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From:   Andreas Schwab <schwab@suse.de>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Palmer Dabbelt <palmer@dabbelt.com>,
        linux-riscv@lists.infradead.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] RISC-V Fixes for 5.7-rc5
References: <mhng-81c83c19-6f5d-4ed1-a0bb-26accf4b7d3a@palmerdabbelt-glaptop1>
        <CAHk-=win0EVU_GuO=GuJu3Ck0WG1B3+ub-CjncM3B1G9x5d9cw@mail.gmail.com>
        <mvmr1vqkhxb.fsf@suse.de>
        <CAHk-=wj8Cks7L2H9ToNWEMmqECYEfX0uyCXpW1OsZ+NAooi2Cw@mail.gmail.com>
Date:   Tue, 12 May 2020 10:53:49 +0200
In-Reply-To: <CAHk-=wj8Cks7L2H9ToNWEMmqECYEfX0uyCXpW1OsZ+NAooi2Cw@mail.gmail.com>
        (Linus Torvalds's message of "Mon, 11 May 2020 12:04:09 -0700")
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On Mai 11 2020, Linus Torvalds wrote:

> Why is glibc doing it in the first place? Is it some historical thing
> that is simply irrelevant on RISC-V simply because RISC-V doesn't have
> that kind of history, perhaps?

It is completely generic.  Even new architectures become old over time
and accumulate cruft.  The idea is that if you configure glibc with
--enable-kernel=VERSION, it assumes that all syscalls from kernel
VERSION are guaranteed to exist, and drops the fallbacks for those
syscalls, or uses them in the first place (if no useful fallback
existed).  From time to time the absolute minimum supported kernel
version is increased (this happend the last time in 2017, when x86 and
x86_64 moved the mininum from 2.6.32 to 3.2, after all other
architectures did that step in 2016), which allows removing the fallback
code that becomes obsolete.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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"And now for something completely different."