linux-kernel - Re: [PATCH] rtc: armada38x: add __ro_after_init to armada38x_rtc

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Date:   Tue, 3 Jan 2017 13:18:29 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     Bhumika Goyal <bhumirks@...il.com>,
        Julia Lawall <julia.lawall@...6.fr>,
        Jason Cooper <jason@...edaemon.net>, andrew@...n.ch,
        gregory.clement@...e-electrons.com,
        sebastian.hesselbarth@...il.com, a.zummo@...ertech.it,
        alexandre.belloni@...e-electrons.com,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>, rtc-linux@...glegroups.com,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rtc: armada38x: add __ro_after_init to armada38x_rtc_ops

On Mon, Jan 2, 2017 at 6:06 AM, Russell King - ARM Linux
<linux@...linux.org.uk> wrote:
> On Mon, Dec 26, 2016 at 05:01:02PM +0530, Bhumika Goyal wrote:
>> The object armada38x_rtc_ops of type rtc_class_ops structure is not
>> modified after getting initialized by armada38x_rtc_probe. Apart from
>> getting referenced in init it is also passed as an argument to the function
>> devm_rtc_device_register but this argument is of type const struct
>> rtc_class_ops *. Therefore add __ro_after_init to its declaration.
>
> What I'd prefer here is for the structure to be duplicated, with one
> copy having the alarm methods and one which does not.  Both can then
> be made "const" (so placed into the read-only section at link time)
> and the probe function select between the two.
>
> I think that's a cleaner and better solution, even though it's
> slightly larger.
>
> I'm not a fan of __ro_after_init being used where other solutions are
> possible.

Can the pointer that points to the struct rtc_class_ops be made ro_after_init?

-Kees

-- 
Kees Cook
Nexus Security