Re: [PATCH 20/20] objtool: Add Direction Flag validation

[Josh Poimboeuf]

On Fri, Mar 08, 2019 at 10:33:43PM +0100, Peter Zijlstra wrote:
> On Fri, Mar 08, 2019 at 03:16:03PM -0600, Josh Poimboeuf wrote:
> > On Thu, Mar 07, 2019 at 12:45:31PM +0100, Peter Zijlstra wrote:
> > > Having DF escape is BAD(tm).
> > > 
> > > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> > 
> > Can you elaborate on why (in the patch description)?  Did this actually
> > find any occurrences?
> 
> Nope, didn't find anything. Also, all DF users are in asm so I didn't
> really expect any. Having it escape would probably result in fairly
> instant wreckage though.
> 
> DF=1 results in things like rep mov going _backwards_.

Ok, I wonder if we really need to add this then.

-- 
Josh