Messages in this thread | | | Date | Sat, 18 Jan 2003 08:53:31 +0000 | From | Jamie Lokier <> | Subject | Re: Bug? Sparc linux defines MAP_LOCKED == MAP_GROWSDOWN |
| |
David S. Miller wrote: > From: Jamie Lokier <jamie@shareable.org> > Date: Sat, 18 Jan 2003 03:29:40 +0000 > > On Sparc and Sparc64, MAP_LOCKED and MAP_GROWSDOWN are both defined > as 0x100. This is a bug, isn't it? > > Unfortunately it's one we're going to have to live with somehow. > Probably by just saying MAP_GROWSDOWN is totally unsupported. > I see no real use for it anyways.
I've never seen the point of it either - MAP_GROWSDOWN just allows the stack to grow until it overwrites the next vma down, as far as I can tell. No guard page or anything.
I think MAP_GROWSDOWN should simply be deleted on all architectures (some don't support it even though they define the flag anyway).
However if that doesn't happen, isn't it best if MAP_LOCKED on the Sparc _doesn't_ imply MAP_GROWSDOWN? That could lead to some peculiar failure modes, if a program pokes an unmapped address (which a few do for one reason or another) and happens to have a MAP_LOCKED region above it.
I.e. I suggest renumbering MAP_GROWSDOWN in <asm-sparc{,64}/mman.h>. Nobody in userspace will be using that, whereas there probably are a few programs using MAP_LOCKED, and getting MAP_GROWSDOWN behaviour as a bonus is a genuine bug.
cheers, -- Jamie - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |