Re: [PATCH] prevent NULL mmap in topdown model

[Linus Torvalds <torvalds@osdl.org>]

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
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