Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Feedback-ID: i56a14606:Fastmail
User-Agent: Cyrus-JMAP/3.9.0-alpha0-372-g43825cb665-fm-20230411.003-g43825cb6
Mime-Version: 1.0
Message-Id: <7d0389aa-4fc0-499b-8f2e-5a96102efa24@app.fastmail.com>
In-Reply-To: <168146523405.6279.3632248068235163346.stgit@skinsburskii.localdomain>
References: <168146523405.6279.3632248068235163346.stgit@skinsburskii.localdomain>
Date:   Sat, 22 Apr 2023 11:02:33 +0200
From:   "Arnd Bergmann" <arnd@arndb.de>
To:     "Stanislav Kinsburskii" <skinsburskii@linux.microsoft.com>
Cc:     "Stanislav Kinsburskii" <stanislav.kinsburskii@gmail.com>,
        "Thomas Gleixner" <tglx@linutronix.de>,
        "Ingo Molnar" <mingo@redhat.com>, "Borislav Petkov" <bp@alien8.de>,
        "Dave Hansen" <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Geert Uytterhoeven" <geert@linux-m68k.org>,
        "Chris Down" <chris@chrisdown.name>,
        "Helge Deller" <deller@gmx.de>, "Omar Sandoval" <osandov@fb.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: asm/io.h: Harden virt_to_phys/isa_virt_to_bus prototypes
Content-Type: text/plain;charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, Apr 14, 2023, at 11:40, Stanislav Kinsburskii wrote:
> From: Stanislav Kinsburskii <stanislav.kinsburskii@gmail.com>
>
> These two helper functions - virt_to_phys and isa_virt_to_bus - don't =
need the
> address pointer to be mutable.
>
> In the same time expecting it to be mutable leads to the following bui=
ld
> warning for constant pointers:
>
>   warning: passing argument 1 of =E2=80=98virt_to_phys=E2=80=99 discar=
ds =E2=80=98const=E2=80=99=20
> qualifier from pointer target type
>

The change looks fine, and this is clearly useful for spreading
more 'const' annotations, but I have two concerns:

- I'd really like this to be done consistently across architectures,
  so at least the asm-generic/io.h version should get the same
  annotation, or ideally all of them in one patch.

- I would not describe this change itself as "hardening", as it
  also does the opposite, when you have a pointer that is actually
  "const" but converting it through virt_to_phys() and back
  through phys_to_virt() ends up losing the annotation.

     Arnd