76 lines
2.4 KiB
Plaintext
76 lines
2.4 KiB
Plaintext
|
What: /sys/firmware/memmap/
|
||
|
|
Date: June 2008
|
||
|
|
Contact: Bernhard Walle <bernhard.walle@gmx.de>
|
||
|
|
Description:
|
||
|
|
On all platforms, the firmware provides a memory map which the
|
||
|
|
kernel reads. The resources from that memory map are registered
|
||
|
|
in the kernel resource tree and exposed to userspace via
|
||
|
|
/proc/iomem (together with other resources).
|
||
|
|
|
||
|
|
However, on most architectures that firmware-provided memory
|
||
|
|
map is modified afterwards by the kernel itself, either because
|
||
|
|
the kernel merges that memory map with other information or
|
||
|
|
just because the user overwrites that memory map via command
|
||
|
|
line.
|
||
|
|
|
||
|
|
kexec needs the raw firmware-provided memory map to setup the
|
||
|
|
parameter segment of the kernel that should be booted with
|
||
|
|
kexec. Also, the raw memory map is useful for debugging. For
|
||
|
|
that reason, /sys/firmware/memmap is an interface that provides
|
||
|
|
the raw memory map to userspace.
|
||
|
|
|
||
|
|
The structure is as follows: Under /sys/firmware/memmap there
|
||
|
|
are subdirectories with the number of the entry as their name::
|
||
|
|
|
||
|
|
/sys/firmware/memmap/0
|
||
|
|
/sys/firmware/memmap/1
|
||
|
|
/sys/firmware/memmap/2
|
||
|
|
/sys/firmware/memmap/3
|
||
|
|
...
|
||
|
|
|
||
|
|
The maximum depends on the number of memory map entries provided
|
||
|
|
by the firmware. The order is just the order that the firmware
|
||
|
|
provides.
|
||
|
|
|
||
|
|
Each directory contains three files:
|
||
|
|
|
||
|
|
======== =====================================================
|
||
|
|
start The start address (as hexadecimal number with the
|
||
|
|
'0x' prefix).
|
||
|
|
end The end address, inclusive (regardless whether the
|
||
|
|
firmware provides inclusive or exclusive ranges).
|
||
|
|
type Type of the entry as string. See below for a list of
|
||
|
|
valid types.
|
||
|
|
======== =====================================================
|
||
|
|
|
||
|
|
So, for example::
|
||
|
|
|
||
|
|
/sys/firmware/memmap/0/start
|
||
|
|
/sys/firmware/memmap/0/end
|
||
|
|
/sys/firmware/memmap/0/type
|
||
|
|
/sys/firmware/memmap/1/start
|
||
|
|
...
|
||
|
|
|
||
|
|
Currently following types exist:
|
||
|
|
|
||
|
|
- System RAM
|
||
|
|
- ACPI Tables
|
||
|
|
- ACPI Non-volatile Storage
|
||
|
|
- Unusable memory
|
||
|
|
- Persistent Memory (legacy)
|
||
|
|
- Persistent Memory
|
||
|
|
- Soft Reserved
|
||
|
|
- reserved
|
||
|
|
|
||
|
|
Following shell snippet can be used to display that memory
|
||
|
|
map in a human-readable format::
|
||
|
|
|
||
|
|
#!/bin/bash
|
||
|
|
cd /sys/firmware/memmap
|
||
|
|
for dir in * ; do
|
||
|
|
start=$(cat $dir/start)
|
||
|
|
end=$(cat $dir/end)
|
||
|
|
type=$(cat $dir/type)
|
||
|
|
printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type"
|
||
|
|
done
|