svn commit: r246706 - head/lib/libc/arm/aeabi

[Andrew Turner]

On Wed, 13 Feb 2013 16:00:06 +0200
Konstantin Belousov <kostikbel at gmail.com> wrote:

> On Wed, Feb 13, 2013 at 10:25:46PM +1300, Andrew Turner wrote:
> > On Tue, 12 Feb 2013 08:32:23 -0600
> > Nathan Whitehorn <nwhitehorn at freebsd.org> wrote:
> > 
> > > A related question to these commits: are EABI binaries
> > > incompatible with systems built for OABI? And vice versa? If so,
> > > should we mint a new MACHINE_ARCH for ARM EABI (or OABI, I
> > > guess)? The usual implication of sharing a uname -p string is
> > > that systems can run each other's binaries -- that being broken
> > > is a strong argument for a new value. -Nathan
> > 
> > Yes OABI and EABI are binary incompatible. The plan is to kill off
> > OABI at some stage in the future when EABI is ready. At some time
> > in the future I plan on flipping the switch to make EABI the
> > default but keep OABI around to allow people a chance to update.
> > 
> > I am relying on ARM being a Tier 2 platform to change the ABI such
> > that we break backward compatibility without changing uname -p. I
> > have the start of a compat layer in the EABI project branch however
> > never finished it. If people are interested in updating this
> > compatibility layer I can point them at the code.
> > 
> > The other point is backwards compatibility should only be an issue
> > for ARMv4 and ARMv5 as these are the only cores we have support for
> > on the any of the current release branches. ARMv6 and ARMv7 is
> > added to 10 and there has not been an MFC to any of the stable
> > branches. Because of this I have even less hesitation to stitch the
> > ABI for TARGET_ARCH=armv6.
> > 
> > In summary my plan is:
> > < 9: No change
> > >= 10: Switch to EABI and remove or depricate OABI
> 
> Does the ABI change happen for the interfaces exported both by
> usermode components and kernel, or only usermode components ? Or,
> does the kernel exported ABI supports both OABI and EABI ?

The ABI change happens on both interfaces.

The kernel only exposes a single ABI. For a kernel built with EABI it
will be EABI. I started a compat layer to export OABI on EABI kernels
however never finished it. If someone is interested in finishing it I
can point them to the code.

Andrew