Re: [PATCH v7 00/27] x86, boot, 64bit: Add support for loadingramdisk and bzImage above 4G

From: Yinghai Lu
Date: Sun Dec 23 2012 - 13:00:23 EST

On Sun, Dec 23, 2012 at 6:33 AM, H. Peter Anvin <hpa@xxxxxxxxx> 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)


remove that change, AMD systems works again.

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