Re: [PATCH] prevent NULL mmap in topdown model

Linus Torvalds
2005-05-18T22:41:47Z

On Wed, 18 May 2005, Rik van Riel wrote:
>
> On Wed, 18 May 2005, Arjan van de Ven wrote:
> > On Wed, 2005-05-18 at 15:57 -0400, Rik van Riel wrote:
> > > This (trivial) patch prevents the topdown allocator from allocating
> > > mmap areas all the way down to address zero. It's not the prettiest
> > > patch, so suggestions for improvement are welcome ;)
> >
> > it looks like you stop at brk() time.. isn't it better to just stop just
> > above NULL instead?? Gives you more space and is less of an artificial
> > barrier..
>
> Firstly, there isn't much below brk() at all.

Guaranteed? What about executables that have fixed code addresses?

Sounds like a dubious approach, in other words.

If you want to, you could make the "how low do you go" thing be an
rlimit-like thing, but I really doubt "brk" makes much sense as the limit.

Linus