Re: [Xen-devel] [Q] GRUB -> __start_xen?

[Josh Triplett <josht@xxxxxxxxxx>]

On Fri, 2005-06-24 at 14:25 -0400, Bharadwaj Yadavalli wrote:
> I am trying to understand the internals of Xen.
> 
> On x86 (and may be other architectures), it appears to me 
> that xen's entry point is 
> 
>          void __init __start_xen(multiboot_info_t *mbi)
> 
> that lives in xeno-unstable.bk/xen/arch/x86/setup.c.
> 
> 1. Who builds the structure mbi and calls __start_xen?

The Grub bootloader creates the structure, and calls a Xen startup
function defined in xen/arch/x86/boot/x86_32.S .  That assembly code
does some minimal setup and then calls the C startup function, passing
the structure pointer.

> 2. How is __satrt_xen registered as the entry point?

The Xen image booted by GRUB has a well-specified format which includes
the location of the entry point.

> Is there a place that I can read to understand the transfer
> of control from multiboot GRUB to xen's entry point?

http://www.gnu.org/software/grub/manual/multiboot/multiboot.html

- Josh Triplett



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