On Wed, Jun 22, 2016 at 12:44 PM, Cyrill Gorcunov [off-list ref] wrote:

On Wed, Jun 22, 2016 at 12:20:13PM -0700, Andy Lutomirski wrote:

quoted

quoted

quoted

As an example, a 32-bit x86 program really could have something mapped
above the 32-bit boundary.  It just wouldn't be useful, but the kernel
should still understand that it's *user* memory.

So you'd have PR_SET_MMAP_LIMIT and PR_GET_MMAP_LIMIT or similar instead.

+1. Also it might be (not sure though, just guessing) suitable to do such
thing via memory cgroup controller, instead of carrying this limit per
each process (or task structure/vma or mm).

I think we'll want this per mm.  After all, a high-VA-limit-aware bash
should be able run high-VA-unaware programs without fiddling with
cgroups.

Wait. You mean to have some flag in mm struct and consider
its value on mmap call?

Exactly.

--Andy

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