Re: [PATCH] Don't mlock guardpage if the stack is growing up

[Milan Broz]

On 05/11/2011 12:57 AM, Alasdair G Kergon wrote:
> (What other software packages make use of mlockall() and under what
> circumstances?)

Another one is cryptsetup for commands which manipulate with keys
in memory.
(Users of libcryptetup library are not forced to lock memory, it is optional
call. But cryptsetup itself as libcryptsetup library user always locks memory.)

And I am not happy with mlockall() as well but the lvm2 workaround
is quite complicated.

Basically it wants to lock memory with explicitly allocated keys
(this can be rewritten to use specific locked page though) but it
also need to lock various libdevmapper buffers when issuing dmcrypt
cfg ioctl (mapping table and messages contains key). So that's why
mlockall(MCL_CURRENT|MCL_FUTURE) was the simplest way (and no problems
reported yet).
(No that it is perfect but better than nothing... Of course
more important is to wipe memory with keys after use.)

Milan
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