Xen's Code location

Xen's Code location

[Ahmed Azab]

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