"Maciej W. Rozycki" wrote:
> On Wed, 4 Sep 2002, Ralf Baechle wrote:
> > > It would be nice if we could keep a single set of syscalls for both (n)64
> > > and n32. The address crop for n32 may be handled the Alpha way. I will
> > > investigate the topic soon.
> > Can you describe how this is handled on the Alpha?
> I'm referring mostly to OSF/1 here as it was first to implement it.
> Linux followed it in the sense it is able to execute OSF/1 binaries marked
> as "32-bit", but native ELF binaries used to be fully 64-bit always. I
> think by a popular demand GNU binutils are now able to create "cropped"
> Alpha/Linux ELF binaries as well, but this is unverified for sure. The
> implementation is two-fold.
> First, the static linker (if given the "-taso" option) maps an executable
> into the low 31-bit address space (coincidentally, this will probably be
> suitable for MIPS as well) and sets a special flag in the executable (it
> does it in a weird place, but this is ECOFF and we have suitable flags in
> the ELF header already).
> Second, seeing the "31-bit" flag set, the kernel returns any maps
> requested within the low 31-bit address space. This way both shared
> libraries (which thus need not be special, i.e. may be regular 64-bit
> ones) and areas allocated by mmap() are addressable by the executable.
> To summarize, nothing much complicated.
> > The primary problem is the differnet calling sequence for o32 and N64.
> But we handle that already.
> > As it looks we'll be able to use either the o32 function or the native
> > syscall to implement all of the necessary N32 syscalls.
> The (n)64 versions seem suitable and the o32 ones do not as n32 only
> crops addresses to 32-bit -- data may still be 64-bit (e.g. file position
Please notice, that a 'long' is 32-bit for n32, so we need to do the same
conversion for a lot of syscalls, as we already do for o32.
> > The question is if we want to reserve another 1000 entries in our already
> > huge syscall table for N32 or if we got a better solution ...
> Aaarrgh, no more entries, please...
> + Maciej W. Rozycki, Technical University of Gdansk, Poland +
> + e-mail: email@example.com, PGP key available +
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