linux-kernel - Re: [PATCH 09/13] tools/nolibc: sys_poll: riscv: use __NR_ppoll

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Message-Id: <afc4944f-9494-4367-906d-06ac47648ab7@app.fastmail.com>
Date:   Sun, 28 May 2023 12:55:47 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Willy Tarreau" <w@....eu>, "Zhangjin Wu" <falcon@...ylab.org>
Cc:     Thomas Weißschuh <thomas@...ch.de>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        "Palmer Dabbelt" <palmer@...belt.com>,
        "Paul Walmsley" <paul.walmsley@...ive.com>
Subject: Re: [PATCH 09/13] tools/nolibc: sys_poll: riscv: use __NR_ppoll_time64 for
 rv32

On Sun, May 28, 2023, at 12:29, Willy Tarreau wrote:
> On Sun, May 28, 2023 at 04:25:09PM +0800, Zhangjin Wu wrote:
>> 
>> * Use __kernel_timespec as timespec
>> * Use 64bit time_t based struct timeval
>>     * Disable gettimeofday syscall completely for 32bit platforms
>>         * And disable the gettimeofday_bad1/2 test case too
>
> When you say "disable", you mean "remap", right ? Or do you mean
> "break in 2023 code that was expected to break only in 2038 after

clock_gettime() has been supported for a very long time, so both
time() and gettimeofday() can be trivial wrappers around that.

Nothing really should be using the timezone argument, so I'd
just ignore that in nolibc. (it's a little trickier for /sbin/init
setting the initial timezone, but I hope we can ignore that here).

clock_gettime() as a function call that takes a timespec argument
in turn should be a wrapper around either sys_clock_gettime64 (on
32-bit architectures) or sys_clock_gettime_old() (on 64-bit
architectures, or as a fallback on old 32-bit kernels after
clock_gettime64 fails).

On normal libc implementations, the low-level
sys_clock_gettime64() and sys_clock_gettime_old(), whatever
they are named, would call vdso first and then fall back
to the syscall, but I don't think that's necessary for nolibc.

I'd define them the same as the kernel, with
sys_clock_gettime64() taking a __kernel_timespec, and
sys_clock_gettime_old() takeing a __kernel_old_timespec.

    Arnd