Re: [PATCHv3 33/33] mm, x86: introduce PR_SET_MAX_VADDR and PR_GET_MAX_VADDR

[Andy Lutomirski]

On Fri, Feb 17, 2017 at 1:01 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Feb 17, 2017 at 12:12 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>>
>> At the very least, I'd want to see
>> MAP_FIXED_BUT_DONT_BLOODY_UNMAP_ANYTHING.  I *hate* the current
>> interface.
>
> That's unrelated, but I guess w could add a MAP_NOUNMAP flag, and then
> you can use MAP_FIXED | MAP_NOUNMAP or something.
>
> But that has nothing to do with the 47-vs-56 bit issue.
>
>> How about MAP_LIMIT where the address passed in is interpreted as an
>> upper bound instead of a fixed address?
>
> Again, that's a unrelated semantic issue. Right now - if you don't
> pass in MAP_FIXED at all, the "addr" argument is used as a starting
> value for deciding where to find an unmapped area. But there is no way
> to specify the end. That would basically be what the process control
> thing would be (not per-system-call, but per-thread ).
>

What I'm trying to say is: if we're going to do the route of 48-bit
limit unless a specific mmap call requests otherwise, can we at least
have an interface that doesn't suck?