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1What: /sys/firmware/memmap/2Date: June 20083Contact: Bernhard Walle <bernhard.walle@gmx.de>4Description:5 On all platforms, the firmware provides a memory map which the6 kernel reads. The resources from that memory map are registered7 in the kernel resource tree and exposed to userspace via8 /proc/iomem (together with other resources).9 10 However, on most architectures that firmware-provided memory11 map is modified afterwards by the kernel itself, either because12 the kernel merges that memory map with other information or13 just because the user overwrites that memory map via command14 line.15 16 kexec needs the raw firmware-provided memory map to setup the17 parameter segment of the kernel that should be booted with18 kexec. Also, the raw memory map is useful for debugging. For19 that reason, /sys/firmware/memmap is an interface that provides20 the raw memory map to userspace.21 22 The structure is as follows: Under /sys/firmware/memmap there23 are subdirectories with the number of the entry as their name::24 25 /sys/firmware/memmap/026 /sys/firmware/memmap/127 /sys/firmware/memmap/228 /sys/firmware/memmap/329 ...30 31 The maximum depends on the number of memory map entries provided32 by the firmware. The order is just the order that the firmware33 provides.34 35 Each directory contains three files:36 37 ======== =====================================================38 start The start address (as hexadecimal number with the39 '0x' prefix).40 end The end address, inclusive (regardless whether the41 firmware provides inclusive or exclusive ranges).42 type Type of the entry as string. See below for a list of43 valid types.44 ======== =====================================================45 46 So, for example::47 48 /sys/firmware/memmap/0/start49 /sys/firmware/memmap/0/end50 /sys/firmware/memmap/0/type51 /sys/firmware/memmap/1/start52 ...53 54 Currently following types exist:55 56 - System RAM57 - ACPI Tables58 - ACPI Non-volatile Storage59 - Unusable memory60 - Persistent Memory (legacy)61 - Persistent Memory62 - Soft Reserved63 - reserved64 65 Following shell snippet can be used to display that memory66 map in a human-readable format::67 68 #!/bin/bash69 cd /sys/firmware/memmap70 for dir in * ; do71 start=$(cat $dir/start)72 end=$(cat $dir/end)73 type=$(cat $dir/type)74 printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type"75 done76