Difference between revisions of "Xbox 360 Backward Compatibility"

From xboxdevwiki
Jump to: navigation, search
(Created page with "Xbox 360 Backward Compatibility is Microsofts original Xbox emulator for the Xbox 360. == References and links == * [http://support.xbox.com/en-US/legacy-devices/original-con...")
 
Line 1: Line 1:
 
Xbox 360 Backward Compatibility is Microsofts original Xbox emulator for the Xbox 360.
 
Xbox 360 Backward Compatibility is Microsofts original Xbox emulator for the Xbox 360.
 +
 +
The emulator binary is called xefu.xex. The first resource is xb1krnl which is a modified version of [[Kernel|xboxkrnl.exe]].
 +
 +
=== Modifications to xboxkrnl.exe ===
 +
 +
The IDEXPDTR section has been dropped, additionally the extra data from the MS-DOS header is gone.
 +
 +
==== Guest to host communication ====
 +
 +
The entrypoint of the kernel looks like:
 +
 +
<pre>
 +
80030878: 56                  push  %esi
 +
80030879: 57                  push  %edi
 +
8003087a: 8d 05 4c ac 02 80    lea    0x8002ac4c,%eax
 +
80030880: 0f 3f                (bad) 
 +
80030882: 04 20
 +
80030884: 8d 05 6c ac 02 80    lea    0x8002ac6c,%eax
 +
8003088a: 0f 3f                (bad) 
 +
8003088c: 04 20
 +
8003088e: 8d 05 8c ac 02 80    lea    0x8002ac8c,%eax
 +
80030894: 0f 3f                (bad) 
 +
80030896: 04 21
 +
80030898: 8d 05 70 94 01 80    lea    0x80019470,%eax
 +
...
 +
</pre>
 +
 +
According to [[https://www.symantec.com/avcenter/reference/Virtual_Machine_Threats.pdf this document by symantec]] (Page 5, Left-hand-side) the patterns <code>0F 3F x1 x2</code> and <code>0F C7 C8 y1 y2</code> are used for communication with the host.
 +
 +
{| class="wikitable"
 +
! x1 !! x2 !! Notes
 +
|-
 +
| 0x04 || 0x20 || Seems to use eax (address) as parameter?
 +
|-
 +
| 0x04 || 0x21 || Seems to use eax (address) as parameter?
 +
|-
 +
| 0x04 || 0x22 || Seems to use eax (address) as parameter?
 +
|-
 +
| 0x04 || 0x23 || Seems to use eax (address) as parameter?
 +
|-
 +
| 0x04 || 0x24 || Seems to use eax (address) as parameter?
 +
|-
 +
| 0x04 || 0x35 || Seems to use eax (address) as parameter?
 +
|-
 +
| 0x04 || 0x50 || Seems to use eax (address) as parameter?
 +
|-
 +
| 0x06 || 0x00 || Seems to use eax (address) and ecx (size) as parameter?
 +
|-
 +
| 0x06 || 0x26 ||
 +
|-
 +
| 0x06 || 0x27 ||
 +
|-
 +
| 0x06 || 0x28 ||
 +
|-
 +
| 0x06 || 0x29 ||
 +
|-
 +
| 0x06 || 0x0B ||
 +
|}
 +
  
 
== References and links ==
 
== References and links ==

Revision as of 00:50, 30 May 2017

Xbox 360 Backward Compatibility is Microsofts original Xbox emulator for the Xbox 360.

The emulator binary is called xefu.xex. The first resource is xb1krnl which is a modified version of xboxkrnl.exe.

Modifications to xboxkrnl.exe

The IDEXPDTR section has been dropped, additionally the extra data from the MS-DOS header is gone.

Guest to host communication

The entrypoint of the kernel looks like: 

80030878:	56                   	push   %esi
80030879:	57                   	push   %edi
8003087a:	8d 05 4c ac 02 80    	lea    0x8002ac4c,%eax
80030880:	0f 3f                	(bad)  
80030882:	04 20
80030884:	8d 05 6c ac 02 80    	lea    0x8002ac6c,%eax
8003088a:	0f 3f                	(bad)  
8003088c:	04 20
8003088e:	8d 05 8c ac 02 80    	lea    0x8002ac8c,%eax
80030894:	0f 3f                	(bad)  
80030896:	04 21
80030898:	8d 05 70 94 01 80    	lea    0x80019470,%eax
...

According to [this document by symantec] (Page 5, Left-hand-side) the patterns 0F 3F x1 x2 and 0F C7 C8 y1 y2 are used for communication with the host.

x1 x2 Notes
0x04 0x20 Seems to use eax (address) as parameter?
0x04 0x21 Seems to use eax (address) as parameter?
0x04 0x22 Seems to use eax (address) as parameter?
0x04 0x23 Seems to use eax (address) as parameter?
0x04 0x24 Seems to use eax (address) as parameter?
0x04 0x35 Seems to use eax (address) as parameter?
0x04 0x50 Seems to use eax (address) as parameter?
0x06 0x00 Seems to use eax (address) and ecx (size) as parameter?
0x06 0x26
0x06 0x27
0x06 0x28
0x06 0x29
0x06 0x0B


References and links

Retrieved from "https://xboxdevwiki.net/index.php?title=Xbox_360_Backward_Compatibility&oldid=5558"