Re: [Qemu-devel] RFC: fix run of 32 bits Linux executables on 64 bits targets

["J. Mayer" <l_indien@magic.fr>]

On Wed, 2007-10-10 at 22:02 +0300, Blue Swirl wrote:
> On 10/10/07, Fabrice Bellard <fabrice@bellard.org> wrote:
> > Thiemo Seufer wrote:
> > > Fabrice Bellard wrote:
> > >> J. Mayer wrote:
> > >>> Following the patches done for elfload32, it appeared to me that there
> > >>> were still problems that would prevent 32 bits executables to run on 64
> > >>> bits target in linux user mode emulation.
> > >>> [...]
> > >> Are you sure it is a good idea to try to add 32 bit executable support to a
> > >> 64 bit target ? In the end you will need to write a 64 bit to 32 bit linux
> > >> syscall converter which would mean duplicating all the linux-user code of
> > >> the corresponding 32 bit target (think of ioctls with strutures, signals
> > >> frames, etc...).
> > >
> > > I would think this feature will be limited to platforms which can handle
> > > 32bit and 64bit binaries with a single personality.
> >
> > I am not sure it is a common case !
> >
> > However, I suggest to emulate a 32 bit user linux system with a 64 bit
> > guest CPU running in 32 bit compatibily mode. It would be useful to test
> > 64 bit CPUs in 32 bit compatibility mode. The only required modification
> > in linux user is to rename target_ulong so that it can have a different
> > size of the CPU word default size.
> 
> I think this would be sufficient for the Sparc and this way there
> would be no need to convert the structures. Brilliant!
> 
> Should we revert the elfload32 patch? What about PPC?

We can keep the elfload32 for now, it does not hurt.
This approach is OK for PPC too. And as I got some 32 bits programs
running in the 64 bits linux-user emulator, the same programs behavior
can be compared to find eventual issues...

-- 
J. Mayer <l_indien@magic.fr>
Never organized