linux-kernel - Re: [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write

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Date:   Fri, 7 Apr 2017 11:37:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     kernel-hardening@...ts.openwall.com,
        Mark Rutland <mark.rutland@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Hoeun Ryu <hoeun.ryu@...il.com>,
        PaX Team <pageexec@...email.hu>,
        Emese Revfy <re.emese@...il.com>,
        Russell King <linux@...linux.org.uk>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC v2][PATCH 04/11] x86: Implement
 __arch_rare_write_begin/unmap()

On Wed, Mar 29, 2017 at 11:15:56AM -0700, Kees Cook wrote:
> +static __always_inline unsigned long __arch_rare_write_end(void)
> +{
> +	unsigned long cr0;
> +
> +	barrier();
> +	cr0 = read_cr0() ^ X86_CR0_WP;
> +	BUG_ON(!(cr0 & X86_CR0_WP));
> +	write_cr0(cr0);
> +	barrier();
> +	preempt_enable_no_resched();

NAK

> +	return cr0 ^ X86_CR0_WP;
> +}