Re: [Xen-users] can't find a register in class `BREG' while reloading `asm'

[Kevin <lists@xxxxxxxxxxxxx>]

Tuan Van wrote:
> Kevin wrote:
>> gcc -O2 -fomit-frame-pointer -DNDEBUG -m32 -march=i686 -Wall
>> -Wstrict-prototypes -Wdeclaration-after-statement -nostdinc -fno-builtin
>> -fno-common -fno-strict-aliasing -iwithprefix include -Werror
>> -Wno-pointer-arith -pipe
>> -I/var/tmp/portage/xen-3.0.2/work/xen-3.0.2/xen/include
>> -I/var/tmp/portage/xen-3.0.2/work/xen-3.0.2/xen/include/asm-x86/mach-generic
>>
>> -I/var/tmp/portage/xen-3.0.2/work/xen-3.0.2/xen/include/asm-x86/mach-default
>>
>> -msoft-float -g -D__XEN__ -c multicall.c -o multicall.o
>> memory.c: In function `guest_remove_page':
>> /var/tmp/portage/xen-3.0.2/work/xen-3.0.2/xen/include/asm/mm.h:206:
>> error: can't find a register in class `BREG' while reloading `asm'
> 
> 
> see http://bugs.gentoo.org/show_bug.cgi?id=130167
> 

Thanks for the pointer, Tuan.  I wasn't aware of it and I should have
checked the gentoo & xen bugzillas before posting here.  My apologies
for not doing so.  I have now checked both gentoo and xen bugzillas and
I don't see anything on BREG or register or pie or ssp or hardened in
the xen bugzilla.

The patch mentioned in the gentoo bug report is, however, merely an
implementation of the advice that Keir Fraser gave to A Streetcar back
in 11/2004, and it does indeed allow me to compile xen-3.0.2 (which I
suspected would be true, but it doesn't get me what I'd really like
which is xen code compiled with PIE/SSP for enhanced security).

Keir Fraser wrote in 11/2004:

"I've checked in a patch to the unstable tree that will allow to build
with PIE/SSP-enabled GCC."

May I ask: what's happened with this?  Was a patch applied?  If so, does
something else need to be patched?  Or was the patch subsequently
removed?  Or do the xen-devs prefer against patching xen this way?

Are there negative implications to building xen with PIE/SSP-enabled
GCC? (or for that matter, not doing so?).  Although I'm no guru on
hardened gentoo or PIE/SSP, I had the overall impression that they were
considered by many (all?) to be a good thing for enhancing security.  Is
that not the case with xen?

TIA for any replies.

-Kevin

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