Re: [PATCH] PR880088 Enable -Wtrampolines for no-exec-stack targets with -Wall.

[Segher Boessenkool <segher@kernel.crashing.org>]

Hi Mark,

On Thu, Nov 29, 2018 at 12:57:03PM +0100, Mark Wielaard wrote:
> On Wed, 2018-11-28 at 15:00 -0600, Segher Boessenkool wrote:
> > On Tue, Nov 27, 2018 at 08:54:07PM +0100, Mark Wielaard wrote:
> > > On Tue, 2018-11-27 at 12:37 -0600, Segher Boessenkool wrote:
> > > > > diff --git a/gcc/config/rs6000/sysv4.h
> > > > > b/gcc/config/rs6000/sysv4.h
> > > > > index 0c67634..9330acf 100644
> > > > > --- a/gcc/config/rs6000/sysv4.h
> > > > > +++ b/gcc/config/rs6000/sysv4.h
> > > > > @@ -972,6 +972,11 @@ ncrtn.o%s"
> > > > >  /* Generate entries in .fixup for relocatable addresses.  */
> > > > >  #define RELOCATABLE_NEEDS_FIXUP 1
> > > > >  
> > > > > +#if defined (POWERPC_LINUX) || defined (POWERPC_FREEBSD)
> > > > > +  #define TARGET_HAS_DEFAULT_NOEXEC_STACK (TARGET_32BIT \
> > > > > +					   || DEFAULT_ABI ==
> > > > > ABI_ELFv2)
> > > > > +#endif
> > > > 
> > > > I don't think this belongs in sysv4.h .
> > > 
> > > I might have gotten lost in the tree of defines/macros.
> > > 
> > > There are two sysv4.h files gcc/config/rs6000/sysv4.h and
> > > gcc/config/powerpcspe/sysv4.h
> > 
> > Forget about powerpcspe please, I am talking about rs6000 only.
> 
> I don't know the differences between the config backends, but it looks
> like at least some of the configs were just copy/pasted which might
> explain why they both define things the same (in sysv4.h). And they

Yes, things are copied.  My point is, my review is for rs6000/ only :-)

> > You want linux.h and freebsd.h, maybe the "64" versions of those separately.
> > Or put this in rs6000.h.  sysv4.h is a random header for this, it doesn't
> > belong there.
> 
> The reason I added it to sysv4.h is because it matches where the
> TARGET_ASM_FILE_END hook is setup. It might make sense to have

Yeah, but it does not make sense to put it there, since you are handling
other ABIs as well.

> So if I understand correctly you would like to have:
> 
> rs6000/linux.h and rs6000/freebsd.h:
> #define TARGET_NEEDS_EXEC_STACK_FLAG_FOR_TRAMPOLINES 1
> 
> rs6000/linux64.h and rs6000/freebsd64.h:
> #define TARGET_NEEDS_EXEC_STACK_FLAG_FOR_TRAMPOLINES (DEFAULT_ABI == ABI_ELFv2)

Something like that yes.  Or in rs6000.h, maybe.  Some location that makes
sense :-)


Segher