Re: [PATCH 00/13] tools/nolibc: riscv: Add full rv32 support

From: "Arnd Bergmann" <arnd@arndb.de>
To: "Zhangjin Wu" <falcon@tinylab.org>
Cc: linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-riscv@lists.infradead.org,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Thomas Weißschuh" <thomas@t-8ch.de>, "Willy Tarreau" <w@1wt.eu>
Subject: Re: [PATCH 00/13] tools/nolibc: riscv: Add full rv32 support
Date: Fri, 26 May 2023 13:13:05 +0200	[thread overview]
Message-ID: <70cf0d8f-ea8e-43b6-9b99-739562ea865d@app.fastmail.com> (raw)
In-Reply-To: <20230526110001.150368-1-falcon@tinylab.org>

On Fri, May 26, 2023, at 13:00, Zhangjin Wu wrote:
>> On Wed, May 24, 2023, at 19:59, Zhangjin Wu wrote:
>> > diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
>
> I have applied this method for ppoll_time64 and clock_gettime64 too,
> this method can save several duplicated lines for us, I have prepared v2
> patches locally for them. 

Ok, that addresses my concern about the possible bugs.

>> I would just use __kernel_timespec64 unconditionally and then
>> use __NR_pselect6_time64 on all 32-bit architectures here,
>> but use __NR_pselect6 on 32-bit architectures.
>>
>
> The 2nd 32-bit you mean is 64-bit?

Yes, sorry for the typo.

> This is related to the timespec64/time64_t definitions as you commented
> in another reply. I will learn how to use the one from
> <linux/time_types.h>, it may require to clean up the existing files in
> tools/include/nolibc/ at first.

Ok, thanks.

>> I think we can also kill off the oldselect and newselect 
>> cases, using pselect6/pselect6_time64 unconditionally here,
>> and no longer care about building against pre-5.1 kernel
>> headers, at least for the copy of nolibc that ships with the
>> kernel.
>
> As Willy commented in another reply, users may want to copy the recent
> one and use them with an old kernel, even if want to drop them, a
> standalone patch may be preferable.

Fair enough. I checked the old versions and see that 5.1 in May 2019
was the first one to include the time64 system call definitions, though
5.6 from March 2020 was the first version that I consider fully working
with time64.

I don't know how common it is to copy nolibc into other projects,
but requiring a three year old kernel might be a little too aggressive
here. They could copy from 6.1-stable to keep the fallback (and miss
rv32) if we do this, but a better cutoff may be Dec 2025 when
linux-5.4 has its "projected EOL" date and one last LTS with the
fallback (linux-6.16 or so) gets released.

      Arnd