linux-kernel - [Y2038] Question regarding support of old time interfaces beyond y2038

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Message-ID: <20190305162351.5aadde66@jawa>
Date:   Tue, 5 Mar 2019 16:23:51 +0100
From:   Lukasz Majewski <lukma@...x.de>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org,
        Joseph Myers <joseph@...esourcery.com>,
        libc-alpha@...rceware.org
Subject: [Y2038] Question regarding support of old time interfaces beyond
 y2038

Dear Arnd,

In your "playground" repository [1] (branch: y2038), the time functions
(stime, settimeofday, etc) are not converted in Linux to be Y2038 aware
(as for example clock_settime{64}() is).

I've also searched on the Internet and I've found some old discussions
regarding them:

SHA1:  d33c577cccd0b3e5bb2425f85037f26714a59363 [2]
From commit message:

"The time, stime, utime, utimes, and futimesat system calls are only
used on older architectures, and we do not provide y2038 safe variants
of them, as they are replaced by clock_gettime64, clock_settime64,
and utimensat_time64."

Moreover, the stime has been even explicitly marked as obsolete [3].

From other discussion [4] - regarding 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."

Has something changed since then? Has any new idea for conversion
emerged?

After observing the development of y2038 on playground [1], I can deduce
that new interfaces are only going to be supported and converted
(clock_settime64/clock_gettime64, etc.)

Considering the above - would it be best to drop Y2038 support on 32
bit machines for old syscalls (stime and friends) and for some others
(settimeofday/gettimeofday) write Y2038 wrappers based on new time
kernel API (clock_gettime/settime) in the C library (i.e. glibc)?

Note:

[1] -
https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/tree/kernel/time/time.c?h=y2038
[2] - git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git
[3] - 
https://elixir.bootlin.com/linux/v2.6.32/source/arch/arm/include/asm/unistd.h#L419
[4] - https://lists.linaro.org/pipermail/y2038/2017-November/002387.html

Best regards,

Lukasz Majewski

--

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