Xen devel - Feb 2006 - question about DomU kernel loading

Hi, 

I was trying to check the integrity the kernel of any DomU. 

Here is my experiment:

1. parse xenU kernel image, extract ".text" section from the image.
2. dump the domU memory from the dsi.v_start upto the size of ".text"
section.
3. compare the results from step 1 and step 2.

I found that the majority of the code are the same, but still about 500 bytes 
are different between these two in various locations.

Could anyone tell me why are not they the same and what made the difference? 

Thanks,

Ying Wang

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On 23 Feb 2006, at 21:26, Ying.U.Wang@asu.edu wrote:
> Here is my experiment:
>
> 1. parse xenU kernel image, extract ".text" section from the
image.
> 2. dump the domU memory from the dsi.v_start upto the size of
".text"
> section.
> 3. compare the results from step 1 and step 2.
>
> I found that the majority of the code are the same, but still about 
> 500 bytes
> are different between these two in various locations.
>
> Could anyone tell me why are not they the same and what made the 
> difference?
The kernel modifies itself to insert the best code sequences for the 
system its running on:
e.g., add synchronisation primitives if the system is multiprocessor.

  -- Keir


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Hi community,

	I''m trying to carefully understand the process of creating a domain
and
vcpu initialization. In particular, I''m currently interested in
understanding exactly which information the "vcpu" structure holds.
	
	Which kind of flags does "arch_vcpu.flags" contain? I saw a comment
/*
TF_ */, but I did not quite get it.

	What is it used for?

	Thanks in advance,
	Eli


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On 24 Feb 2006, at 16:31, Elizeu Santos-Neto wrote:
> 	I''m trying to carefully understand the process of creating a
domain
> and
> vcpu initialization. In particular, I''m currently interested in
> understanding exactly which information the "vcpu" structure
holds.
> 	
> 	Which kind of flags does "arch_vcpu.flags" contain? I saw a
comment /*
> TF_ */, but I did not quite get it.
>
> 	What is it used for?
They''re defined in asm/processor.h. There''s only one right now
--
TF_kernel mode, which indicates whether the guest is currently running 
in kernel mode or not. This is needed on x86/64 since guest 
applications and guets kernel both run in ring 3 and so there is no way 
to distinguish the two modes without maintaining a sfotware flag in 
Xen.

  -- Keir


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