Subject: Re: direct copy() between two proc address spaces
To: der Mouse <mouse@Rodents.Montreal.QC.CA>
From: Thor Lancelot Simon <>
List: tech-kern
Date: 06/21/2004 15:20:09
On Mon, Jun 21, 2004 at 02:47:21PM -0400, der Mouse wrote:
> > I guess i understand now: application allocates memory region from
> > private address space and next shares it some way with other process.
> > I also cannot recall anything with this functionality.  Well, on the
> > other hand, what's the advantage of this scheme ?
> It
> (a) doesn't need a cooperative common ancestor (unlike the
>     mmap(MAP_ANON|MAP_SHARED)+fork method)
> (b) doesn't need a writeable file large enough to hold the memory
>     (unlike the mmap-a-file method)

Here's a question: what happens if you pass an fd to /dev/zero to an
unrelated process, then mmap it MAP_SHARED on each side?

I know what I _think_ should happen, but somehow I'm not so sure it

 Thor Lancelot Simon	                            
   But as he knew no bad language, he had called him all the names of common
 objects that he could think of, and had screamed: "You lamp!  You towel!  You
 plate!" and so on.              --Sigmund Freud