Re: fs/exec.c: use BUILD_BUG_ON for VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP

From: Linus Torvalds
Date: Thu Jun 16 2011 - 00:46:04 EST


On Wed, Jun 15, 2011 at 9:35 PM, Randy Dunlap <randy.dunlap@xxxxxxxxxx> wrote:
>
> fwiw, I just reported that this causes a build error in UML on x86_64
> in mmotm-2011-06-15:

Gaah. That sounds really familiar. Have we done this same mistake once
before already, or is it just deja-vu for some other reason.

On x86-64 UML, we have

#define VM_STACK_DEFAULT_FLAGS vm_stack_flags

so VM_STACK_FLAGS ends up not being a constant, even though it really
looks like one.

UML is _really_ confused in this area, btw. It seems to re-define that
thing if TIF_IA32 is defined. That's some crazy stuff. Doesn't the
compiler warn about it?

I guess I should just revert that commit, though. Even if it does seem
to be the case that UML is just being crazy. Andrew?

Linus
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