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

From: Andrew Pinski
Date: Fri Nov 13 2015 - 10:38:55 EST

On Fri, Nov 13, 2015 at 7:34 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Thursday 12 November 2015 14:47:18 Andreas Schwab wrote:
>> Arnd Bergmann <arnd@xxxxxxxx> writes:
>> > On Thursday 12 November 2015 10:44:55 Andreas Schwab wrote:
>> >> Arnd Bergmann <arnd@xxxxxxxx> 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.


> Arnd
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