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Re: [PATCH 3/4] Consolidate pread/pread64 implementations

On 05 Jan 2016 17:19, Adhemerval Zanella wrote:
> On 05-01-2016 17:11, Mike Frysinger wrote:
> > On 05 Jan 2016 10:49, Adhemerval Zanella wrote:
> >> On 04-01-2016 22:53, Mike Frysinger wrote:
> >>> On 04 Jan 2016 10:42, Adhemerval Zanella wrote:
> >>>> On 29-12-2015 15:28, Mike Frysinger wrote:
> >>>>> On 18 Nov 2015 12:02, Adhemerval Zanella wrote:
> >>>>>> This patch consolidates all the pread/pread64 implementation for Linux
> >>>>>> in only one (sysdeps/unix/sysv/linux/pread.c).  It also removes the
> >>>>>> syscall from the auto-generation using assembly macros.
> >>>>>>
> >>>>>> For pread{64} offset argument placement the new SYSCALL_LL{64} macro
> >>>>>> is used.  For pread ports that do not define __NR_pread will use
> >>>>>> __NR_pread64 and for pread64 ports that dot define __NR_pread64 will
> >>>>>> use __NR_pread for the syscall.
> >>>>>
> >>>>> pretty sure you just broke sh here.  while it doesn't have the 64-bit
> >>>>> arg alignment issue, it has a wart where it copied the kernel interface
> >>>>> of one.  you can see it in the files you deleted:
> >>>>
> >>>> Indeed, my understanding is SH also requires __ASSUME_ALIGNED_REGISTER_PAIRS.
> >>>> I will change it for the 1/4 patch part.
> >>>
> >>> just to be clear, SuperH (the ABI) does not have these 64-bit register
> >>> pair requirements like ARM/EABI.  its syscall ABI for pread64/pwrite64
> >>> has legacy cruft where there's a dummy reg before the 64-bit value.  so
> >>> you can (and want) to use the same logic just for these two syscalls as
> >>> the result happens to look the same.
> >>
> >> Right, so for SuperH kernel interface the 64-bit pair cruft is only for
> >> pread64/pwrite64 or is it for all 64-bits arguments?
> > 
> > just pread64/pwrite64:
> >
> sigh... so __ASSUME_ALIGNED_REGISTER_PAIRS is not the way to go on SH. I 
> would prefer to avoid this, but since kernel interface is what it is I
> think for SH it would be better to provide specific implementations.
> I will change that, thanks for the information.

i think your patches are the right way to go.  what we did in uClibc was
add a sh-specific pread/write file that had a comment and then defined
__ASSUME_ALIGNED_REGISTER_PAIRS before including the common one.

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