Request for review/comments: 32-bit compat for non-x86
jhb at freebsd.org
Wed Mar 10 15:50:53 UTC 2010
On Wednesday 10 March 2010 9:39:15 am Nathan Whitehorn wrote:
> John Baldwin wrote:
> > On Tuesday 09 March 2010 11:14:27 pm Nathan Whitehorn wrote:
> >> The patch at http://people.freebsd.org/~nwhitehorn/compat_freebsd32.diff
> >> (pre-generated freebsd32 syscalls stuff is included, which will be done
> >> in two steps on commit) provides groundwork for supporting 32-bit
> >> compatibility for 64-bit MIPS and PowerPC systems. It has been tested on
> >> amd64 and powerpc64, and compile-tested on ia64. There are two main
> >> parts to the patch:
> >> 1) COMPAT_IA32 is renamed COMPAT_FREEBSD32, in analogy to
> >> COMPAT_LINUX32, etc. This requires updating kernel configurations, but
> >> is less painful than filling machine-independent bits of the kernel with
> >> #if defined(COMPAT_IA32) || defined(COMPAT_PPC32) ||
> >> defined(COMPAT_MIPS32) || ..., and is no less descriptive than the old name.
> >> 2) Modifications to the freebsd32 compat layer to support big-endian
> >> architectures.
> >> I would appreciate any comments, bugs, or test results on ia64.
> > This doesn't look right for non-x86 32-bit ABIs:
> > Index: sys/kern/imgact_elf.c
> > ===================================================================
> > --- sys/kern/imgact_elf.c (revision 204681)
> > +++ sys/kern/imgact_elf.c (working copy)
> > @@ -1439,7 +1439,7 @@
> > ehdr->e_ident[EI_ABIVERSION] = 0;
> > ehdr->e_ident[EI_PAD] = 0;
> > ehdr->e_type = ET_CORE;
> > -#if defined(COMPAT_IA32) && __ELF_WORD_SIZE == 32
> > +#if defined(COMPAT_FREEBSD32) && __ELF_WORD_SIZE == 32
> > ehdr->e_machine = EM_386;
> > #else
> > ehdr->e_machine = ELF_ARCH;
> Good catch! Such are the dangers of sed. How about defining an
> ELF_ARCH32 in machine/elf.h for this case?
Yes, that sounds good.
> > It would be nice to eliminate having <compat/ia32*> includes in MI code by
> > instead including those headers in appropriate headers in <machine/*>. For
> > example, we could change <machine/reg.h> on amd64 and ia64 to include these
> > headers, perhaps under an #ifdef COMPAT_FREEBSD32.
> > Hmm, actually, I'm quite convinced now that <machine/reg.h> for ia64 and amd64
> > should include <compat/ia32/ia32_reg.h> in the #ifdef _KERNEL section to avoid
> > polluting those includes in MI code. I'm not sure what the various
> > <machine/fpu.h> includes are for, but fixing ia32_reg.h would be a good first
> > step. It would make your diffs smaller I think.
> This is how it works on powerpc64. I didn't modify amd64 and ia64 in
> order to avoid making too many changes, but I think you're right that
> this is a good idea. I'll add that to the patch when fixing the EM_386
> bit you pointed out above.
More information about the freebsd-amd64