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+What:           /sys/firmware/memmap/
+Date:           June 2008
+Contact:        Bernhard Walle <bwalle@suse.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
+                  - reserved
+
+                Following shell snippet can be used to display that memory
+                map in a human-readable format:
+
+                -------------------- 8< ----------------------------------------
+                  #!/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
+                -------------------- >8 ----------------------------------------