Re: [PATCH 0/2] mm: introduce MAP_FIXED_SAFE

[John Hubbard]

On 12/06/2017 04:19 PM, Kees Cook wrote:
> On Wed, Dec 6, 2017 at 1:08 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
>> On Wed 06-12-17 08:33:37, Rasmus Villemoes wrote:
>>> On 2017-12-06 05:50, Michael Ellerman wrote:
>>>> Michal Hocko <mhocko@xxxxxxxxxx> writes:
>>>>
>>>>> On Wed 29-11-17 14:25:36, Kees Cook wrote:
>>>>> It is safe in a sense it doesn't perform any address space dangerous
>>>>> operations. mmap is _inherently_ about the address space so the context
>>>>> should be kind of clear.
>>>>
>>>> So now you have to define what "dangerous" means.
>>>>
>>>>>> MAP_FIXED_UNIQUE
>>>>>> MAP_FIXED_ONCE
>>>>>> MAP_FIXED_FRESH
>>>>>
>>>>> Well, I can open a poll for the best name, but none of those you are
>>>>> proposing sound much better to me. Yeah, naming sucks...
>>>
>>> I also don't like the _SAFE name - MAP_FIXED in itself isn't unsafe [1],
>>> but I do agree that having a way to avoid clobbering (parts of) an
>>> existing mapping is quite useful. Since we're bikeshedding names, how
>>> about MAP_FIXED_EXCL, in analogy with the O_ flag.
>>
>> I really give up on the name discussion. I will take whatever the
>> majority comes up with. I just do not want this (useful) funtionality
>> get bikeched to death.
> 
> Yup, I really want this to land too. What do people think of Matthew
> Wilcox's MAP_REQUIRED ? MAP_EXACT isn't exact, and dropping "FIXED"
> out of the middle seems sensible to me.

+1, MAP_REQUIRED does sound like the best one so far, yes. Sorry if I contributed
to any excessive bikeshedding. :)

thanks,
john h

> 
> MIchael, any suggestions with your API hat on?
> 
> -Kees
>