linux-kernel - Re: [PATCH 0/9] posix_clocks: Prepare syscalls for 64 bit time

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Date:   Fri, 17 Nov 2017 11:40:48 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Arnd Bergmann <arnd@...db.de>
cc:     Deepa Dinamani <deepa.kernel@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
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        Catalin Marinas <catalin.marinas@....com>,
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        Will Deacon <will.deacon@....com>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH 0/9] posix_clocks: Prepare syscalls for 64 bit time_t
 conversion

On Fri, 17 Nov 2017, Arnd Bergmann wrote:
> On Fri, Nov 17, 2017 at 10:54 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> > On Fri, 17 Nov 2017, Arnd Bergmann wrote:
> >> On Fri, Nov 17, 2017 at 9:58 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> >>
> >> No, syscall that existing 32-bit user space enters would be handled by
> >> compat_sys_nanosleep() on both 32-bit and 64-bit kernels at that
> >> point. The idea here is to make the code path more uniform between
> >> 32-bit and 64-bit kernels.
> >
> > So on a 32bit system compat_sys_nanosleep() would be the legacy
> > sys_nanosleep() with the existing syscall number, but you don't want to
> > introduce a new sys_nanosleep64() for 32bit. That makes a lot of sense.
> >
> > So back to your original question whether to use #if (MAGIC logic) or a
> > separate config symbol. Please use the latter, these magic logic constructs
> > are harder to read and prone to get wrong at some point. Having the
> > decision logic in one place is always the right thing to do.
> 
> How about this:
> 
> config LEGACY_TIME_SYSCALLS
>       def_bool 64BIT || !64BIT_TIME
>       help
>         This controls the compilation of the following system calls:
> time, stime,
>         gettimeofday, settimeofday, adjtimex, nanosleep, alarm, getitimer,
>         setitimer, select, utime, utimes, futimesat, and
> {old,new}{l,f,}stat{,64}.
>         These all pass 32-bit time_t arguments on 32-bit architectures and
>         are replaced by other interfaces (e.g. posix timers and clocks, statx).
>         C libraries implementing 64-bit time_t in 32-bit architectures have to
>         implement the handles by wrapping around the newer interfaces.

s/handles/handling/ ????

>         New architectures should not explicitly disable this.

New architectures should never enable this, right?

Thanks,

	tglx