Bug 42630 - memtest=n kernel parameter tests only low memory on 32-bit x86
Summary: memtest=n kernel parameter tests only low memory on 32-bit x86
Status: RESOLVED WILL_NOT_FIX
Alias: None
Product: Memory Management
Classification: Unclassified
Component: Other (show other bugs)
Hardware: All Linux
: P1 low
Assignee: Andrew Morton
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2012-01-22 14:08 UTC by Maxim Kammerer
Modified: 2021-06-09 11:36 UTC (History)
5 users (show)

See Also:
Kernel Version: 3.0.4
Subsystem:
Regression: No
Bisected commit-id:

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Description Maxim Kammerer 2012-01-22 14:08:58 UTC 
On 3.0.4 (and probably all other recent kernel versions), HIGHMEM memory (HIGHMEM64G in my tests) is apparently ignored during memtest.

Looking at arch/x86/mm/memtest.c, no special mapping is performed (kmap/kunmap?), so it seems that at most ~895 MiB can be tested in 32-bit x86 kernels.

This might not appear like an important issue (as there are other memory testing tools available), but memtest is extremely useful for anti-forensic memory wiping on shutdown/reboot in security-oriented distributions like Liberté Linux and Tails, and there is no other good substitute.

See, for instance, some background in Debian bug
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=646361.

I tried posting to the linux-mm mailing list, but the mails were ignored.
Comment 1 Alan 2012-08-30 13:59:47 UTC 
If you want it fixed I think you will need to write the code and submit it. Nobody else seems to be concerned about it.
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