5 TB | fffffffeffffffff | 16.5 TB | kasan
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 39-bit one from here on:
____________________________________________________________|____________________________________________________________
| | | |
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
__________________|____________|__________________|_________|____________________________________________________________
RISC-V Linux Kernel SV57
------------------------
::
========================================================================================================================
Start addr | Offset | End addr | Size | VM area description
========================================================================================================================
| | | |
0000000000000000 | 0 | 00ffffffffffffff | 64 PB | user-space virtual memory, different per mm
__________________|____________|__________________|_________|___________________________________________________________
| | | |
0100000000000000 | +64 PB | feffffffffffffff | ~16K PB | ... huge, almost 64 bits wide hole of non-canonical
| | | | virtual memory addresses up to the -64 PB
| | | | starting offset of kernel mappings.
__________________|____________|__________________|_________|___________________________________________________________
|
| Kernel-space virtual memory, shared between all processes:
____________________________________________________________|___________________________________________________________
| | | |
ff1bfffffea00000 | -57 PB | ff1bfffffeffffff | 6 MB | fixmap
ff1bffffff000000 | -57 PB | ff1bffffffffffff | 16 MB | PCI io
ff1c000000000000 | -57 PB | ff1fffffffffffff | 1 PB | vmemmap
ff20000000000000 | -56 PB | ff5fffffffffffff | 16 PB | vmalloc/ioremap space
ff60000000000000 | -40 PB | ffdeffffffffffff | 32 PB | direct mapping of all physical memory
ffdf000000000000 | -8 PB | fffffffeffffffff | 8 PB | kasan
__________________|____________|__________________|_________|____________________________________________________________
|
| Identical layout to the 39-bit one from here on:
____________________________________________________________|____________________________________________________________
| | | |
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
ffffffff80000000 | -2 GB | ffffffffffffffff | 2 GB | kernel
__________________|____________|__________________|_________|____________________________________________________________
|
