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Discussione: [X360 Reversing] Chapter 6: Find and patch Kernel Errors

  1. #1
    Moderatore L'avatar di DrSchottky
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    [X360 Reversing] Chapter 6: Find and patch Kernel Errors


    Find and patch Kernel Errors

    Black screen with white text saying to contact customer service, followed by a Exx.
    Those are kernel errors, and some of them (mainly DVD, HDD and ETH errors) can be bypassed
    with kernel patches (obviously you bypass the error, the device you excluded from kernel won't work).

    How can we find those checks in kernel?
    VdDisplayFatalError is a function that takes the error as parameter (r3, as always) and shows it on Video/ROL.
    Once you have your kernel (and symbols) you can find a pattern that uniquely identifies the function and search
    for it in your CE+CG image (IDC scripting is the way!).

    Once you found the function in your kernel you simply look for callers. The last byte of r3 before the bl is the hex
    of the error that will be shown.

    An example of a error that COULD be easily bypassed? E64.
    An example of a error that COULD NOT be easily bypassed? E74.



    Here's a little gift
    Codice:
    #include <idc.idc>
    
    static main()
    {
    	auto addr = 0;
    	addr = FindBinary(addr,SEARCH_DOWN,"DB E1 FF D0 94 21 FE D0");
    	MakeNameEx(addr - 8, "VdDisplayFatalError", 0);
    }


    Credits:
    xeBuild Team
    Free60
    RGLoader
    Ultima modifica di DrSchottky; 19-10-2015 alle 14:29
    Tommino81, Sk8er000 and amon76 like this.

  2. Likes Sk8er000 Ha dato un "mi piace" per questo post
    Thanks zeruel85, Sk8er000, Tommino81 Ha ringraziato per questo post
  3. #2
    Moderatore L'avatar di DrSchottky
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    Thread updated, IDC snippet added.

  4. Likes zeruel85 Ha dato un "mi piace" per questo post

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