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dmidecode reports No SMBIOS nor DMI entry point found (/dev/mem exists, missing 000F0000 range) #6874

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@jrgerber

Description

@jrgerber

Windows Build Number

Microsoft Windows [Version 10.0.19042.928]

WSL Version

  • WSL 2
  • WSL 1

Kernel Version

Linux version 5.4.72-microsoft-standard-WSL2

Distro Version

Ubuntu 20.04 and openSUSE-Leap-15.2

Other Software

No response

Repro Steps

$ sudo dmidecode
# dmidecode 3.2
Scanning /dev/mem for entry point.
# No SMBIOS nor DMI entry point found, sorry.

The reason is a hole in the range 000F0000 to 000FFFFF where SMBIOS entry point and table is normally found.

sudo hd /dev/mem|more
0009ea70  01 00 00 00 01 00 00 00  00 00 00 00 00 00 00 00  |................|
0009ea80  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000e0000  52 53 44 20 50 54 52 20  f1 56 52 54 55 41 4c 02  |RSD PTR .VRTUAL.|
000e0010  00 00 10 00 24 00 00 00  00 00 10 00 00 00 00 00  |....$...........|
000e0020  cc 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000e0030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00100000  58 53 44 54 44 00 00 00  01 50 56 52 54 55 41 4c  |XSDTD....PVRTUAL|
00100010  4d 49 43 52 4f 53 46 54  01 00 00 00 4d 53 46 54  |MICROSFT....MSFT|
00100020  01 00 00 00 00 10 10 00  00 00 00 00 54 11 10 00  |............T...|
00100030  00 00 00 00 3c f3 11 00  00 00 00 00 cc f5 11 00  |....<...........|
00100040  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*

Expected Behavior

Normally SMBIOS is found in /dev/mem in the 000F0000-000FFFFF range. Azure Ubuntu example:

dmidecode -u|more
# dmidecode 3.1
Getting SMBIOS data from sysfs.
SMBIOS 2.3 present.
338 structures occupying 17307 bytes.
Table at 0x000F93D0.
... etc.

Correspondingly /dev/mem (use hd to dump) contains the SMBIOS entry point and table in the expected range:

000f93d0  00 14 00 00 01 02 00 f0  03 03 90 da cb 7f 00 00  |................|
000f93e0  00 00 34 01 41 6d 65 72  69 63 61 6e 20 4d 65 67  |..4.American Meg|
000f93f0  61 74 72 65 6e 64 73 20  49 6e 63 2e 00 30 39 30  |atrends Inc..090|
000f9400  30 30 38 20 00 31 32 2f  30 37 2f 32 30 31 38 00  |008 .12/07/2018.|
000f9410  00 01 19 01 00 01 02 03  04 ad 72 18 0b 34 20 dc  |..........r..4 .|
000f9420  4b 96 5e c7 32 8a 9f 68  c2 06 4d 69 63 72 6f 73  |K.^.2..h..Micros|
000f9430  6f 66 74 20 43 6f 72 70  6f 72 61 74 69 6f 6e 00  |oft Corporation.|
000f9440  56 69 72 74 75 61 6c 20  4d 61 63 68 69 6e 65 00  |Virtual Machine.|
000f9450  37 2e 30 00 30 30 30 30  2d 30 30 30 30 2d 37 39  |7.0.0000-0000-79|
000f9460  39 35 2d 31 35 30 32 2d  31 37 35 33 2d 34 36 39  |95-1502-1753-469|

Actual Behavior

The range 000F0000-000FFFFF is empty.

000e0030  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00100000  58 53 44 54 44 00 00 00  01 50 56 52 54 55 41 4c  |XSDTD....PVRTUAL|

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