From: Arnd Bergmann <arnd@arndb.de>
To: Andreas Schwab <schwab@suse.de>
Cc: linux-arm-kernel@lists.infradead.org,
        Yury Norov <ynorov@caviumnetworks.com>, pinskia@gmail.com,
        Prasun.Kapoor@caviumnetworks.com, catalin.marinas@arm.com,
        Nathan_Lynch@mentor.com, linux-kernel@vger.kernel.org, agraf@suse.de,
        klimov.linux@gmail.com,
        Andrew Pinski <Andrew.Pinski@caviumnetworks.com>, broonie@kernel.org,
        jan.dakinevich@gmail.com, Andrew Pinski <apinski@cavium.com>,
        ddaney.cavm@gmail.com, bamvor.zhangjian@huawei.com,
        philipp.tomsich@theobroma-systems.com, andrey.konovalov@linaro.org,
        christoph.muellner@theobroma-systems.com
Subject: Re: [PATCH v6 13/17] arm64:ilp32: add sys_ilp32.c and a separate table (in entry.S) to use it
Date: Thu, 12 Nov 2015 00:23:43 +0100
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On Thursday 12 November 2015 00:07:41 Andreas Schwab wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
> 
> > On Wednesday 11 November 2015 18:54:00 Andreas Schwab wrote:
> >> Yury Norov <ynorov@caviumnetworks.com> writes:
> >> 
> >> > +#define sys_clock_gettime       compat_sys_clock_gettime
> >> > +#define sys_clock_settime       compat_sys_clock_settime
> >> 
> >> You also need to redirect sys_clock_nanosleep.
> >
> > Note that based on my comment, that table would be turned around, and
> > only the syscalls get overridden that do not have the normal
> > compat mode behavior (mostly the ones that pass a 64-bit register).
> 
> Is it intented that _all_ off_t-like syscalls are implemented by the
> 64bit variants?  Currently, this isn't fully implemented (lseek is
> implemented by sys_llseek and mmap by an mmap2 wrapper).

I think either way is fine for the two examples. I think it's clear
that we want __NR_llseek as 62 and __NR_mmap2 as 222. Whether those
use the compat_sys_llseek/compat_sys_mmap2_wrapper or
sys_lseek/sys_mmap entry points is not overly important, we can use
whatever is more convenient to glibc: if we can kill off an
architecture specific wrapper function in glibc by adding one line
to the kernel, that seems worthwhile.

It's a bit confusing, because user space off_t matches the kernel's
off_t, loff_t, but not the __kernel_off_t from the uapi headers.

	Arnd
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