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Subject: Re: [PATCH v6 2/4] x86/syscalls: Specific usage of
 verify_pre_usermode_state
To: Thomas Garnier <thgarnie@google.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
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        Ingo Molnar <mingo@kernel.org>, Oleg Nesterov <oleg@redhat.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Pavel Tikhomirov <ptikhomirov@virtuozzo.com>,
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        Catalin Marinas <catalin.marinas@arm.com>,
        Mark Rutland <mark.rutland@arm.com>, James Morse <james.morse@arm.com>
References: <20170404174727.35478-1-thgarnie@google.com>
 <20170404174727.35478-2-thgarnie@google.com>
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From: "H. Peter Anvin" <hpa@zytor.com>
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Date: Tue, 4 Apr 2017 11:11:03 -0700
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On 04/04/17 10:47, Thomas Garnier wrote:
> Implement specific usage of verify_pre_usermode_state for user-mode
> returns for x86.
> 
> Signed-off-by: Thomas Garnier <thgarnie@google.com>
>  
> +	/*
> +	 * If address limit is not based on user-mode, jump to slow path for
> +	 * additional security checks.
> +	 */
> +	movq	$TASK_SIZE_MAX, %rcx
> +	cmp	%rcx, TASK_addr_limit(%r11)
> +	jnz	1f
> +
>  	LOCKDEP_SYS_EXIT

Nitpick: use jne not jnz when comparing for equality.  Same instruction
but more readable.

	-hpa