[fedora-arm] Thumb mode IT instruction requirements and -mimplicit-it assembler flag

[Henrik Nordström]

sön 2011-09-18 klockan 14:10 -0400 skrev Jon Masters:
> On Sun, 2011-09-18 at 16:21 +0200, Henrik Nordström wrote:
> 
> > There is no redhat-rpm-config package in the armv7 repositories, so yum
> > picks the one from primary-noarch (F15 gold /
> > redhat-rpm-config-9.1.0-5.fc14.noarch).
> 
> Argh. It should be installed properly on the host (this is something we
> did previously explicitly in the images that we made) so would be used
> by mock anyway. If that's not happening, we need to fix that by pulling
> in the right set of macros. It's not a disaster since interworking[0]
> renders the two compatible and won't break anything, and when we rebuild
> again in Koji, we'll just make sure we do it right that time.

Having it in the buildnode rootfs is not relevant for the builds.
rpmbuild runs within the mock chroot and uses whatever is there. mock
would break horribly if is used rpmbuild from the rootfs as it may be
building for a completely different distro than the rootfs (and often is
in other uses).

> Let's regroup tomorrow on IRC and fix this - I'm heading out now. Thanks
> for raising it. For now, we can just fix it up for subsequent builds.

> [0] We always switch to ARM mode on entry to library calls and then use
> trampolines that can handle either Thumb or ARM mode. It's not an ABI
> break, it's not an issue. It's just that we didn't want Thumb on. So
> really, this isn't a problem if it's widespread in the stage4.

The ARMv7 ABI we use have -mthumbs-interwork enabled by default. There
is no problem mixing thumb and non-thumb code in the ARMv7 builds, at
least not in theory (there probably is special cornercases as usual..)

ARMv5 is a different story. thumb can not be used there at all for qt
and a couple of other packages, and the ABI used there do not include
-mthumb-interwork by default I think. So there thumb most likely is not
an option.

Regards
Henrik