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

[Yinghai Lu]

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)

 #ifdef CONFIG_HOTPLUG_CPU
 /*

remove that change, AMD systems works again.

Yinghai
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