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). > 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 +
