Re: [Tails-dev] from sdmem to memtest, and testing procedure…

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Autor: anonym
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A: The Tails public development discussion list
Assumpte: Re: [Tails-dev] from sdmem to memtest, and testing procedures
12/28/2011 11:53 PM, intrigeri:
> Hi,
>
> as far as Tails is concerned, I'm thinking of:
>   - on 64-bit hardware, kexec to a 64-bit kernel and use memtest=
>     there; Maxim, have you confirmed by actual testing this works for
>     more than 3GB?


I just tried your implementation of this in the bugfix/kexec_amd64
branch on bare-metal, and I'm sad to say that it's not working. The
following lists the number of occurrences of the pattern for certain
segments of memory (in megabytes):

0   -  10: 348
10  -  20: 244233
30  - 200: 0
200 - 600: each 10 MB block in this segment has ~655K hits*
600 -2180: 0
2180-2190: 511
2190-2330: 0
2330-2340: 174
Rest     : 0


* Note that a 10 MB block can contain at most 655360 occurrences of a
16 byte pattern (like ours) so this memory segment is completely
untouched by the wipe.

>   - on 32-bit hardware, kexec to a 32-bit kernel and go on using
>     sdmem; it's still limited to 3GB, but arguably 32-bit computers
>     with more than 3GB of RAM are very rare.


Didn't test.