Re: RFC: Add 32bit x86-64 support to binutils

[Richard Guenther <richard dot guenther at gmail dot com>]

On Thu, Dec 30, 2010 at 8:30 PM, Joseph S. Myers
<joseph@codesourcery.com> wrote:
> On Thu, 30 Dec 2010, H.J. Lu wrote:
>
>> On Thu, Dec 30, 2010 at 10:42 AM, Joseph S. Myers
>> <joseph@codesourcery.com> wrote:
>> > On Thu, 30 Dec 2010, H.J. Lu wrote:
>> >
>> >> Hi,
>> >>
>> >> This patch adds 32bit x86-64 support to binutils. Support in compiler,
>> >> library and OS is required to use it. ?It can be used to implement the
>> >> new 32bit OS for x86-64. ?Any comments?
>> >
>> > Do you have a public psABI document? ?I think the psABI at the ELF level
>> > needs to come before the binutils bits, at the function call level needs
>> > to come before the GCC bits, etc.
>>
>> The psABI is the same as x86-64 psABI, except for 32bit ELF instead of
>> 64bit.
>
> I don't think that's an adequate description. ?If the "ILP32" name is
> accurate then it's certainly wrong at the C level since some type sizes
> are different, with effects in turn on such things as the description of
> initial stack layout storing argv. ?At the ELF level are you saying that
> each relocation applies to a relocatable field of the same width as for
> 64-bit (but with the width of the addend being restricted, of course)? ?Do
> any relocations applying to word64 fields need 32-bit variants applying to
> word32 for the ILP32 ABI?
>
> The right thing to do would be to go through the ABI sources and prepare a
> patch adding a description of the ILP32 ABI at least place where any
> change is needed.
>
>> > the problems that have plagued the MIPS n32 syscall ABI, which seems like
>> > a similar case?
>>
>> Can you describe MIPS n32 problems?
>
> Syscalls sometimes need three different versions in the kernel; sometimes
> the wrong version gets put in the n32 syscall table. ?Special syscall
> wrappers are often needed in glibc; although for most purposes the glibc
> port is a 32-bit one, including having separate functions for 32-bit and
> 64-bit off_t, syscalls tend to need to be called in the 64-bit way (long
> long values as single arguments, in particular).

Would be nice if LFS would be mandatory on the new ABI, thus
off_t being 64bits.

Richard.