1What: /sys/firmware/memmap/ 2Date: June 2008 3Contact: Bernhard Walle <bernhard.walle@gmx.de> 4Description: 5 On all platforms, the firmware provides a memory map which the 6 kernel reads. The resources from that memory map are registered 7 in the kernel resource tree and exposed to userspace via 8 /proc/iomem (together with other resources). 9 10 However, on most architectures that firmware-provided memory 11 map is modified afterwards by the kernel itself, either because 12 the kernel merges that memory map with other information or 13 just because the user overwrites that memory map via command 14 line. 15 16 kexec needs the raw firmware-provided memory map to setup the 17 parameter segment of the kernel that should be booted with 18 kexec. Also, the raw memory map is useful for debugging. For 19 that reason, /sys/firmware/memmap is an interface that provides 20 the raw memory map to userspace. 21 22 The structure is as follows: Under /sys/firmware/memmap there 23 are subdirectories with the number of the entry as their name:: 24 25 /sys/firmware/memmap/0 26 /sys/firmware/memmap/1 27 /sys/firmware/memmap/2 28 /sys/firmware/memmap/3 29 ... 30 31 The maximum depends on the number of memory map entries provided 32 by the firmware. The order is just the order that the firmware 33 provides. 34 35 Each directory contains three files: 36 37 ======== ===================================================== 38 start The start address (as hexadecimal number with the 39 '0x' prefix). 40 end The end address, inclusive (regardless whether the 41 firmware provides inclusive or exclusive ranges). 42 type Type of the entry as string. See below for a list of 43 valid types. 44 ======== ===================================================== 45 46 So, for example:: 47 48 /sys/firmware/memmap/0/start 49 /sys/firmware/memmap/0/end 50 /sys/firmware/memmap/0/type 51 /sys/firmware/memmap/1/start 52 ... 53 54 Currently following types exist: 55 56 - System RAM 57 - ACPI Tables 58 - ACPI Non-volatile Storage 59 - Unusable memory 60 - Persistent Memory (legacy) 61 - Persistent Memory 62 - Soft Reserved 63 - reserved 64 65 Following shell snippet can be used to display that memory 66 map in a human-readable format:: 67 68 #!/bin/bash 69 cd /sys/firmware/memmap 70 for dir in * ; do 71 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 done 76