projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 69ac9cd6 BW |
1 | What: /sys/firmware/memmap/ |
| 2 | Date: June 2008 | |
| 97bef7dd | 3 | Contact: Bernhard Walle <bernhard.walle@gmx.de> |
| 69ac9cd6 BW |
4 | Description: |
| 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 | start : The start address (as hexadecimal number with the | |
| 38 | '0x' prefix). | |
| 39 | end : The end address, inclusive (regardless whether the | |
| 40 | firmware provides inclusive or exclusive ranges). | |
| 41 | type : Type of the entry as string. See below for a list of | |
| 42 | valid types. | |
| 43 | ||
| 44 | So, for example: | |
| 45 | ||
| 46 | /sys/firmware/memmap/0/start | |
| 47 | /sys/firmware/memmap/0/end | |
| 48 | /sys/firmware/memmap/0/type | |
| 49 | /sys/firmware/memmap/1/start | |
| 50 | ... | |
| 51 | ||
| 52 | Currently following types exist: | |
| 53 | ||
| 54 | - System RAM | |
| 55 | - ACPI Tables | |
| 56 | - ACPI Non-volatile Storage | |
| 57 | - reserved | |
| 58 | ||
| 59 | Following shell snippet can be used to display that memory | |
| 60 | map in a human-readable format: | |
| 61 | ||
| 62 | -------------------- 8< ---------------------------------------- | |
| 63 | #!/bin/bash | |
| 64 | cd /sys/firmware/memmap | |
| 65 | for dir in * ; do | |
| 66 | start=$(cat $dir/start) | |
| 67 | end=$(cat $dir/end) | |
| 68 | type=$(cat $dir/type) | |
| 69 | printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type" | |
| 70 | done | |
| 71 | -------------------- >8 ---------------------------------------- |