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[Xen-devel] Xen's Code location


  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Ahmed Azab <amazab@xxxxxxxx>
  • Date: Tue, 23 Jun 2009 11:58:48 -0400
  • Delivery-date: Tue, 23 Jun 2009 08:59:30 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

Hi all,

I was inspecting Xen trying to understand the mechanism of booting the hypervisor and the way Xen's memory is managed inside its own address space. I am using x86/32-bit Xen with PAE. According to the documents, Xen should occupy the highest 168 MB of the address space (i.e. higher than 0xf5800000). I have two questions:

1- What are the boundaries of the different sections (code, ro data, heap, etc..) with this address space?

I searched within Xen's source but I got now clue about the location Xen's code is mapped. I used objdump on the booted Xen kernel and is said that there is only one section, which is .text, that should be loaded at 0x0010000 which is not even a high address. I inspected the function __start_xen in setup.c but it does not do any code address relocation. Finally, I inspected Xen's GDT and I found that it used a flat segmentation structure (4 GB per segment)

2-Is there any page protection within Xen's address space?

I noticed that all mapped pages are executable which is supposed to include Xen's stack and heap.

Thanks,
Ahmed

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