1 What: /sys/firmware/memmap/ 1 What: /sys/firmware/memmap/
2 Date: June 2008 2 Date: June 2008
3 Contact: Bernhard Walle <bernhard.walle@ 3 Contact: Bernhard Walle <bernhard.walle@gmx.de>
4 Description: 4 Description:
5 On all platforms, the firmware 5 On all platforms, the firmware provides a memory map which the
6 kernel reads. The resources fr 6 kernel reads. The resources from that memory map are registered
7 in the kernel resource tree an 7 in the kernel resource tree and exposed to userspace via
8 /proc/iomem (together with oth 8 /proc/iomem (together with other resources).
9 9
10 However, on most architectures 10 However, on most architectures that firmware-provided memory
11 map is modified afterwards by 11 map is modified afterwards by the kernel itself, either because
12 the kernel merges that memory 12 the kernel merges that memory map with other information or
13 just because the user overwrit 13 just because the user overwrites that memory map via command
14 line. 14 line.
15 15
16 kexec needs the raw firmware-p 16 kexec needs the raw firmware-provided memory map to setup the
17 parameter segment of the kerne 17 parameter segment of the kernel that should be booted with
18 kexec. Also, the raw memory ma 18 kexec. Also, the raw memory map is useful for debugging. For
19 that reason, /sys/firmware/mem 19 that reason, /sys/firmware/memmap is an interface that provides
20 the raw memory map to userspac 20 the raw memory map to userspace.
21 21
22 The structure is as follows: U 22 The structure is as follows: Under /sys/firmware/memmap there
23 are subdirectories with the nu 23 are subdirectories with the number of the entry as their name::
24 24
25 /sys/firmware/memmap/0 25 /sys/firmware/memmap/0
26 /sys/firmware/memmap/1 26 /sys/firmware/memmap/1
27 /sys/firmware/memmap/2 27 /sys/firmware/memmap/2
28 /sys/firmware/memmap/3 28 /sys/firmware/memmap/3
29 ... 29 ...
30 30
31 The maximum depends on the num 31 The maximum depends on the number of memory map entries provided
32 by the firmware. The order is 32 by the firmware. The order is just the order that the firmware
33 provides. 33 provides.
34 34
35 Each directory contains three 35 Each directory contains three files:
36 36
37 ======== ==================== 37 ======== =====================================================
38 start The start address (a 38 start The start address (as hexadecimal number with the
39 '0x' prefix). 39 '0x' prefix).
40 end The end address, inc 40 end The end address, inclusive (regardless whether the
41 firmware provides in 41 firmware provides inclusive or exclusive ranges).
42 type Type of the entry as 42 type Type of the entry as string. See below for a list of
43 valid types. 43 valid types.
44 ======== ==================== 44 ======== =====================================================
45 45
46 So, for example:: 46 So, for example::
47 47
48 /sys/firmware/memmap/0 48 /sys/firmware/memmap/0/start
49 /sys/firmware/memmap/0 49 /sys/firmware/memmap/0/end
50 /sys/firmware/memmap/0 50 /sys/firmware/memmap/0/type
51 /sys/firmware/memmap/1 51 /sys/firmware/memmap/1/start
52 ... 52 ...
53 53
54 Currently following types exis 54 Currently following types exist:
55 55
56 - System RAM 56 - System RAM
57 - ACPI Tables 57 - ACPI Tables
58 - ACPI Non-volatile Storage 58 - ACPI Non-volatile Storage
59 - Unusable memory 59 - Unusable memory
60 - Persistent Memory (legacy) 60 - Persistent Memory (legacy)
61 - Persistent Memory 61 - Persistent Memory
62 - Soft Reserved 62 - Soft Reserved
63 - reserved 63 - reserved
64 64
65 Following shell snippet can be 65 Following shell snippet can be used to display that memory
66 map in a human-readable format 66 map in a human-readable format::
67 67
68 #!/bin/bash 68 #!/bin/bash
69 cd /sys/firmware/memmap 69 cd /sys/firmware/memmap
70 for dir in * ; do 70 for dir in * ; do
71 start=$(cat $dir/start) 71 start=$(cat $dir/start)
72 end=$(cat $dir/end) 72 end=$(cat $dir/end)
73 type=$(cat $dir/type) 73 type=$(cat $dir/type)
74 printf "%016x-%016x (%s) 74 printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type"
75 done 75 done
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