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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Sep 25, 2017 at 01:55:03PM +0100, Wei Liu wrote:
> On Mon, Sep 25, 2017 at 05:54:41AM -0600, Jan Beulich wrote:
> > >>> On 25.09.17 at 13:43, <wei.liu2@xxxxxxxxxx> wrote:
> > > 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.
> > 
> > You mean older one (which would be no problem, as said) or even
> > up-to-date ones (due to the way they're being configured)?
> 
> Let me be precise because I don't know which version you count as old or
> up-to-date.
> 
> Gcc <5.4 has -pie but no -no-pie. IIRC passing -no-pie will cause the
> linker to return an error. I don't have a machine that old to verify it
> though.
> 

Actually I do have a wheezy chroot to verify that:

(wheezy)wei@zion:/local/work$ gcc --version
gcc (Debian 4.6.3-14) 4.6.3

(wheezy)wei@zion:/local/work$ gcc -no-pie
gcc: error: unrecognized option '-no-pie'
gcc: fatal error: no input files
compilation terminated.

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