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From:   Andrew Bresticker <abrestic@rivosinc.com>
Date:   Thu, 8 Sep 2022 14:14:08 -0400
Message-ID: <CALE4mHpz6DpV+jq2uqic7DCqv3a0qcYqov8+wjhZSVx5-2nkEw@mail.gmail.com>
Subject: Re: [PATCH] riscv: Allow PROT_WRITE-only mmap()
To:     SS JieJi <c141028@gmail.com>
Cc:     Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Atish Patra <atishp@atishpatra.org>,
        Celeste Liu <coelacanthus@outlook.com>,
        dram <dramforever@live.com>, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org
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On Thu, Sep 8, 2022 at 1:28 PM SS JieJi <c141028@gmail.com> wrote:
>
> > https://fars.ee/1sPb, showing *inconsistent* read results on -r- pages
> > before/after a write attempt performed by the kernel.
>
> That said, maybe prohibit mmap-ing -w- pages is not the best fix for
> this issue. If -w- pages are irreplaceable for some use cases (and
> hence need to be allowed), I'd suggest at least we need to re-fix the
> read result inconsistency issue somewhere else despite simply
> reverting the patch.

Ah, this is because do_page_fault() also needs to be made aware of
write-implying-read. Will send a v2 shortly.

-Andrew

>
> Yours, Pan Ruizhe