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
Alias: None
Product: Memory Management
Classification: Unclassified
Component: Other (show other bugs)
Hardware: All Linux
: P1 low
Assignee: Andrew Morton
Depends on:
Reported: 2012-01-22 14:08 UTC by Maxim Kammerer
Modified: 2012-08-30 13:59 UTC (History)
1 user (show)

See Also:
Kernel Version: 3.0.4
Tree: Mainline
Regression: No


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

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.

Note You need to log in before you can comment on or make changes to this bug.