Re: [Xen-devel] [PATCH] x86emul/test: disable pie for 64-bit builds

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Sep 25, 2017 at 05:35:05AM -0600, Jan Beulich wrote:
> >>> On 25.09.17 at 12:49, <wei.liu2@xxxxxxxxxx> wrote:
> > PIE may (and commonly will) result in the binary being loaded above
> > the 4Gb boundary, which can't work with at least the VZEROUPPER compat
> > mode test.
> > 
> > Reported-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> > ---
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > 
> > With this patch, vzeroupper passes, but one other test fails.
> > Testing SSE packed single 64-bit code sequence...[line 368] failed!
> 
> Feel free to mail me the binary again, albeit that one's going to
> be more difficult to debug without being able to see it myself.
> 
> > @@ -98,7 +98,9 @@ asm:
> >  
> >  asm/%: asm ;
> >  
> > -HOSTCFLAGS += $(CFLAGS_xeninclude) -I.
> > +HOSTCFLAGS-x86_64 :=
> > +$(call cc-option-add,HOSTCFLAGS,HOSTCC,-no-pie)
> > +HOSTCFLAGS += $(CFLAGS_xeninclude) -I. $(HOSTCFLAGS-$(XEN_COMPILE_ARCH))
> 
> I don't understand this change to my original patch: You now
> conditionally add -no-pie to HOSTCFLAGS (i.e. also for 32-bit builds),
> and HOSTCFLAGS-x86_64 remains empty. I also don't see why the

My bad. The flag should be conditionally added to HOSTCFLAGS-x86_64.

> addition needs to be conditional: In order to be able to build the
> entire test, a reasonably new tool chain is needed anyway (much
> newer than what we require for building everything else). And finally

It needs to be conditional because not all gcc versions support -no-pie.

> - is there a difference between -no-pie and -fno-PIE / -fno-pie?
> 

I can't tell the difference by reading the manpage TBH. I only know one
works while the other doesn't by trial and error.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel