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Re: [PATCH 3/4] Consolidate pread/pread64 implementations
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org, Adhemerval Zanella <adhemerval dot zanella at linaro dot com>
- Date: Tue, 5 Jan 2016 17:19:09 -0200
- Subject: Re: [PATCH 3/4] Consolidate pread/pread64 implementations
- Authentication-results: sourceware.org; auth=none
- References: <1447855356-4140-1-git-send-email-adhemerval dot zanella at linaro dot org> <1447855356-4140-4-git-send-email-adhemerval dot zanella at linaro dot org> <20151229172810 dot GO25803 at vapier dot lan> <568A68A6 dot 9000906 at linaro dot org> <20160105005340 dot GE25548 at vapier dot lan> <568BBBC9 dot 8020104 at linaro dot org> <20160105191153 dot GJ25548 at vapier dot lan>
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:
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/sh/kernel/sys_sh32.c?h=v4.3
> -mike
>
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.