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Date: Sun, 23 Dec 2012 10:00:26 -0800 From: Yinghai Lu <yinghai@...nel.org> To: "H. Peter Anvin" <hpa@...or.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>, "Eric W. Biederman" <ebiederm@...ssion.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v7 00/27] x86, boot, 64bit: Add support for loading ramdisk and bzImage above 4G On Sun, Dec 23, 2012 at 6:33 AM, H. Peter Anvin <hpa@...or.com> wrote: > Explanation please? > you have following change in the patch /* Finally jump to run C code and to be on real kernel address * Since we are running on identity-mapped space we have to jump * to the full 64bit address, this is only possible as indirect * jump. In addition we need to ensure %cs is set so we make this - * a far return. + * a far jump. */ - movq initial_code(%rip),%rax pushq $0 # fake return address to stop unwinder - pushq $__KERNEL_CS # set correct cs - pushq %rax # target address in negative space - lretq + /* gas 2.22 is buggy and mis-assembles ljmpq */ + rex64 ljmp *initial_code(%rip) #ifdef CONFIG_HOTPLUG_CPU /* remove that change, AMD systems works again. Yinghai -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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