Bug 42630

Summary:	memtest=n kernel parameter tests only low memory on 32-bit x86
Product:	Memory Management	Reporter:	Maxim Kammerer (mk)
Component:	Other	Assignee:	Andrew Morton (akpm)
Status:	RESOLVED WILL_NOT_FIX
Severity:	low	CC:	alan, goldgold098123, grouplinksweb, macedonia88888, zackki13597
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	3.0.4	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	Android Game

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.