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

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Message-ID: <CAK8P3a1J0C5A+SzVWDz52ZkawG1HZYj2cR6oc=DL=QrXgYaiHg@mail.gmail.com>
Date:   Fri, 17 Nov 2017 11:46:37 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Deepa Dinamani <deepa.kernel@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
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Subject: Re: [PATCH 0/9] posix_clocks: Prepare syscalls for 64 bit time_t conversion

On Fri, Nov 17, 2017 at 11:40 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 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/ ????

I meant "handlers".

>>         New architectures should not explicitly disable this.
>
> New architectures should never enable this, right?

Right, I got an extra "not". I guess if Deepa incorporates the new option,
she can also improve my English ;-)

         Arnd