"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 > pointers). > 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: macro@ds2.pg.gda.pl, PGP key available + -- _ _ ____ ___ Carsten Langgaard Mailto:carstenl@mips.com |\ /|||___)(___ MIPS Denmark Direct: +45 4486 5527 | \/ ||| ____) Lautrupvang 4B Switch: +45 4486 5555 TECHNOLOGIES 2750 Ballerup Fax...: +45 4486 5556 Denmark http://www.mips.com
