linux-kernel - Re: [PATCH][RFC] x86_64: Reload CS when startup

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Date:	Mon, 21 Aug 2006 12:19:09 +0200
From:	Andi Kleen <ak@...e.de>
To:	Magnus Damm <magnus@...inux.co.jp>
Cc:	fastboot@...ts.osdl.org, linux-kernel@...r.kernel.org,
	ebiederm@...ssion.com
Subject: Re: [PATCH][RFC] x86_64: Reload CS when startup_64 is used.


>  
> +	/* Reload CS with a value that is within our GDT. We need to do this
> +	 * if we were loaded by a 64 bit bootloader that happened to use a 
> +	 * CS that is larger than the GDT limit. This is true if we came here
> +	 * from kexec running under Xen.
> +	 */
> +	movq	%rsp, %rdx
> +	movq	$__KERNEL_DS, %rax
> +	pushq	%rax /* SS */
> +	pushq	%rdx /* RSP */
> +	movq	$__KERNEL_CS, %rax
> +	movq	$cs_reloaded, %rdx
> +	pushq	%rax /* CS */
> +	pushq	%rdx /* RIP */
> +	lretq

Can't you just use a normal far jump? That might be simpler.

-Andi
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