linux-kernel - Re: [PATCH v2 2/8] arm64: mm: mark fault_info __ro_after

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Message-ID: <20170329112326.GE23442@leverpostej>
Date:   Wed, 29 Mar 2017 12:23:26 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Doug Berger <opendmb@...il.com>
Cc:     robh+dt@...nel.org, catalin.marinas@....com, will.deacon@....com,
        computersforpeace@...il.com, gregory.0xf0@...il.com,
        f.fainelli@...il.com, bcm-kernel-feedback-list@...adcom.com,
        wangkefeng.wang@...wei.com, james.morse@....com, mingo@...nel.org,
        sandeepa.s.prabhu@...il.com, shijie.huang@....com,
        linus.walleij@...aro.org, treding@...dia.com, jonathanh@...dia.com,
        olof@...om.net, mirza.krak@...il.com, suzuki.poulose@....com,
        bgolaszewski@...libre.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 2/8] arm64: mm: mark fault_info __ro_after_init

On Tue, Mar 28, 2017 at 02:34:25PM -0700, Doug Berger wrote:
> The fault_info table must be made writeable to allow installation
> of custom memory abort handlers, but it can be made read-only
> after initialization to provide some protection.
> 
> Signed-off-by: Doug Berger <opendmb@...il.com>

Thanks for putting this together. I agree that making this RO is good.

However, I also think that we should not allow arbitrary hooking of
fault codes, and thus this can be const.

Thanks,
Mark.

> ---
>  arch/arm64/mm/fault.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index cdf1260f1005..43319ed58a47 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -493,7 +493,7 @@ static struct fault_info {
>  	int	sig;
>  	int	code;
>  	const char *name;
> -} fault_info[] = {
> +} fault_info[] __ro_after_init = {
>  	{ do_bad,		SIGBUS,  0,		"ttbr address size fault"	},
>  	{ do_bad,		SIGBUS,  0,		"level 1 address size fault"	},
>  	{ do_bad,		SIGBUS,  0,		"level 2 address size fault"	},
> -- 
> 2.12.0
>