Re: FIXMAP-related change to mm/memory.c

[Anton Blanchard <anton@samba.org>]

> >  			static struct vm_area_struct fixmap_vma = {
> >   				/* Catch users - if there are any valid
> >   				   ones, we can make this be "&init_mm" or
> >   				   something.  */
> >   				.vm_mm = NULL,
> >  -				.vm_start = FIXADDR_START,
> >  -				.vm_end = FIXADDR_TOP,
> >  +				.vm_start = FIXADDR_USER_START,
> >  +				.vm_end = FIXADDR_USER_END,
> >   				.vm_page_prot = PAGE_READONLY,
> >   				.vm_flags = VM_READ | VM_EXEC,
> >   			};
> 
> Note that the current version of this code does not compile for User Mode
> Linux.  Its FIXADDR_TOP is not a constant.   It would be nice to fix that
> this time around.
> 
> It appears that this patch will break x86_64, parisc and um.

Its a problem on ppc64 too. I want to put the signal trampolines into
a fixmap area above the stack, ie different places on 32bit and 64bit
executables.

Anton