[PATCH v2] arm: fix memset-related crashes caused by recent GCC (4.7.2) optimizations

[Nicolas Pitre]

On Sun, 10 Mar 2013, Russell King - ARM Linux wrote:

> On Sun, Mar 10, 2013 at 06:06:11PM +0100, Alexander Holler wrote:
> > Am 07.03.2013 16:17, schrieb Russell King - ARM Linux:
> >> On Wed, Mar 06, 2013 at 08:15:17PM +0100, Dirk Behme wrote:
> >>> Am 11.02.2013 13:57, schrieb Ivan Djelic:
> >>>> Recent GCC versions (e.g. GCC-4.7.2) perform optimizations based on
> >>>> assumptions about the implementation of memset and similar functions.
> >>>> The current ARM optimized memset code does not return the value of
> >>>> its first argument, as is usually expected from standard implementations.
> >
> > I've just tried this patch with kernel 4.8.2 on an armv5-system where I  
> > use gcc 4.7.2 since several months and where most parts of the system  
> > are compiled with gcc 4.7.2 too.
> >
> > And I had at least one problem which manifested itself with
> 
> Yes, the patch _is_ wrong.  Reverted.  I was trusting Nicolas' review
> of it, but the patch is definitely wrong.  Look carefully at this
> fragment of code:

Dang.  Indeed.

Sorry about that.


Nicolas