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

[Thiemo Seufer <ths@networkno.de>]

Fabrice Bellard 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.

Doesn't work for MIPS64, since it doesn't quite have a compatibility mode
in the traditional sense. It needs to retain 64bit register width when
running N32 ABI binaries. (Thus the somewhat odd overrides I added for
the preliminary N32 support.)


Thiemo