Re: [patch 00/14] remap_file_pages protection support

[Ulrich Drepper]

Nick Piggin wrote:
> I see no reason why they couldn't both go in. In fact, having an mmap
> flag for
> adding guard regions around vmas (and perhaps eg. a system-wide /
> per-process
> option for stack) could almost go in tomorrow.

This would have to be flexible, though.  For thread stacks, at least,
the programmer is able to specify the size of the guard area.  It can be
arbitrarily large.

Also, consider IA-64.  Here we have two stacks.  We allocate them with
one mmap call and put the guard somewhere in the middle (the optimal
ratio of CPU and register stack size is yet to be determined) and have
the stack grow toward each other.  This results into three VMAs in the
moment.  Anything which results on more VMAs obviously isn't good.

-- 
â Ulrich Drepper â Red Hat, Inc. â 444 Castro St â Mountain View, CA â

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