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

[Peter Zijlstra]

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_.