linux-kernel - Re: [PATCH] riscv: Allow PROT

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Date:   Thu, 8 Sep 2022 14:14:08 -0400
From:   Andrew Bresticker <abrestic@...osinc.com>
To:     SS JieJi <c141028@...il.com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Atish Patra <atishp@...shpatra.org>,
        Celeste Liu <coelacanthus@...look.com>,
        dram <dramforever@...e.com>, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: Allow PROT_WRITE-only mmap()

On Thu, Sep 8, 2022 at 1:28 PM SS JieJi <c141028@...il.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