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

["Jan Beulich" <JBeulich@xxxxxxxx>]

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

Jan


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