69ac9cd629
This patch adds /sys/firmware/memmap interface that represents the BIOS
(or Firmware) provided memory map. The tree looks like:
/sys/firmware/memmap/0/start (hex number)
end (hex number)
type (string)
... /1/start
end
type
With the following shell snippet one can print the memory map in the same form
the kernel prints itself when booting on x86 (the E820 map).
--------- 8< --------------------------
#!/bin/sh
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
--------- >8 --------------------------
That patch only provides the needed interface:
1. The sysfs interface.
2. The structure and enumeration definition.
3. The function firmware_map_add() and firmware_map_add_early()
that should be called from architecture code (E820/EFI, for
example) to add the contents to the interface.
If the kernel is compiled without CONFIG_FIRMWARE_MEMMAP, the interface does
nothing without cluttering the architecture-specific code with #ifdef's.
The purpose of the new interface is kexec: While /proc/iomem represents
the *used* memory map (e.g. modified via kernel parameters like 'memmap'
and 'mem'), the /sys/firmware/memmap tree represents the unmodified memory
map provided via the firmware. So kexec can:
- use the original memory map for rebooting,
- use the /proc/iomem for setting up the ELF core headers for kdump
case that should only represent the memory of the system.
The patch has been tested on i386 and x86_64.
Signed-off-by: Bernhard Walle <bwalle@suse.de>
Acked-by: Greg KH <gregkh@suse.de>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: kexec@lists.infradead.org
Cc: yhlu.kernel@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
71 lines
2.3 KiB
Text
71 lines
2.3 KiB
Text
What: /sys/firmware/memmap/
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Date: June 2008
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Contact: Bernhard Walle <bwalle@suse.de>
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Description:
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On all platforms, the firmware provides a memory map which the
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kernel reads. The resources from that memory map are registered
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in the kernel resource tree and exposed to userspace via
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/proc/iomem (together with other resources).
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However, on most architectures that firmware-provided memory
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map is modified afterwards by the kernel itself, either because
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the kernel merges that memory map with other information or
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just because the user overwrites that memory map via command
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line.
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kexec needs the raw firmware-provided memory map to setup the
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parameter segment of the kernel that should be booted with
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kexec. Also, the raw memory map is useful for debugging. For
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that reason, /sys/firmware/memmap is an interface that provides
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the raw memory map to userspace.
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The structure is as follows: Under /sys/firmware/memmap there
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are subdirectories with the number of the entry as their name:
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/sys/firmware/memmap/0
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/sys/firmware/memmap/1
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/sys/firmware/memmap/2
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/sys/firmware/memmap/3
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...
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The maximum depends on the number of memory map entries provided
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by the firmware. The order is just the order that the firmware
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provides.
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Each directory contains three files:
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start : The start address (as hexadecimal number with the
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'0x' prefix).
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end : The end address, inclusive (regardless whether the
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firmware provides inclusive or exclusive ranges).
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type : Type of the entry as string. See below for a list of
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valid types.
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So, for example:
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/sys/firmware/memmap/0/start
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/sys/firmware/memmap/0/end
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/sys/firmware/memmap/0/type
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/sys/firmware/memmap/1/start
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...
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Currently following types exist:
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- System RAM
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- ACPI Tables
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- ACPI Non-volatile Storage
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- reserved
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Following shell snippet can be used to display that memory
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map in a human-readable format:
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-------------------- 8< ----------------------------------------
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#!/bin/bash
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cd /sys/firmware/memmap
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for dir in * ; do
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start=$(cat $dir/start)
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end=$(cat $dir/end)
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type=$(cat $dir/type)
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printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type"
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done
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-------------------- >8 ----------------------------------------
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