Re: Can I run an application compiled with gcc ABI 2.95 on a kernel compiled with gcc ABI 3.4?

["George G. Davis" <gdavis@mvista.com>]

Hi,

On Fri, May 15, 2009 at 02:55:57PM +0100, Ben Dooks wrote:
> On Fri, May 15, 2009 at 02:51:05PM +0100, Jamie Lokier wrote:
> > Eek, can you say a bit more about the ARM EABI mismatch?
> > 
> > I would like to run a shiny modern ARM EABI kernel and userspace, but
> > also need to run one or two OABI binaries (from the gcc 2.95 era) on
> > the same kernel which I cannot recompile because they're built with
> > closed source libraries only supplied as OABI.
> > 
> > Does that not work at all?
> 
> There are a few ioctl() incompatibilities between the two ABIs, the
> main problems are within the ALSA API. Mostly it will work, but there
> are a couple of caveats.

Right, you can run ARM OABI binaries on an ARM eABI kernel by enabling
OABI_COMPAT.  However, as Ben notes, there are (more than, IMNSHO ; )
"a couple of caveats".  Most of the "easy" ABI compatibility fixups
should be handled already via OABI_COMPAT.  However, it's practically
impossible to fixup all OABI/eABI compatibility issues due to register
assignment, parameter alignment and/or packing differences between
the two ABIs.  You would have to analyze all kernel and driver
user interfaces to reassign parameters to registers, align and/or
repack data structures, etc.,.  In fact, some of the existing fixups
include side effects that in some cases can cause userspace code to
fail, depending on how it is using I/O parameters, e.g. in some cases,
library code may try to validate parameters which are relocated and
those tests fail due to reshuffling of parameters.  It's a nasty
path to go down, quite frankly. I would not recommend trying to
support OABI binaries on an eABI kernel using OABI_COMPAT.

--
Regards,
George

> 
> -- 
> Ben
> 
> Q:      What's a light-year?
> A:      One-third less calories than a regular year.
> 
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