[PATCH v6 13/17] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it

[Andrew Pinski]

On Fri, Nov 13, 2015 at 7:34 AM, Arnd Bergmann <arnd at arndb.de> wrote:
> On Thursday 12 November 2015 14:47:18 Andreas Schwab wrote:
>> Arnd Bergmann <arnd at arndb.de> writes:
>>
>> > On Thursday 12 November 2015 10:44:55 Andreas Schwab wrote:
>> >> Arnd Bergmann <arnd at arndb.de> writes:
>> >>
>> >> > What do you mean with 32-bit off_t?
>> >>
>> >> An ABI with 32-bit off_t, ie. all currently implemented 32-bit ABIs.
>> >>
>> >> > Do you mean that glibc emulates a 32-bit off_t on top of the 64-bit
>> >> > __kernel_loff_t?
>> >>
>> >> Glibc is bridging the user-space ABI to the kernel ABI.
>> >
>> > Ok, but why?
>>
>> That's how the ABI is defined right now.  I didn't make that up.
>
> Ok, I guess it will remain a mystery then.

The biggest question is here is how much compatibility do we want with
other 32bit ABIs?
Do we want off_t to be 32bit or 64bit?

>
> Should we perhaps define __ARCH_WANT_SYSCALL_OFF_T for the unistd.h
> file then, so we provide both the off_t and the loff_t based syscalls?

I think that is backwards ...

>
> That would avoid the extra wrapper in glibc when using a 32-bit
> off_t if that is the preferred mode for user space.


Other targets like tilegx does not do that and has a pure 32bit mode.
Only score does that.

Thanks,
Andrew

>
>         Arnd