Re: [Etherboot-developers] Comboot - Local Boot Support

Michael Brown wrote:
> On Monday 29 September 2008 19:58:31 Daniel Verkamp wrote:
>> Where should I store the register values for the PM version? It will
>> run in PHYS_CODE; can I still use CS to access data in .text16?
> 
> No; %cs will be a flat, zero-based 4GB code descriptor at that point.  There's 
> no absolute address you can use.  However, _virt_to_phys will preserve all 
> (non-segment) registers and flags and will modify %esp to point to the same 
> physical location as before the call; you can probably do something with 
> this.  (You can trivially do everything *apart* from load %esp with an 
> arbitrary value: just have the asm load up %esp with the address of a 
> register dump structure and then have a series of "pop" instructions followed 
> by a "ret".)
> 

How do you set %esp itself then, other than using self-modifying code? 
(This is the reason I started using self-modifying code in the Syslinux 
case, and once I was doing it there, I figured I might as well use it 
for all the cases.)

	-hpa

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