windows-xp/Source/XPSP1/NT/net/config/dbgext/readme.txt

README file for sample WINDBG (old stlye) extension simple.dll


This extsnsion dll shows how to write a simple extension and demostrates use of APIs in wdbgexts.h


Mandatory routines which must be implemented and exported for windbg style extensions:
VOID
WinDbgExtensionDllInit(
    PWINDBG_EXTENSION_APIS lpExtensionApis,
    USHORT MajorVersion,
    USHORT MinorVersion
    )

This is called on loading extension dll. Global variables and flags for extension should be initialized in this routine. One 
of the useful things to initialize is WINDBG_WNTENSION_APIS which has some commonly used APIS for memory reads and I/O.



LPEXT_API_VERSION
ExtensionApiVersion(
    VOID
    )
This tells debugger about version of the extension dll. The values returned by this will determine how extension of this
dll will be called. A common error while writing extensions is mismatched values of version returned be this routine as 
compared to what version dll was built with.

This has ApiVersion = { (VER_PRODUCTVERSION_W >> 8), 
                   (VER_PRODUCTVERSION_W & 0xff), 
                   EXT_API_VERSION_NUMBER64, 
                    0 };


VOID
CheckVersion(
    VOID
    )
This is called after the dll is loaded by the debugger. The extension dll can verify here if it was loaded for correct target.




Extension Calls
---------------

EXT_API_VERSION_NUMBER64 is needed for making 64-bit aware extensions, all addresses for these will then be ULONG64s, for this
an extension is defined as:
CPPMOD VOID 
extension(
        HANDLE                 hCurrentProcess,
        HANDLE                 hCurrentThread,
        ULONG64                dwCurrentPc,
        ULONG                  dwProcessor,
        PCSTR                  args
     )


Extensions
----------


help

Every extension dll should have one extension called 'help' which shows descriptions for extensions that are present in the dll.