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From:   Andrew Bresticker <abrestic@rivosinc.com>
Date:   Thu, 8 Sep 2022 15:18:02 -0400
Message-ID: <CALE4mHpO5eFk9-G=RCk97JiwnBMMFLiB4qvV-XXO+N8oxz0QTA@mail.gmail.com>
Subject: Re: [PATCH v2] riscv: Make mmap() with PROT_WRITE imply PROT_READ
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 2:57 PM SS JieJi <c141028@gmail.com> wrote:
>
> The v2 patch looks great,
> > -       if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ)))
> > -               return -EINVAL;
> > -
> This also removes the check for --x pages, which used to be present in
> previous versions (before the submission of the to-be-reverted patch).
> Is this intended? Thanks!

There's no change in behavior for --X mappings; those have always been
allowed as it's a valid set of PTE permissions.

This patch does allow -WX mappings, which were originally disallowed
in commit e0d17c842c0f ("RISC-V: Don't allow write+exec only page
mapping request in mmap"), by implying read permissions for such
mappings as well. I have a note in the commit message about this.

-Andrew