Re: UVM and the NULL page

[David Holland <dholland-tech%netbsd.org@localhost>]

On Fri, Jul 29, 2016 at 10:08:48AM +0200, Maxime Villard wrote:
 > >IIRC some software relies on this feature, like emulators/wine. If
 > >really so then something like a sysctl to allow it again would be helpful.
 > 
 > I thought about that. The only emulator-related problem I found is [1],
 > because HardenedBSD too increased VM_MIN_ADDRESS [2] to 64k - like Windows.
 > I know that OSX too has increased the limit, but I don't know the exact
 > value.
 > 
 > It is not possible to keep a sysctl, since VM_MIN_ADDRESS is a constant
 > used in assembly, so it won't be turned to a variable.

...so at the risk of stirring up more trouble, I'll stick my oar in:
why should this be happening anywhere near anything written in
assembly?

Any VM_MINUSER_ADDRESS should be handled in MI uvm code when mappings
are established.

 > I will commit [3] soon.

Please don't yet.

-- 
David A. Holland
dholland%netbsd.org@localhost